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2004-2005 Final ReportENVIRONMENTAL QUALITY OF WILMINGTON AND NEW HANOVER COUNTY WATERSHEDS 2004-2005 by Michael A. Mallin, Lawrence B. Cahoon, Martin H. Posey, Virginia L. Johnson, Douglas C. Parsons, Troy D. Alphin, Byron R. Toothman, Michelle L. Ortwine and James F. Merritt CMS Report 06-01 Center for Marine Science University of North Carolina Wilmington Wilmington, N.C. 28409 www.uncw.edu/cmsr/aquaticecology/tidalcreeks March 2006 Funded by: The City of Wilmington, New Hanover County and the North Carolina Clean Water Management Trust Fund 1 Executive Summary This report represents combined results of Year 11 of the New Hanover County Tidal Creeks Project and Year 7 of the Wilmington Watersheds Project. Water quality data are presented from a watershed perspective, regardless of political boundaries. The combined programs involved 11 watersheds and 54 sampling stations. In this summary we first present brief water quality overviews for each watershed from data collected between August 2004 – September 2005, and then discuss key results of several special studies conducted over the past two years. Barnards Creek – Barnards Creek drains into the Cape Fear River Estuary. There was only one station sampled in this watershed during 2005, lower Barnard’s Creek at River Road. This site had no algal bloom, BOD or turbidity problems; but it had poor water quality in terms of fecal coliform counts and low dissolved oxygen. It also had among the highest suspended solids, ammonium, total nitrogen and total phosphorus levels among all the local watersheds. Bradley Creek – Bradley Creek drains the largest tidal creek watershed in the area, including much of the UNCW campus, into the Atlantic Intracoastal Waterway (ICW). Seven sites are sampled, all from shore. Turbidity was not problematic during 2004- 2005. Dissolved oxygen was good to fair at all sites except the branch at College Acres (BC-CA) where it fell below 5.0 mg/L on three occasions during summer. Elevated nitrogen and phosphorus levels enter the creek in both the north and south branches, and one minor and one major algal bloom occurred in the creek in the south branch (BC-SB) at Wrightsville Avenue. Fecal coliform bacterial samples were only collected at BC-CA, where contamination was excessive during six of the seven samples collected in 2005. Burnt Mill Creek – Burnt Mill Creek drains an extensive urban area into Smith Creek. The number of sampling stations on Burnt Mill Creek was increased from three to six in 2005, because of additional funding from the EPA319 program through North Carolina State University. There were no turbidity or suspended solids problems in 2005, but the creek showed poor water quality in terms of substandard dissolved oxygen, with four out six stations having dissolved oxygen concentrations below the State standard > 25% of the time sampled. High fecal coliform counts were a problem, with five out of six sites exceeding the human contact standard > 25% of occasions sampled. There were also some algal bloom problems at Anne McCrary Pond on Randall Parkway and at the Princess Place station. The effectiveness of Ann McCrary wet detention pond as a pollution control device was poor during 2005. While the pond led to a significant reduction in fecal coliform bacteria and an increase in dissolved oxygen, it failed to reduce nutrient concentrations including ammonium, nitrate, total nitrogen, orthophosphate and total phosphorus. Several water quality parameters indicated a subsequent worsening of the creek from where it exited the pond to the downstream Wallace Park and Princess Place sampling stations. The constructed wetland on Kerr Avenue led to a significant decrease in ammonium, but none of the other nutrient species. Fecal coliform bacteria counts did not decrease through that pond in 2005, nor did BOD. Sampling of the sediments for potential toxicants showed some problems 2 with elevated lead concentrations, and problems with excessive concentrations of polycyclic aromatic hydrocarbons (PAHs) at all sites tested. Futch Creek – Futch Creek is situated on the New Hanover-Pender County line and drains into the ICW. Six locations are sampled by boat. Futch Creek maintained good microbiological water quality, as it has since channel dredging at the mouth occurred in 1995 and 1996. Algal blooms, turbidity, and low dissolved oxygen were not problems in 2004-2005. This creek continues to display some of the best water quality in the New Hanover County tidal creek system, due to generally low development and impervious surface coverage in its watershed. Greenfield Lake – This urban lake is sampled at three in-lake sites and at three tributary sites. The three tributaries of Greenfield Lake (near Lake Branch Drive, Jumping Run Branch, and Lakeshore Commons Apartments) all suffered from severe low dissolved oxygen problems. All three of the tributaries also had frequent high fecal coliform counts, and maintained geometric mean counts in excess of the state standard for human contact waters. There were some algal bloom problems at the Jumping Run Branch site. In spring 2005 several steps were taken by the City of Wilmington to restore viability to the lake. During February, 1,000 sterile grass carp were introduced to the lake to control (by grazing) the overabundant aquatic macrophytes. During that same month four SolarBee water circulation systems were installed in the lake to improve circulation and force dissolved oxygen from the surface downward toward the bottom. Finally, from April through June a contract firm applied the herbicide Sonar to further reduce the amount of aquatic macrophytes. These actions led to a major reduction in aquatic macrophytes lake wide. However, six algal blooms exceeding the state standard of 40 mg/L were recorded among the three in-lake sampling stations during July-September 2005 (an increase over the previous year). Despite the blooms, there was also an improvement in dissolved oxygen concentrations over the previous two years, possibly through the use of the SolarBees. Fecal coliform bacteria pollution was a problem in the main lake, particularly at the park station. Thus, during 2005 Greenfield Lake was impaired by algal blooms, high fecal coliform counts and low dissolved oxygen concentrations, although there was definite improvement in dissolved oxygen concentrations compared with the previous two years. Whereas in 2004 average summer surface dissolved oxygen concentrations ranged from 2.9-6.8 mg/L, in summer 2005 average surface dissolved oxygen concentrations ranged from 8.2-9.9 mg/L. Hewletts Creek – Hewletts Creek drains a large watershed into the ICW, which is sampled by boat at four sites and from shore at eight sites. Hewletts Creek was impacted by two sewage spills during summer 2005. Nutrient loading from one of these spills (in July) caused two major algal blooms in the north branch (NB-GLR) and the south branch (SB-PGR) plus a minor bloom at SB-PGR. There were several incidents of hypoxia seen in our regular monthly 2004-2005 sampling; two at NB-GLR, three at NWB and four at SB-PGR, and several additional incidents of hypoxia following the July sewage spill. The hypoxia from the spill also caused a large fish kill on the creek during the July 4th weekend, and subsequent mortality of some ducks. Fecal coliform counts were low to moderate at the lower and mid-creek sites, and high in terms of the N.C. 3 human contact standard of 200 CFU/100 mL at the north and middle branches, but moderate at the south branch. The sewage spills led to high July and September water column fecal coliform counts, and prolonged occurrences (over two months) of high fecal bacteria counts in the sediments of the upper branches. Since January 2004 five non-tidal sites have been sampled in the Hewletts Creek watershed. One site is PVGC-9, draining Pine Valley Country Club. This stream had no dissolved oxygen, turbidity, or algal bloom problems, and relatively high nitrate levels. Fecal coliform bacteria counts exceeded State standards 86% of the time in 2005 at PVGC-9, an increase over last year. The other sites are being sampled to gain background information on the water quality of streams entering (DB-1, DB-2, DB-3) and exiting (DB-4) a proposed constructed wetland/future park area known as the Dobo site, draining into the headwaters of Hewletts Creek. In 2005 all nutrient species had the highest concentrations at DB-1 and lowest at DB-2. There was some reduction of nutrients at DB-4 compared with DB-1, showing that the property already has some water quality improvement function. The exception was nitrate, which had similar concentrations at DB-1 and DB-4. Dissolved oxygen was low only at DB-1, and turbidity was low at all four sites. Suspended solids concentrations were periodically elevated at DB-1, but low at the other three sites. Fecal coliform bacteria counts were a problem at all four sites, and were highest at DB-1 followed by DB-4 and DB-2. The data suggest that fecal coliform bacteria and nitrogen should be targeted in particular for removal by the treatment facility. Howe Creek – Howe Creek drains into the ICW. Five stations were sampled in Howe Creek in 2004-2005. Turbidity did not exceed North Carolina water quality standards at any of the stations. Dissolved oxygen concentrations were generally good in Howe Creek, with HW-GP below the standard of 5.0 mg/L on two occasions. Nutrient levels were generally low except for nitrate at HW-DT. Nitrate levels showed a decrease over levels in 2003-2004, especially at the uppermost stations, probably a reflection of lower rainfall and runoff. There was one minor algal bloom of 38 mg/L as chlorophyll a at HW- DT. Since wetland enhancement was performed in 1998 above Graham Pond the creek below the pond at HW-GP has had fewer and smaller algal blooms than before the enhancement. Fecal coliform bacterial abundances were low near the Intracoastal Waterway, moderate in mid-creek, and high in the uppermost station, with HW-DT exceeding the State standard on seven of 12 occasions. The 2004-2005 data show an improvement in fecal coliform counts after a sharp decrease in bacterial water quality seen in 2003-2004. Less urban runoff as a result of the drought of 2005 may be responsible for the lowered counts. Motts Creek – Motts Creek drains into the Cape Fear River Estuary. This creek was sampled at only one station, at River Road. Dissolved oxygen concentrations were below 4.5 mg/L from May through September 2005 (range 2.8-4.4 mg/L) similar to previous years. Unlike previous years, neither turbidity nor suspended solids were problematic in 2005, possibly a result of low rainfall. Fecal coliform contamination was a problem in Motts Creek, with the geometric mean of 353 CFU/100 mL exceeding the State standard of 200 CFU/100 mL, and samples exceeding this standard on six of seven occasions. Fecal coliform contamination increased over that of previous years. Nutrient levels were similar to the previous year’s study, but chlorophyll a 4 concentrations generally decreased, with no algal blooms detected in 2005. BOD5 samples yielded a mean value of 1.3 mg/L and a median value of 1.2 mg/L, generally lower than the previous years. Thus, this creek showed mixed water quality, with algal blooms and BOD decreasing, and dissolved oxygen and fecal coliform counts somewhat poorer compared with last year. Pages Creek – Pages Creek drains into the ICW. This creek was sampled at three stations, two of which receive drainage from developed areas near Bayshore Drive (PC- BDUS and PC-BDDS). During the past sample year turbidity was low with no incidents of turbidity exceeding the state standard of 25 NTU. However, there were three incidents of hypoxia during summers of 2004 and 2005, all at the station draining upper Bayshore Drive. Fecal coliform bacteria were not sampled at this creek during the past year. Nitrate and orthophosphate concentrations were similar to the previous year, and phytoplankton biomass as chlorophyll a was low with only one minor algal bloom of 23 mg/L noted at PC-BDUS. Because of the relatively low watershed development and low amount of impervious surface coverage in the watershed, this is one of the least- polluted creeks in New Hanover County. Smith Creek – Smith Creek drains into the lower Northeast Cape Fear River just upstream of where it merges with the Cape Fear River. Two estuarine sites on Smith Creek proper, SC-23 and SC-CH were sampled in 2005. Dissolved oxygen concentrations were below 5.0 mg/L on three of seven occasions at SC-23 and on four of seven occasions at SC-CH between June and September 2005. Thus, low dissolved oxygen continued to be a water quality problem in Smith Creek. The North Carolina turbidity standard for estuarine waters (25 NTU) was not exceeded during 2005, an improvement over last year. Nutrient concentrations remained similar to last year's levels, and algal blooms exceeding the State standard were not found in 2005. However, lesser algal blooms of 35 mg/L and 25 mg/L occurred at SC-23 and SC-CH, respectively, in August, and a bloom of 25 mg/L occurred at SC-23 in July. Fecal coliform bacteria concentrations were above 200 CFU/100 mL on only one occasion (at SC-CH), an improvement over the past two years. BOD5 was sampled at SC-CH, with a mean value of 1.4 mg/L and a median value of 1.5 mg/L, similar to last year. Whiskey Creek – Whiskey Creek is the southernmost large tidal creek in New Hanover County that drains into the ICW. Five stations are sampled from shore along this creek. Whiskey Creek had moderate nutrient loading but generally low chlorophyll a concentrations in 2004-2005, with the exception of one minor algal bloom. Dissolved oxygen concentrations were below the State standard on only one of 12 occasions at both WC-MLR and WC-AB in 2004-2005, and high turbidity was not a problem. Fecal coliform bacteria were not sampled in 2004-2005 in Whiskey Creek. Water Quality Station Ratings – The NC Division of Water Quality (NCDEHNR 1996) utilizes an EPA-based system to help determine if a water body supports its designated use (described in Appendix A). We applied these numerical standards to the water bodies described in this report, based on 2004-2005 data, and have designated each station as good, fair, and poor accordingly (Appendix B). Our analysis shows that (based on fecal coliform standards for human contact waters) the Barnards Creek station was rated as poor water quality. Five of the six stations in Burnt Mill Creek were 5 rated as poor in 2005, and the other was rated fair. The one Bradley Creek station sampled for fecal coliforms was rated as poor. Futch Creek was rated as good for fecal coliform bacteria, including for shellfishing in the lower creek. The Greenfield Lake tributaries were rated as poor microbiological water quality and the in-lake stations as fair to poor. The lower tidal stations in Hewletts Creek were rated good to fair for fecal coliforms; the middle stations as fair, and two upper tidal stations were poor and fair, respectively. The non-tidal freshwater stations in the Hewletts Creek watershed were poor throughout. The uppermost two stations in Howe Creek were rated poor and fair, respectively, and the lower three were rated good. Lower Motts Creek was rated poor, and the two stations in Smith Creek were good and fair, respectively. We also list our ratings for chlorophyll a, dissolved oxygen and turbidity in Appendix B. Fecal coliform bacterial conditions for the entire Wilmington City and New Hanover County Watersheds system (40 sites) showed 30% to be in good condition, 20% in fair condition, and 50% in poor condition. Dissolved oxygen conditions system-wide (54 sites) showed 59% of the sites were in good condition, 9% were in poor condition, and 32% were in poor condition. Sediment Fecal Bacteria Study - A study was performed to determine the abundance of fecal bacteria in Bradley Creek sediments and to see if their concentrations were related to sediment phosphorus (P), sediment carbon (C), salinity and water temperature. The concentrations of fecal indicator bacteria in sediments of Bradley Creek were highly variable, spanning over 3 orders of magnitude. Fecal coliform concentrations had a geometric mean of 179 CFU/cm2 (std. dev. = 411, range = 0 – 3,230) in a total of 154 samples. This geometric mean value corresponds to a value of 179 CFU/100 ml if all these bacteria were suspended in a water column 1 meter deep, a value just below that required to close the water to human body contact (200 CFU/100 ml). The regulatory standard for shellfishing is much lower, 14 CFU/100 ml; 113 of the 154 samples exceeded this value using analogous assumptions. Fecal enterococcus concentrations had a geometric mean value of 285 CFU/cm2 (std. dev. = 433, range = 0-1726). This geometric mean value corresponds to a value of 285 CFU per 100 ml if all these bacteria were suspended in a water column 1 meter deep, a value well above that required to close the water to human body contact (33 CFU/100 ml). Thus, the levels of fecal indicator bacteria measured in Bradley Creek sediments frequently represent serious potential problems for human uses of these waters. We further note that mixing will add the sediment fecal bacteria to the high levels already present in the water column of Bradley Creek. Sediment fecal coliform bacteria were negatively correlated with salinity and positively correlated with water temperature, but enterococcus had no significant relationship to these factors. Rainfall in the 24-hour period preceding sampling was also significantly related to fecal coliform counts. Laboratory experiments showed that both fecal coliform bacteria and enterococcus bacteria counts were positively related to increasing concentrations of usable (or bioavailable) carbon (dextrose). However, only enterococcus was significantly correlated to sediment P concentrations, and only when background P concentrations were low. Bioavailable C is abundant in stormwater runoff. Because of this, and the fact that sediment fecal bacteria counts were positively related to rainfall, we conclude that storm water runoff is the most significant factor driving sediment contamination. 6 Evaluation of Oyster Characteristics in Pages, Howe, and Hewletts Creeks – The UNCW Benthic Ecology Laboratory examined oyster characteristics and reef characteristics in Pages, Howe, and Hewletts Creeks, but there were few clear patterns indicating a difference in oyster health among the creeks. We had expected Pages Creek to show characteristics of healthier oysters or better-developed reefs compared to either Hewletts or Howe Creeks. Percent shell coverage was greatest in Pages Creek, on average ~10% greater coverage than oyster reefs in Hewletts Creek and ~28% greater coverage than oyster reefs in Howe Creek. It seems likely that that lower coverage of exposed shell in Howe and Hewletts Creeks may be a function of increased suspended solids and subsequent sedimentation compared to Pages Creek, rather than increased oyster production in Pages Creek. Howe Creek showed the greatest oyster density of the three creeks and no apparent difference in oyster size was seen among the creeks. Where we did detect differences in reef height and shell cover, these differences supported the idea that greater sedimentation impacted Hewletts and Howe Creeks compared to Pages Creek. While we know that water quality in Hewletts Creek has suffered for some time, the current data does not provide evidence for population differences among the creeks. However, oyster population measures may reflect regional conditions more than local creek conditions because of interchange among the creek systems through the IntraCoastal Waterway. Even with similar densities and reef form, differences may be apparent with physiological or condition measures such as tissue weight and disease incidence. Currently we are evaluating the disease intensity for oysters in these three target creeks and will compare disease intensity and condition of these oyster populations. 