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1998-1999 Final Report ENVIRONMENTAL QUALITY OF WILMINGTON AND NEW HANOVER COUNTY WATERSHEDS 1998-1999 by Michael A. Mallin, Scott H. Ensign, Douglas C. Parsons and James F. Merritt CMSR Report 99-02 Center for Marine Science Research University of North Carolina at Wilmington Wilmington, N.C. 28403 December, 1999 Funded by: City of Wilmington New Hanover County Northeast New Hanover Conservancy Executive Summary This report represents combined results of Year 6 of the New Hanover County Tidal Creeks Project and Year 2 of the Wilmington Watersheds Project. Water quality data are presented from a watershed perspective, regardless of political boundaries. The combined programs involved eleven watersheds and 46 sampling stations. Barnards Creek – There were no major surface water quality problems at the upper stations sampled in the Barnards Creek watershed. Incoming and outflowing water at the wet detention pond on Echo Farms Golf course were sampled, with orthophosphate, conductivity and pH all significantly higher in the stream exiting the course. Other nutrients were somewhat higher in waters exiting the course than in the inflowing waters. However, the concentrations of those nutrients were low in comparison to other area golf courses sampled, possibly because of nutrient uptake in a natural wetland through which the outfall stream passes before leaving the course. Lower Barnard’s Creek at River Road had occasional poor water quality as judged by turbidity, dissolved oxygen, and fecal coliform counts. However, a comparison station sampled in lower Mott’s Creek at River Road showed severe water quality impairment in terms of persistently high turbidity and fecal coliform counts. Bradley Creek – Turbidity was a periodic problem in this watershed, particularly downstream of construction areas in the north and south branches of Bradley Creek. Low dissolved oxygen was an occasional problem in brackish waters of the creek during summer. Elevated nitrogen and phosphorus levels enter the creek in both the north and south branches, but algal blooms were not a problem during 1998-1999. Fecal coliform pollution remains particularly problematic in Bradley Creek, especially in the south branch and in suburban streams feeding the north branch. Burnt Mill Creek – A sampling station on Burnt Mill creek at Princess Place had substandard dissolved oxygen during 27% of the sampling trips. This station also had poor microbiological water quality, exceeding the standard for human contact in nine of 11 samples. The effectiveness of Ann McCrary wet detention pond on Randall Parkway as a pollution control device improved over last year. The pond led to significant reductions in ammonium, nitrate, conductivity and fecal coliform bacteria levels. However, all water quality parameters indicated a subsequent worsening of the creek from where it exited the pond to the downstream Princess Place sampling station. Analysis of EPA priority pollutant metals showed concentrations of copper, lead, and zinc that were potentially harmful to aquatic life at the Princess Place sampling site. Futch Creek – Futch Creek maintained good microbiological water quality, as it has since channel dredging at the mouth occurred in 1995 and 1996. Algal blooms were not a problem in 1998-1999. Periodic low summer dissolved oxygen concentrations were the only problems noted this past year. A series of bioassay experiments was conducted in 1998-1999 to determine what nutrient most controlled formation of algal blooms in Futch Creek. Results from both an upstream and a downstream station demonstrated that nitrogen was the controlling, or limiting, nutrient in spring and summer. Thus, efforts to keep nitrogen inputs at low levels should keep phytoplankton blooms from occurring in Futch Creek. Greenfield Lake – The three tributaries of Greenfield Lake (near Lake Branch Drive, Jumping Run Branch, and Lakeshore Commons Apartments) all suffered from low dissolved oxygen problems on numerous occasions. All three of these tributaries also had frequent high fecal coliform counts, and maintained geometric mean counts in excess of the state standard for human contact waters. The stream near Lakeshore Commons also maintained high nitrate and phosphate concentrations. Stations within the lake all experienced algal blooms at times, consisting mainly of green and blue- green species. Generally, nutrient loading was highest at a station (GL-2340) located in the south end that receives several urban and suburban inputs. Nutrient addition bioassays were carried out in fall, spring, and summer to determine what nutrient (nitrogen or phosphorus) was most limiting to algal growth. In most cases nitrogen was the principal limiting nutrient in all three areas of the lake tested. Thus, efforts to reduce inputs of nitrogen, primarily nitrate, should be undertaken to reduce the persistent algal bloom formation in Greenfield Lake. A large regional wet detention pond on the tributary Silver Stream did a very good job of reducing pollutant loads to the lake from this drainage. Statistically significant reductions in nitrate, total nitrogen, orthophosphate, total phosphorus, conductivity, and fecal coliform bacteria were all realized. The design of this pond consists of two interconnected basins containing large amounts of diverse aquatic vegetation, with most inputs directed into the upper basin. This could serve as a potential model for future pond design. Analysis of EPA priority pollutant metals from Greenfield Lake sediments showed that GL-YD, located in the lake near the terminus of Yaupon Drive, had potentially harmful levels of arsenic, chromium, copper, lead and zinc, and lead levels were also high in sediments at the park (GL-P). Hewletts Creek – This creek receives high nutrient loading in its three upper branches, with consequent periodic algal blooms especially in the south branch near Pine Grove Road. The middle branch had the highest nutrient concentrations, largely derived from two golf courses. Low dissolved oxygen occurred in this system in July, August, and September. Howe Creek – Lower Howe Creek near the ICW maintained generally good water quality. Nutrient loading and algal bloom problems were most severe near and upstream of the Graham Pond input area. Turbidity and low dissolved oxygen were problems in the upper areas of Howe Creek. Land clearing and construction activities in the upper watershed are undoubtedly the cause of non-point source pollution to the upper creek. A series of nutrient addition bioassays indicated that, with the exception of early spring, nitrogen was the principal limiting nutrient in Howe Creek. Thus, efforts to reduce nitrate inputs to the creek should result in reduced incidents of algal bloom formation. Pages Creek – This creek maintained generally good water quality during 1998-1999. Nutrient loading and phytoplankton growth was low to moderate, even at the most anthropogenically-impacted stations. However, there was periodic hypoxia in warmer months, particularly at a station draining upper Bayshore Drive (PC-BDUS -hypoxia on five of 12 sampling occasions). Smith Creek – Turbidity was problematic at all three stations sampled in this watershed. Runoff from highway construction and ditching and draining of wetlands near Smith Creek parkway were contributing factors to this. Mean and maximum turbidity levels were higher in Smith Creek than in the nearby Northeast Cape Fear River, indicating the source of the turbidity was along the creek, rather than the river. Nutrient concentrations were elevated in the creek compared with most other nearby watershed sites, but algal blooms were not a problem in Smith Creek. However, fecal coliform bacterial counts exceeded the state standard for human contact waters at all three sites on a number of occasions. Upper and Lower Cape Fear Watersheds – Water quality at the one station on the stream draining the Upper Cape Fear watershed (behind the Wilmington police station) had high nitrate