7 Table of Contents 1.0 Introduction 8 1.1 Methods 8 2.0 Barnards Creek 10 3.0 Bradley Creek 13 4.0 Burnt Mill Creek 16 5.0 Futch Creek 22 6.0 Greenfield Lake 26 6.1 Preliminary Assessment of Greenfield Lake Restoration Measures 30 7.0 Hewletts Creek 40 7.1 The 2005 Major Sewage Spill in Hewletts Creek 47 8.0 Howe Creek 52 9.0 Motts Creek 56 10.0 Pages Creek 59 11.0 Smith Creek 61 12.0 Whiskey Creek 64 13.0 Sediment Fecal Bacteria Study 67 14.0 Evaluation of Oyster Characteristics 78 15.0 References Cited 85 16.0 Acknowledgments 87 17.0 Appendix A: Selected N.C. water quality standards 88 18.0 Appendix B: UNCW Watershed Station Ratings Based on DWQ Chemical Standards 89 19.0 Appendix C: GPS coordinates for the New Hanover County Tidal Creek and Wilmington Watersheds Program sampling stations 91 20.0 Appendix D: UNCW reports and papers related to tidal creeks 93 8 1.0 Introduction In 1993 scientists at the UNC Wilmington Center for Marine Science Research began studying five tidal creeks in New Hanover County. This project, funded by New Hanover County, the Northeast New Hanover Conservancy, and UNCW, yielded a comprehensive report detailing important findings from 1993-1997, and produced a set of management recommendations for improving creek water quality (Mallin et al. 1998a). In 1999-2000 Whiskey Creek was added to the matrix of tidal creek watersheds analyzed in our program. In October 1997 the Center for Marine Science began a project (funded by the City of Wilmington Engineering Department) with the goal of assessing water quality in Wilmington City watersheds under base flow conditions. Also, certain sites were analyzed for sediment heavy metals concentrations (EPA Priority Pollutants). In the past six years we have produced combined Tidal Creeks – Wilmington City Watersheds reports (Mallin et al. 1998b; 1999; 2000a; 2002a; 2003; 2004). In the present report we present results of continuing studies from August 2004 - July 2005 in the tidal creek complex and January - September 2005 in the City of Wilmington watersheds. The UNCW Aquatic Ecology Laboratory is also involved with a project headed up by North Carolina State University (NCSU) and funded through the EPA 319 Grant program that is designed to provide stream restoration to Burnt Mill Creek. Thus, three stations have been added to the Burnt Mill creek sampling matrix under this program. The water quality data within is presented from a watershed perspective. Some of the watersheds cross political boundaries (i.e. parts of the same watershed may lie in the County but not the City). Bradley and Hewletts Creeks are examples. Water quality parameters analyzed in the tidal creeks include water temperature, pH, dissolved oxygen, salinity/conductivity, turbidity, nitrate, ammonium, orthophosphate, chlorophyll a, and in selected creeks fecal coliform bacteria. Similar analyses were carried out in the City watersheds with the addition of total Kjeldahl nitrogen (TKN), total nitrogen (TN), total phosphorus (TP), total suspended solids (TSS) and biochemical oxygen demand (BOD) at selected sites. 1.1 Methods Field parameters were measured at each site using a YSI 6920 Multiparameter Water Quality Probe (sonde) linked to a YSI 650 MDS display unit. Individual probes within the instruments measured water temperature, pH, dissolved oxygen, turbidity, salinity, and conductivity. YSI Model 85 and 55 dissolved oxygen meters were also used on occasion. The instruments were calibrated prior to each sampling trip to ensure accurate measurements. The UNCW Aquatic Ecology laboratory is State-Certified for field measurements (temperature, conductivity, dissolved oxygen and pH) and for laboratory chlorophyll a measurements. The light attenuation coefficient k was determined (at locations where depth permitted), from data collected on site using vertical profiles obtained by a Li-Cor LI-1000 integrator interfaced with a Li-Cor LI-193S spherical quantum sensor. 9 For the six tidal creeks, water samples were collected monthly, at or near high tide. For nitrate+nitrite (hereafter referred to as nitrate) and orthophosphate assessment, three replicate acid-washed 125 mL bottles were placed ca. 10 cm below the surface, filled, capped, and stored on ice until processing. In the laboratory the triplicate samples were filtered simultaneously through 25 mm Millipore AP40 glass fiber filters (nominal pore size 1.0 micrometer) using a manifold with three funnels. The pooled filtrate was stored frozen until analysis. Nitrate+nitrite and orthophosphate were analyzed using a Bran-Luebbe AutoAnalyzer following EPA protocols. Samples for ammonium were collected in duplicate, field-preserved with phenol, stored on ice, and analyzed in the laboratory according to the methods of Parsons et al. (1984). Fecal coliform samples were collected by filling pre-autoclaved containers ca. 10 cm below the surface, facing into the stream. Samples were stored on ice until processing (< 6 hr). Fecal coliform concentrations were determined using a membrane filtration (mFC) method (APHA 1995). North Carolina water quality standards relevant to this report are listed in Appendix A. The analytical method used to measure chlorophyll a is described in Welschmeyer (1994) and US EPA (1997). Chlorophyll a concentrations were determined from the 1.0 micrometer glass fiber filters used for filtering samples for nitrate+nitrite and orthophosphate analyses. All filters were wrapped individually in aluminum foil, placed in an airtight container and stored in a freezer. During the analytical process, the glass filters were separately immersed in 10 ml of a 90% acetone solution. The acetone was allowed to extract the chlorophyll from the material for 18-24 hours. The solution containing the extracted chlorophyll was then analyzed for chlorophyll a concentration using a Turner AU-10 fluorometer. This method uses an optimal combination of excitation and emission bandwidths that reduces the errors inherent in the acidification technique. Samples were collected on seven occasions within the Wilmington City watersheds from January through September 2005. Field measurements were taken as indicated above. Nutrients (nitrate, ammonium, total Kjeldahl nitrogen, total nitrogen, orthophosphate, and total phosphorus) and total suspended solids (TSS) were analyzed by a state-certified contract laboratory using EPA and APHA techniques. We also computed inorganic nitrogen to phosphorus molar ratios for relevant sites (N/P). Chlorophyll a was run at UNCW-CMS as described above, except filters were ground using a Teflon grinder prior to extraction. For a large wet detention pond (Ann McCrary Pond on Burnt Mill Creek) and for a constructed wetland on Kerr Avenue (at the headwaters area of Burnt Mill Creek) we collected data from input (control) and outfall stations. We used these data to test for statistically significant differences in pollutant concentrations between pond input and output stations. The data were first tested for normality using the Shapiro-Wilk test. Normally distributed data parameters were tested using the paired-difference t-test, and non-normally distributed data parameters were tested using the Wilcoxon Signed Rank test. Statistical analyses were conducted using SAS (Schlotzhauer and Littell 1987). 10 2.0 Barnards Creek The water quality of lower Barnard’s Creek is an important issue as single family and multifamily housing construction has occurred upstream of Carolina Beach Rd. in the St. Andrews Dr. area. Another major housing development is planned for the area east of River Road and between Barnards and Motts Creeks. In 2005 we collected data at a station located on Barnards Creek at River Road (BNC-RR) that drains part of this area (Fig. 2.1). Sampling at two other sites, BNC-CB site near Carolina Beach Road and BNC-TR at Titanium Rd. has been discontinued. BNC-RR had an average salinity of 5.7 ppt with a range of 2.0-11.4 ppt. This station had dissolved oxygen levels ranging from 2.8-3.5 from June through September. Concentrations of nutrients (total nitrogen, nitrate, ammonium, orthophosphate and total phosphorus) were among the highest in the Wilmington area (Table 2.1). Turbidity on average was moderate (16 NTU), and did not exceed the state standard for estuarine waters of 25 NTU. Total suspended solids concentrations were among the highest among area creeks, particularly May through July, but there were no algal bloom problems (Table 2.1). BOD5 was sampled seven times at BNC-RR last year, yielding a median of 1.1 mg/L and a mean of 1.4 mg/L, which was down from the BOD5 concentrations found in previous years (Mallin et al. 2003; 2004). Median and mean BOD20 in 2005 were 4.4 and 5.0 mg/L, not problematic values. Fecal coliform counts exceeded the state standard on two of seven occasions for a 29% non-compliance rate, slightly poorer than the previous year. Thus, this station can be considered impaired by low dissolved oxygen and fecal coliform bacteria, with comparatively high nutrient concentrations as well. 11 Table 2.1. Mean and standard deviation of water quality parameters in Barnards Creek watershed, January - September 2005. Fecal coliforms as geometric mean; N/P ratio as median (n = 7 for all parameters). _____________________________________________________________________ Parameter BNC-RR _____________________________________________________________________ DO (mg/L) 5.1 (2.9) Turbidity (NTU) 16 (5) TSS (mg/L) 18.4 (8.3) Nitrate (mg/L) 0.217 (0.106) Ammonium (mg/L) 0.161 (0.129) TN (mg/L) 1.424 (0.367) Phosphate (mg/L) 0.040 (0.046) TP (mg/L) 0.146 (0.080) N/P molar ratio 35.4 Chlorophyll a (mg/L) 6.3 (6.0) BOD5 1.4 (0.7) BOD20 5.7 (1.3) Fecal coliform bacteria (/100 mL) 105 _____________________________________________________________________ 12 13 3.0 Bradley Creek The Bradley Creek watershed has been a principal location for Clean Water Trust Fund mitigation activities, including the purchase and renovation of Airlie Gardens by the County. The development of the former Duck Haven property bordering Eastwood Road is of great concern in terms of its potential water quality impacts to the creek. This creek is one of the most polluted in New Hanover County, particularly by fecal coliform bacteria (Mallin et al. 2000b). Seven stations were sampled in the past year, both fresh and brackish (Fig. 3.1). As with last year, turbidity was not a major problem during 2004-2005 (Table 3.1). The standard of 25 NTU was not exceeded during our sampling. There were only minor problems with low dissolved oxygen (hypoxia), with BC-NB having DO < 5.0 mg/L on two occasions and BC-CA having substandard dissolved oxygen conditions on three of seven sampling occasions (Appendix B). Table 3.1 Water quality parameter concentrations at Bradley Creek sampling stations, August 2004-July 2005. Data as mean (SD) / range, fecal coliform bacteria as geometric mean / range (for BC-CA, n = 7 months). _____________________________________________________________________ Station Salinity Turbidity Dissolved Oxygen Fecal coliforms (ppt) (NTU) (mg/L) (CFU/100 mL) _____________________________________________________________________ BC-76 31.3 (2.3) 3 (3) 7.3 (2.0) NA 26.3-33.8 0-10 4.3-10.1 BC-SB 9.7 (11.0) 6 (5) 7.4 (2.0) NA 0.2-29.6 0-16 4.8-10.8 BC-SBU 0.1 (0.0) 2 (1) 7.2 (1.7) NA 0.1-0.1 0-5 4.5-10.9 BC-NB 22.8 (10.0) 4 (3) 7.2 (2.6) NA 4.6-32.7 0-8 2.9-10.9 BC-NBU 0.1 (0.0) 9 (14) 7.4 (0.8) NA 0.1-0.2 0-52 6.0-8.4 BC-CR 0.1 (0.0) 1 (2) 7.8 (0.7) NA 0.1-0.1 0-8 6.0-8.4 BC-CA 0.1 (0.1) 6 (5) 5.1 (2.7) 1207 0.1-0.1 1-16 2.3-9.1 210-3400 _____________________________________________________________________ NA = not analyzed Only BC-CA was sampled for fecal coliform concentrations last year, with elevated counts exceeding the State standard of 200 CFU/100 mL occurring during six of seven 14 collections for an 86% exceedence rate (Table 3.1). We consider BC-CA to have poor water quality in terms of fecal coliform bacteria counts (Appendix B). Nitrate concentrations were highest at stations BC-CR, BC-SBU (upper south branch) and BC-NBU. Nitrate decreased slightly in the south branch in comparison to the previous year. Ammonium was elevated at BC-CA, but low at other locations. The highest orthophosphate levels were found at BC-CA, with relatively low orthophosphate levels at the rest of the stations (Table 3.2). Bradley Creek did not host excessive algal blooms in 2004-2005, except for a minor bloom in April at BC-SB (26 mg/L) and a major bloom (52 mg/L) in July at that station (Table 3.2). Table 3.2. Nutrient and chlorophyll a data at Bradley Creek sampling stations, August 2004-July 2005. Data as mean (SD) / range, nutrients in mg/L, chlorophyll a as mg/L. _____________________________________________________________________ Station Nitrate Ammonium Orthophosphate Chlorophyll a _____________________________________________________________________ BC-76 0.011 (0.008) 0.019 (0.009) 0.008 (0.003) 1.9 (2.1) 0.003-0.033 0.014-0.042 0.005-0.016 0.2-6.4 BC-SB 0.034 (0.030) 0.026 (0.018) 0.011 (0.006) 8.9 (15.5) 0.005-0.090 0.014-0.073 0.005-0.025 0.3-52.0 BC-SBU 0.076 (0.025) NA 0.012 (0.007) 0.8 (0.8) 0.037-0.132 0.004-0.023 0.1-2.7 BC-NB 0.024 (0.027) 0.033 (0.044) 0.010 (0.005) 3.0 (3.6) 0.004-0.088 0.014-0.158 0.005-0.021 0.3-11.6 BC-NBU 0.098 (0.065) NA 0.003 (0.002) 0.6 (0.5) 0.047-0.291 0.001-0.009 0.0-1.6 BC-CR 0.267 (0.091) NA 0.005 (0.002) 0.6 (0.8) 0.071-0.478 0.001-0.009 0.0-2.4 BC-CA 0.140 (0.209) 0.164 (0.124) 0.027 (0.022) 3.3 (2.8) 0.030-0.600 0.020-0.420 0.005-0.050 0.9-8.7 _____________________________________________________________________ NA = not analyzed 15 Figure 3.1. Bradley Creek watershed and sampling sites. 16 4.0 Burnt Mill Creek Since 1997 the Burnt Mill Creek watershed (Fig. 4.1) has been sampled just upstream of Ann McCrary Pond on Randall Parkway (BMC-AP1), about 40 m downstream of the pond outfall (BMC-AP3). Ann McCrary Pond is a large (28.8 acres) regional wet detention pond draining 1,785 acres, with an apartment complex at the upper end near BMC-AP1. The pond itself usually maintains a thick growth of submersed aquatic vegetation, particularly Hydrilla verticillata, Egeria densa, Alternanthera philoxeroides, Ceratophyllum demersum and Valliseneria americana. A survey in late summer 1998 indicated that approximately 70% of the pond area was vegetated. There have been efforts to control this growth, including addition of triploid grass carp as grazers. Our survey also found that this pond is host to Lilaeopsis carolinensis, which is a threatened plant species in North Carolina. The ability of this detention pond to reduce suspended sediments and fecal coliform bacteria, and its failure to reduce nutrient concentrations, was detailed in a scientific journal article (Mallin et al. 2002b). In 2005 sampling began on the inflow (BMC-KA1) and outflow (BMC-KA3) channels of the Kerr Avenue constructed wetland (Fig. 4.1). This new sampling began as a part of a larger project (with NCSU funded by the EPA 319 Program) to provide stream restoration to Burnt Mill Creek. Construction of the 0.7 acre Kerr Avenue Wetland was funded by the N.C. Wetlands Restoration Program, now known as the Ecosystem Enhancement Program. Wetland construction was completed in November 2000 and the first aquatic macrophyte planting (sponsored by Cape Fear River Watch) occurred later that month (various rushes, sedge, pickerelweed, lizard’s tail, water tupelo, wax myrtle, black gum, pond pine, bald cypress, etc.). Since then there have been many supplemental plantings as well as tree donations. The vegetation coverage is presently so dense that macrophytes from this site have been transplanted into other wetland restoration sites. The wetland has a forebay to collect sediment, and the system is designed to retain and treat the first 0.5 inches of a rainfall event before an overflow channel is utilized. This Best Management Practice (BMP) lies in the headwaters of Burnt Mill Creek, which is on the State 303(d) list for poor biological condition. Another new station is located along the main stem of the creek in the Wallace Park area (BMC- WP) and an older station is also on the creek at the bridge at Princess Place (BMC-PP - Fig. 4.1). Kerr Avenue Wetland: This represents the first statistically comparative data useful for assessing the efficacy of this pond as a pollutant removal device. Results of the seven sampling trips showed that turbidity and suspended solids were low both entering and leaving the pond, with no significant difference (Table 4.1). One nutrient parameter, ammonium, was significantly lowered by the pond, while there was no difference in the other nutrient species (which were not in high concentrations entering the pond). BOD5 and BOD20 were not elevated entering the pond and there was no significant difference in concentrations leaving the pond. Fecal coliform bacteria were somewhat elevated entering the pond, and had similar concentrations leaving the pond. The presence of a number of dumpsters surrounding the site, and consequent small mammal foraging and defecating, may be a localized source of fecal coliform bacteria and organic nutrients. Ann McCrary Pond: Turbidity and suspended solids concentrations entering and leaving the pond were low to moderate. Fecal coliform concentrations entering Ann McCrary 17 Pond at BMC-AP1 were very high, however (Table 4.1), possibly a result of pet waste runoff from the apartment complex and runoff from urban upstream areas. All seven samples collected in 2005 at BMC-AP1 had counts exceeding 200 CFU/100 mL; however, only one sample at BMC-AP3 exceeded the standard. There were minor algal blooms at BMC-AP1 in June and August, but three major (chlorophyll a > 40 mg/L) and two minor algal blooms (chlorophyll a > 20 mg/L) at BMC-AP3, the largest amount of bloom activity we have witnessed since the inception of this project in 1997. The efficiency of Ann McCrary Pond as a pollutant removal device was poor last year. Fecal coliforms were significantly reduced during passage through the pond (Table 4.1). Total suspended solids and turbidity were low entering the pond this year and there was no significant difference in removal of these two parameters. Neither ammonium, nitrate, total nitrogen, orthophosphate nor total phosphorus were significantly reduced during passage through the pond this year (Table 4.1). As in previous years, it is likely that inputs of nutrients have entered the pond from a suburban drainage stream midway down the pond across from our former BMC-AP2 site (Fig. 4.1), short circuiting the ability of the pond to remove nutrients. Also, intensive waterfowl use of the pond, particularly at a tributary near the outfall, may have contributed to nutrient loading in the pond and along its shoreline. There was no significant decrease in conductivity through the pond. Dissolved oxygen significantly increased through the pond, probably because of in-pond photosynthesis and aeration by passage over the final dam at the outfall. There was a significant increase in pH, probably due to utilization of CO2 during photosynthesis in the pond. Lower Burnt Mill Creek: Both the Wallace Park (BMC-WP) and the Princess Place location (BMC-PP) experienced several water quality problems during the sample period (Appendix B). Dissolved oxygen was substandard (between 2.0 and 5.0 mg/L) three of six times at BMC-WP and four of seven times at BMC-PP. No problems were seen with turbidity or suspended solids. Nutrients were unremarkable at either site except for an unusual maximum of TN (which was mainly organic nitrogen) at BMC-PP in May. No algal blooms exceeded the State standard for chlorophyll a at Wallace Park, although an unusually high pulse of chlorophyll a (646 mg/L) occurred at Princess Place in May, when the field team reported the waters there to be unusually brown and foamy. This bloom accounted for the unusually high TN levels (TP levels were also elevated to 0.230 mg/L). An important issue, from a public health perspective, was the excessive fecal coliform counts, which maintained geometric means (958 CFU/100 mL at BMC-WP and 479 CFU/100 mL at BMC-PP) well in excess of the State standard for human contact waters (200 CFU/100 mL). Fecal coliform counts were greater than 200 CFU/100 mL in five of six months at Wallace Park and five of seven months at Princess Place, respectively. It is notable that fecal coliform bacteria, ammonium, nitrate, TP and orthophosphate concentrations all increased along the passage from BMC-AP3 to the Princess Place location, while dissolved oxygen decreased (Table 4.1). BOD5 and BOD20 analyses were performed at Wallace Park, with no unusually high concentrations reported. 18 Table 4.1. Mean and (standard deviation) of water quality parameters in upper Burnt Mill Creek, Jan. – Sep. 2005. Fecal coliforms as geometric mean; N/P as median. _____________________________________________________________________ Parameter KA-1 KA-3 BMC-AP1 BMC-AP3 _____________________________________________________________________ DO (mg/L) 4.1 (1.2) 4.9 (1.3) 7.5 (0.8) 10.1 (1.3)* Cond. (mS/cm) 333 (20) 358 (32) 259 (62) 242 (20) pH 6.7 (0.4) 6.8 (0.2) 7.3 (0.4) 7.7 (0.2)* Turbidity (NTU) 6 (3) 5 (2) 11 (19) 6 (3) TSS (mg/L) 3.5 (0.5) 3.3 (1.0) 9.1 (15.9) 13.9 (10.2) Nitrate (mg/L) 0.052 (0.031) 0.054 (0.034) 0.117 (0.108) 0.076 (0.083) Ammonium (mg/L) 0.177 (0.084) 0.023 (0.008)* 0.051 (0.036) 0.036 (0.017) TN (mg/L) 0.717 (0.181) 0.533 (0.207) 0.676 (0.191) 0.993 (0.362) OrthoPhos. (mg/L) 0.006 (0.002) 0.007 (0.003) 0.019 (0.022) 0.007 (0.004) TP (mg/L) 0.053 (0.026) 0.062 (0.016) 0.061 (0.043) 0.070 (0.046) N/P molar ratio 110.7 26.6 37.6 35.4 Chlor. a (mg/L) 0.7 (0.7) 4.8 (5.5) 8.4 (8.6) 45.4 (40.6) Fec. col. (/100 mL) 587 436 793 112* BOD5 1.1 (0.6) 1.2 (0.4) NA NA BOD20 4.3 (1.9) 4.1 (1.1) NA NA _____________________________________________________________________ * Indicates statistically significant difference between inflow and outflow at p<0.05 NA = not analyzed Table 4.2. Mean and (standard deviation) of water quality parameters in lower Burnt Mill Creek, Jan. – Sep. 2005. Fecal coliforms as geometric mean; N/P as median. _____________________________________________________________________ Parameter BMC-WP BMC-PP _____________________________________________________________________ DO (mg/L) 5.0 (1.2) 5.5 (2.7) Cond. (mS/cm) 358 (18) 353 (40) pH 7.0 (0.1) 7.1 (0.2) Turbidity (NTU) 8 (3) 6 (3) TSS (mg/L) 6.5 (4.0) 8.9 (9.7) Nitrate (mg/L) 0.143 (0.091) 0.116 (0.084) Ammonium (mg/L) 0.108 (0.040) 0.091 (0.055) TN (mg/L) 0.872 (0.174) 1.697 (2.245) OrthoPhos. (mg/L) 0.008 (0.003) 0.012 (0.009) TP (mg/L) 0.067 (0.021) 0.107 (0.059) N/P molar ratio 51.4 30.5 Chlor. a (mg/L) 7.2 (4.4) 98.3 (241.6) Fec. col. (/100 mL) 958 479 BOD5 1.4 (0.5) NA BOD20 5.5 (1.2) NA _____________________________________________________________________ NA = not analyzed Figure 4.1. Burnt Mill Creek watershed and sampling sites. 19 20 Sediment Metals and PAH Concentrations As part of the stream restoration effort funded through NCSU and EPA 319 program, we collected sediment samples on one occasion throughout Burnt Mill Creek for analysis of sediment metals and polycyclic aromatic hydrocarbons (PAHs). The State of North Carolina has no official guidelines for sediment concentrations of metals and organic pollutants in reference to protection of invertebrates, fish and wildlife. However, academic researchers (Long et al. 1995) have produced guidelines (Appendix D) based on extensive field and laboratory testing that are used by the US Environmental Protection Agency in their National Coastal Condition Report II (US EPA 2004). Table 4.3. Guideline values for sediment metals and organic pollutant concentrations (ppm, or mg/g, dry wt.) potentially harmful to aquatic life (Long et al. 1995; U.S. EPA 2004). ERL = (Effects range low). Concentrations below the ERL are those in which harmful effects on aquatic communities are rarely observed. ERM = (Effects range median). Concentrations above the ERM are those in which harmful effects would frequently occur. Concentrations between the ERL and ERM are those in which harmful effects occasionally occur. _____________________________________________________________________ Metal ERL ERM _____________________________________________________________________ Arsenic (As) 8.2 70.0 Cadmium (Cd) 1.2 9.6 Chromium (Cr) 81.0 370.0 Copper (Cu) 34.0 270.0 Lead (Pb) 46.7 218.0 Mercury (Hg) 0.15 0.71 Nickel (Ni) 20.9 51.6 Silver (Ag) 1.0 3.7 Zinc (Zn) 150.0 410.0 Total PCBs 0.0227 0.1800 Total PAHs 4.02 44.80 Total DDT 0.0016 0.0461 _____________________________________________________________________ Most of the stations had sediment metals concentrations that were well below levels considered potentially toxic to benthic organisms. An exception was lead, which exceeded the ERL (Table 4.3) at the Wallace Park station BMC-WP (Table 4.4). Lead concentrations at BMC-KA1 and Princess Place (BMC-PP) approached harmful concentrations but did not exceed them. Mercury did not exceed the ERL but concentrations were close to it at BMC-PP (Table 4.4). All of the PAH sediment samples exceeded the ERM (Table 4.4). 21 Table 4.4. Concentrations of sediment metals and polycyclic aromatic hydrocarbons (PAHs) in Burnt Mill Creek, 2005 (as mg/kg = ppm). Concentrations in bold type exceed the level at which harmful effects to benthic organisms may occur, and italicized concentrations are near potentially harmful levels (see Table 4.3 for more detail). _____________________________________________________________________ Parameter KA1 KA3 AP1 AP3 WP PP _____________________________________________________________________ Antimony 0.147 <0.077 <0.078 <0.90 <0.08 0.127 Arsenic <0.125 <0.125 <0.128 <0.127 <0.143 <0.151 Beryllium 0.060 0.026 <0.026 0.026 0.270 0.248 Cadmium 0.172 0.039 <0.026 0.067 0.727 0.471 Chromium 4.740 0.979 0.211 1.450 11.60 6.93 Copper 7.48 7.69 0.834 3.25 20.80 8.73 Lead 24.20 4.38 2.08 8.49 95.60 33.90 Mercury <0.003 <0.003 <0.003 0.006 0.134 0.094 Nickel 3.910 0.701 0.224 1.150 2.830 3.040 Selenium 0.132 <0.127 <0.128 0.133 <0.151 <0.140 Silver <0.125 <0.127 <0.128 <0.127 <0.143 <0.151 Thallium <0.026 <0.026 <0.020 0.025 0.063 <0.060 Zinc 48.80 14.00 5.38 20.50 74.20 30.40 Total PAH 8,873 8,847 287 BDL 2,202 115 TN 3,475 3,281 138 238 2.0 2.3 TP 120.0 74.2 27.0 45.3 474.0 352.0 TOC 79.4 46.5 39.7 99.5 431.0 408.0 _____________________________________________________________________ BDL = below detection limit Polycyclic aromatic hydrocarbons (PAHs) are organic compounds with a fused ring structure. PAHs with two to five rings are of considerable environmental concern. They are compounds of crude and refined petroleum products and coal and are also produced by incomplete combustion of organic materials (US EPA 2000). They are characteristic of urban runoff as they derive from tire wear, automobile oil and exhaust particles, and leaching of asphalt roads. Other sources include domestic and industrial waste discharge, atmospheric deposition, and spilled fossil fuels. They are carcinogenic to humans, and bioconcentrate in aquatic animals. In these organisms they form carcinogenic and mutagenic intermediaries and cause tumors in fish (US EPA 2000). 22 5.0 Futch Creek Six stations have been sampled in Futch Creek since 1993. During 1995 and 1996 two channels were dredged in the mouth of Futch Creek (Fig. 5.1) to improve circulation from the ICW and hopefully reduce fecal coliform bacterial concentrations. The result was a statistically significant increase in salinity in the creek in the months following dredging, significantly lower fecal coliform counts, and the lower creek was reopened to shellfishing (Mallin et al. 2000c). During 2004-2005, there were no incidences of creek stations having turbidity levels exceeding the state standard of 25 NTU (Table 5.1). Low dissolved oxygen, was not a problem except for July 2005, when concentrations at four sites dropped below the State standard (Table 5.1; Appendix B). Table 5.1. Physical parameters at Futch Creek sampling stations, August 2004 - July 2005. Data given as mean (SD) / range. _____________________________________________________________________ Station Salinity Turbidity Light attenuation Dissolved oxygen (ppt) (NTU) (k/m) (mg/L) _____________________________________________________________________ FC-4 32.1 (6.1) 4 (3) 1.0 (1.3) 7.9 (2.1) 13.0-35.0 0-9 0.3-3.7 5.4-11.6 FC-6 30.8 (7.7) 5 (5) 1.5 (1.9) 7.7 (2.2) 6.6-34.5 0-16 0.3-5.6 5.3-11.6 FC-8 29.8 (7.6) 5 (5) 1.3 (1.5) 7.5 (2.2) 6.7-34.5 0-16 0.2-4.8 4.9-11.5 FC-13 25.7 (8.3) 6 (7) 1.5 (1.8) 7.1 (2.4) 1.2-30.6 0-22 0.2-6.2 4.1-11.3 FC-17 19.3 (10.0) 7 (6) 1.6 (1.3) 7.2 (2.5) 0.1-29.3 1-23 0.5-4.2 3.6-11.2 FOY 25.1 (9.1) 5 (4) 1.7 (2.1) 7.5 (2.7) 0.1-33.2 0-10 0.5-6.4 4.0-11.6 _____________________________________________________________________ Nutrient concentrations in Futch Creek remained generally low, with a general decrease in nitrate over the previous year in the upper stations FC-13 and FC-17 (Table 5.2). One source of nitrate has been identified as groundwater inputs entering the marsh in springs existing in the area stretching from upstream of FC-17 downstream to FC-13 (Mallin et al. 1998b). The drought of 2005 would lead to less surface runoff and groundwater pumping of nitrate. The creek was free from algal blooms during our sampling visits (Table 5.2), even in the upper stations. 23 Table 5.2. Nutrient and chlorophyll a data from Futch Creek, August 2004-July 2005. Data as mean (SD) / range, nutrients in mg/L, chlorophyll a as mg/L. _____________________________________________________________________ Station Nitrate Ammonium Orthophosphate Chlorophyll a _____________________________________________________________________ FC-4 0.011 (0.013) 0.023 (0.012) 0.008 (0.004) 1.2 (1.4) 0.003-0.050 0.014-0.045 0.005-0.019 0.1-3.9 FC-6 0.012 (0.012) NA 0.009 (0.005) 1.2 (1.3) 0.003-0.049 0.005-0.022 0.1-3.6 FC-8 0.016 (0.013) NA 0.011 (0.005) 1.6 (1.8) 0.004-0.051 0.006-0.023 0.2-5.1 FC-13 0.035 (0.029) NA 0.013 (0.007) 2.5 (2.7) 0.005-0.103 0.005-0.030 0.2-8.3 FC-17 0.057 (0.055) 0.035 (0.025) 0.013 (0.008) 2.8 (2.9) 0.008-0.198 0.014-0.081 0.004-0.036 0.2-8.4 FOY 0.019 (0.011) 0.029 (0.022) 0.009 (0.003) 1.5 (1.3) 0.004-0.047 0.014-0.076 0.005-0.016 0.3-4.4 _____________________________________________________________________ NA = not analyzed As reportedly previously (Mallin et al. 2000c) the dredging experiment proved to be successful and the lower portion of the creek was reopened to shellfishing. During 2004-2005 the lower creek through FC-8 maintained excellent microbiological water quality for shellfishing (Table 5.3), and the mid-creek areas had good microbiological water quality as well. The uppermost stations continued to have fecal coliform bacterial concentrations below those of the pre-dredging period, with only one station (FC-17) having a single incident of fecal coliform counts exceeding 200 CFU/mL. There was a slight improvement in microbiological water quality at the upper stations compared with the previous year (Fig. 5.2), probably a result of less runoff during this drought period. All stations had geometric mean fecal coliform counts that were well within safe limits for human contact waters (Appendix B). In summary, Futch Creek had the best water quality of all watersheds sampled for this report (Appendix B). 24 Figure 5.1. Futch Creek watershed and sampling sites. 25 Table 5.3. Futch Creek fecal coliform bacteria data, including percent of samples exceeding 43 CFU per 100 mL, August 2004 - July 2005. _____________________________________________________________________ Station FC-4 FC-6 FC-8 FC-13 FC-17 FOY Geomean (CFU/100 mL) 1 3 4 16 37 9 % > 43 /100ml 9 9 9 33 27 17 _____________________________________________________________________ Figure 5.2 Geometric mean fecal coliform bacteria counts over time at selected Futch Creek stations, 1994-2005 0 50 100 150 200 250 19951996199719981999200020012002200320042005 Year Fe c a l c o l i f o r m s ( C F U / 1 0 0 m L ) FC8 FC13 FC17 FOY Channel dredging in mouth of creek 26 6.0 Greenfield Lake Water Quality Three tributaries of Greenfield Lake were sampled for physical, chemical, and biological parameters (Table 6.1, Fig. 6.1). All three tributaries suffered from hypoxia, with GL-LB (creek at Lake Branch Drive) and GL-LC (creek beside Lakeshore Commons) both showing average concentrations below the state standard (DO < 5.0 mg/L). Dissolved oxygen levels periodically were 1.0 mg/L or less on three occasions at GL-LB during the summer months (Table 6.1; Appendix B). Turbidity and suspended solids were generally low in the tributary stations (Table 6.1). Total nitrogen and nitrate concentrations were highest at GL-LC, somewhat lower at GL-LB, and lowest at GL- JRB (Jumping Run Branch) (Table 6.1). Ammonium concentrations were highest at GL-LB, and generally similar across the other two tributary stations. Phosphorus concentrations were similar at these three sites. All three of these input streams maintained fecal coliform levels indicative of poor water quality, with fecal coliform counts exceeding the state standard for human contact waters (200 CFU/100 mL) three of seven times at GL-LB, three of seven times at GL-LC, and five of seven times at GL- JRB. There was one major algal bloom in June at GL-JRB, with a chlorophyll a level of 40.4 mg/L. Lesser blooms of 25.5 and 34 mg/L occurred at GL-JRB and GL-LC, respectively, in September, and a bloom of 30 mg/L at GL-LB in March. Table 6.1. Mean and (standard deviation) of water quality parameters in tributary stations of Greenfield Lake, January - September 2005. Fecal coliforms as geometric mean; N/P ratio as median; n = 7 samples for all parameters. _____________________________________________________________________ Parameter GL-JRB GL-LB GL-LC _____________________________________________________________________ DO (mg/L) 5.7 (2.0) 2.7 (3.2) 3.5 (1.5) Turbidity (NTU) 1 (1) 2 (2) 2 (2) TSS (mg/L) 2.7 (0.8) 2.2 (0.9) 2.8 (1.5) Nitrate (mg/L) 0.056 (0.019) 0.123 (0.099) 0.177 (0.149) Ammonium (mg/L) 0.054 (0.024) 0.250 (0.122) 0.133 (0.069) TN (mg/L) 0.796 (0.170) 0.956 (0.250) 1.033 (0.282) Orthophosphate (mg/L) 0.017 (0.013) 0.016 (0.013) 0.020 (0.015) TP (mg/L) 0.089 (0.069) 0.089 (0.039) 0.080 (0.041) N/P molar ratio 20.5 75.3 46.2 Fec. col. (/100 mL) 353 217 325 Chlor. a (mg/L) 13.2 (14.6) 6.5 (10.5) 7.5 (12.1) _____________________________________________________________________ Three in-lake stations were sampled (Table 6.2). Station GL-2340 represents an area receiving a considerable influx of urban/suburban runoff, GL-YD is downstream and receives some outside impacts, and GL-P is at Greenfield Lake Park, away from inflowing streams but in a high-use waterfowl area (Fig. 6.1). Low dissolved oxygen was only a problem at GL-2340, with general improvement shown over the last two years (see Section 6.1). Turbidity and suspended solids were low to moderate at these three sites, except for high TSS (52 mg/L) in September at GL-2340. Fecal coliform concentrations were only problematic at GL-P (Appendix B) with two of seven samples exceeding the State standard in 2005. 27 Nitrogen concentrations were generally highest at GL-P, followed by GL-2340, while phosphorus concentrations were highest at GL-YD. (Table 6.2). There were TN maxima of 3.5 mg/L at GL-P in June and 2.9 mg/L at GL-2340 in May. There were low chlorophyll a concentrations during those periods so these maxima were likely a result of high summer ammonium and organic N resulting from decaying aquatic macrophyte material. Inorganic N/P molar ratios can be computed from ammonium, nitrate, and orthophosphate data and can help determine what the potential limiting nutrient can be in a water body. Ratios well below 16 (the Redfield ratio) can indicate potential nitrogen limitation, and ratios well above 16 can indicate potential phosphorus limitation (Hecky and Kilham 1988). Based on the median N/P ratios (Table 6.2), phytoplankton growth in Greenfield Lake was somewhat below the Redfield ratio, indicating nitrogen limitation. Our previous bioassay work indicated that nitrogen was usually the limiting nutrient in this lake (Mallin et al. 1999). Two major and one minor algal bloom occurred at GL-P, three major blooms occurred at GL-2340, and two major and one minor bloom occurred at GL-YD. The magnitude of the major in-lake blooms ranged from 47-110 mg/L of chlorophyll a. Phytoplankton blooms are periodically problematic in Greenfield Lake, and usually consist of green or blue-green algal species, or both together. These blooms have occurred during all seasons, but are primarily a problem in spring and summer. Seven algal blooms exceeding the state standard of 40 mg/L were recorded in our sampling during 2005 (an increase over the previous year), but the former heavy surface scum of duckweed was removed due to remedial action by the City (see Section 6.1). Thus, during 2005 Greenfield Lake was impaired by algal blooms, high fecal coliform counts and low dissolved oxygen concentrations, although there was definite improvement with the latter parameter. The tributary stations were also impaired by high fecal coliform counts and low dissolved oxygen. These same problems have occurred in the lake for several years (Mallin et al. 1999; 2000; 2002; 2003; 2004; 2005). 28 Table 6.2. Mean and (standard deviation) of water quality parameters in Greenfield Lake sampling stations, January - September 2005. Fecal coliforms given as geometric mean, N/P ratio as median; n = 7 samples collected. _____________________________________________________________________ Parameter GL-2340 GL-YD GL-P _____________________________________________________________________ DO (mg/L) 7.9 (4.8) 9.3 (3.6) 7.8 (3.2) Turbidity (NTU) 5 (10) 1 (2) 3 (4) TSS (mg/L) 10.9 (18.3) 5.7 (5.1) 6.8 (7.4) Nitrate (mg/L) 0.075 (0.059) 0.046 (0.069) 0.081 (0.106) Ammonium (mg/L) 0.070 (0.093) 0.029 (0.011) 0.043 (0.045) TN (mg/L) 1.416 (0.759) 1.134 (0.397) 1.466 (0.979) OrthopPhosphate (mg/L) 0.016 (0.012) 0.021 (0.016) 0.018 (0.017) TP (mg/L) 0.049 (0.026) 0.139 (0.127) 0.127 (0.132) N/P molar ratio 14.4 6.1 12.2 Fec. col. (/100 mL) 79 41 165 Chlor. a (mg/L) 43.0 (48.0) 34.2 (41.4) 24.9 (27.3) ____________________________________________________________________ 29 30 6.1 A Preliminary Assessment of the Efficacy of the 2005 Greenfield Lake Restoration Measures Michael A. Mallin and Virginia L. Johnson Center for Marine Science University of North Carolina Wilmington Introduction Greenfield Lake is a 37 ha blackwater system located in the City of Wilmington, North Carolina. It was first dammed and filled as a millpond in 1750, and purchased for a city park in 1925. It has an average depth of 1.2-1.5 m, it is about 8,530 m around the shoreline, and its watershed drains approximately 1025 ha (2532 acres). The lake has one outfall, but is fed by six perennial inflowing streams (as well as intermittent ditches). The lake is surrounded by a watershed that is comprised mainly of residential, office, institutional and commercial areas, with an overall watershed impervious surface coverage of 30% (Matt Hayes, City of Wilmington, personal communication). In recent decades a number of water quality problems have become chronic within the lake, including high fecal coliform bacterial counts, low dissolved oxygen problems, nuisance aquatic macrophyte growths, algal blooms and fish kills. Some of these problems are typically related to eutrophication, a process driven by loading of excessive nutrients to a body of water. The State of North Carolina Division of Water Quality considers the lake to have a problem with aquatic weeds (NCDENR 2005). Periodic phytoplankton blooms have occurred in spring, summer and fall. Some of the most frequent bloom forming taxa are the cyanobacterium Anabaena cylindrica and the chlorophytes Spirogyra and Mougeotia spp. The free-floating macrophyte Lemna sp. (duckweed) is frequently observed on the surface, and below a massive Lemna bloom in summer 2004 dissolved oxygen concentrations at the park station were nearly anoxic. In-situ monitoring instruments have demonstrated that dissolved oxygen concentrations can decrease by as much as 45% at night compared with daytime DO measurements. In 2005 several steps were taken by the City of Wilmington to restore viability to the lake (David Mayes, City of Wilmington Stormwater Services, personal communication). During February one thousand sterile grass carp were introduced to the lake to control (by grazing) the overabundant aquatic macrophytes. During that same month four SolarBee water circulation systems were installed in the lake to improve circulation and force dissolved oxygen from the surface downward toward the bottom. Finally, from April through June a contract firm applied the herbicide Sonar to further reduce the amount of aquatic macrophytes. Since 1998 the University of North Carolina Wilmington's Aquatic Ecology Laboratory, located at the Center for Marine Science, has been performing water quality sampling and associated experiments on Greenfield Lake. The City of Wilmington Engineering Department has funded this effort. Monitoring of various physical, chemical, and biological parameters has occurred monthly. These data allow us to perform a 31 preliminary assessment of the effectiveness of the City's lake restoration efforts by comparing summer data from 2003 and 2004 (before restoration efforts) with data from summer 2005 (after restoration efforts have begun). Results To assess the results so far we have chosen several parameters to examine over time. One parameter that is not quantified is surface coverage by nuisance macrophyte vegetation. In the summers of 2003 and 2004 extensive mats of duckweed (Lemna sp.), mixed with algae and other vegetation covered large areas of the lake's surface, with visible estimates for some coves exceeding 95% coverage. In summer of 2005 surface coverage was minimal; with most lake areas 95% clear of surface mats. Dissolved oxygen: During 2003 and 2004 hypoxia (DO < 4.0 mg/L) was common in surface waters (Figs. 6.2a and 6.2b. Areas beneath thick Lemna mats were anoxic or nearly so, especially at GL-P, the main Park area (Fig. 6.2a). Following the onset of herbicide addition in April 2005, the May DO showed a distinct decrease; however, it subsequently rose in June and remained at or above the State standard of 5 mg/L through the rest of the summer (Fig. 6.2b). Turbidity: Turbidity was not excessive in the lake during the two years prior to restoration efforts (Fig. 6.3). It remained low following these efforts, except for a pulse up to approximately 30 NTU at GL-2340 