concentrations, although they were lower than in 1997-1998. In contrast to 1997-1998, geometric mean fecal coliform concentrations exceeded the state standard for human contact waters. Use Support Ratings – The NC Division of Water Quality utilizes an EPA-based system to determine if a water body supports its designated use (described in Appendix C). We applied these standards to the water bodies described in this report, based on the past two years of data. Our analysis shows that (based on fecal coliform standards for human contact waters) upper Barnards Creek is partially supporting while lower Barnard’s Creek is non-supporting. Bradley Creek is non-supporting throughout, except near the ICW. Futch Creek is fully supporting for fecal coliform bacteria, including for shellfishing in the lower four stations. Greenfield Lake and its tributaries are non-supporting throughout. Upper Howe Creek is non-supporting while lower Howe Creek is fully supporting for human contact (although not for shellfishing). Lower Motts Creek is non-supporting, and all of Smith Creek is non-supporting. We also list support categories for dissolved oxygen and turbidity in Appendix C. Table of Contents 1.0 Introduction 1 1.1 Methods 1 2.0 Barnards Creek 4 3.0 Bradley Creek 8 4.0 Burnt Mill Creek 12 5.0 Futch Creek 15 6.0 Greenfield Lake 19 7.0 Hewletts Creek 23 8.0 Howe Creek 28 9.0 Pages Creek 34 10.0 Smith Creek 36 11.0 Upper and Lower Cape Fear 38 16.0 References Cited 72 17.0 Acknowledgments 75 18.0 Appendix A: Sediment metals harmful concentrations 76 19.0 Appendix B: Selected N.C. water quality standards 77 20.0 Appendix C: UNCW reports related to tidal creeks 78 Cover photo: Algal bloom on Greenfield Lake, Wilmington, N.C. (by M. Mallin) 1.0 Introduction Since 1993, scientists at the UNC Wilmington Center for Marine Science Research have been 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). Additionally, in October 1997 the Center for Marine Science Research 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. Additionally, certain sites were analyzed for sediment heavy metals concentrations (EPA Priority Pollutants). Last year we produced the first combined Tidal Creeks – City Watersheds report (Mallin et al. 1998b). In the present report we present results of continuing studies from 1998-1999 in the tidal creek complex and the City of Wilmington watersheds (Fig. 1.1). 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, total nitrogen (TN), total phosphorus (TP), and suspended solids. An important additional study carried out last year was a series of nutrient addition bioassays designed to determined what nutrients (nitrogen or phosphorus) limit phytoplankton production (algal bloom formation) in Greenfield Lake. Nutrient limitation bioassays were also carried out in Howe and Futch Creeks. 1.1 Methods Field parameters were measured at each site using either a YSI 6920 Multiparameter Water Quality Probe (sonde) linked to a YSI 610 display unit, or a Solomat 803PS Multiparameter sonde coupled with a Solomat 803 datalogger. 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. For the five 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 1.0 µM glass fiber filters using a manifold with three funnels. The pooled filtrate was stored frozen until analysis. Nitrate+nitrite and orthophosphate were analyzed using a Technicon 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 B. The analytical method used to measure chlorophyll a is described in Welschmeyer (1994) and US EPA (1997). Chlorophyll a concentrations were determined directly from the 1.0 micron 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 containing drierite, and stored in the freezer. During the analytical process, the glass filters were separately immersed in 10 ml of a 90% acetone solution for 24 hours. The acetone extracts the chlorophyll a from the glass filters into solution. Each solution was then analyzed for chlorophyll a concentrations using a Turner AU-10 fluorometer. This method uses an optimal combination of excitation and emission bandwidths which reduces the errors inherent in the acidification technique. Samples were collected monthly within the Wilmington City watersheds from October 1998 through July 1999. Field measurements were taken as indicated above. Nutrients (nitrate, ammonium, total Kjeldahl nitrogen (TKN), total nitrogen (TN), orthophosphate, and total phosphorus (TP)) 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-CMSR as described above. Sediment analyses for EPA priority pollutants were run in triplicate from eight sites in the Wilmington watershed system. EPA methods were used for digestion (Method 3050B) and ICP analysis (Method 200.7). Guidelines for what various sediment metals concentrations represent in terms of potential harm to aquatic life are presented in Appendix A. For three detention ponds (Ann McCrary Pond on Burnt Mill Creek, Silver Stream Pond in the Greenfield Lake watershed, and the main pond on Echo Farms Golf Course in the Barnards Creek watershed) we were able to obtain 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). 2.0 Barnards Creek The water quality of lower Barnard’s Creek is becoming an important issue as a major housing development is commencing construction activities in the area east of River Road and between Barnard’s and Mott’s Creeks. We report data collected at a station located on Barnard’s Creek at River Road (BC-RR) for the past year, and also include a year’s worth of data collected from 1997-1998 on Mott’s Creek at River Road (MC-RR). The BNC-TR site in Barnard’s Creek watershed drains a wooded area and was considered a control site for nutrients and physical parameters (Fig.2.1). The BNC- CB site is near Carolina Beach Road and drains an area hosting construction activities. Whereas last year inorganic nutrients (nitrate, ammonium, and orthophosphate) and turbidity were all considerably larger at BNC-CB than BNC-TR, levels have decreased at BNC-CB and only nitrate and ammonia are higher there than at the control site. We also note that the control is now near an active road construction area on Titanium Road, or Independence Road extension (Table 2.1). Total N and P were somewhat larger at BNC-TR than BNC-CB, reflecting the larger organic nutrient quantity found in the wooded stream site. The Barnard’s Creek watershed hosts the Echo Farms Country Club. Much of the course drainage enters a large (1.75 acre) pond, which discharges through a wooded wetland. We sampled a pond input station draining a suburban area (BNC-EF) and the pond outflow exiting the riparian wetland (BNC-AW). A primary goal was to assess the efficacy of golf course nutrient removal by this pond during the period August 1998 – July 1999. Golf course loading led to significant increases in orthophosphate only, among nutrients (Table 2.2), whereas last year increases were seen in nitrate, ammonium, and TP. There were input-output increases in both conductivity and pH, as well (Fig.2.2). We also point out that overall concentrations of inorganic nutrients in the output stream were low in comparison with output from other area golf courses (Mallin and Wheeler 2000). The design of a wet detention pond followed by a natural wetland area does a good job of keeping nutrient concentrations low in the course outfall. Mott’s Creek 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. We report here water quality data from the two estuarine sites on River Road. BNC-RR had average salinity of 4.9 ppt with a range of 0.3-15.7 ppt; MC-RR had average salinity of 2.8 ppt with a range of 0-18.9 ppt. Lower Barnard’s Creek had dissolved oxygen levels below 5 ppm on three occasions out of 11 samples in 1998-1999. Turbidity on average was moderately high, but below the state standard. Fecal coliform counts exceeded the state standard three of 11 occasions. The lower Mott’s Creek station demonstrated poor water quality, based on state standards, in 1997-1998 (Table 2.1). Dissolved oxygen levels were below 5.0 ppm three times out of 11 samples, and turbidity exceeded the state estuarine standard of 25 NTU nine out of 11 times. Fecal coliform concentrations at lower Mott’s Creek exceeded the state standard of 200 CFU/ 100 mL six out of 11 times, and the geometric mean was 250 CFU/100 mL. Thus, this creek already has severe water quality problems. Development activities upstream, if not done in an environmentally-sound manner, will only lead to further degradation of both Mott’s and Barnard’s Creeks. Table 2.1. Mean and standard deviation of water quality parameters in Barnard’s Creek watershed, October 1998-July 1999. A station on Mott’s Creek at River Road is included for comparison. Fecal coliforms as geometric mean; N/P ratio as median. _____________________________________________________________________ Parameter BNC-TR BNC-CB BNC-RR MC-RR (1997-98) _____________________________________________________________________ DO (mg/L) 6.5 (2.1) 6.6 (2.3) 7.4 (2.2) 5.9 (1.5) Turbidity (NTU) 3.8 (4.2) 6.9 (3.5) 18.4 (5.7) 31.1 (15.4) TSS (mg/L) 4.6 (3.2) 2.8 (1.9) 16.3 (7.2) 11.8 (10.8) Nitrate (mg/L) 0.022 (0.028) 0.043 (0.027) 0.191 (0.138) 0.185 (0.119) Ammon. (mg/L) 0.019 (0.018) 0.031 (0.023) 0.122 (0.072) 0.073 (0.053) TN (mg/L) 0.486 (0.489) 0.339 (0.227) 0.816 (0.347) 0.996 (0.367) Phosphate (mg/L) 0.019 (0.013) 0.012 (0.008) 0.091 (0.036) 0.051 (0.024) TP (mg/L) 0.038 (0.013) 0.033 (0.024) 0.121 (0.025) 0.074 (0.016) N/P molar ratio 5.3 15.5 7.6 9.0 Chlor. a (µg/L) 1.3 (0.8) 1.1 (0.7) 3.8 (3.2) 7.4 (9.5) Fec. col.(/100 mL) 154 173 59 250 _____________________________________________________________________ Table 2.2 Mean and standard deviation of water quality parameters in Barnard’s Creek watershed, including a comparison of pollutant concentrations in input (BNC-EF) and output (BNC-AW) waters of wet detention pond on Echo Farms Country Club, August 1998-July 1999. _____________________________________________________________________ Parameter BNC-EF BNC-AW _____________________________________________________________________ DO (mg/L) 6.2 (1.5) 6.3 (1.7) Cond. (µS/cm) 164 (16) 273 (39)** pH 7.2 (0.3) 7.4 (0.3)** Turbidity (NTU) 4.9 (6.3) 4.3 (3.4) TSS (mg/L) 4.1 (4.0) 3.4 (1.8) Nitrate (mg/L) 0.012 (0.012) 0.031 (0.030) Ammon. (mg/L) 0.017 (0.016) 0.146 (0.427) TN (mg/L) 0.394 (0.266) 0.570 (0.500) Phosphate (mg/L) 0.020 (0.011) 0.055 (0.068)** TP (mg/L) 0.045 (0.021) 0.079 (0.070) N/P molar ratio 4 4 Chlor. a (µg/L) 4.2 (7.8) 1.7 (1.4) Fec. col.(/100 mL) 92 170 _____________________________________________________________________ * Indicates significant difference between input and output concentration at p<0.05 **Indicates significant difference between input and output concentration at p<0.01 Sediment metals concentrations were assessed at the River Road bridge sites for both Barnard’s Creek (BNC-RR) and Mott’s Creek (MC-RR). The data indicated that sediment metals were below concentrations considered harmful to aquatic life at both stations (Table 2.2). Table 2.2. Mean and (standard deviation) of sediment metals concentrations in lower Barnard’s Creek at River road (BNC-RR), including a comparison with lower Mott’s Creek at River Road (MC-RR). _____________________________________________________________________ Parameter BNC-RR MC-RR _____________________________________________________________________ Al (mg/kg) 31,413 (6,277) 13,111 99,145) As (mg/kg) 5.86 (3.19) 1.75 (0.45) Cd (mg/kg) 0.02 (0) 0.02 (0) Cr (mg/kg) 45.1 (3.3) 13.5 (8.9) Cu (mg/kg) 15.75 (14.93) 12.3 (9.8) Fe (mg/kg) 26,136 (5,576) 10,639 (1,225) Pb (mg/kg) 46.53 (14.09) 46.3 (9.5) Hg (mg/kg) 0.003 (0.001) 0.005 (0.003) Ni (mg/kg) 13.30 (2.33) 4.29 (3.04) Zn (mg/kg) 88.0 (73.6) 36.9 (29.6) _____________________________________________________________________ 3.0 Bradley Creek The Bradley Creek watershed is of particular current interest as a principal location for Clean Water Trust Fund mitigation activities, including the recent purchase and renovation of Airlie Gardens by the County. This creek is one of the most polluted in New Hanover County, particularly by fecal coliform bacteria (Mallin et al. 1998). Seven stations were sampled in the past year, in both fresh and brackish waters (Fig. 3.1). Turbidity is a periodic problem in Bradley Creek (Table 3.1). Average turbidity values decreased from last year at both BC-SB and BC-NB, although the state turbidity standard was exceeded on a number of occasions at BC-NBU, near Eastwood Road, which was particularly impacted by road construction (Table 3.1). In June, July and August the downstream brackish stations periodically had hypoxic (< 5.0 mg/L) dissolved oxygen conditions. BC-CA had substandard dissolved oxygen conditions on four of 11 sampling occasions. Sediment loading and low dissolved oxygen are environmental factors that can affect habitat and impair the fishery nursery function of Bradley Creek. Table 3.1 Physical parameters at Bradley Creek sampling stations, 1999-1999. Data as mean (SD) / range. _____________________________________________________________________ Station Salinity (ppt) Turbidity (NTU) Dissolved oxygen (mg/L) _____________________________________________________________________ BC-76 31.8 (2.4) 8.9 (7.1) 6.9 (1.9) 26.9-34.5 2.2-26.2 4.1-10.6 BC-SB 9.6 (10.5) 16.8 (11.6) 7.5 (2.4) 0.7-29.0 3.1-40.5 4.0-11.6 BC-SBU 0.1 (0.0) 5.5 (3.4) 6.9 (1.7) 0.1-0.2 2.1-13.9 4.6-9.9 BC-NB 24.6 (7.3) 10.5 (6.4) 7.2 (2.9) 10.8-32.5 2.9-23.0 4.3-14.7 BC-NBU 0.1 (0.1) 18.6 (23.8) 7.7 (1.2) 0.1-0.2 1.7-80.0 6.2-9.5 BC-CR 0.1 (0.0) 3.1 (3.0) 7.7 (1.2) 0.0-0.1 0.7-8.9 6.2-10.0 BC-CA 0.1 (0.1) 13.9 (20.4) 6.0 (1.7) 0.1-0.2 2.9-73.8 3.9-8.6 _____________________________________________________________________ Nitrate concentrations were highest at stations BC-CR (draining a suburban residential area along Clear Run Drive) and BC-SBU (upper south branch) and BC-CA (draining apartment complexes and construction areas upstream). Particularly high orthophosphate levels were found at BC-CA, with somewhat elevated orthophosphate levels at both BC-SB and BC-SBU (Table 3.2). Ammonium was also elevated at BC- CA. In contrast to previous years (Mallin et al. 1998) Bradley Creek was relatively free of algal blooms in 1998-1999 (Table 3.2). Median inorganic molar N/P ratios were 7.7 for BC-76, 13.5 for BC-SB, and 11.9 for BC-NB. This indicates that phytoplankton growth at all three stations was likely nitrogen-limited, but this contrasts with 1997-1998 when very high N/P ratios prevailed in the two tributary stations. Table 3.2. Nutrient and chlorophyll a data at Bradley Creek sampling stations, 1998- 1999. Data as mean (SD) / range, nutrients in mg/L, chlorophyll a as µg/L. _____________________________________________________________________ Station Nitrate Ammonium Orthophosphate Chlorophyll a _____________________________________________________________________ BC-76 0.009 (0.007) 0.018 (0.008) 0.007 (0.027) 1.4 (0.9) 0.002-0.026 0.007-0.029 0.003-0.012 0.3-3.0 BC-SB 0.070 (0.058) 0.046 (0.028) 0.014 (0.014) 6.8 (7.1) 0.002-0.175 0.010-0.087 0.003-0.051 1.5-27.9 BC-SBU 0.126 (0.078) NA 0.009 (0.006) 1.7 (1.0) 0.041-0.320 0.004-0.024 0.6-4.4 BC-NB 0.027 (0.034) 0.044 (0.045) 0.006 (0.004) 2.1 (1.4) 0.002-0.114 0.012-0.123 0.001-0.012 0.5-4.6 BC-NBU 0.132 (0.034) NA 0.003 (0.005) 0.7 (0.4) 0.085-0.192 0.001-0.017 0.3-1.4 BC-CR 0.239 (0.020) NA 0.006 (0.005) 0.8 (0.6) 0.210-0.261 0.002-0.016 0.2-2.5 BC-CA 0.084 (0.067) 0.082 (0.047) 0.037 (0.023) 3.5 (1.7) 0.020-0.240 0.005-0.140 0.005-0.090 1.3-5.9 _____________________________________________________________________ Fecal coliform concentrations were generally high in this watershed (Table 3.3). In particular the south branch maintained geometric mean concentrations exceeding the 200 CFU/100 mL standard for human contact, and the north branch was elevated to a somewhat lesser extent. The suburban feeder station BC-CR increased fecal coliform concentrations from last year and concentrations at BC-CA were even higher (Table 3.3). Both of these stations drain into the north branch of Bradley Creek (Fig. 3.1). During 1998-1999 four stations maintained