in September. However, even this value is below the freshwater State standard of 50 NTU. Ammonium: Ammonia/ammonium is a common degradation product of organic material, and is an excretory product of fish and other organisms. The addition of grass carp and the herbicide usage did not appear to raise ammonium concentrations in the lake (Fig. 6.4). Potentially some of the ammonium produced may have been utilized by phytoplankton. Nitrate: Nitrate is an inorganic form of nitrogen that is known to enter the lake during rainfall and runoff periods (Mallin et al. 2002). The concentrations of nitrate in the lake do not appear to have been influenced by the restoration efforts (Fig. 6.5). Total nitrogen: Total nitrogen (TN) is a combination of all inorganic and organic forms of nitrogen. Mean concentrations and concentrations at individual stations appeared to be unaffected by the restoration efforts (Fig. 6.6). Orthophosphate: Orthophosphate is the most common inorganic form of phosphorus, and is utilized as a key nutrient by aquatic macrophytes and phytoplankton. Orthophosphate was not found at excessive concentrations in the water column either before or after the restoration effort (Fig. 6.7). Total phosphorus: Total phosphorus (TP) is a combination of all organic and inorganic forms of phosphorus in the water. Although a pulse of TP occurred in summer 2005, it was similar in magnitude to pulses of TP seen in 2003 and 2004 (Fig. 6.8), so the restoration efforts do not seem to have impacted TP levels in the lake. 32 Chlorophyll a: Chlorophyll a is the principal measure used to estimate phytoplankton biomass in water bodies. As mentioned above, algal blooms have been a common occurrence in this lake. However, they are generally patchy in space, usually occurring at one or two stations at a time (Fig. 6.9a). However, in summer 2005 extensive phytoplankton blooms occurred at all three in-lake stations, with levels well exceeding the State standard of 40 mg/L (Figs. 6.9a and 6.9b). Algal blooms are the result of nutrient inputs, either from outside the lake or from release from decaying material. Fecal coliform bacteria: Fecal coliform bacteria are commonly used to provide an estimate of the microbial pollution in a water body. Greenfield Lake is chronically polluted by high fecal coliform counts, well exceeding the state standard of 200 CFU/100 mL (Figs. 6.10a and 6.10b). In summer 2005 there were particularly large fecal coliform counts at each in-lake station, though the individual stations did not have pulses during the same months (Fig. 6.10a). Discussion A risk that is taken when applying herbicides to lakes is the creation of biochemical oxygen demand (BOD) from decomposing organic matter that is a product of dead or dying plant material. This would serve to drive the lake DO concentrations downward. However, DO levels in summer 2005 were nearly twice what they were during summers of 2003 and 2004. It is very likely that the use of the SolarBee circulation systems maintained elevated DO even when there was an obvious BOD source. Water column nutrient concentrations did not appear to change notably after the introduction of grass carp or use of herbicide. Certainly ammonium, an excretory and decomposition product would be expected to rise following the consumption and death of large quantities of plant material. Likewise phosphorus did not increase, although it is a common excretory product. However, ammonium (like orthophosphate) is readily used as a primary nutrient by phytoplankton. Nutrient addition bioassay experiments have demonstrated that phytoplankton in this lake is limited by nitrogen (Mallin et al. 1999). It is likely that ammonium produced by fish excretion or dying plant material was utilized by phytoplankton to produce the excessive algal blooms that characterized the lake in the summer of 2005. The phytoplankton blooms were dominated by blue green algae (cyanobacteria) including species containing heterocysts. These species have the added ability to fix atmospheric nitrogen when phosphorus is replete. Thus, while large amounts of macrophyte material disappeared from the lake, some of the resultant nutrients were utilized by phytoplankton to produce the blooms. A potential problem with algal blooms is that when they die, they become labile forms of organic material, or BOD. Previous research has demonstrated that chlorophyll a in this lake is strongly correlated with BOD (Mallin et al. 2005). The apparent increase in fecal coliform bacteria does not appear to be related to any of the restoration activities. Fecal coliform bacteria enter the environment from the feces of warm blooded animals, so it is possible that increases in waterfowl or dogs brought to the lake by their owners could lead to increased fecal coliform bacteria counts, but we have no data to support this speculation either way. 33 References Cited Mallin, M.A., V.L. Johnson, S.H. Ensign and T.A. MacPherson. 2006. Factors contributing to hypoxia in rivers, lakes and streams. Limnology and Oceanography 51:690-701. Mallin, M.A., S.H. Ensign, D.C. Parsons and J.F. Merritt. 1999. Environmental quality of Wilmington and New Hanover County watersheds 1998-1999. CMSR Report 99-02. Center for Marine Science Research, University of North Carolina at Wilmington, Wilmington, N.C. Mallin, M.A., L.B. Cahoon, M.H. Posey, L.A. Leonard, D.C. Parsons, V.L. Johnson, E.J. Wambach, T.D. Alphin, K.A. Nelson and J.F. Merritt. 2002. Environmental Quality of Wilmington and New Hanover County Watersheds, 2000-2001. CMS Report 02-01, Center for Marine Science, University of North Carolina at Wilmington, Wilmington, N.C. NCDENR. 2005. Cape Fear River Basinwide Water Quality Plan (draft). North Carolina Department of Environment and Natural Resources, Division of Water Quality / Planning, Raleigh, NC, 27699-1617. 34 Figure 6.2a. Greenfield Lake dissolved oxygen (mg/L) by station, February 2003-September 2005. 0 2 4 6 8 10 12 14 16 Fe b Ap r Ju n Ju l Au g Se p Ja n Ma r Ma y Ju n Ju l Au g Se p Ja n Ma r Ma y Ju n Ju l Au g Se p Di s s o l v e d O x y g e n GL-2340 GL-YD GL-P 2003 2004 2005 Figure 6.2b. Greenfield Lake mean dissolved oxygen (mg/L), February 2003-September 2005. 0 2 4 6 8 10 12 Fe b Ap r Ju n Ju l Au g Se p Ja n Ma r Ma y Ju n Ju l Au g Se p Ja n Ma r Ma y Ju n Ju l Au g Se p Di s s o l v e d O x y g e n 2003 2004 2005 35 Figure 6.3. Greenfield Lake turbidity (NTU) by station, February 2003-September 2005. 0 5 10 15 20 25 30 35 Fe b Ap r Ju n Ju l Au g Se p Ja n Ma r Ma y Ju n Ju l Au g Se p Ja n Ma r Ma y Ju n Ju l Au g Se p Tu r b i d i t y GL-2340 GL-YD GL-P 2003 2004 2005 Figure 6.4. Greenfield Lake mean ammonium concentrations (as mg/L), February 2003-September 2005. 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 Fe b Ap r Ju n Ju l Au g Se p Ja n Ma r Ma y Ju n Ju l Au g Se p Ja n Ma r Ma y Ju n Ju l Au g Se p Am m o n i a 2003 2004 2005 36 Figure 6.5. Greenfield Lake nitrate-nitrite (mg/L) by station, February 2003-September 2005. 0.00 0.10 0.20 0.30 0.40 0.50 0.60 Fe b Ap r Ju n Ju l Au g Se p Ja n Ma r Ma y Ju n Ju l Au g Se p Ja n Ma r Ma y Ju n Ju l Au g Se p Ni t r a t e - n i t r i t e GL-2340 GL-YD GL-P 2003 2004 2005 Figure 6.6. Greenfield Lake total nitrogen (mg/L) by station, February 2003-September 2005. 0.0 2.0 4.0 6.0 8.0 10.0 12.0 Fe b Ap r Ju n Ju l Au g Se p Ja n Ma r Ma y Ju n Ju l Au g Se p Ja n Ma r Ma y Ju n Ju l Au g Se p To t a l n i t r o g e n GL-2340 GL-YD GL-P 2003 2004 2005 37 Figure 6.7. Greenfield Lake orthophosphate (mg/L) by station, February 2003-September 2005. 0.00 0.02 0.04 0.06 0.08 0.10 0.12 Fe b Ap r Ju n Ju l Au g Se p Ja n Ma r Ma y Ju n Ju l Au g Se p Ja n Ma r Ma y Ju n Au g Se p Or t h o p h o s p h a t e GL-2340 GL-YD GL-P 2003 2004 2005 Figure 6.8. Greenfield Lake total phosphorus (mg/L) by station, February 2003-September 2005. 0 0.1 0.2 0.3 0.4 0.5 0.6 Fe b Ap r Ju n Ju l Au g Se p Ja n Ma r Ma y Ju n Ju l Au g Se p Ja n Ma r Ma y Ju n Ju l Au g Se p To t a l p h o s p h o r u s GL-2340 GL-YD GL-P 2003 2004 2005 38 Figure 6.9a. Greenfield Lake chlorophyll a (mmmmg/L) by station, February 2003-September 2005. 0 20 40 60 80 100 120 140 160 180 Fe b Ap r Ju n Ju l Au g Se p Ja n Ma r Ma y Ju n Ju l Au g Se p Ja n Ma r Ma y Ju n Ju l y Au g Se p Ch l o r o p h y l l a GL-2340 GL-YD GL-P 2003 2004 2005 Figure 6.9b. Greenfield Lake mean chlorophyll a (mmmmg/L), February 2003-September 2005. 0 20 40 60 80 100 120 Fe b Ap r Ju n Ju l Au g Se p Ja n Ma r Ma y Ju n Ju l Au g Se p Ja n Ma r Ma y Ju n Ju l y Au g Se p Ch l o r o p h y l l a 2003 2004 2005 39 Figure 6.10a. Greenfield Lake fecal coliform bacterial abundance (colonies/100mL), February 2003-September 2005. 0 500 1,000 1,500 2,000 2,500 3,000 3,500 4,000 4,500 5,000 Fe b Ap r Ju n Ju l Au g Se p Ja n Ma r Ma y Ju n Ju l Au g Se p Ja n Ma r Ma y Ju n Ju l y Au g Se p Fe c a l c o l i f o r m b a c t e r i a GL-2340 GL-YD GL-P 2003 2004 2005 Figure 6.10b. Greenfield Lake mean fecal coliform bacterial abundance (colonies/100mL), February 2003-September 2005. 0 200 400 600 800 1,000 1,200 1,400 1,600 1,800 Fe b Ap r Ju n Ju l Au g Se p Ja n Ma r Ma y Ju n Ju l Au g Se p Ja n Ma r Ma y Ju n Ju l y Au g Se p Fe c a l c o l i f o r m b a c t e r i a 2003 2004 2005 40 7.0 Hewletts Creek Hewletts Creek was sampled at seven tidally-influenced areas (HC-M, HC-2, HC-3, NWB, NB-GLR, MB-PGR and SB-PGR) and a freshwater runoff collection area draining Pine Valley Country Club (PVGC-9 - Fig. 7.1). Four new freshwater stations in the headwaters of the south branch (Fig. 7.2) were added in 2004. Physical data indicated that turbidity was well within State standards during this sampling period (Tables 7.1 and 7.2). There were several incidents of hypoxia seen in our regular monthly 2004- 2005 sampling; two at NB-GLR, three at NWB and four at SB-PGR, and several additional incidents of hypoxia following a sewage spill (see Section 7.1). Nitrate concentrations were somewhat high in the middle branch (MB-PGR), which drains both Pine Valley and the Wilmington Municipal Golf Courses (Fig. 7.1; Mallin and Wheeler 2000). Nitrate concentrations were slightly lower than 2003-2004, likely a result of drought and less runoff. The monthly chlorophyll a data (Table 7.1) showed that Hewletts Creek hosted a major algal bloom at NB-GLR on July 7 (43 mg/L of chlorophyll a) and additional one of 80 mg/L of chlorophyll a was seen two weeks later; both were caused by nutrient inputs from a sewage spill (Section 7.1). Station SB-PGR had two major algal blooms of 133 and 60 mg/L of chlorophyll a and a minor bloom of 30 mg/L of chlorophyll a following the sewage spill (Section 7.1). Algal blooms have been common in upper Hewletts Creek in the past (Mallin et al. 1998a; 1999; 2002a; 2004; 2005). Fecal coliform bacterial counts collected during regular monthly sampling showed a pattern of generally clean water in the lower creek, moderate pollution in mid-creek and the south branch at SB-PGR, and severe pollution in the middle and north branches (MB-PGR and NB-GLR - Tables 7.1 and 7.2; Fig. 7.3; Appendix B). However, sewage spills in July and September (Section 7.2) severely polluted the creek with fecal bacteria during this period. Nitrate concentrations were elevated leaving the golf course at PVGC-9 relative to the other stations (Tables 7.1 and 7.2). Nitrate leaving the course decreased over the previous year (2003-4) study (Mallin et al. 2005). Fecal coliform bacteria counts exceeded State standards 86% of the time in 2005 at PVGC-9, an increase over last year. An earlier assessment (Mallin and Wheeler 2000) noted higher fecal coliform counts entering the course from suburban neighborhoods upstream than counts at PVGC-9 leaving the course. 41 Table 7.1. Selected water quality parameters at lower and middle creek stations in Hewletts Creek watershed as mean (standard deviation) / range, August 2004-July 2005. Fecal coliform bacteria presented as geometric mean / range. _____________________________________________________________________ Parameter HC-M HC-2 HC-3 HC-NWB _____________________________________________________________________ Salinity 33.3 (1.9) 33.2 (1.4) 30.3 (5.3) 23.8 (6.4) (ppt) 31.4-35.3 30.8-35.2 15.2-34.6 14.0-31.8 Turbidity 4 (3) 3 (2) 5 (4) 7 (3) (NTU) 1-10 1-7 0-17 3-14 DO 8.3 (1.9) 8.0 (1.8) 7.8 (2.0) 7.1 (2.6) (mg/L) 5.9-11.7 5.7-11.7 5.0-11.7 4.1-12.0 Nitrate 0.007 (0.004) 0.006 (0.004) 0.012 (0.016) 0.024 (0.017) (mg/L) 0.003-0.015 0.002-0.016 0.003-0.058 0.005-0.054 Ammonium 0.018 (0.048) 0.019 (0.005) NA 0.039 (0.027) (mg/L) 0.014-0.028 0.014-0.025 0.011-0.079 Orthophosphate 0.007 (0.002) 0.007 (0.002) 0.010 (0.007) 0.012 (0.008) (mg/L) 0.004-0.010 0.004-0.010 0.005-0.025 0.006-0.031 Mean N/P 8.5 8.7 NA 11.6 Median 8.8 9.1 7.3 Light attenuation 0.6 (0.1) 0.6 (0.2) 1.0 (0.6) 1.1 (0.6) (K/m) 0.4-0.7 0.4-1.1 0.4-2.3 0.6-2.0 Chlor a 1.1 (0.8) 1.4 (1.4) 2.2 (3.0) 7.9 (12.0) (mg/L) 0.2-2.5 0.2-4.8 0.2-10.6 0.3-10.5 Fecal col. 1 2 12 46 CFU/100 mL 0-202 0-158 1-930 5-660 _____________________________________________________________________ NA = not analyzed 42 43 44 Figure 7.3 Geometric mean fecal coliform bacteria counts by sampling year at selected Hewletts Creek stations. 0 50 100 150 200 250 300 350 400 HC-2NB-GLRMB-PGRSB-PGR Station Fe c a l c o l i f o r m s ( C F U / 1 0 0 m L ) 1993-94 2000-01 2003-04 2004-05 N.C. standard for human contact water The New Hanover County Tidal Creeks Advisory Board, using funds from the North Carolina Clean Water Management Trust Fund, purchased a former industrial area owned by the Dobo family in August 2002. This property is to be used as a passive treatment facility for the improvement of non-point source runoff drainage water before it enters Hewletts Creek. As such, the City of Wilmington is contracting with outside consultants to create a wetland on the property for this purpose. Baseline data were needed to assess water quality conditions before and after the planned improvements. In January 2004 the UNCW Aquatic Ecology Laboratory began sampling three inflowing creeks and the single outflowing creek (Fig. 7.2). DB-1 is a creek entering the southern side of the property adjacent to Brookview Road. DB-2 is a small stream entering the property along Bethel Road. DB-3 is a deeply-incised stream running along the northern edge of the property. DB-4 is the outflowing stream, sampled at Aster Court. 45 Table 7.2. Selected water quality parameters at upstream stations in Hewletts Creek watershed, as mean (standard deviation) / range, fecal coliforms as geometric mean / range, August 2004-July 2005; for PVGC-9, n = 7 months. _____________________________________________________________________ Parameter NB-GLR SB-PGR MB-PGR PVGC-9 _____________________________________________________________________ Salinity 11.5 (9.5) 16.5 (8.3) 0.3 (0.8) 0.1 (0.0) (ppt) 0.2-27.2 2.9-31.0 0.1-2.6 0.1-0.1 Turbidity 7 (5) 7 (4) 4 (2) 2 (1) (NTU) 1-17 1-13 0-7 1-3 DO 7.9 (2.4) 7.5 (2.6) 8.0 (1.6) 7.1 (1.7) (mg/L) 4.8-12.3 4.6-12.6 5.9-11.7 5.5-9.7 Nitrate 0.091 (0.051) 0.043 (0.036) 0.204 (0.068) 0.299 (0.131) (mg/L) 0.016-0.199 0.005-0.135 0.113-0.328 0.070-0.500 Ammonium 0.029 (0.013) 0.030 (0.015) 0.057 (0.032) 0.046 (0.016) (mg/L) 0.014-0.062 0.014-0.060 0.021-0.102 0.020-0.070 Orthophosphate 0.018 (0.012) 0.024 (0.035) 0.019 (0.015) 0.011 (0.010) (mg/L) 0.006-0.044 0.006-0.127 0.006-0.053 0.005-0.030 Mean N/P ratio 16.0 12.6 62.1 96.3 Median 15.6 12.0 57.7 118.5 Light attenuation 2.4 (2.3) 2.3 (1.7) NA NA (K/m) 0.8-6.9 0.9-5.5 Chlor a 7.9 (12.0) 7.7 (8.7) 0.5 (0.2) 4.5 (3.5) (mg/L) 0.2-42.7 0.3-29.5 0.2-0.9 1.5-11.7 Fecal coliforms 219 150 159 400 CFU/100 mL 22-4200 23-4150 2-1620 100-1500 _____________________________________________________________________ NA = not analyzed In 2004 all nutrient species had the highest concentrations at DB-1 and lowest at DB-2 (Table 7.3). There was some reduction of nutrients at DB-4 compared with DB-1, showing that the property already has some function in water quality improvement. The exception was nitrate, which had similar concentrations at DB-1 and DB-4. Dissolved oxygen was low only at DB-1, and turbidity was low at all four sites. Suspended solids concentrations were periodically elevated at DB-1, but low at the other three sites. Fecal coliform bacteria counts were highest at DB-1 followed by DB-4 and DB-2 (Table 46 7.3). The data suggest that fecal coliform bacteria and nitrogen should be targeted in particular for removal by the treatment facility. Table 7.3. Selected water quality parameters at non-tidal Dobo site stations in Hewletts Creek watershed, as mean (standard deviation) / range, fecal coliforms as geometric mean / range, January - September 2005. n = 7. _____________________________________________________________________ Parameter DB-1 DB-2 DB-3 DB-4 _____________________________________________________________________ Turbidity 6 (6) 2 (1) 8 (4) 7 (3) (NTU) 1-3 1-18 4-15 3-13 TSS 16.3 (21.8) 3.7 (1.7) 5.9 (2.0) 4.0 (1.5) mg/L 2-63 2-7 3-9 3-7 DO 5.3 (2.9) 6.1 (2.3) 6.8 (1.1) 7.5 (1.6) (mg/L) 1.7-9.5 3.8-9.9 5.8-8.7 6.2-10.4 Nitrate 0.085 (0.058) 0.039 (0.020) 0.066 (0.042) 0.084 (0.048) (mg/L) 0.025-0.170 0.013-0.070 0.025-0.140 0.040-0.180 Ammonium 0.419 (0.347) 0.114 (0.074) 0.206 (0.031) 0.151 (0.040) (mg/L) 0.040-0.930 0.020-0.250 0.160-0.250 0.100-0.200 TN 1.667 (0.359) 0.809 (0.274) 0.980 (0.074) 0.873 (0.155) (mg/L) 1.140-2.180 0.370-1.280 0.870-1.070 0.660-1.070 Orthophosphate 0.034 (0.020) 0.010 (0.006) 0.022 (0.018) 0.016 (0.013) (mg/L) 0.005-0.060 0.005-0.060 0.005-0.050 0.005-0.040 TP 0.221 (0.196) 0.080 (0.068) 0.089 (0.027) 0.060 (0.022) (mg/L) 0.080-0.650 0.030-0.230 0.050-0.120 0.020-0.090 Chlor a 4.4 (7.9) 4.5 (3.9) 2.3 (2.2) 2.2 (1.9) (mg/L) 0.5-21.9 0.5-10.0 0.2-6.3 0.5-5.6 Fecal coliforms 860 484 220 461 CFU/100 mL 182-2900 100-484 73-550 82-1650 _____________________________________________________________________ 47 7.1. The 2005 Major Sewage Spill in Hewletts Creek Introduction On Friday, July 1, 2005 the middle branch of Hewletts Creek at Pine Grove Road was subjected to a raw sewage spill of 3,000,000 gallons. This occurred when a 24-inch force main coupling repair burst apart. This line carried sewage from Wrightsville Beach to a pump station on Bradley Creek, then to a pump station (#34) on Hewletts Creek (near the breach) then on to the Wilmington South Side Wastewater Treatment plant on River Road (the plant discharge is near Channel Marker 54 in the Cape Fear River Estuary). This line had been built in the mid 1980s using EPA funds. A citizen had called the City approximately 6:20 AM with a complaint; city workers were on site at 7:10 AM and found an obvious major leak. The workers turned the pump off but sewage continued to flow into the creek. During the course of the day they dug down 6- 8 feet to find the problem, finally finishing a temporary repair at 10:30 PM. The workers estimated that the spill had begun about 5:00 AM; thus the sewage spill occurred over a near-18 hour period (Hugh Caldwell, City of Wilmington, personal communication). Some waste flowed into the creek or nearby swamp forest, and some flowed into the nearest storm drains, which drain directly into Hewletts Creek. Both the North Carolina Division of Water Quality (DWQ) and the N.C. Shellfish Sanitation Section were alerted that morning, and as a result the N.C. Division of Marine Fisheries closed the creek and a large section of the Intracoastal Waterway (ICW) to shellfishing, and Shellfish Sanitation closed that area to swimming. This section of the ICW encompassed the area between the Wrightsville Beach Bridge and ICW Channel Marker 141 near Peden Point, including all tributaries between. Materials and Methods During the first day the waste traveled down the creek into the ICW, then across the ICW and out to the ocean through the Masonboro Channel, according to strong sewage odors detected by citizens recreating on the ICW and the captain of a UNCW research vessel passing down the ICW. Regulators from the N.C. DWQ sampled the area on Saturday, July 2, then again on July 4 and 6. Researchers from the UNCW Aquatic Ecology Laboratory sampled the water column in the area on July 3, 5, 7, 15, 21, and on August 8. Researchers from the UNCW Department of Biological Sciences collected sediment samples for fecal bacteria on July 6, 6, 8, 11, 13, 15, 18, 20, 22, 26, 29, August 2 and August 11. Most water column samples included on-site temperature, pH, turbidity, salinity/conductivity and dissolved oxygen, fecal coliform bacteria, ammonium, nitrate, total nitrogen, orthophosphate and total phosphorus, and chlorophyll a. Sediment samples included fecal coliform bacteria and enterococci. Stations sampled included MB-PGR (spill site), SB-PGR (south branch at Pine Grove Rd.), NB-GLR (north branch at Greenville Loop Rd.), HC-M (creek mouth), HC-3 (at a dock on the north shore of the creek), HC-NWB (the northwest branch of the creek between