geometric mean counts in excess of the state water quality standard for human contact (Table 3.3). Bradley Creek watershed is the most highly developed watershed in New Hanover County with the greatest percent impervious surface areal coverage, a critical factor exacerbating fecal coliform pollutant loading (Mallin et al. 1998). Table 3.3. Fecal coliform abundance (geometric mean) at Bradley Creek sampling stations, August 1998-July 1999. _____________________________________________________________________ Station BC-76 BC-SB BC-SBU BC-NB BC-NBU BC-CR BC-CA GEOMEAN 7 363 393 81 155 235 616 _____________________________________________________________________ 4.0 Burnt Mill Creek The Burnt Mill Creek watershed was sampled just upstream of Ann McCrary Pond on Randall Parkway (AP1), along shore at mid-pond (AP2), about 40 m downstream of the pond outfall (AP3), and in the creek from the bridge at Princess Place (BMC-PP - Fig. 4.1). Ann McCrary Pond is a large (28.8 acres) regional wet detention pond draining 1,785 acres, with a newly-constructed apartment complex at the upper end near 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. Turbidity and suspended solids concentrations decreased from the previous year, possibly a result of cessation of the extensive apartment construction and land-clearing activities during this study. Fecal coliform concentrations entering Ann McCrary Pond at AP1 were very high, however (Table 4.1), possibly a result of increased pet waste runoff from the apartment complex. The efficiency of this pond as a pollutant removal device was mixed. Fecal coliforms were significantly reduced during passage through the pond (Table 4.1). Except for one peak in January 1999, total suspended solids and turbidity were low entering the pond this year and there was no significant difference in removal of these two parameters. In contrast to last year, both ammonium and nitrate concentrations were significantly reduced during passage through the pond this year (Table 4.1). Total nitrogen, total phosphorus, and orthophosphate were not reduced, however. It is likely that inputs of nutrients have entered the pond from suburban drainage stream midway down the pond across from our AP2 site. 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. Whereas last year peak nitrate, TN, and TP concentrations were in mid-pond, this year highest levels were generally at AP1 (Table 4.1). 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 as well, probably due to utilization of CO2 during photosynthesis in the pond. The Princess Place location experienced some water quality problems during the sample period. Dissolved oxygen was substandard on three of 11 sampling trips. The most important issue, from a public health perspective, was the excessive fecal coliform counts, which maintained a geometric mean (512 CFU/100 mL) 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 nine of 11 samples. It is notable that all nutrient species increased considerably along the passage from BMC-AP3 to the Princess Place location (Table 4.1). Table 4.1. Mean and (standard deviation) of water quality parameters in Burnt Mill Creek watershed. Fecal coliforms given as geometric mean; N/P ratio as median. _____________________________________________________________________ Parameter BMC-PP BMC-AP1 BMC-AP2 BMC-AP3 _____________________________________________________________________ DO (mg/L) 6.0 (1.7) 7.8 (1.1) 9.0 (2.2) 9.6 (1.7)** Cond. (µS/cm) 355 (67) 283 (20) 244 (54) 242 (59)* pH 7.1 (0.4) 6.5 (0.4) 6.9 (0.5) 7.2 (0.4)** Turbidity (NTU) 6.9 (4.1) 20.8 (55.8) 4.0 (2.7) 3.9 (2.6) TSS (mg/L) 7.0 (6.1) 20.6 (59.2) 2.5 (1.4) 2.7 (1.4) Nitrate (mg/L) 0.117 (0.061) 0.076 (0.048) 0.033 (0.028) 0.021 (0.023)** Ammonium (mg/L) 0.079 (0.058) 0.055 (0.030) 0.015 (0.018) 0.019 (0.020)** TN (mg/L) 0.530 (0.306) 0.400 (0.230) 0.344 (0.221) 0.340 (0.184) Phosphate (mg/L) 0.035 (0.011) 0.018 (0.015) 0.015 (0.010) 0.020 (0.014) TP (mg/L) 0.082 (0.038) 0.085 (0.113) 0.027 (0.015) 0.040 (0.025) N/P molar ratio 13 27 8 4 Fec. col. (/100 mL) 512 624 69 54** Chlor. a (µg/L) 4.9 (5.9) 2.8 (2.9) 3.0 (2.9) 3.1 (2.2) _____________________________________________________________________ * Indicates statistically significant difference between AP1 and AP3 at p<0.05 **Indicates statistically significant difference between AP1 and AP3 at p<0.01 Sediment metals were analyzed from the station (BMC-PP) where Princess Place crosses Burnt Mill Creek (Table 4.2). Concentrations of copper, lead, and zinc were at levels potentially harmful to aquatic life (see Appendix A). Table 4.2. Mean and standard deviation of sediment metals concentrations in Burnt Mill Creek at Princess Place Dr. (BMC-PP). _____________________________________________________________________ Parameter (mg/kg) BMC-PP _____________________________________________________________________ Al 13,461 (8,077) As 5.7 (2.8) Cd 0.17 (0.26) Cr 49.1 (48.8) Cu 46.9 (28.0)* Fe 8,318 (4,832) Pb 296.7 (206.4) Hg 0.002 (0) Ni 7.32 (4.45) Zn 268.0 (176.1) _____________________________________________________________________ * Bolding Indicates metal concentration exceeds either the ERL or ERM (see Appendix A) and is potentially harmful to aquatic life. 5.0 Futch Creek During 1995 and 1996 two channels were dredged in the mouth of Futch Creek (Fig. 5.1) to improve circulation and hopefully reduce fecal coliform bacterial concentrations. There was a statistically significant increase in salinity in the creek in the months following dredging (Mallin et al. 1996; Mallin et al. 2000). Salinity continued to remain relatively high even in the upper portions of the creek in 1998-1999, demonstrating the continued effectiveness of the dredging operation (Table 5.1). None of the creek stations had average turbidity exceeding the state standard of 25 NTU, and there were only two incidents where readings exceeded the turbidity standard. The months of April and July 1999 were characterized by incidences of substandard dissolved oxygen at most of the stations, with the lowest DO at FC-17 and FC-20. Table 5.1. Physical parameters at Futch Creek sampling stations, 1998-1999. Data as mean (SD) / range. _____________________________________________________________________ Station Salinity (ppt) Turbidity (NTU) Dissolved oxygen (mg/L) _____________________________________________________________________ FC-2 34.4 (1.3) 8.5 (4.4) 7.7 (2.2) 31.9-36.0 2.5-16.3 3.8-10.5 FC-4 33.8 (1.4) 7.9 (4.8) 7.9 (1.8) 31.2-35.7 3.5-18.8 4.8-10.5 FC-6 32.7 (1.7) 8.9 (4.9) 7.9 (1.9) 30.0-35.1 3.8-19.1 4.7-10.6 FC-8 31.9 (1.7) 11.9 (12.5) 7.3 (1.8) 29.7-34.1 3.2-40.9 4.2-9.5 FC-13 27.6 (2.8) 12.7 (11.7) 7.1 (1.9) 22.8-30.9 2.8-42.2 3.3-9.4 FC-17 24.0 (7.1) 8.9 (4.7) 6.9 (2.3) 4.2-30.0 3.0-16.9 3.2-9.9 FC-20 24.0 (5.0) 10.1 (4.5) 7.0 (2.0) 11.5-29.9 4.3-18.0 3.4-9.6 FOY 26.2 (4.0) 8.4 (4.0) 7.6 (2.2) 17.2-30.0 2.2-17.2 2.8-9.9 _____________________________________________________________________ Nutrient concentrations in Futch Creek were generally low, with the exception of periodic nitrate pulses in the upper stations FC-17 and FC-20 (Table 5.2). The source of these pulses has been identified as groundwater inputs entering the marsh is springs between FC-19 and FC-13 (Mallin et al. 1998b). The creek was free from algal blooms during our sampling visits (Table 5.2), even in the upper stations. Computed median inorganic N/P molar ratios were 11.5 for FC-4 (indicating potential N limitation of phytoplankton growth), but 34.0 and 45.0 for FC-17 and FOY, respectively (indicating potential P limitation of phytoplankton growth). N/P expressed no particular seasonality over the year. Table 5.2. Nutrient and chlorophyll a data at Futch Creek sampling stations, 1997- 1998. Data as mean (SD) / range, nutrients in mg/L, chlorophyll a as µg/L. _____________________________________________________________________ Station Nitrate Ammonium Orthophosphate Chlorophyll a _____________________________________________________________________ FC-2 0.006 (0.006) NA 0.003 (0.002) 1.1 (0.8) 0.001-0.018 0.001-0.006 