HC-3 and the tributary stations), the Masonboro Channel on the ICW south of the creek mouth, and the Shinn Creek Channel on the ICW north of the creek mouth. Stations sampled for sediment bacteria include MB-PGR, SB-PGR, NB-GLR and MS- DOCK, a control site located near the junction of Hewletts Creek and the ICW. 48 Results and Discussion Dissolved Oxygen and Fish: The day following the spill N.C. DWQ personnel did not report any dead fish in the creek or waterway, and creek dissolved oxygen (DO) concentrations were all at 5.0 mg/L or higher (Table 7.4). A day later, July 3, showed a much different landscape. While the ICW remained clear, UNCW researchers sampling by boat began encountering dead fish about halfway up the creek from the ICW. About 100 were counted in the main channel, including 15 eels, 8 flounder, mullet and numerous small fish. There were many decomposing gobs of flesh, with birds and crabs feeding on them (dissolved oxygen was 1.9 mg/L). The researchers then proceeded by truck to NB-GLR where about 200 dead fish were counted (DO 4.4 mg/L); then on to SB-PGR, where about 140 dead fish were counted, and many more seen floating upstream. There was a strong sewage odor present, and DO was 2.4 mg/L. The sewage had obviously been carried downstream from MB-GLR toward the ICW, then much of it was sloshed back upstream into the north and south branches, where the BOD load from the sewage caused a decrease in DO. Many fish were trapped by the rising tide in hypoxic waters and died along the marsh edge. The high water temperatures (25-28ºC) led to rapid decomposition of the fish, contributing additional BOD to the sewage BOD load. The dead fish decomposed or were consumed by scavengers over the next two days; however, hypoxic water < 3.0 mg/L DO were present on July 4 and waters with DO < 4.0 mg/L were encountered on July 5. From July 6 on all water sampled had DO values of 4.0 mg/L or higher (Table 7.4). Animal mortality was not confined to fish, however. On July 7 UNCW researchers photographed several ducks along the shore of the creek that were obviously sick and dying. Table 7.4. Water column dissolved oxygen concentrations by date and station following the July 1, 2005 Hewlett’s creek sewage spill (as mg/L). _____________________________________________________________________ Station 7/2 7/3 7/4 7/6 7/7 7/15 7/21 8/8 _____________________________________________________________________ HC-M 5.5 7.7 NA 5.4 6.6 5.0 4.9 6.0 HC-3 5.0 3.5 5.7 5.1 6.3 6.3 4.0 5.5 HC-NWB NA 1.9 NA NA 4.1 NA NA NA SB-PGR NA 2.4 2.5 6.3 4.8 9.6 4.0 4.6 MB-PGR NA 7.6 NA NA 7.0 6.1 6.1 6.5 NB-GLR NA 7.7 2.8 6.7 6.5 6.5 6.5 4.2 _____________________________________________________________________ NA = not analyzed Fecal Bacteria: On July 2 fecal coliform counts were high; at HC-3 they were 270,000 CFU/100 mL, and in the creek mouth they ranged from 2,000 to 3,200 CFU/100 mL (Table 7.5). However, counts were all below 100 CFU/100 mL in the ICW. Fecal coliform bacteria counts in the water column of the creek were high (15,000-21,000 CFU/mL) on July 3, and then decreased to 2,000 CFU/100 mL in the channel on July 4. After July 4 main channel fecal coliform bacteria counts generally stayed below 100 CFU/100 mL. In contrast the tributaries (SB-PGR and NB-GLR) had counts 49 approximately 3,000 CFU/100 mL until July 6, then a brief decrease, then an increase again on July 15 to 2,900 CFU/100 mL following a rain event (Table 7.5). From then on tributary fecal coliform counts decreased to normal levels. In the main channel during the first few days, loss of fecal coliforms from the water column followed a roughly logarithmic decrease. Loss of fecal coliforms from the water column can occur from predation by protozoans, mortality from sunlight (UV radiation), dilution by incoming tides and sedimentation. As will be seen in the following section, sedimentation of fecal bacteria was a critically important issue following this sewage spill. Table 7.5. Water column fecal coliform bacteria counts by date and station following the July 1, 2005 Hewletts creek sewage spill (as CFU/100 mL). _____________________________________________________________________ Station 7/2 7/3 7/4 7/6 7/7 7/15 7/21 8/8 _____________________________________________________________________ HC-M 3,200 176 NA 1 9 5 46 1 HC-3 270,000 21,000 220 69 21 24 96 2 HC-NWB NA 15,800 NA NA 242 NA NA NA SB-PGR NA NA 3,000 358 211 312 362 30 MB-PGR NA 2,100 780 NA 224 900 291 128 NB-GLR NA NA NA 3,200 546 2,900 655 180 _____________________________________________________________________ NA – not analyzed Post-spill sediment bacteria sampling was initiated by Dr. Larry Cahoon’s laboratory on July 6. Reference samples were available for Hewletts Creek as a WRRI-sponsored project regarding sediment fecal bacteria had been ongoing since 2004. Results (Table 7.6) showed that post spill samples were an order of magnitude higher than pre-spill counts. Counts appeared to decrease after a few days, but the rain event (noted above) caused high sediment counts again (7/15). Sampling was continued until early August. The latter dates showed a general decrease to background levels, with high counts periodically occurring. The fecal bacteria in the sediments form a reservoir of viable fecal microbes that is available to enter the water column following a mixing/stirring event such as a rainstorm or people or pets wading or otherwise disturbing the sediments. As an on-site test, on 7/7 researchers for the Aquatic Ecology Laboratory collected a fecal coliform sample from the water at HC-3, and then proceeded to pass the motor over the site, stirring the water and sediments below. Counts taken from before the stirring were 21 CFU/100 mL while counts taken after the stirring were nearly three times greater, 60 CFU/100 mL. The presence and persistence of the sediment fecal bacteria demonstrate that water column sampling of fecal bacteria is insufficient when analyzing an area for human contact safety after a pollution event; sediment sampling also produces necessary data. 50 Table 7.6. Sediment fecal coliform bacteria counts by date and station following the July 1, 2005 Hewletts Creek sewage spill (as CFU/cm2). Samples collected 10/31/04 and 1/28/05 are shown as control (non-spill) counts for comparison. _____________________________________________________________________ Station 10/31/04 1/28/05 7/6 7/11 7/15 7/22 8/2 8/11 _____________________________________________________________________ MS-DOCK NA NA 0 0 23 0 0 11 SB-PGR 488 358 2743 526 5335 396 732 1886 MB-PGR NA NA 5106 1151 1448 777 457 80 NB-GLR 53 579 3506 442 991 663 1315 914 _____________________________________________________________________ NA = not analyzed Nutrients and Algal Blooms: Nutrient concentrations in the raw sewage were high (TKN = 40.2 mg/L; ammonium = 23.3 mg/L, total phosphorus = 5.3 mg/L - Dolores Bradshaw, City of Wilmington, personnel communication). Upon reaching the creek, nutrient concentrations apparently decreased at a surprisingly fast rate. Even on July 2 TKN levels were < 2.0 mg/L, ammonium < 1.0 mg/L, nitrate < 0.3 mg/L and TP was < 0.06 mg/L. By July 5 TKN decreased to < 0.7 mg/L and no unusual pulses of that or other nutrient species were encountered. Some of the nutrients were taken up by phytoplankton; blooms were recorded at NB-GLR on July 7 and July 21 of 43 and 80 mg/l chlorophyll a, respectively, and blooms of 30, 133 and 60 mg/L chlorophyll a were recorded at SB-PGR on July 7, July 15 and July 21, respectively. One of the blooms (7/15) was analyzed by microscopy. At SB-PGR the bloom was dominated by cryptomonads, primarily Chroomonas amphioxiae. AT NB-GLR the flora was a mixture of Nitzschia closterium, small naviculoid diatoms, cryptomonads, the euglenoid Eutreptia sp. and the dinoflagellate Gymnodinium sp. In addition to the phytoplankton, clearly, the salt marsh must have absorbed a large amount of the nutrient load from the sewage into the soils (and probably removed some via microbial denitrification), and some was taken up by Spartina, Juncus and other macrophytes, and the periphyton. Additional Comments Related to the Spill: Regulatory authorities lifted the ban on swimming in the ICW after a two-week period. However, due to the persistence of the fecal bacteria in the sediments and the increases noted after rain events, the ban on swimming in Hewletts Creek remained in effect for the remainder of the summer of 2005. Coincidentally, several individuals who were swimming or otherwise recreating in the ICW during the Fourth of July weekend came down with infections. The City made permanent repairs on the break Tuesday August 9 with a heavy-duty coupler made of cast iron. As an additional complimentary measure a low flow alarm was installed at Southside Wastewater Treatment Plant to detect low flow from the pump station on Hewlett’s Creek. The City was fined $50,000 by the North Carolina Division of Water Quality as a result of the spill. That was not the only pollution incident to affect Hewletts Creek in 2005, however. Another sewage spill occurred in the Hewletts Creek watershed September 15 when a 24-inch line ruptured and spilled an unknown volume of sewage onto Shipyard Drive and ditches and yards along Pine Valley Drive. Some of the waste entered storm drains, and from there entered Hewletts Creek. Repairs were completed the next 51 morning. Samples collected in Hewletts Creek by the UNCW Aquatic Ecology Laboratory found elevated fecal coliform bacteria counts in the upper tributary stations (PVGC-9 – 2487 CFU/100 mL; MB-PGR – 2790 CFU/100 ML; SB-PGR – 2195 CFU/100 mL; NB-GLR – 840 CFU/100 mL). Station MB-PGR is located downstream from PVGC-9 (Fig. 7.1). Subsequent sampling on September 19 showed a considerable water-column decrease in fecal coliform bacteria (PVGC9 – 380 CFU/100 mL; MB-PGR – 700 CFU/100 mL; SB-PGR – 160 CFU/100 mL; NB-GLR – 400 CFU/100 mL) to levels commonly found at these locations (Table 7.2), although the main channel sites were still elevated (HC-3 – 60 CFU/100 mL; HC-2 – 100 CFU/100 mL). The July 1 sewage spill demonstrated two important points. First, following a major pollution incident where human or animal waste is involved, sampling the water column for fecal bacteria is not sufficient to obtain a complete picture of the system in terms of human health issues. Large quantities of the polluting bacteria settled to the sediments and remained viable for several weeks, and were clearly subject to resuspension in the water column after a mixing event. This has been demonstrated previously following a large swine waste lagoon spill that entered the New River (Burkholder et al. 1997). There, significant quantities of fecal bacteria remained in the sediments for nearly three months after the spill. Fecal bacteria on or in the sediments are largely protected from UV radiation, a principal means of death or deactivation in the water column. Also, the sediments contain carbon, nitrogen, and phosphorus, which are key nutrients for bacterial survival and growth. We recommend that regulatory authorities devise sampling and assessment plans for pollution incidents that consider sediment- associated fecal bacteria. A second point of interest is the function of the salt marsh as a nutrient removal mechanism. Raw sewage has very high nutrient concentrations, yet the nutrients rapidly disappeared from the water column. While post-spill phytoplankton blooms indicated some nutrient uptake by these primary producers, it is likely that additional uptake occurred into benthic and epiphytic microalgae (periphyton) and salt marsh macrophytes, such as Spartina. Microbial denitrification also likely removed nitrogen from the system. Thus, the spill demonstrated the important role salt marshes play in removal of nutrient pollution. Reference Cited Burkholder, J.M., M.A. Mallin, H.B. Glasgow, Jr., L.M. Larsen, M.R. McIver, G.C. Shank, N. Deamer-Melia, D.S. Briley, J. Springer, B.W. Touchettte and E. K. Hannon. 1997. Impacts to a coastal river and estuary from rupture of a swine waste holding lagoon. Journal of Environmental Quality 26:1451-1466. 52 8.0 Howe Creek Water Quality Howe Creek was sampled for physical parameters, nutrients, chlorophyll a , and fecal coliform bacteria at five locations during 2003-2004 (HW-M, HW-FP, HW-GC, HW-GP and HW-DT- Fig. 8.1). Turbidity was low near the ICW and did not exceed North Carolina water quality standards at any of the other stations (Table 8.1; Appendix B). Dissolved oxygen concentrations were generally good in Howe Creek, with HW-GP below the standard of 5.0 mg/L on two occasions (Appendix B). Nutrient levels were generally low except for nitrate at HW-DT (Table 8.2). Nitrate levels showed a decrease over levels in 2003-2004, especially at the uppermost stations (Mallin et al. 2004), probably a reflection of lower rainfall and runoff. Median inorganic molar N/P ratios were low, reflecting low nitrate levels, and indicating that nitrogen was probably the principal nutrient limiting phytoplankton growth at all stations. There was one minor algal bloom of 38 mg/L as chlorophyll a at HW-DT. Since wetland enhancement was performed in 1998 above Graham Pond the creek below the pond at HW-GP has had fewer and smaller algal blooms than before the enhancement (Fig. 8.2). Light attenuation showed generally clear water except for an elevated reading of 3.4/m at HW-DT in June. Table 8.1. Water quality summary statistics for Howe Creek, August 2004-July 2005, as mean (st. dev.) / range. Fecal coliform bacteria as geometric mean / range. Salinity Diss. oxygen Turbidity Light Chlor a Fecal coliforms (ppt) (mg/L) (NTU) (K/m) (mg/L) (CFU/100 mL) _____________________________________________________________________ HW-M 33.3 (1.9) 7.5 (1.7) 3 (2) 0.7 (0.2) 1.2 (0.9) 1 28.7-35.1 5.1-9.8 0-8 0.4-1.0 0.2-2.6 0-38 HW-FP 32.9 (2.3) 7.5 (1.7) 3 (2) 0.6 (0.3) 1.2 (1.1) 1 27.9-35.0 4.9-9.9 0-7 0.3-1.2 0.2-3.0 0-80 HW-GC 29.0 (5.7) 7.2 (1.8) 4 (3) 1.3 (1.1) 1.4 (1.2) 9 18.0-34.1 4.2-9.8 1-11 0.5-3.7 0.2-3.3 1-106 HW-GP 14.4 (11.8) 7.2 (1.8) 6 (4) 2.0 (0.7) 5.7 (5.3) 72 1.6-31.3 4.5-9.8 0-12 0.7-2.7 0.3-14.7 8-355 HW-DT 3.7 (4.6) 8.3 (1.7) 10 (4) 2.4 (0.7) 9.5 (10.5) 265 0.2-11.9 5.7-11.0 2-15 1.5-3.4 0.6-38.3 65-780 Figure 8.1. Howe Creek watershed and sampling sites. 53 54 Figure 8.2. Chlorophyll a concentrations (algal blooms) in Howe Creek below Graham Pond before and after 1998 wetland enhancement in upper Graham Pond. 0 10 20 30 40 50 60 70 80 90 100AugustFebr uar y August Febr uar y August Febr uar y August Febr uar y August Febr uar y August Febr uar y August Febr uar y August Febr uar y August Febr uar y August Febr uar y August Febr uar y August Febr uar y Ch l o r o p h y l l a ( p p b ) 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 NC chlorophyll a standard for impaired waters wetland enhancement Table 8.2. Nutrient concentration summary statistics for Howe Creek, August 2004-July 2005, as mean (standard deviation) / range, N/P ratio as mean / median. _____________________________________________________________________ Nitrate Ammonium Orthophosphate Molar (mg/L) (mg/L) (mg/L) N/P ratio _____________________________________________________________________ HW-M 0.007 (0.005) 0.027 (0.016) 0.008 (0.002) 9.8 0.003-0.015 0.014-0.062 0.006-0.012 7.6 HW-FP 0.008 (0.005) 0.024 (0.011) 0.008 (0.002) 8.4 0.002-0.017 0.014-0.045 0.005-0.014 8.8 HW-GC 0.010 (0.008) NA 0.009 (0.003) NA 0.001-0.032 0.005-0.015 HW-GP 0.012 (0.011) 0.023 (0.011) 0.014 (0.008) 6.1 0.001-0.035 0.014-0.045 0.006-0.030 5.9 HW-DT 0.033 (0.026) 0.032 (0.023) 0.010 (0.003) 14.6 0.002-0.077 0.014-0.084 0.006-0.017 9.6 ____________________________________________________________________ NA = not analyzed 55 Fecal coliform bacterial abundances were low near the Intracoastal Waterway, moderate in mid-creek, and high in the uppermost stations (Table 8.1; Fig. 8.3). HW- GP exceeded the North Carolina human contact standard on two of 12 occasions, and HW-DT exceeded the standard on seven of 12 occasions (Appendix B). The 2004- 2005 data show an improvement in fecal coliform counts after a sharp decrease in bacterial water quality seen in 2003-2004 Howe Creek (Fig. 8.3). Station HW-GP in particular showed improvement. Since a previous analysis associated with the opening of Mason’s Inlet (Mallin et al. 2003) showed that fecal coliform counts in the uppermost stations were strongly correlated with rainfall, the drought of 2005 may be responsible for the lowered counts. Figure 8.3. Geometric mean fecal coliform bacteria counts for Howe Creek over time, 1993 - 2005 0 100 200 300 400 500 600 HW-MHW-FPHW-GCHW-GPHW-DT STATION FE C A L C O L I F O R M S ( C F U / 1 0 0 mL ) 1993-1994 1996-1997 1999-2000 2001-2002 2002-2003 2003-2004 2004-2005 NC fecal coliform standard for human contact creek mouth area station farthest upstream 56 9.0 Motts Creek Motts Creek drains into the Cape Fear River Estuary (Fig. 9.1), and the creek area near River Road has been classified by the State of North Carolina as a Natural Heritage Site because of the area’s biological attributes. These include the pure stand wetland communities, including a well-developed sawgrass community and unusually large flats dominated by Lilaeopsis chinensis and spider lily, with large cypress in the swamp forest. Thus, it is important that these attributes should be protected from land and water-disturbing activities. UNCW scientists sampled Motts Creek at the River Road bridge (Fig. 9.1). A large residential development is scheduled for construction upstream of the sampling site between Motts and Barnards Creeks. In recent years extensive commercial development occurred along Carolina Beach Road near its junction with Highway 421. Dissolved oxygen concentrations were below 4.5 mg/L from May through September (range 2.8-4.4 mg/L) similar to previous years (Mallin et al. 2003; 2004). Unlike previous years, neither turbidity nor suspended solids were problematic in 2005, possibly a result of low rainfall. Fecal coliform contamination was a problem in Motts Creek, with the geometric mean of 353 CFU/100 mL exceeding the State standard of 200 CFU/100 mL, and samples exceeding this standard on six of seven occasions (Appendix B). Fecal coliform contamination increased over that of previous years. Total nitrogen, ammonium, and total phosphorus levels were similar to the previous year’s study, but chlorophyll a concentrations generally decreased, with no algal blooms detected in 2005 (Table 9.1). BOD5 was sampled on seven occasions in 2005, yielding a mean value of 1.3 mg/L and a median value of 1.2 mg/L, generally lower than the previous years (Mallin et al. 2003; 2004; 2005). Thus, this creek showed mixed water quality, with algal blooms and BOD decreasing, and dissolved oxygen and fecal coliform counts somewhat poorer compared with last year. 57 Table 9.1. Selected water quality parameters at a station (MOT-RR) draining Motts Creek watershed before entering the Cape Fear Estuary, as mean (standard deviation) and range, January-September 2005. Fecal coliforms as geometric mean / range. _____________________________________________________________________ Parameter MOT-RR Mean (SD) Range _____________________________________________________________________ Salinity (ppt) 0.3 (0.3) 0.2-0.9 TSS (mg/L) 7.9 (3.2) 10.0-32.0 Turbidity (NTU) 10 (4) 4-15 DO (mg/L) 4.9 (2.4) 2.8-9.7 Nitrate (mg/L) 0.107 (0.048) 0.060-0.190 Ammonium (mg/L) 0.057 (0.046) 0.030-0.150 Total nitrogen (mg/L) 0.966 (0.266) 0.640-1.470 Orthophosphate (mg/L) 0.007 (0.004) 0.002-0.013 Total phosphorus (mg/L) 0.060 (0.016) 0.040-0.090 Mean N/P ratio 85.2 Median 55.1 Chlor a (mg/L) 4.2 (3.2) 0.6-8.7 BOD5 (mg/L) 1.3 (0.6) 0.8-2.7 BOD20 5.0 (1.5) 3.9-7.9 Fecal coliforms (CFU/100 mL) 353 45-900 _____________________________________________________________________ 58 59 10.0 Pages Creek Pages Creek was sampled at three stations, two of which receive drainage from developed areas near Bayshore Drive (PC-BDUS and PC-BDDS - Fig. 10.1). During the past sample year turbidity was low with no incidents of turbidity exceeding the state standard of 25 NTU (Table 10.1). However, there were a few incidents of hypoxia during summers of 2004 and 2005, three at the station draining upper Bayshore Drive (Appendix B). Fecal coliform bacteria were not sampled at this creek during the past year. Nitrate and orthophosphate concentrations were similar to the previous year, and phytoplankton biomass as chlorophyll a was low with only one minor algal bloom of 23 mg/L noted at PC-BDUS (Table 10.1). Median inorganic nitrogen-to-phosphorus molar ratios were well below 16, indicating that phytoplankton growth in this creek is probably nitrogen limited. Because of the relatively low watershed development and low amount of impervious surface coverage in the watershed (Mallin et al. 1998a; 2000b), this is one of the least-polluted creeks in New Hanover County. Table 10.1. Selected water quality parameters in Pages Creek as mean (standard deviation) / range, August 2004-July 2005. _____________________________________________________________________ Parameter PC-M PC-BDDS PC-BDUS _____________________________________________________________________ Salinity (ppt) 33.9 (1.2) 28.4 (9.0) 12.1 (8.6) 31.8-35.5 3.3-33.8 1.6-24.0 Turbidity (NTU) 4 (4) 5 (3) 5 (2) 0-11 1-10 2-8 DO (mg/L) 7.8 (1.7) 7.0 (2.0) 6.8 (1.5) 5.2-10.2 3.9-10.0 4.6-8.9 Nitrate (mg/L) 0.007(0.002) 0.036(0.043) 0.026(0.014) 0.005-0.010 0.007-0.156 0.011-0.060 Ammonium (mg/L) 0.017(0.005) 0.037(0.047) 0.051(0.030) 0.014-0.029 0.014-0.166 0.014-0.114 Orthophosphate (mg/L) 0.007(0.002) 0.013(0.004) 0.016(0.005) 0.005-0.010 0.004-0.023 0.007-0.025 Mean N/P Ratio 7.6 9.9 11.3 median 7.6 6.0 8.0 Chlor a (mg/L) 1.4 (1.4) 2.1 (2.1) 5.6 (7.3) 0.2-4.1 0.3-7.1 0.3-22.8 _____________________________________________________________________ 60 Figure 10.1. Pages Creek watershed and sampling sites. 61 11.0 Smith Creek Smith Creek drains into the lower Northeast Cape Fear River just before it joins with the mainstem Cape Fear River at Wilmington (Fig. 11.1). Two estuarine sites on Smith Creek proper, SC-23 and SC-CH (Fig. 11.1) were sampled in 2005. Dissolved oxygen concentrations were below 5.0 mg/L on three occasions at SC-23 and on four occasions at SC-CH between June and September 2005. Thus, low dissolved oxygen continued to be a water quality problem in Smith Creek (Appendix B). The North Carolina turbidity standard for estuarine waters (25 NTU) was not exceeded during 2005, an improvement over last year. Suspended solids concentrations in Smith Creek were second only to Barnards Creek in the Wilmington watersheds system. Nutrient concentrations remained similar to last year's levels (Table 11.1), and algal blooms exceeding the State standard were not found in 2005. However, lesser algal blooms of 35 mg/L and 25 mg/L occurred at SC-23 and SC-CH, respectively, in August, and a bloom of 25 mg/L occurred at SC-23 in July. Fecal coliform bacteria concentrations were above 200 CFU/100 mL on only one occasion (at SC-CH), an improvement over the past two years (Mallin et al. 2004; 2005) and all months tested well above the shellfishing standard (14 CFU/100 mL) in the estuarine portion of the creek (Table 11.1). BOD5 was sampled on seven occasions in 2005 at SC-CH, with a mean value of 1.4 mg/L and a median value of 1.5 mg/L, similar to last year. 62 Table 11.1. Selected water quality parameters in Smith Creek watershed as mean (standard deviation) / range. January - September 2005. _____________________________________________________________________ Parameter SC-23 SC-CH Mean (SD) Range Mean (SD) Range _____________________________________________________________________ Salinity (ppt) 2.3 (3.6) 0.0-15.7 0.2 (0.1) 0.1-0.3 Dissolved oxygen (mg/L) 6.1 (2.4) 3.2-9.6 5.8 (2.7) 3.1-10.2 Turbidity (NTU) 10 (5) 5-16 13 (6) 7-25 TSS (mg/L) 10.3 (4.7) 5.0-19.0 16.1 (5.8) 7.0-22.0 Nitrate (mg/L) 0.070 (0.035) 0.030-0.130 0.169 (0.101) 0.050-0.320 Ammonium (mg/L) 0.037 (0.015) 0.010-0.050 0.063 (0.023) 0.040-0.110 Total nitrogen (mg/L) 0.802 (0.283) 0.400-1.100 1.127 (0.208) 0.840-1.440 Orthophosphate (mg/L) 0.008 (0.004) 0.005-0.013 0.013 (0.010) 0.005-0.030 Total phosphorus (mg/L) 0.072 (0.028) 0.050-0.120 0.097 (0.039) 0.070-0.180 Mean N/P ratio 43.2 57.4 Median 48.7 61.4 Chlor. a (mg/L) 14.1 (12.1) 1.5-34.7 9.0 (9.7) 0.9-24.9 Fecal col. /100 mL 53 9-290 65 18-173 (geomean / range) BOD5 (mg/L) NA NA 1.4 (0.3) 1.0-1.8 BOD20 (mg/L) NA NA 5.5 (1.2) 3.8-7.1 _____________________________________________________________________ NA = not analyzed 63 64 12.0 Whiskey Creek Whiskey Creek drains into the ICW. Sampling of this creek began in August 1999. Five stations were sampled in 2004-2005; WC-M (at the marina near the creek mouth), WC-AB (off a private dock upstream), WC-MLR (from the bridge at Masonboro Loop Road), WC-SB (in fresh to oligohaline water along the south branch at Hedgerow Lane), and WC-NB (in fresh to oligohaline water along the north branch at Navajo Trail – Fig. 12.1). Dissolved oxygen concentrations were below the State standard on only one of 12 occasions each at WC-MLR and WC-AB in 2004-2005 (Table 12.1). Turbidity was within state standards for tidal waters on all sampling occasions (Table 12.1; Appendix B). There was one minor algal bloom of 18 mg/L at WC-MLR in June 2005; chlorophyll a concentrations are usually low in this creek (Table 12.1). Nitrate concentrations were highest upstream at WC-NB, followed by WC-SB (Table 12.2), similar to previous years. Nitrate was slightly lower than 2003-2004, likely as result of less runoff from drought conditions. Ammonium levels were highest at WC-NB and WC-SB, and these levels were among the highest of all the tidal creek stations sampled. Phosphate concentrations were similar among all stations except for WC-SB. Phosphate, ammonium and nitrate at WC-MB were highest among all creek mouth stations in the tidal creek system. Fecal coliform bacteria were not sampled in 2004- 2005. Whiskey Creek is presently closed to shellfishing by the N.C. Division of Marine Fisheries. Table 12.1. Water quality summary statistics for Whiskey Creek, August 2004-July 2005, presented as mean (standard deviation) / range. Salinity Dissolved oxygen Turbidity Chlor a Light attenuation (ppt) (mg/L) (NTU) (mg/L) (k/m) _____________________________________________________________________ WC-MB 30.4 (2.1) 7.6 (2.0) 3 (2) 3.1 (2.2) 1.0 (0.3) 26.3-33.6 5.0-10.8 0-9 0.3-7.2 0.7-1.6 WC-AB 27.7 (3.0) 7.6 (2.4) 6 (3) 2.8 (2.3) NA 21.7-32.5 4.6-11.6 2-11 0.2-8.4 NA WC-MLR 23.0 (4.2) 7.5 (2.6) 7 (5) 4.3 (4.9) NA 16.6-31.7 3.9-12.5 2-20 0.3-18.1 NA WC-SB 0.1 (0.0) 7.2 (0.8) 6 (4) 0.8 (0.6) NA 0.0-0.1 6.2-9.0 2-15 0.1-1.7 NA WC-NB 0.1 (0.1) 7.3 (1.2) 4 (2) 0.3 (0.2) NA 0.1-0.2 5.1-10.2 2-7 0.0-0.8 NA _____________________________________________________________________ NA = not analyzed 65 Table 12.2. Nutrient concentration summary statistics for Whiskey Creek, August 2004- July 2005, as mean (standard deviation) / range, N/P ratio as mean / median. _____________________________________________________________________ Nitrate Ammonium Phosphate Molar N/P ratio (mg/L) (mg/L) (mg/L) _____________________________________________________________________ WC-MB 0.021 (0.020) 0.023 (0.011) 0.010 (0.003) 9.4 0.006-0.065 0.014-0.044 0.006-0.015 8.7 WC-AB 0.024 (0.019) NA 0.011 (0.004) NA 0.005-0.069 0.007-0.021 WC-MLR 0.030 (0.023) 0.044 (0.033) 0.012 (0.005) 12.4 0.010-0.075 0.014-0.108 0.006-0.023 13.2 WC-SB 0.057 (0.012) 0.156 (0.102) 0.002 (0.001) 658.9 0.041-0.082 0.057-0.396 0.001-0.004 265.8 WC-NB 0.161 (0.061) 0.136 (0.075) 0.012 (0.009) 92.3 0.094-0.265 0.052-0.326 0.003-0.031 64.9 _____________________________________________________________________ NA = not analyzed 66 Figure 12.1. Whiskey Creek. Watershed and sampling sites. 67 13.0 Fecal contamination of tidal creek sediments: Factors controlling indicator bacteria concentrations Byron R. Toothman, Michelle L. Ortwine, Lawrence B. Cahoon1 Department of Biology and Marine Biology UNC Wilmington 1-910-962-3706, Cahoon@uncw.edu Abstract A study was performed to determine the abundance of fecal bacteria in Bradley Creek sediments and to see if their concentrations were related to sediment phosphorus (P), sediment carbon (C), salinity and water temperature. The concentrations of fecal indicator bacteria in sediments of Bradley Creek were highly variable, spanning over 3 orders of magnitude. Fecal coliform concentrations had a geometric mean of 179 CFU cm-2 (std. dev. = 411, range = 0 – 3,230) in a total of 154 samples. This geometric mean value corresponds to a value of 179 CFU/100 mls if all these bacteria were suspended in a water column 1 meter deep, a value just below that required to close the water to human body contact (200 CFU/100 ml). The regulatory standard for shellfishing is much lower, 14 CFU/100 ml; 113 of the 154 samples exceeded this value using analogous assumptions. Fecal enterococcus concentrations had a geometric mean value of 285 CFU cm-2 (std. dev. = 433, range = 0-1726). This geometric mean value corresponds to a value of 285 CFU per 100 ml if all these bacteria were suspended in a water column 1 meter deep, a value well above that required to close the water to human body contact (33 CFU/100 ml). Thus, the levels of fecal indicator bacteria measured in Bradley Creek’s sediments frequently represent serious potential problems for human uses of these waters. Sediment fecal coliform bacteria were negatively correlated with salinity and positively correlated with water temperature, but enterococcus had no significant relationship to these factors. Rainfall in the 24 hour period preceding sampling was also significantly related to fecal coliform counts. Laboratory experiments showed that both fecal coliform bacteria and enterococcus bacteria counts were positively related to increasing concentrations of usable (or bioavailable) carbon (dextrose). However, only enterococcus was significantly correlated to sediment P concentrations, and only when background P concentrations were low. Bioavailable C is abundant in stormwater runoff. Because of this, and the fact that sediment fecal bacteria counts were positively related to rainfall, we conclude that storm water runoff is the most significant factor driving sediment contamination. Introduction Fecal contamination of coastal waters is one of the most serious and well-known forms of pollution in our region, mandating closure of large areas to shellfishing and creating a potential human health threat. In addition to shellfishing closures in estuarine waters mandated by the N.C. Division of Shellfish Sanitation’s routine sampling, surveys of 68 tributaries to New Hanover County’s tidal creeks show fecal contamination levels, expressed as counts of fecal coliform bacteria (Colony Forming Units (CFU)/100 ml) that often exceed designated use standards (Mallin et al., 2002). Our earlier data from the Bradley Creek drainage showed fecal coliform levels on the order of 106 CFU m-2 of sediment (Cahoon et al., 2005). These observations suggested that fecal coliform bacteria may have a natural refuge in tidal creek sediments, where they are shielded from harmful solar radiation, obtain needed nutrients, and find surfaces on which to attach and survive or even grow (Dale, 1974; Tate, 1978; Henis, 1987). Furthermore, even minor sediment disturbance may suspend sufficient numbers of sediment- associated fecal coliforms to cause non-attainment of use standards, even if no “new” fecal coliforms have been washed into the system (Doyle, 1985; Gary and Adams, 1985; Seyfried and Harris, 1986; Palmer, 1988; Struck, 1988; Pettibone et al., 1996). Major sewage spills in the Hewletts Creek drainage during 2005 drove significant increases in the concentrations of fecal indicator bacteria in creek sediments (see discussion elsewhere in this report). Rain events shortly after these spills also caused increases in sediment concentrations of fecal indicator bacteria, illustrating the importance of storm water runoff as a source mechanism for this contamination. However, fecal bacteria contamination even weeks after storm events or spills argue for persistence of these bacteria in tidal creek ecosystems. In addition, variation in bacteria concentrations among sampling times and locations suggests that factors other than variable recruitment control bacterial concentrations in sediments. Therefore, we investigated the effects of the macronutrients phosphorus and bio-available carbon as factors controlling growth of sediment populations of fecal indicator bacteria. We measured the concentrations of two kinds of fecal indicator bacteria, fecal coliforms and fecal enterococcus, in sediments, as regulators have established standards for these two groups in estuarine ecosystems. We concurrently measured temperature, salinity, and the concentrations of sediment phosphorus and total carbohydrate for comparison to bacterial concentrations. We also compared responses of sediment bacteria populations to rainfall history. Finally, we conducted experiments that examined responses of sediment fecal indicator bacteria to combinations of added phosphorus and bio-available carbon. Methods Field Sampling: Sampling sites were located in the Bradley Creek drainage, using locations previously sampled so as to maintain continuity (Fig. 1). These locations were sampled at least monthly for sediment phosphorus, sediment fecal coliforms and enterococci, temperature and salinity. The top 2.0 centimeters of estuarine sediments were cored at each site. Three sediment cores were taken randomly at each site using sterile 2.20 cm ID acrylic tubing for sediment fecal indicator bacteria analyses. Following methods developed by Rowland (2002), each sample was transferred to a previously weighed, sterile 50ml polypropylene centrifuge tube and placed on ice. The three samples were each mixed with 1L of sterile phosphate-buffered rinse water inside a sterile 1L flask with a stir bar. Each sample was gently stirred for 2 minutes prior to performing the membrane filtration technique. From the mixture of sterile phosphate- buffered rinse water and sediment, three 10 ml and three 1 ml samples were used for fecal coliform analysis using standard methods for membrane filtration of fecal coliform 69 bacteria, method 9222 (APHA, 2001). The sediment and rinse water solution were mixed before each sample withdrawal to reduce fecal coliform burial and homogenize the bacteria suspension. All plates were incubated in a water bath for 24 hours at 44.5° C. After the 24-hour incubation period, each plate was inspected for dark blue colonies. Each dark blue colony represented one colony-forming unit (CFU). Similar methods were used to estimate fecal enterococci following method 9230 C.3.a (APHA, 2001). Bacterial colonies satisfying the respective criteria for each method were counted after incubations using either the naked eye, or for plates with numerous colonies, an Olympus SZ-III stereomicroscope. Counts from each 10ml sample from each of the three cores from each site were averaged and expressed as the number of colony forming units per square centimeter (CFU cm-2) + one std. dev. Sediment phosphate was analyzed on a second triplicate set of sediment cores taken randomly at each sampling site simultaneously with fecal bacteria samples. Sediment cores destined for chemical analyses were iced immediately, frozen initially at -20 oC, then stored at -85 oC for 24 hours prior to lyophilization using a Virtis Benchtop 3.3 Vacu-Freeze lyophilizer. Lyophilized sediment samples were homogenized and stored in sealed containers at room temperature prior to sub-sampling for chemical analyses. Sub-samples of dried sediments were weighed and analyzed for phosphate content following digestion with the persulfate-boric acid method of Valderrama (1981). This method oxidizes labile forms of phosphorus to orthophosphate, and likely represents bio-available phosphorus in sediments, in contrast to more robust extraction and digestion methods that quantify additional phosphorus that may be less bio-available. Sediment phosphate content was expressed as ug P (g sediment)-1. The carbohydrate content of sediment samples was analyzed by the phenol-sulfuric acid method of Underwood et al. (1995). Approximately 0.2-0.5 g of lyophilized, homogenized sediment was suspended in 1.0 ml of distilled water, to which 1 ml of 5% aqueous phenol solution and 5 ml of concentrated sulfuric acid were added while stirring vigorously. Resulting absorbance was measured at 485 nm on a Milton-Roy Spectronic 401 spectrophotometer in a 1 cm cuvet against a reagent blank. Standard curves were established using a dilution series of dextrose (C6H12O6) and total carbohydrate contents were expressed as mg C (g sediment)-1. The average of three replicate values from each sample site was calculated along with standard deviation. 70 Figure 1. Map showing sampling locations (and corresponding Tidal Creeks Program site designations) in the Bradley Creek watershed, named for nearby streets or tributaries. A=Andover (BC-SBU), BWP=Bluthenthal Wildflower Preserve, CR=Clear Run (BC-CA), CRT=Clear Run Branch Tributary, E=Eastwood (BC-NBU), M=Mallard (BC-CR), REC=Recreation Center Pond, S=Softwind (BC-SB), W=Wrightsville (BC- NB). ________________________________________________________________ Experimental Protocols: Sediment cores were collected as above at sampling locations in the Bradley Creek watershed (Fig. 1) and one other location (“210”, at the point where Prince George’s Creek crosses NC Hwy 210) for experimental determinations of responses of fecal indicator bacteria to added P and organic carbon. A randomly selected triplicate set of sediment cores was analyzed for initial concentrations of fecal coliform and fecal enterococcus bacteria as above. Four treatments were used in a 2 x 2 design, executed in triplicate: 3 sediment cores were incubated with 1 liter of incubation medium (0.4% NaCl buffered to pH 8.0 with sodium borate) +100 mg P/liter (as KH2PO4), 3 sediment cores were incubated with 1 liter of incubation medium + 1000 mg dextrose C/liter, 3 sediment cores were incubated with 1 liter of incubation medium + 100 mg P/liter + 1000 ug dextrose C/liter, and 3 sediment cores were incubated with 1 liter of incubation medium only. Incubations lasted 24 71 hours at 37 oC, after which sediment cores were processed for analyses of fecal coliform and fecal enterococcus bacteria as above. Statistical Analyses: All statistical analyses were performed on SAS Institute’s JMP version 4.0, except as noted. Data sets were examined for normality using the Shapiro- Wilk test. Non-normal data sets were transformed as appropriate; bacteria concentration data were typically log-transformed (Log[counts+1]). When transformation could not yield a normal distribution, non-parametric statistical tests were used to analyze original data. The effects of sediment P, carbohydrate, and other variables on bacterial concentrations were analyzed by linear regression and multiple linear regressions. Results of experimental incubations employing a 2 x 2 design were log-transformed and analyzed by 2-way ANOVA (Sokal and Rohlf, 1995); pooled experimental results were analyzed by a Kruskal-Wallis test. Results The concentrations of fecal indicator bacteria in sediments of Bradley Creek were highly variable, spanning over 3 orders of magnitude. Fecal coliform concentrations had a geometric mean of 179 CFU/ cm2 (std. dev. = 411, range = 0 – 3,230) in a total of 154 samples (sites x times) collected between January, 2003 and March, 2005. This geometric mean value corresponds to a value of 179 CFU/100 mls if all these bacteria were suspended in a water column 1 meter deep, a value just below that required to close the water to human body contact (200 CFU/100 ml). The regulatory standard for shellfishing is much lower, 14 CFU/100 mls; 113 of the 154 samples exceeded this value using analogous assumptions. Mean values for the respective sampling sites were highly variable (Table 1), but all sites had at least one value exceeding 200 CFU cm-2. Fecal enterococcus concentrations had a geometric mean value of 285 CFU cm-2 (std. dev. = 433, range = 0-1726) in a total of 45 samples (sites x times) collected between July, 2004 and March, 2005. This geometric mean value corresponds to a value of 285 CFU per 100 mls if all these bacteria were suspended in a water column 1 meter deep, a value well above that required to close the water to human body contact (33 CFU/100 ml). Thus, the levels of fecal indicator bacteria measured in Bradley Creek’s sediments frequently represent serious potential problems for human uses of these waters. Table 1. Concentrations of fecal indicator bacteria in sediments at sampling sites within the Bradley Creek drainage, CFU/cm2. Fecal coliforms= FC, fecal enterococcus = FE. site designations as in Fig. 1. Site A CR E M S W_ FC Mean 340 33 186 257 125 132 Std. Dev. 697 69 274 550 301 152 FE Mean 332 203 365 65 251 528 Std. Dev. 587 294 494 90 448 732 Analysis of correlations between fecal indicator bacteria concentrations and other parameters revealed mostly non-significant relationships. Neither fecal coliform nor 72 fecal enterococcus concentrations in sediments were related to sediment phosphorus concentration, sediment carbohydrate content, or rainfall in the 24 or 48 hour periods prior to sampling (Table 2). There was a significant relationship between salinity and fecal coliform concentration in sediments (Fig. 2), but not between salinity and fecal enterococcus concentrations in sediments (Table 2), and between temperature and sediment fecal coliform concentrations (Fig. 3) but not between temperature and fecal enterococcus concentrations in sediments (Table 2). However, both significant relationships had