0.2-2.5 FC-4 0.008 (0.007) 0.024 (0.014) 0.004 (0.002) 1.0 (0.7) 0.001-0.019 0.011-0.047 0.001-0.006 0.2-2.7 FC-6 0.011 (0.009) NA 0.003 (0.003) 1.2 (1.0) 0.001-0.027 0.001-0.010 0.3-3.5 FC-8 0.018 (0.015) NA 0.004 (0.003) 1.5 (1.4) 0.005-0.040 0.001-0.012 0.2-4.2 FC-13 0.056 (0.045) NA 0.006 (0.004) 3.1 (3.5) 0.005-0.140 0.001-0.012 0.2-11.2 FC-17 0.128 (0.126) 0.051 (0.027) 0.008 (0.005) 3.5 (4.9) 0.011-0.396 0.014-0.083 0.001-0.017 0.5-18.0 FC-20 0.090 (0.069) NA 0.007 (0.004) 3.5 (4.2) 0.018-0.222 0.001-0.013 0.6-15.3 FOY 0.110 (0.140) 0.043 (0.031) 0.006 (0.004) 2.4 (2.4) 0.002-0.486 0.023-0.088 0.001-0.012 0.5-8.8 _____________________________________________________________________ As reportedly previously (Mallin et al. 1996; 1998) the dredging experiment proved to be successful and the lower portion of the creek was reopened to shellfishing. During 1998-1999 the lower creek maintained excellent microbiological water quality for shellfishing (Table 5.3). The mid-creek areas had good microbiological water quality as well, and the uppermost stations continued to have fecal coliform bacterial concentrations well below those of the pre-dredging period. Table 5.3. Futch Creek fecal coliform bacteria data, including percent of samples exceeding 43 CFU per 100 mL, 1998-1999. _____________________________________________________________________ Station FC-2 FC-4 FC-6 FC-8 FC-13 FC-17 FC-20 FOY ALL Geomean 2 2 2 6 16 41 55 17 20 % > 43 /100ml 0 0 0 0 17 50 55 25 18 _____________________________________________________________________ In addition to the standard sampling described in the Methods, nutrient addition bioassays were performed on water from FC-4 and FC-17 during spring and summer. These bioassays consisted of collecting creek water in 20-L carboys, transporting them to the laboratory, and dispensing 3 L into each of 30 gallon-sized cubitainers. The cubitainers were then spiked with different nutrients (nitrate-N as 100 ppb (µg/L), nitrate- N as 50 ppb, phosphate-P as 50 ppb, phosphate-P as 25 ppb, and no additions, which was the control). All treatments were in triplicate. The cubitainers were incubated outdoors in pools covered with 2 layers of neutral-density screening to avoid photostress. The water and cubitainers were kept gently agitated with an aquarium pump. Chlorophyll a samples were collected daily for three days, with results compared statistically using SAS. Treatments yielding significantly higher chlorophyll a (p < 0.05) were considered to contain the nutrient most limiting to phytoplankton growth. Experiments conducted in May 1999 demonstrated that phytoplankton at both FC-4 and FC-17 showed statistically significant chlorophyll a increases with inputs of nitrate-N at both 100 µg/L and 50 µg/L (Fig. 5.2). While the N/P ratio was 19 at FC-4, the lack of P limitation at FC-17 during May is surprising, given the very high N/P ratio (148) computed for this station in May. Significant N limitation was likewise repeated during experiments in June and July 1999 (Figs. 5.3 and 5.4). The N/P ratios were 12 and 13 at FC-4 in June and July, and 20 at FC-17 in July. The only exception to consistent N-stimulation was a significant positive response to phosphate-P at 50 µg/L at FC-17 in June (Fig. 5.3). The N/P ratio was 34.5 during this month, indicating potential P limitation. Other general patterns included higher chlorophyll a responses at FC-17 compared with FC-4, and increasing experimental chlorophyll a concentrations temporally from May through July (Figs. 5.2; 5.3; and 5.4). The high chlorophyll response at FC-17 is a result of the higher background nutrient and chlorophyll levels (Table 5.2). The greater response in July and June compared with May is a result of increased water temperatures and daylength (more light availability). Even though there is a groundwater source of nitrate in the south branch (Mallin et al. 1998b), phytoplankton growth in Futch Creek is primarily limited by nitrogen inputs. 6.0 Greenfield Lake One of the major pollution mitigation features in the Greenfield Lake watershed is an extensive wet detention pond along the Silver Stream branch (Fig. 6.1). The pond drains approximately 280.5 acres, of which about 43% is impervious surface area. The pond is divided into a 1.25 acre upper and a 1.48 acre lower basin by a causeway pierced by three pipes connecting the flow. In early summer 1998 approximately 70% of the upper pond was covered by a mixture of floating and emergent aquatic macrophyte vegetation, with about 40% of the lower pond covered by vegetation. Principal species in the upper basin were alligatorweed Alternanthera philoxeroides, pennywort Hydrocotyle umbellate, water primrose Ludwigia leptocarpa and cattail Typha latifolia, while the lower basin vegetation was dominated by alligatorweed, water primrose, and cattail. This pond functioned very well as a nutrient removal system (Table 6.1). Particularly efficient removal of orthophosphate (80%), nitrate (83%), TP (65%) and ammonium (50%) was achieved. The decreases in nitrate, TN, orthophosphate, TP, and conductivity were all statistically significant. Turbidity and TSS were generally low at both locations this past year, and there were no statistically significant changes. Dissolved oxygen significantly increased, probably in part because of aeration while passing through the outfall. Increased oxygenation through photosynthesis was likely an important factor as well, as the significant increase in pH was probably related to increased CO2 uptake through pond photosynthesis. Passage through the pond significantly reduced fecal coliform counts by 84% (Table 6.1). Table 6.1. Comparison of pollutant concentrations in input (SS1) and output (SS2) waters of regional wet detention pond on Silver Stream, in Greenfield Lake watershed, August 1998 – July 1999. _____________________________________________________________________ Parameter SS1 SS2 _____________________________________________________________________ DO (mg/L) 5.7 (2.2) 7.8 (1.9)** Cond. (µS/cm) 207 (38) 177 (25)** pH 6.6 (0.6) 6.8 (0.6)** Turbidity (NTU) 3.5 (3.9) 4.0 (1.9) TSS (mg/L) 3.8 (4.1) 9.3 (22.0) Nitrate (mg/L) 0.23 (0.19) 0.04 (0.04)** Ammonium (mg/L) 0.06 (0.03) 0.03 (0.04) TN (mg/L) 0.73 (0.41) 0.41 (0.26)* Phosphate (mg/L) 0.10 (0.04) 0.02 (0.01)** TP (mg/L) 0.17 (0.05) 0.06 (0.02)** Chlorophyll a (µg/L) 2.5 (3.4) 4.0 (3.1) Fecal col. (CFU/100 mL) 193 31** _____________________________________________________________________ * indicates significant difference between input and output concentration at p<0.05 **Indicates significant difference between input and output concentration at p<0.01 Sediment metals were analyzed at two stations in Greenfield Lake (GL-YD and GL-P), and one tributary before entering the lake (GL-LB). Station GL-YD, in the lake near the terminus of Yaupon Dr., had some of the highest sediment metals concentrations in the Wilmington watersheds system, and several metals (As, Cr, Cu, Pb and Zn) are at concentrations known to be potentially harmful to aquatic life (Table 6.2; Appendix A). Copper and lead were also at potentially harmful levels in sediments collected from the park area (GL-P). When lead was commonly added to gasoline auto emissions were sources of this pollutant near heavily traveled roads or parking lots. However, even is there is a reservoir of lead at these sites from previous years, that cannot account for the many other elevated metals in the lake sediments at GL-YD. Concentrations at the input station GL-LB were all at safe levels (Table 6.2). Table 6.2. Mean and standard deviation of sediment metals concentrations in Greenfield Lake watershed. _____________________________________________________________________ Parameter GL-YD GL-LB GL-P _____________________________________________________________________ Al (mg/kg) 19,710 (4,539) 907 (33) 3,485 (1,352) As (mg/kg) 14.90 (1.84)* 0.31 (0.05) 2.95 (3.31) Cd (mg/kg) 0.02 (0) 0.07 (0.02) 0.02 (0) Cr (mg/kg) 180.3 (37.5) 6.0 (4.9) 11.6 (5.0) Cu (mg/kg) 118.6 (61.8) 3.1 (0.5) 85.8 (121.7) Fe (mg/kg) 8,318 (4,832) 1,519 (257) 2,103 (542) Pb (mg/kg) 278.7 (109.2) 9.6 (1.5) 68.8 (26.6) Hg (mg/kg) 0.012 (0.010) 0.002 (0) 0.002 (0) Ni (mg/kg) 13.38 (3.15) 1.52 (0.14) 2.68 (1.50) Zn (mg/kg) 222.0 (54.7) 27.7 (7.0) 61.4 (19.4) _____________________________________________________________________ * Bolding Indicates that metal concentration exceeds either the ERL or ERM (see Appendix A) and is potentially harmful to aquatic life. Three tributaries of Greenfield Lake were sampled for physical, chemical, and biological parameters (Table 6.3, Fig. 6.1). Two of the tributaries suffered from extreme hypoxia, with both GL-LB (creek at Lake Branch Drive) and GL-LC (creek beside Lakeview Commons) showing average concentrations below the state standard (DO < 5.0 mg/L). Dissolved oxygen levels were substandard five of 12 times at GL-JRB, seven of 12 times at GL-LC, and 10 of 12 times at GL-LB. Turbidity and suspended solids were generally low in the tributary stations (Table 6.3). Nitrate concentrations were highest at GL-LC, moderate at GL-LB and lowest at GL-JRB (Table 6.3). Additional samples were collected in September and October upstream of GL-LC near the Wilmington Athletic club where the stream emerges from passing under 17th St. Both samples showed nitrate levels of approximately 0.9 mg/L, somewhat higher than levels downstream at GL-LC (0.7-0.8 mg/L) during those months. Ammonium concentrations were highest at GL-LC, followed in turn by GL-LB and GL-JRB. Orthophosphate concentrations were high at GL-LC, ranging to moderate at GL-LB and GL-JRB. Overall, GL-LC maintained the highest nutrient concentrations of any of the input streams tested. 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) eight of 12 times at GL-LB, eight of 12 times at GL-LC, and six of 12 times at GL-JRB. Chlorophyll a levels were generally low in these streams (Table 6.3). Table 6.3. Mean and (standard deviation) of water quality parameters in tributary stations of Greenfield Lake. Fecal coliforms presented as geometric mean; N/P ratio as median. _____________________________________________________________________ Parameter GL-JRB GL-LB GL-LC _____________________________________________________________________ DO (mg/L) 5.4 (2.5) 2.6 (2.2) 4.3 (2.8) Turbidity (NTU) 3.4 (1.7) 4.4 (3.5) 2.6 (1.5) TSS (mg/L) 2.8 (1.4) 2.7 (1.5) 2.5 (1.6) Nitrate (mg/L) 0.083 (0.059) 0.180 (0.169) 0.572 (0.381) Ammonium (mg/L) 0.048 (0.037) 0.101 (0.095) 0.085 (0.064) TN (mg/L) 0.631 (0.369) 0.603 (0.340) 0.959 (0.539) Phosphate (mg/L) 0.038 (0.020) 0.037 (0.016) 0.060 (0.060) TP (mg/L) 0.095 (0.085) 0.073 (0.028) 0.098 (0.062) N/P molar ratio 8 13 42 Fec. col. (/100 mL) 204 298 354 Chlor. a (µg/L) 2.2 (0.9) 1.4 (1.6) 1.9 (1.9) _____________________________________________________________________ Three in-lake stations were sampled (Table 6.4). 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 an important factor only at GL-2340, where hypoxia was detected on five of 17 sample trips. Turbidity and suspended solids were low at all three sites. Fecal coliform concentrations were well within state standards at GL-2340 and GL-YD, but the annual geometric mean exceeded the state standard at GL-P (Table 6.4). At that station the state standard was exceeded on nine of 11 occasions in 1998-1999. We note that the large waterfowl populations frequently utilize that area of the lake and may be a source of fecal coliform bacteria. Nitrate concentrations were relatively high at GL-2340, reflecting the proximity of three tributary streams. Nitrate levels decreased considerably toward the park (Table 6.4). Orthophosphate levels were similar at GL-2340 and GL-YD and decreased at the park (Table 6.4). Total nitrogen, ammonium, and orthophosphate at GL-P were higher than or approximately equal to concentrations at thew other lake stations (Table 6.4); possibly this is a result of nutrient loading from the abundant local waterfowl community. 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). The changing nitrate dynamics were reflected by the N/P ratios, the median values of which decreased from 11 at GL-2340 down to 2 at GL-P. These overall ratios indicated potential limitation of phytoplankton growth by nitrogen inputs at all three stations, although N/P ratios at GL-2340 were much higher in winter and spring, indicating potential phosphorus limitation during those periods (Table 6.4). 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. In 1998-1999 most blooms occurred at GL-2340, although a bloom also occurred at GL-P in May 1999. Additionally, large blooms of duckweed Lemna sp. often cover the surface; these blooms are not reflected by chlorophyll a measures as we clear the surface scum before sampling the subsurface water. Table 6.4. Mean and (standard deviation) of water quality parameters in Greenfield Lake sampling stations. Fecal coliforms given as geometric mean, N/P ratio as median. _____________________________________________________________________ Parameter GL-2340 GL-YD GL-P _____________________________________________________________________ DO (mg/L) 8.4 (3.1) 8.9 (3.2) 10.2 (2.5) Turbidity (NTU) 5.0 (3.9) 4.3 (3.3) 8.0 (12.9) TSS (mg/L) 5.8 (4.0) 3.7 (1.3) 4.3 (3.6) Nitrate (mg/L) 0.113 (0.115) 0.068 (0.072) 0.047 (0.133) Ammonium (mg/L) 0.022 (0.019) 0.028 (0.025) 0.030 (0.044) TN (mg/L) 0.601 (0.437) 0.652 (0.317) 0.706 (0.317) Phosphate (mg/L) 0.025 (0.013) 0.025 (0.014) 0.023 (0.015) TP (mg/L) 0.072 (0.040) 0.078 (0.026) 0.063 (0.030) N/P molar ratio 11 7 3 Fec. col. (/100 mL) 141 48 414 Chlor. a (µg/L) 17.3 (20.7) 7.4 (5.0) 9.6 (10.3) ____________________________________________________________________ We conducted a series of nutrient addition bioassay experiments to further investigate what nutrient factors control algal growth in Greenfield Lake. Nutrient addition bioassays were performed on water from GL-2340, GL-YD and GL-P during spring, summer and fall in 1998 and 1999. These bioassays consisted of collecting lake water in 20-L carboys, transporting them to the laboratory, and dispensing 3 L into each of 30 gallon-sized cubitainers. The cubitainers were then spiked with different nutrients (nitrate-N as 100 ppb (µg/L), phosphate-P as 50 ppb, a combination N100 and P50 treatment, and no additions, which was the control). All treatments were in triplicate. The cubitainers were incubated outdoors in pools covered with 2 layers of neutral-density screening to avoid photostress. The water and cubitainers were kept gently agitated with an aquarium pump. Chlorophyll a samples were collected daily for three days, with results compared statistically using SAS. Treatments yielding significantly higher chlorophyll a (p < 0.05) were considered to contain the nutrient most limiting to phytoplankton growth. The September 1998 sample yielded statistically significant algal growth with the N100 and N+P combination additions at both GL-2340 and GL-YD, but only the N+P combination yielded significant growth at GL-P (Fig. 6.2). During this month the inorganic N/P ratios were all five or less, indicating the strong potential for nitrogen limitation. The October 1998 experiment demonstrated significant algal growth responses to the N100 addition at both GL-YD and GL-P, and N+P at GL-P as well (Fig. 6.3). The inorganic N/P ratios were four at GL-YD and five at GL-P, but 23 at GL-2340. The April 1999 bioassay yielded statistically significant algal growth over control in both the N100 and the N+P combination treatments at GL-YD and GL-P (Fig. 6.4). Overall chlorophyll a growth was low, and none of the treatments stimulated growth at the uppermost station GL-2340. All three stations had inorganic N/P ratios of seven or less. In June, the N100 and the N+P combination treatments yielded significant results at both GL-YD and GL-P, but only the N+P combination did at GL-2340 (Fig. 6.5). The inorganic N/P ratio was three at GL-2340, but 40 at GL-YD. In this case the ratios did not correspond with the experimental results. In August 1999 the N100 and the N+P combination treatments proved significant