very low correlation coefficients (r2 values), indicating poor explanatory power. Table 2. Results of regression analyses between sediment fecal indicator bacteria concentrations (log[CFU/cm2]) and environmental parameters. Significant effects in bold. Parameter Coliforms Enterococcus r2 F df p r2 F df p Salinity -0.04 6.77 1,150 0.01 0.003 0.11 1,43 0.74 Temperature 0.05 7.9 1,150 0.006 0.07 3.05 1,43 0.08 Sediment P 3x10-7 0.00 1,151 >0.99 0.001 0.07 1,41 0.80 Sed. Carbohydrate 0.02 2.38 1,139 0.13 0.06 2.55 1,43 0.12 24 hr Rainfall 0.006 0.86 1,147 0.35 0.09 3.73 1,37 0.06 48 hr Rainfall 0.001 0.21 1,147 0.65 0.10 3.94 1,37 0.054 Fig. 2. Effects of salinity on fecal coli- Fig. 3. Effects of temperature on fecal coli- forms in Bradley Creek. forms in Bradley Creek. Multiple regression was used to evaluate the possibility that interactions among the environmental parameters may have obscured relationships between concentrations of fecal indicator bacteria and environmental parameters (using 72 hr rainfall instead of 48 hr rainfall). Results of this analysis are shown in Table 3, and demonstrate a significant effect of 24 hr rainfall on fecal coliform bacteria concentrations in sediments. The significant pair-wise relationships between fecal coliforms and temperature and salinity are not significant in this analysis, suggesting that interactions among parameters mask 73 responses of fecal coliforms to individual parameters. Identification of a significant rainfall effect agrees with observations from the July 1 sewage spill at Hewletts Creek and subsequent spike in fecal coliform and enterococcus concentrations after a heavy rain on July 14, 2005, discussed elsewhere in this report. ________________________________________________________________ Table 3. Results of multiple regression analysis of the effects of temperature, salinity, carbohydrate, phosphorus, and 24 hr and 72 hr rainfall on fecal coliform concentrations in sediments at Bradley Creek sites, Jan. 2003 – March, 2005. Significant effects in bold. Overall model r2 value was 0.16. Source df SS MS F p Model 6 4022134 670356 3.91 0.0013 Temperature 1 112 112 0.0007 0.9796 Salinity 1 4021.5 4021.5 0.0235 0.8784 Carbohydrate 1 458146 458146 2.675 0.1044 Phosphorus 1 135988 135988 0.7941 0.3746 24 hr rainfall 1 2994796 2994796 17.49 <0.001 72 hr rainfall 1 143975 143975 0.84 0.3609 Error 125 21404399 171235 Total 131 25426533 Experimental manipulations of the availability of phosphorus and carbohydrate evaluated the responses of fecal coliforms and enterococcus in sediment samples from several locations with varying natural sediment P and carbohydrate levels. Results of six experiments at five locations were analyzed by 2-way ANOVA and are shown in Table 4. Added phosphorus supported significant growth of fecal enterococcus bacteria when initial sediment P levels were relatively low, but fecal coliforms never responded to added P. This latter response was consistent with the lack of any correlation between sediment P and sediment fecal coliforms described earlier (Tables 2 and 3). However, fecal coliform bacteria responded significantly to added dextrose, a form of bio- available carbon, in three of six individual experiments and in the overall analysis. Fecal enterococcus did not respond as frequently to added dextrose, but also showed a significant response in the overall analysis, suggesting that both groups of fecal indicator bacteria are more frequently limited by bio-available organic substrate than by phosphorus. Table 4. Effects of added phosphorus (P) and dextrose (C) and interactions of P and C (I) on changes in fecal coliform (FC) and fecal enterococcus (FE) concentrations in sediment samples from locations in New Hanover County. All treatment combinations run in triplicate and bacteria concentrations log-transformed prior to analysis by 2-way ANOVA. Significant effects in bold. 74 Initial P Initial C FC _____ FE _____ Site Date µg P/g sed. µg C/g sed. Effect F p F p E 8/19 19.6 420 C 29.9 0.001 11.9 0.009 P 0.65 0.44 7.00 0.029 I 0.89 0.37 0.01 0.92 E 7/22 31.2 628 C 0.02 0.89 2.38 0.16 P 3.53 0.09 5.71 0.04 I 57.6 0.001 0.00 1.00 BWP 8/29 47.0 290 C 1.71 0.23 4.5 0.07 P 1.05 0.34 0.50 0.49 I 0.39 0.55 0.50 0.49 210 9/1 74.4 290 C 2.60 0.15 0.08 0.78 P 3.36 0.10 0.50 0.49 I 8.04 0.02 0.50 0.49 REC 8/24 102 2990 C 7.71 0.02 4.91 0.06 P 0.22 0.65 0.48 0.51 I 0.47 0.51 0.78 0.40 CRT 9/6 176 3600 C 17.8 0.003 0.08 0.60 P 0.91 0.37 0.50 0.19 I 3.06 0.12 0.50 0.19 Combined Data C 32.1 0.001 6.93 0.02 P 0.73 0.40 0.09 0.77 I 0.73 0.40 1.24 0.28 Analysis of storm water runoff in one event at a pond on the UNCW campus in the Bradley Creek drainage revealed that soluble carbohydrates (a measure of bio- available carbon) increased significantly, but temporarily, over background levels (Table 5). Thus, storm water runoff may provide fresh bio-available carbon in addition to its role as a source mechanism for fecal bacteria that contaminate sediments. Table 5. Response of soluble carbohydrates to rain events in a pond on the UNCW campus. Date Condition [Soluble Carbohydrates], mg C/L Std. Dev. 8/3/05 Dry 525 462 8/9/05 Rain 1330 811 8/12/05 Dry 525 349 75 8/13/05 Dry 553 131 Discussion Sediments in the Bradley Creek drainage frequently harbored significant populations of fecal coliform and enterococcus bacteria, particularly during the warmer times of year when children are most likely to play in these waters. As other studies have shown that fecal indicator bacteria concentrations in sediments correlate with the presence of other fecal pathogens (Rittenberg et al., 1958; Lipp et al., 2001), it is important to consider the public health risk associated with this poorly known reservoir of contaminants. Many water-borne diseases are not properly tracked to their sources, so a significant problem may be occurring without real awareness of its cause. Human contact with these contaminated sediments must be considered as a serious problem for heavily developed coastal areas, such as the Bradley Creek drainage. Given the attributes of the Bradley Creek watershed, it is likely that animals, both wild and domestic, were the most important fecal contamination sources. One conclusion, therefore, is that pet waste management should be addressed for all residential areas in coastal watersheds, not just beach communities. Moreover, a significant population of “wildlife” that actually associates with human communities, eating human garbage and unsecured pet foods, such as raccoons and opossums, likely lives in this watershed and contributes to the fecal contamination problem. Educational efforts can reduce this problem as well. It is important to note that animal wastes can be as dangerous a source of pathogens to humans as human waste, particularly because some of the animal-derived pathogens, such as infectious protozoans, can cause infections that are difficult to diagnose and treat. For example, an AP story published recently in the Wilmington Star-News discussed how infections from a widely distributed pathogenic amoeba, Naegleria fowleri, have caused fatal brain inflammations in swimmers. We must also consider the dangers posed by human sources of fecal contamination, particularly spills from sewage systems, however, as dramatically demonstrated by the spills in Hewletts Creek. Such large spills are fortunately rare, but analysis of the NC Division of Water Quality violations data base revealed that sewage spills occurred at a frequency of about once/week in New Hanover County during the period 1997-2004. At such a high frequency, repeated contamination of sediments, where fecal indicator bacteria are known to persist for weeks following initial recruitment, would drive continuously elevated concentrations of these pollutants. Moreover, sewage itself is a concentrated source of both phosphorus and bio-available organic carbon, so sewage contamination provides both the microbes and their substrates, independent of any storm water runoff effects. Obviously such spills must be reduced if New Hanover County’s Tidal Creeks are to be kept safe for human uses. Management of sediment contamination by fecal indicator bacteria and the pathogens they represent could include efforts to limit inputs of the resources supporting their survival and growth. Our results indicate that the macronutrient, phosphorus, does appear to limit fecal enterococcus bacteria when present at very low concentrations. However, in most aquatic sites we studied, sediment phosphorus concentrations were 76 higher than this threshold, indicating another limiting factor, which is likely to be bio- available organic matter. Relatively little is known about sources and variability of bio- available organic matter in this context, so it is premature to advocate management approaches based on that criterion. The clear conclusion from our statistical analysis, however, is that storm water runoff is the most significant factor driving sediment contamination. Obviously, the challenge is to adopt and use effective storm water management techniques if we intend to manage the threat posed by sediment bacteria and pathogens successfully. Acknowledgments: This research was supported by grants from the UNC Water Resources Research Institute Project #2004NC36B and UNC Sea Grant R/MER-50 to LBC and MAM. Literature Cited APHA. 2001. Standard methods for the examination of water and waste water, 21st ed. American Public Health Association. Washington, D.C., A.E. Greenberg, ed. Cahoon, L.B., B.R. Toothman, M.L. Ortwine, R.N. Harrington, R.S. Gerhart, S.L. Alexander, and T.D. Blackburn. 2005. Fecal contamination of tidal creek sediments – relationships to sediment phosphorus and among indicator bacteria, pp. 48-55, in Environmental quality of Wilmington and New Hanover County watersheds 2003- 2004, CMS Report 05-01, UNCW Center for Marine Science Research. Dale, N.G. 1974. Bacteria in intertidal sediments: factors related to their distribution. Limnol. Oceanogr. 19:509-518. Doyle, J.D. 1985. Analyses of recreational water quality as related to sediment resuspension. Dissertation Abstracts International. Part B. Science and Engineering. Vol. 6, No.4 pp 79. Gary, H.L. and J.C. Adams. 1985. Indicator bacteria in water and stream sediments near the Snowy Range in Southern Wyoming. Water Air Soil Pollut. 25:133-144. Henis, Y, ed. 1987. Survival and dormancy of microorganisms. New York: John Wiley and Sons. Pp.1-35. Lipp, E.K., R. Kurz, R. Vincent, C. Rodriguez-Palacios, S.R. Farrah, and J.B. Rose. 2001. The effects of seasonal variability and weather on microbial fecal pollution and enteric pathogens in a subtropical estuary. Estuaries 24:266-276. Mallin, M.A., L.B. Cahoon, M.H. Posey, L.A. Leonard, D.C. Parsons, V.L. Johnson, E.J. Wambach, T.D. Alphin, K.A. Nelson, and J.F. Merritt. 2002. Environmental quality of Wilmington and New Hanover County watersheds. CMS Report 02-01. Palmer, M. 1988. Bacterial loadings from resuspended sediments in recreational beaches. Can. J. Civ. Eng. 15:450-455. 77 Pettibone, G.W., K.N. Irvine, and K.M. Monohan. 1996. Impact of a ship passage on bacteria levels and suspended sediment characteristics in the Buffalo River, New York. Water Res. 30:2517-2521. Rittenberg, S.C., T. Mittwer, and O. Ivier. 1958. Coliform bacteria in sediments around three marine sewage outfalls. Limnol. Oceanogr. 3:101-108. Rowland, K.R. 2002. Survival of sediment-bound fecal coliform bacteria and potential pathogens in relation to phosphate concentration in estuarine sediments. Unpublished M.S. thesis, UNC Wilmington, Wilmington, N.C. Seyfried, P.L., and E.M. Harris. 1986. Detailed bacteriological water quality study examining the impact of sediment and survival times. Technology Transfer Conference. Part B: Water Quality Research. pp. 347-391. Sokal, R.R., and F.J. Rohlf. 1995. Biometry, 3rd ed. W.H. Freeman & Company, New York, 887 pp. Struck, P.H. 1988. Relationship between sediment and fecal coliform levels in a Puget Sound Estuary. J. Env. Health. 50:403-407. Tate, R.L., III. 1978. Cultural and environment factors affecting the longevity of Escherichia coli in Histosols. Appl. Environ. Microbiol. 35:925-929. Underwood, G.J.C., D.M. Paterson, and R.J. Parkes. 1995. The measurement of microbial carbohydrate exopolymers from intertidal sediments. Limnol. Oceanogr. 40:1243-1254. Valderrama, J.C. 1981. The simultaneous analysis of total nitrogen and phosphorus in natural waters. Mar. Chem. 10:109-122. 14.0 Evaluation of Oyster Characteristics in Pages, Howe, and Hewletts Creeks Martin Posey and Troy Alphin Center for Marine Science University of North Carolina Wilmington Introduction The ecological health of the tidal creeks in New Hanover County has been a topic of concern for the last decade. With increased development within the watershed and associated increased inputs from upland areas, storm water runoff, and unexpected 78 inputs from failing sewer lines, the public scrutiny of these issues and the question of the human health and safety associated with the tidal creeks also has become a central issue over the last two years. Some of the long-time residents within the tidal creek watersheds have expressed concern over what they see as a decline in the fishery resource within the creeks and changes in the physical characteristics of the tidal creeks based on anecdotal accounts of channel depth. Likewise, concerns have been expressed by the local oystermen and commercial fishermen who relay accounts of dwindling shellfish beds and increased fishing pressure on the remaining open, managed bottom areas. Similar concerns have been expressed by conservation groups. The Southeastern Regional Oyster Steering Committee gathered comments from a number of groups and individuals including residents, fishermen, and grassroots community environmentalists during 2004 and 2005. Although a variety of opinions were expressed, there was agreement on a number of issues: 1) Oyster stocks within the southern regions (especially New Hanover and Onslow Counties) seem to be declining, 2) This decline is directly related to the closure of shellfish grounds due to failure of these areas to meet shellfish sanitation standards, 3) The reduction in overall acreage available to shellfish harvest has increased the fishing pressure on the remaining shellfish bottom, in some instances leading to “apparent” overharvest, and 4) Closure of public bottom to shellfish harvest seems to closely track upland development within the watershed. Several recommendations were taken to MFC’s Shellfish Advisory Committee from this group, including a request for more managed bottom areas within the southern region and a request for greater restrictions on harvest limits. Currently DMF has reviewed these requests and in most instances the director has proclamation authority, meaning he can establish additional managed areas and revise catch limits as needed. However these proposed changes do not address the under lying issues of impaired estuarine ecosystem function and potential impacts to ecosystem health. Rationale The UNCW Benthic Ecology Laboratory has conducted work in the tidal creek systems of New Hanover County since 1990 on projects ranging from general bivalve surveys to evaluations of eutrophication, and most recently evaluation of ecosystem health through indicator species such as the oyster Crassostrea virginica. Oysters represent both an important commercial target species with a dockside value in NC of over $10 million. During the 2005 sampling year we concentrated our effort on three target creeks; Pages Creek, Howe Creek, and Hewletts Creek. In general, Pages Creek has been considered the least impacted of the three systems, supporting shellfish and a PNA (primary nursery area), indicating that this area is critical to supporting local populations of commercially and recreationally important finfish and crustaceans. Howe Creek has experienced problems in previous years with increased sediment loads and nutrients from surrounding developments. Hewletts Creek is considered one 79 of the most impacted of the tidal creeks in New Hanover County due to increased sedimentation, nutrient runoff and shellfish closures throughout most of the creek. Our study focused on evaluating the actual condition of the oyster stocks in each of these creek systems. Oyster density, size, and condition were evaluated for three independent reefs in each creek. Methods In summer 2005, the Benthic Ecology Laboratory sampled oyster populations in Hewletts Creek, Howe Creek, and Pages Creek. Live oyster density, percent shell cover, size demography, condition, shell height, and rugosity (vertical complexity) were measured on three randomly selected oyster reefs in the lower portion of each creek. Previous work and aerial photography indicated that oyster coverage within the three creeks was greatest in the lower kilometer of each, although the extent of coverage varied among creeks. Quadrate sampling: Each reef was sampled by random placement of ten 50cm x 50cm square quadrates. Percent shell cover was estimated visually by observing the percent of the area within a quadrate covered by oyster shell (both shell hash and live oysters). In order to determine oyster density, the number of live oysters within a quadrate was counted. The size demography of the oysters on each reef was calculated by measuring a random selection of twenty live oysters per quadrate. For the purposes of this study, size was represented as shell height (long axis of the oyster from umbo to outer edge expressed in mm). Reef characteristic: The average height of the shell matrix on a reef was determined by measuring the highest point in each quadrate, from the sediment to the tip of the tallest shell. Rugosity was randomly sampled at five points per reef. A 100cm chain was draped across the reef in a straight line. The straight distance of the conformed chain was then measured from end to end and its length recorded. The shorter the length the more rugose or “jagged” (vertically complex) the topography of the reef. Oyster characteristics: Oyster condition was assessed visually using 15 oysters from each of 2 size classes (i.e. small- 40-50mm, large- +75mm). Each oyster was given a numerical condition code depending on the appearance of their tissues (Quick and Mackin 1971). Condition index, a ratio of soft tissue dry weight to internal shell volume, will also be calculated for those oysters and information made available in future reports. This is a measure of soft tissue growth and is considered to be an indicator of oyster health. In order to determine the internal shell volume, a water displacement method will be used. The volume of water displaced when the whole oyster and when the shucked oyster (i.e. empty shell) is placed in a graduated cylinder will be recorded. Dry tissue weight will be obtained once the oyster tissues have been dried for 24 hours at 70°C. Results and Discussion Oyster Characteristics: Overall oyster populations in the three creek systems seem very similar with only modest differences in most parameters. Percent shell cover was greatest in Pages Creek, on average ~10% greater coverage that oyster reefs in Hewletts 80 Creek and ~28% greater coverage than oyster reefs in Howe Creek (Figure 1). It seems likely that that lower cover of exposed shell in Howe and Hewletts Creeks may be a function of increased suspended solids and subsequent sedimentation compared to Pages Creek, rather than increased oyster production in Pages creek. Oyster size, indicated here as shell height (long axis of the oyster from umbo to outer edge), showed no difference among creeks (Figure 2). Mean size was ~54mm in Hewletts and Howe Creeks and ~58mm in Pages creek. Legal harvest size of oysters is three inches (~77mm). Average density of oysters did vary among creeks, with greater densities in Howe Creek (68 oyster m2) and lowest in Pages (42 oyster m2) while densities in Hewletts Creek fell in the middle of this range (Figure 3). While these mean densities are not surprising, peak densities have previously been recorded that exceed 125 live oysters per 0.25 m2 (Alphin and Posey unpublished data). Reef Characteristics: Vertical complexity is a good indicator of reef function as habitat and suitability for spat settlement. Here we use rugosity as a proxy for vertical complexity, where a lower number indicates more vertical relief of a reef, with numerous upright oyster clumps, and a higher number (approaching 1) would indicate a reef that may be in decline or suffering from high sedimentation. A priori we expected reefs in Pages Creek to exhibit a greater degree of vertical complexity. This was not the case since all three creeks showed similar measures of complexity, with Hewletts Creek showing slightly higher rugosity and Howe Creek slightly lower than Pages Creek (Figure 4). The other reef characteristic that we measured was shell height (distance from substrate surface to the top of the reef). This provides a measure of reef development and mounding of the oyster reefs. Reef height has also been suggested as a potential response variable to sedimentation, since oysters settling in areas experiencing heavy sedimentation would have a greater chance of survival by setting on the upper edge of the reef. It follows that in areas with heavy sedimentation that the upper edges of the reef are also the areas most likely to provide clean settlement substrates, since shells within the reef are more likely to be cover with sediment. Results of the current study show a trend towards greater reef height in Hewletts Creek (Figure 5). Conclusions For both oyster characteristics and reef characteristics there were few clear patterns indicating a difference in oyster health among the creeks. A priori we had expected Pages Creek to show characteristics of healthier oysters or better-developed reefs compared to either Hewletts or Howe Creeks. Percent shell cover was greatest in Pages Creek, on average ~10% greater coverage that oyster reefs in Hewletts Creek and ~28% greater coverage than oyster reefs in Howe Creek. It seems likely that that lower cover of exposed shell in Howe and Hewletts Creeks may be a function of increased suspended solids and subsequent sedimentation compared to Pages Creek, rather than increased oyster production in Pages creek. Howe Creek showed the greatest oyster density and no apparent difference in oyster size was seen among the creeks. Where we did detect differences (reef height and shell cover) these supported the idea of increased sedimentation in Hewletts and Howe Creeks compared to Pages Creek. While we know that water quality in Hewletts Creek has suffered for some time, the current data does not provide evidence for population differences among the 81 creeks. However, population measures may reflect regional conditions more than local creek conditions because of interchange among the creek systems through the IntraCoastal Waterway. Even with similar densities and reef form, differences may be apparent with physiological or condition measures such as tissue weight and disease incidence. Ongoing work is examining both condition index and disease. Currently we are using the traditional thyoglycate method for evaluate the disease intensity for oysters in these three target creeks and will compare disease intensity and condition of these oyster populations. Percent Shell Cover 82.77 64.9 91.83 0 10 20 30 40 50 60 70 80 90 100 Figure 1. Mean percent shell cover, including live oysters and dead shell. Sh e l l C o v e r ( % ) Hewletts Howe Pages 82 Oyster Size 54.57 54.82 58.52 0 10 20 30 40 50 60 70 80 90 100 Figure 2. Mean size (shell height) of oyster per creek. Si z e ( m m ) Hewletts Howe Pages Oyster Density 51.13 68.07 42.23 0 10 20 30 40 50 60 70 80 90 100 Figure 3. Mean live oyster density per creek. De n s i t y ( p e r . 