at all three sites, and the P50 alone treatment was also significant at GL-2340 (Fig. 6.6). The inorganic N/P ratios were six at GL-2340, one at GL-YD, and 18 (approximately the Redfield ratio) at GL-P. We emphasize that the nitrate-N concentration used (100 ug/L) is relatively low, and often found at GL-2340 and occasionally at GL-YD. Most of the experimental results, as well as most of the computed N/P ratios, indicate that nitrogen was singly or in combination with phosphorus the principal nutrient limiting to phytoplankton growth in Greenfield Lake. These results contrast with a generally held concept that phosphorus is the primary limiting nutrient in most freshwater systems (Hecky and Kilham 1988). The implications of this research are that phosphorus is usually abundant enough in Greenfield Lake to support algal blooms, but requires pulses of nitrogen to stimulate the bloom formation. Another piece of evidence supporting this is the periodic formation of Anabaena sp. blooms in Greenfield Lake. Anabaena is a blue-green alga that can form blooms when phosphorus is sufficient, and then fix nitrogen from the atmosphere to support the bloom. Phosphorus sources generally include sewage, fertilizers, and animal waste (it is notable that a sizeable waterfowl population inhabits Greenfield Lake, and likely contributes to this phosphorus load). Thus, reducing the frequency of algal bloom formation in Greenfield Lake should be largely dependent upon reducing nitrogen inputs to the system. This should most likely take the form of reducing non-point source inputs into the lake (primarily fertilizers from lawns, gardens, and golf courses. However, even if nitrogen inputs are reduced, nitrogen-fixing blue-green algae may still form blooms (i.e. Anabaena). Thus, efforts should also be made to identify phosphorus sources and control them as well. 7.0 Hewletts Creek Hewletts Creek was sampled at four tidally-influenced areas (HC-2, NB-GLR, MB-PGR and SB-PGR) and one freshwater runoff collection area near Longleaf Mall (HC-LO - Fig. 7.1). Physical data indicated that turbidity was excessive on some occasions at both NB-GLR and SB-PGR , but on average remained below the state standard for estuarine water (Table 7.1). There were several incidents of hypoxia in the summer months of July, August and September. Nitrate concentrations were 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). Both NB-GLR and SB-PGR also periodically receive elevated nutrient loading as well. Median N/P molar ratios demonstrated that both HC-2 and SB-PGR should be primarily nitrogen limited, while NB-GLR tends toward potential phosphorus limitation. Our spring and summer experiments from 1997-1998 confirmed that phytoplankton growth at HC-2 was limited by nitrogen (Mallin et al. 1998b; Mallin and Wheeler 2000). The chlorophyll a data (Table 7.1) showed that Hewletts Creek (especially SB-PGR) continues to host periodic algal blooms, as it has in the past (Mallin et al. 1998a). Table 7.1. Selected water quality parameters at tidally-influenced stations in Hewletts Creek watershed as mean (standard deviation) / range, August 1998-July 1999. _____________________________________________________________________ Parameter HC-2 NB-GLR MB-PGR SB-PGR _____________________________________________________________________ Salinity (ppt) 30.3 (5.1) 5.8 (5.1) 0.1 (0.0) 12.6 (4.2) 18.4-35.9 0.4-15.3 0.0-0.2 5.1-18.6 Turbidity (NTU) 9.9 (6.9) 15.3 (9.2) 8.5 (8.0) 21.7 (16.5) 1.7-20.8 5.9-36.8 1.7-28.0 7.0-63.3 DO (mg/L) 8.3 (2.9) 7.8 (2.6) 7.1 (1.2) 7.3 (2.3) 4.9-15.1 4.3-11.6 5.4-9.3 3.8-10.8 Nitrate (mg/L) 0.014 (0.015) 0.105 (0.061) 0.226 (0.084) 0.060 (0.046) 0.001-0.049 0.005-0.163 0.045-0.371 0.001-0.148 Ammonium (mg/L) 0.027 (0.020) 0.039 (0.046) NA 0.014 (0.013) 0.008-0.065 0.001-0.105 0.001-0.033 Phosphate (mg/L) 0.006 (0.004) 0.019 (0.015) 0.014 (0.006) 0.014 (0.010) 0.003-0.014 0.001-0.059 0.004-0.036 0.004-0.036 Mean N/P ratio 12.4 124.5 NA 23.1 Median 11.9 18.1 14.6 Chlor a (ug/L) 1.0 (0.8) 7.1 (7.4) 1.3 (1.3) 9.9 (10.8) 0.4-2.7 1.1-23.3 0.3-5.0 0.9-35.0 _____________________________________________________________________ We collected sediment samples for EPA primary pollutant metals at a station (PVGC-6) upstream of the Pine valley Country Club and a station (PVGC-9) draining the country club. The analysis (Table 7.2) indicated that metals concentrations at both sites were well below concentrations that can be harmful to aquatic life (see Appendix A). Table 7.2. Mean and standard deviation of sediment metals concentrations at Station PVGC-6 (upstream of Pine Valley Country Club) and PVGC-9 (downstream of Pine Valley Country Club) _____________________________________________________________________ Parameter (mg/kg) PVGC-6 PVGC-9 _____________________________________________________________________ Al 616.3 (173.6) 327.0 (33.0) As 0.1 (0) 0.1 (0) Cd 0.02 (0) 0.02 (0) Cr 0.99 (0.25) 0.70 (0.21) Cu 0.71 (0.16) 1.02 (0.67) Fe 102.3 (71.1) 106.4 (26.0) Pb 3.0 (0.5) 1.2 (0.3) Hg 0.002 (0) 0.002 (0) Ni 0.29 (0.08) 0.25 (0.12) Zn 3.46 (1.06) 1.70 (0.35) _____________________________________________________________________ 8.0 Howe Creek Water Quality Howe Creek was sampled for physical parameters, nutrients, and chlorophyll a at three locations during 1998-1999 (HW-FP, HW-GC, and HW-GP, Fig. 8.1). In addition to the standard sampling described in the Methods, nutrient addition bioassays were performed on water from HW-FP and HW-GP during spring and summer. These bioassays consisted of collecting creek water in 20-L carboys, transporting them to the laboratory, and dispensing 3 L into each of 30 gallon-sized cubitainers. The cubitainers were then spiked with different nutrients (nitrate-N as 100 ppb (µg/L), nitrate-N as 50 ppb, phosphate-P as 50 ppb, phosphate-P as 25 ppb, and no additions, which was the control). All treatments were in triplicate. The cubitainers were incubated outdoors in pools covered with 2 layers of neutral-density screening to avoid photostress. The water and cubitainers were kept gently agitated with an aquarium pump. Chlorophyll a samples were collected daily for three days, with results compared statistically using SAS. Treatments yielding significantly higher chlorophyll a (p < 0.05) were considered to contain the nutrient most limiting to phytoplankton growth. Howe Creek, as in past years, portrayed a tidal creek with good water quality near the ICW and poor water quality in the oligohaline to mesohaline regions. Turbidity is low near the ICW but exceeded North Carolina water quality standards on two occasions in the upper reaches (Table 8.1). The upper Howe Creek watershed maintains several land clearing and construction projects that appear to affect the water quality by non-point source sediment runoff. All three of the stations had incidences of substandard (< 5.0 mg/L) dissolved oxygen (Table 8.1), with HW-GP having the most incidents (three). As mentioned, both turbidity and low dissolved oxygen impair the fisheries primary nursery function of an estuary. As development continues in the upper watershed, we expect continuing degradation of upper and middle Howe Creek from non-point source runoff. Nutrient levels are low near the ICW but can be elevated in the creek near Graham Pond (Table 8.1). Algal bloom conditions occur periodically in spring and summer at Station HW-GP (Table 8.1; Mallin et al. 1998). Median inorganic molar N/P ratios are low, indicating that nitrogen is probably the principal limiting nutrient at HW- FP and often at HW-GP, although periodic nitrate loading events will drive the ratio upward at times in the upper stations (Table 8.1). An August 1998 sample of a city water blowdown pipe near Graham Pond showed nitrate levels of 0.851 mg/L and orthophosphate levels of 0.364 mg/L (these levels are much higher than the normal concentrations in the creek nearby). If sufficient quantities of water from this pipe have drained into Howe Creek, than this pipe has served as a nutrient source to this algal bloom-prone area. Table 8.1. Selected water