2 5 m s q ) Hewletts Howe Pages 83 Reef Rugosity 68.95 61.17 66.2 0 10 20 30 40 50 60 70 80 90 100 Figure 4. Mean vertical complexity Ru g o s i t y ( c m ) Hewletts Howe Pages Reef Height 15.37 13.48 12.53 0 2 4 6 8 10 12 14 16 18 20 Figure 5. Mean reef height from substrate surface to top of reef. He i g h t ( m m ) Hewletts Howe Pages 84 15.0 Report References Cited APHA. 1995. Standard Methods for the Examination of Water and Wastewater, 19th ed. American Public Health Association, Washington, D.C. Hecky, R.E. and P. Kilham. 1988. Nutrient limitation of phytoplankton in freshwater and marine environments: A review of recent evidence on the effects of enrichment. Limnology and Oceanography 33:796-822. Long, E.R., D.D. McDonald, S.L. Smith and F.D. Calder. 1995. Incidence of adverse biological effects within ranges of chemical concentrations in marine and estuarine sediments. Environmental Management 19:81-97. Mallin, M.A., L.B. Cahoon, J.J. Manock, J.F. Merritt, M.H. Posey, R.K. Sizemore, W.D. Webster and T.D. Alphin. 1998a. A Four-Year Environmental Analysis of New Hanover County Tidal Creeks, 1993-1997. CMSR Report No. 98-01, Center for Marine Science Research, University of North Carolina at Wilmington, Wilmington, N.C. Mallin, M.A., L.B. Cahoon, J.J. Manock, J.F. Merritt, M.H. Posey, T.D. Alphin, D.C. Parsons and T.L. Wheeler. 1998b. Environmental Quality of Wilmington and New Hanover County Watersheds, 1997-1998. CMSR Report 98-03. Center for Marine Science Research, University of North Carolina at Wilmington, Wilmington, N.C. Mallin, M.A., S.H. Ensign, D.C. Parsons and J.F. Merritt. 1999. Environmental Quality of Wilmington and New Hanover County Watersheds, 1998-1999. CMSR Report No. 99-02. Center for Marine Science Research, University of North Carolina at Wilmington, Wilmington, N.C. Mallin, M.A. and T.L. Wheeler. 2000. Nutrient and fecal coliform discharge from coastal North Carolina golf courses. Journal of Environmental Quality 29:979-986. Mallin, M.A., S.H. Ensign, D.C. Parsons, V.L. Johnson and J.F. Merritt. 2000a. Environmental Quality of Wilmington and New Hanover County Watersheds, 1999- 2000. CMSR Report No. 00-02. Center for Marine Science, University of North Carolina at Wilmington, Wilmington, N.C. Mallin, M.A., K.E. Williams, E.C. Esham and R.P. Lowe. 2000b. Effect of human development on bacteriological water quality in coastal watersheds. Ecological Applications 10:1047-1056. Mallin, M.A., L.B. Cahoon, R.P. Lowe, J.F. Merritt, R.K. Sizemore and K.E. Williams. 2000c. Restoration of shellfishing waters in a tidal creek following limited dredging. Journal of Coastal Research 16:40-47. Mallin, M.A., L.B. Cahoon, M.H. Posey, L.A. Leonard, D.C. Parsons, V.L. Johnson, E.J. Wambach, T.D. Alphin, K.A. Nelson and J.F. Merritt. 2002a. Environmental Quality of Wilmington and New Hanover County Watersheds, 2000-2001. CMS Report 02- 85 01, Center for Marine Science, University of North Carolina at Wilmington, Wilmington, N.C. Mallin, M.A., S.H. Ensign, T.L. Wheeler and D.B. Mayes. 2002b. Pollutant removal efficacy of three wet detention ponds. Journal of Environmental Quality 31:654-660. Mallin, M.A., L.B. Cahoon, M.H. Posey, D.C. Parsons, V.L. Johnson, T.D. Alphin and J.F. Merritt. 2003. Environmental Quality of Wilmington and New Hanover County Watersheds, 2001-2002. CMS Report 03-01, Center for Marine Science, University of North Carolina at Wilmington, Wilmington, N.C. Mallin, M.A., H.A. CoVan and D.H. Wells. 2003. Water Quality Analysis of the Mason Inlet Relocation Project. CMS Report 03-02. Center for Marine Science, University of North Carolina at Wilmington, Wilmington, N.C. Mallin, M.A., L.B. Cahoon, M.H. Posey, V.L. Johnson, T.D. Alphin, D.C. Parsons and J.F. Merritt. 2004. Environmental Quality of Wilmington and New Hanover County Watersheds, 2002-2003. CMS Report 04-01, Center for Marine Science, University of North Carolina at Wilmington, Wilmington, N.C. NCDEHNR. 1996. Water Quality Progress in North Carolina, 1994-1995 305(b) Report. Report No. 96-03. North Carolina Department of Environment, Health, and Natural Resources, Division of Water Quality. Raleigh, N.C. Parsons, T.R., Y. Maita and C.M. Lalli. 1984. A Manual of Chemical and Biological Methods for Seawater Analysis. Pergamon Press, Oxford. 173 pp. Schlotzhauer, S.D. and R.C. Littell. 1987. SAS system for elementary statistical analysis. SAS Institute, Inc., SAS Campus Dr., Cary, N.C. U.S. EPA. 1997. Methods for the Determination of Chemical Substances in Marine and Estuarine Environmental Matrices, 2nd Ed. EPA/600/R-97/072. National Exposure Research Laboratory, Office of Research and Development, U.S. Environmental Protection Agency, Cincinnati, Ohio. US EPA. 2004. National Coastal Condition Report II. EPA-620/R-03/002. United States Environmental Protection Agency, Office of Research and Development, Office of Water, Washington, D.C. Welschmeyer, N.A. 1994. Fluorometric analysis of chlorophyll a in the presence of chlorophyll b and phaeopigments. Limnology and Oceanography 39:1985-1993. 86 16.0 Acknowledgments Funding for this research was provided by New Hanover County, the City of Wilmington, the North Carolina Clean Water Management Trust Fund, the US EPA 319 Program through North Carolina State University, and the University of North Carolina at Wilmington. For project facilitation and helpful information we thank Dexter Hayes, Matt Hayes, David Mayes, Chris O’Keefe, Ed Beck and Dave Weaver. For field and laboratory assistance we thank Matt McIver, Brad Rosov, Rena Spivey, Kimberly Duernberger and Cinnamon Williams 87 17.0 Appendix A. North Carolina Water Quality standards for selected parameters (NCDEHNR 1996). _____________________________________________________________________ Parameter Standard _____________________________________________________________________ Dissolved oxygen 5.0 ppm (mg/L) Turbidity 25 NTU (tidal saltwater) 50 NTU (freshwater) Fecal coliform counts 14 CFU/100 mL (shellfishing waters), and more than 10% of the samples cannot exceed 43 CFU/100 mL. 200 CFU/100 mL (human contact waters) Chlorophyll a 40 ppb (mg/L) _____________________________________________________________________ CFU = colony-forming units mg/L = milligrams per liter = parts per million mg/L = micrograms per liter = parts per billion 88 18.0 Appendix B. UNCW ratings of sampling stations in Wilmington and New Hanover County tidal creek watersheds based on August 2004 – July 2005 data for tidal creeks and January -September 2005 data for Wilmington watersheds, where available, for chlorophyll a, dissolved oxygen, turbidity, and fecal coliform bacteria based on North Carolina state chemical standards for freshwater or tidal saltwater. _____________________________________________________________________ G (good quality) – state standard exceeded in < 10% of the measurements F (fair quality) – state standard exceeded in 11-25% of the measurements P (poor quality) – state standard exceeded in >25% of the measurements _____________________________________________________________________ Watershed Station Chlor a DO Turbidity Fecal coliforms* Barnard’s Creek BNC-RR G P G P Bradley Creek BC-CA G P G P BC-CR G G G - BC-SB G G G - BC-SBU G G G - BC-NB G F G - BC-NBU G G G - BC-76 G G G - Burnt Mill Creek BMC-KA1 G P G P BMC-KA3 G P G P BMC-AP1 G G F P BMC-AP3 P G G F BMC-WP G P G P BMC-PP F P G P Futch Creek FC-4 G G G G FC-6 G G G G FC-8 G G G G FC-13 G G G G FC-17 G G G G FOY G G G G Greenfield Lake GL-LC G P G P GL-JRB F P G P GL-LB G P G P GL-2340 P P G F GL-YD P F G F GL-P P G G P 89 Watershed Station Chlor a DO Turbidity Fecal coliforms* Hewletts Creek** HC-M G G G F HC-2 G G G G HC-3 G G G G HC-NWB G P G F NB-GLR G F G P MB-PGR G G G P SB-PGR G P G F PVGC-9 G G G P DB-1 G P G P DB-2 G P G P DB-3 G G G P DB-4 G G G P Howe Creek HW-M G G G G HW-FP G G G G HW-GC G G G G HW-GP G F G F HW-DT G G G P Motts Creek MOT-RR G P G P Pages Creek PC-M G G G - PC-BDDS G G G - PC-BDUS G F G - Smith Creek SC-23 G P G F SC-CH G P G G Whiskey Creek WC-NB G G G - WC-SB G G G - WC-MLR G G G - WC-AB G G G - WC-MB G G G - _____________________________________________________________________ *fecal coliform category used here is based on the human contact standard of 200 CFU/100 mL, not the shellfishing standard of 14 CFU/100 mL. **These ratings are based only on the results of the regular monthly sampling program. The July sewage spill temporarily led to excessive July fecal coliform counts and algal blooms, and low dissolved oxygen. 90 19.0 Appendix C. GPS coordinates for New Hanover County Tidal Creek stations and the Wilmington Watersheds Project sampling stations. _____________________________________________________________________ Watershed Station GPS coordinates Barnard’s Creek BNC-TR N 34.16823 W 77.93218 BNC-CB N 34.15867 W 77.91190 BNC-EF N 34.16937 W 77.92485 BNC-AW N 34.16483 W 77.92577 BNC-RR N 34.15873 W 77.93795 Bradley Creek BC-CA N 34.23257 W 77.86658 BC-CR N 34.23077 W 77.85235 BC-SB N 34.21977 W 77.84578 BC-SBU N 34.21725 W 77.85410 BC-NB N 34.22150 W 77.84405 BC-NBU N 34.23265 W 77.92362 BC-76 N 34.21473 W 77.83357 Burnt Mill Creek BMC-KA1 N 34.22207 W 77.88506 BMC-KA3 N 34.22280 W 77.88601 BMC-AP1 N 34.22927 W 77.86658 BMC-AP2 N 34.22927 W 77.89792 BMC-AP3 N 34.22927 W 77.90143 BMC-WP N 34.24083 W 77.92419 BMC-PP N 34.24252 W 77.92510 Futch Creek FC-4 N 34.30127 W 77.74635 FC-6 N 34.30298 W 77.75070 FC-8 N 34.30423 W 77.75415 FC-13 N 34.30352 W 77.75790 FC-17 N 34.30378 W 77.76422 FOY N 34.30705 W 77.75707 Greenfield Lake GL-SS1 N 34.19963 W 77.92447 GL-SS2 N 34.20038 W 77.92952 GL-LC N 34.20752 W 77.92980 GL-JRB N 34.21260 W 77.93140 GL-LB N 34.21445 W 77.93553 GL-2340 N 34.19857 W 77.93560 GL-YD N 34.20702 W 77.93120 GL-P N 34.21370 W 77.94362 91 Hewletts Creek HC-M N 34.18230 W 77.83888 HC-2 N 34.18723 W 77.84307 HC-3 N 34.19023 W 77.85083 HC-NWB N 34.19512 W 77.86155 NB-GLR N 34.19783 W 77.86317 MB-PGR N 34.19807 W 77.87088 SB-PGR N 34.19025 W 77.86472 PVGC-9 N 34.19165 W 77.89175 DB-1 N 34.1764 W 77.8775 DB-2 N 34.1781 W 77.8805 DB-3 N 34.1799 W 77.8798 DB-4 N 34.1789 W 77.8752 Howe Creek HW-M N 34.24765 W 77.78718 HW-FP N 34.25443 W 77.79488 HW-GC N 34.25448 W 77.80512 HW-GP N 34.25545 W 77.81530 HW-DT N 34.25562 W 77.81952 Motts Creek MOT-RR N 34.15867 W 77.91605 Pages Creek PC-M N 34.27008 W 77.77133 PC-OL N 34.27450 W 77.77567 PC-CON N 34.27743 W 77.77763 PC-OP N 34.28292 W 77.78032 PC-LD N 34.28067 W 77.78495 PC-BDDS N 34.28143 W 77.79417 PC-WB N 34.27635 W 77.79582 PC-BDUS N 34.27732 W 77.80153 PC-H N 34.27508 W 77.79813 Smith Creek SC-23 N 34.25795 W 77.91967 SC-CH N 34.25897 W 77.93872 Upper and Lower UCF-PS N 34.24205 W 77.94838 Cape Fear LCF-GO N 34.21230 W 77.98603 Whiskey Creek WC-NB N 34.16803 W 77.87648 WC-SB N 34.15935 W 77.87470 WC-MLR N 34.16013 W 77.86633 WC-AB N 34.15967 W 77.86177 WC-MB N 34.15748 W 77.85640 _____________________________________________________________________ 92 20.0 Appendix D. University of North Carolina at Wilmington reports and papers concerning water quality in New Hanover County’s tidal creeks. Reports Merritt, J.F., L.B. Cahoon, J.J. Manock, M.H. Posey, R.K. Sizemore, J. Willey and W.D. Webster. 1993. Futch Creek Environmental Analysis Report. Center for Marine Science Research, University of North Carolina at Wilmington, Wilmington, N.C. Mallin, M.A., L.B. Cahoon, E.C. Esham, J.J. Manock, J.F. Merritt, M.H. Posey and R.K. Sizemore. 1994. Water Quality in New Hanover County Tidal Creeks, 1993-1994. Center for Marine Science Research, University of North Carolina at Wilmington, Wilmington, N.C. 62 pp. Mallin, M.A., L.B. Cahoon, J.J. Manock, J.F. Merritt, M.H. Posey, T.D. Alphin and R.K. Sizemore. 1995. Water Quality in New Hanover County Tidal Creeks, 1994-1995. Center for Marine Science Research, University of North Carolina at Wilmington, Wilmington, N.C. 67 pp. Mallin. M.A., L.B. Cahoon, J.J. Manock, J.F. Merritt, M.H., Posey, R.K. Sizemore, T.D. Alphin, K.E. Williams and E.D. Hubertz. 1996. Water Quality in New Hanover County Tidal Creeks, 1995-1996. Center for Marine Science Research, University of North Carolina at Wilmington, Wilmington, N.C. 67 pp. Mallin, M.A., L.B. Cahoon, J.J. Manock, J.F. Merritt, M.H. Posey, R.K. Sizemore, W.D. Webster and T.D. Alphin. 1998. A Four-Year Environmental Analysis of New Hanover County Tidal Creeks, 1993-1997. CMSR Report No. 98-01, Center for Marine Science Research, University of North Carolina at Wilmington, Wilmington, N.C. Mallin, M.A., L.B. Cahoon, J.J. Manock, J.F. Merritt, M.H. Posey, T.D. Alphin, D.C. Parsons and T.L. Wheeler. 1998. Environmental Quality of Wilmington and New Hanover County Watersheds, 1997-1998. CMSR Report 98-03. Center for Marine Science Research, University of North Carolina at Wilmington, Wilmington, N.C. Mallin, M.A., S.H. Ensign, D.C. Parsons and J.F. Merritt. 1999. Environmental Quality of Wilmington and New Hanover County Watersheds, 1998-1999. CMSR Report No. 99-02. Center for Marine Science Research, University of North Carolina at Wilmington, Wilmington, N.C. Mallin, M.A., L.B. Cahoon, S.H. Ensign, D.C. Parsons, V.L. Johnson and J.F. Merritt. 2000. Environmental Quality of Wilmington and New Hanover County Watersheds, 1999-2000. CMS Report No. 00-02. Center for Marine Science, University of North Carolina at Wilmington, Wilmington, N.C. Mallin, M.A., L.B. Cahoon, M.H. Posey, L.A. Leonard, D.C. Parsons, V.L. Johnson, E.J. Wambach, T.D. Alphin, K.A. Nelson and J.F. Merritt. 2002. Environmental Quality of Wilmington and New Hanover County Watersheds, 2000-2001. CMS Report 02-01, 93 Center for Marine Science, University of North Carolina at Wilmington, Wilmington, N.C. Mallin, M.A., H.A. CoVan and D.H. Wells. 2003. Water Quality Analysis of the Mason inlet Relocation Project. CMS Report 03-02. Center for Marine Science, University of North Carolina at Wilmington, Wilmington, N.C. Mallin, M.A., L.B. Cahoon, M.H. Posey, D.C. Parsons, V.L. Johnson, T.D. Alphin and J.F. Merritt. 2003. Environmental Quality of Wilmington and New Hanover County Watersheds, 2001-2002. CMS Report 03-01, Center for Marine Science, University of North Carolina at Wilmington, Wilmington, N.C. Mallin, M.A., L.B. Cahoon, M.H. Posey, V.L. Johnson, T.D. Alphin, D.C. Parsons and J.F. Merritt. 2004. Environmental Quality of Wilmington and New Hanover County Watersheds, 2002-2003. CMS Report 04-01, Center for Marine Science, University of North Carolina at Wilmington, Wilmington, N.C. Mallin, M.A., H.A. Wells and M.R. McIver. 2004. Baseline Report on Bald Head Creek Water Quality. CMS Report No. 04-03, Center for Marine Science, University of North Carolina at Wilmington, Wilmington, N.C. Mallin, M.A., H.A. Wells, T.A. MacPherson, T.D. Alphin, M.H. Posey and R.T. Barbour. 2004. Environmental Assessment of Surface Waters in the Town of Carolina Beach. CMS Report No. 04-02, Center for Marine Science, University of North Carolina at Wilmington, Wilmington, N.C. Mallin, M.A., L.B. Cahoon, M.H. Posey, V.L. Johnson, D.C. Parsons, T.D. Alphin, B.R. Toothman and J.F. Merritt. 2005. Environmental Quality of Wilmington and New Hanover County Watersheds, 2003-2004. CMS Report 05-01, Center for Marine Science, University of North Carolina at Wilmington, Wilmington, N.C. Peer-Reviewed Journal Papers Mallin, M.A., E.C. Esham, K.E. Williams and J.E. Nearhoof. 1999. Tidal stage variability of fecal coliform and chlorophyll a concentrations in coastal creeks. Marine Pollution Bulletin 38:414-422. Mallin, M.A. and T.L. Wheeler. 2000. Nutrient and fecal coliform discharge from coastal North Carolina golf courses. Journal of Environmental Quality 29:979-986. Mallin, M.A., K.E. Williams, E.C. Esham and R.P. Lowe. 2000. Effect of human development on bacteriological water quality in coastal watersheds. Ecological Applications 10:1047-1056. Mallin, M.A., L.B. Cahoon, R.P. Lowe, J.F. Merritt, R.K. Sizemore and K.E. Williams. 2000. Restoration of shellfishing waters in a tidal creek following limited dredging. Journal of Coastal Research 16:40-47. 94 Mallin, M.A., J.M. Burkholder, L.B. Cahoon and M.H. Posey. 2000. The North and South Carolina coasts. Marine Pollution Bulletin 41:56-75. Mallin, M.A., S.H. Ensign, M.R. McIver, G.C. Shank and P.K. Fowler. 2001. Demographic, landscape, and meteorological factors controlling the microbial pollution of coastal waters. Hydrobiologia 460:185-193. Mallin, M.A., S.H. Ensign, T.L.Wheeler and D.B. Mayes. 2002. Pollutant removal efficacy of three wet detention ponds. Journal of Environmental Quality 31:654-660. Posey, M.H., T.D. Alphin, L.B. Cahoon, D.G. Lindquist, M.A. Mallin and M.E. Nevers. 2002, Resource availability versus predator control: questions of scale in benthic infaunal communities. Estuaries 25:999-1014. Cressman, K.A., M.H. Posey, M.A. Mallin, L.A. Leonard and T.D. Alphin. 2003. Effects of oyster reefs on water quality in a tidal creek estuary. Journal of Shellfish Research 22:753-762. Mallin, M.A. and A.J. Lewitus. 2004. The importance of tidal creek ecosystems. Journal of Experimental Marine Biology and Ecology 298:145-149. Mallin, M.A., D.C. Parsons, V.L. Johnson, M.R. McIver and H.A. CoVan. 2004. Nutrient limitation and algal blooms in urbanizing tidal creeks. Journal of Experimental Marine Biology and Ecology 298:211-231. Nelson, K.A., L.A. Leonard, M.H. Posey, T.D. Alphin and M.A. Mallin. 2004. Transplanted oyster (Crassostrea virginica) beds as self-sustaining mechanisms for water quality improvement in small tidal creeks. Journal of Experimental Marine Biology and Ecology 298:347-368. Mallin, M.A., S.H. Ensign, D.C. Parsons, V.L. Johnson, J.M. Burkholder and P.A. Rublee. 2005. Relationship of Pfiesteria spp. and Pfiesteria-like organisms to environmental factors in tidal creeks draining urban watersheds. pp 68-70 in Steidinger, K.A., J.H. Landsberg, C.R. Tomas and G.A. Vargo, (Eds.) XHAB, Proceedings of the Tenth Conference on Harmful Algal Blooms, 2002, Florida Fish and Wildlife Conservation Commission, Florida Institute of Oceanography, and Intergovernmental Commission of UNESCO.