quality parameters in Howe Creek as mean (standard deviation) / range, August 1998-July 1999. _____________________________________________________________________ Parameter HW-FP HW-GC HW-GP _____________________________________________________________________ Salinity (ppt) 33.9 (1.6) 28.2 (6.4) 13.5 (11.6) 31.1-36.2 18.7-35.7 0.3-33.3 Turbidity (NTU) 5.2 (4.0) 12.2 (7.0) 14.7 (7.4) 0.7-13.2 5.4-26.0 4.9-29.0 DO (mg/L) 7.5 (2.1) 7.4 (2.1) 7.5 (3.1) 4.1-11.8 3.6-10.0 4.0-15.3 Nitrate (mg/L) 0.004 (0.003) 0.012 (0.019) 0.035 (0.034) 0.001-0.009 0.001-0.067 0.001-0.091 Ammonium (mg/L) 0.019 (0.013) NA 0.013 (0.012) 0.001-0.037 0.001-0.029 Phosphate (mg/L) 0.006 (0.005) 0.007 (0.007) 0.013 (0.009) 0.001-0.019 0.001-0.025 0.003-0.037 Mean N/P ratio 6.9 NA 17.4 Median 4.8 19.1 Chlor a (µg/L) 1.4 (1.4) 2.0 (1.9) 8.0 (11.2) 0.2-5.1 0.4-6.8 0.7-39.2 _____________________________________________________________________ Nutrient addition bioassay experiments from February 1999 showed a statistically significant response to nitrate-N of 100 µg/L at HW-FP, and a significant response to phosphate-P of 50 υg/L at HW-GP (Fig. 8.2). There was also somewhat elevated N/P ratio in February at HW-GP (28.6) confirming potential P limitation. Overall chlorophyll a responses were very low during this month, however. Bioassay results from May, June, and July 1999 all showed significant responses at both sites to nitrate-N additions for both the 100 µg/l and 50 µg/L treatments, with no phosphorus stimulation (Figs. 8.3; 8.4; and 8.5). Molar N/P ratios were low during all months except May at HW-GP, where a slightly elevated ratio (25.1) could indicate potential P limitation. However, N/P ratios do vary among individual algal species; thus, ratios alone provide only part of the story. In general, higher chlorophyll a yields occurred at HW-GP than HW-FP, with highest biomass levels in May and July 1999. These experiments demonstrated that, with exception of early spring, nitrogen is limiting to phytoplankton growth in Howe Creek and even very low levels will induce a statistically significant increase in phytoplankton growth. Thus, strategies focused on keeping nitrate out of Howe Creek will likely reduce the formation of algal blooms. 9.0 Pages Creek Pages Creek was sampled at three stations, two of which receive drainage from developed areas (PC-BDUS and PC-BDDS) and a well-flushed one near the ICW (PC-M - Fig. 9.1). This is one of the least-polluted tidal creeks in New Hanover County (Mallin et al. 1998). There has been recent land-clearing activity and drainage system modification in the vicinity of PC-BDUS. During the past sample year turbidity was low to moderate with two incidents of turbidity exceeding the state standard of 25 NTU (Table 9.1). However, there were several incidents of hypoxia during summers of 1998 and 1999, including five at the station draining upper Bayshore Drive (BC-BDUS). Nutrient concentrations were normally low, and phytoplankton biomass was low to moderate (Table 9.1). Inorganic nitrogen-to-phosphorus molar ratios were near or below 16, indicating that phytoplankton growth in this creek is probably nitrogen limited. Table 9.1. Selected water quality parameters in Pages Creek as mean (standard deviation) / range, August 1998-July 1999. _____________________________________________________________________ Parameter PC-M PC-BDDS PC-BDUS _____________________________________________________________________ Salinity 34.1 (1.7) 22.9 (10.9) 20.7 (9.9) 30.1-36.1 5.3-34.2 3.3-32.0 Turbidity (NTU) 7.8 (5.7) 13.2 (7.8) 12.6 (8.5) 0.5-16.9 2.0-31.1 3.6-30.1 DO (mg/L) 7.0 (2.0) 7.0 (2.3) 6.1 (2.4) 4.1-10.5 3.5-10.0 2.7-9.9 Nitrate (mg/L) 0.005 (0.038) 0.031(0.04) 0.017(0.015) 0.001-0.014) 0.029-0.124 0.001-0.047 Ammonium (mg/L) 0.012 (0.009) 0.032 (0.013) 0.054 (0.043) 0.001-0.025 0.017-0.058 0.032-0.128 Phosphate (mg/L) 0.006 (0.002) 0.009 (0.006) 0.014 (0.008) 0.001-0.009 0.001-0.020 0.001-0.029 Mean N/P Ratio 8.2 17.4 8.2 median 8.8 16.9 6.5 Chlor a (µg/L) 1.7 (1.8) 2.6 (3.4) 5.2 (6.0) 0.2-5.5 0.3-13.0 0.9-19.0 _____________________________________________________________________ 10.0 Smith Creek The three stations sampled in this watershed were SC-GT, a tributary of Smith Creek draining a highway construction area (Smith Creek Parkway), and two estuarine sites on Smith Creek proper, SC-23 and SC-CH (Fig. 10.1). Dissolved oxygen concentrations were below 5.0 ppm on four of 11 occasions at SC-CH and five of 11 occasions at SC-23. The North Carolina turbidity standard for estuarine waters (25 NTU) was exceeded on five of 11 occasions at SC-CH and three of 11 occasions at SC- 23. All three Smith Creek stations had overall mean turbidities just below this standard at 23 NTU (Table 10.1). Total suspended solids were periodically high at SC-GT, probably as a result of construction activities. The high turbidity and suspended solids concentrations at SC-GT ceased after January 1999, likely due to cessation of construction activities and subsequent opening of the Smith Creek Parkway to traffic. However, both mean and median turbidity levels for the year at all three Smith Creek stations were higher than those in the adjacent Northeast Cape Fear River, indicating the turbidity sources were from within the watershed, not coming in on the tide (Mallin et al. 1999). Besides the highway construction, there was considerable ditching and draining of freshwater wetlands in the watershed, which is also a likely source of the high turbidity. On average, most nutrient concentrations were unremarkable, and there was a tendency for concentrations to increase downstream toward the Cape Fear River (Table 10.1). Fecal coliform bacteria levels exceeded the North Carolina standard for human contact waters (200 CFU/100 mL) three times at SC-GT, four times at SC-23, and two times at SC-CH during the eleven sample trips. The geometric mean fecal coliform concentration was below the human contact standard at all three stations but well above the shellfishing standard (14 CFU/100 mL) in the estuarine portion of the creek (Table 10.1). Table 10.1. Selected water quality parameters in Smith Creek watershed as mean (standard deviation) / range. _____________________________________________________________________ Parameter SC-GT SC-23 SC-CH _____________________________________________________________________ Salinity (ppt) 0.1 (0.0) 0.9 (2.0) 2.2 (3.8) 0.1-0.1 0.1-6.9 0.1-12.2 Dissolved oxygen 6.9 (1.8) 6.1 (2.3) 6.1 (2.1) (mg/L) 3.9-9.3 3.0-9.8 3.5-9.6 Turbidity (NTU) 23.2 (27.6) 23.0 (15.8) 23.0 (12.7) 3.0-93.0 8.0-58.2 5.2-42.0 TSS (mg/L) 7.5 (8.5) 11.5 (5.9) 13.7 (8.5) 0.5-27.0 2.5-19.0 3.5-31.0 Nitrate (mg/L) 0.09 (0.20) 0.10 (0.08) 0.19 (0.13) 0.01-0.70 0.01-0.25 0.05-0.41 Ammonium (mg/L) 0.03 (0.03) 0.07 (0.06) 0.07 (0.06) 0.01-0.08) 0.01-0.20 0.01-0.20 Phosphate (mg/L) 0.05 (0.04) 0.05 (0.03) 0.07 (0.04) 0.01-0.13 0.01-0.09 0.01-0.12 Chlor. a (µg/L) 1.0 (0.7) 6.3 (4.40 3.5 (2.7) 0.4-2.5 1.2-13.8 1.2-8.9 Fecal col. /100 mL 168 124 95 (geomean / range) 95-485 15-974 14-930 _____________________________________________________________________ 11.0 Upper and Lower Cape Fear Within the Wilmington City limits drainage directly to the Cape Fear River (CFR) was sampled at one location each in the Upper and Lower Cape Fear Watersheds. The stream draining the Upper CFR was sampled behind the Wilmington Police Station between 2nd and 3rd Streets (Fig. 11.1). Concentrations of most physical, chemical and biological constituents were low to moderate except for nitrate (Table 11.1). Nitrate concentrations in this stream were the highest in any of the City or County drainage basins. The source of this nitrate is currently not defined, but additional spot samples taken in September and October showed slightly higher concentrations near the 4th St. bridge. In September nitrate levels were 2.4 mg/L at 4th St. compared with 1.7 mg/L at UCF-PS, and in October nitrate levels were 2.3 mg/L at 4th St. compared with 1.8 mg/L at UCF-PS. We note that overall nitrate decreased from 1997-98 to 1998-99, but fecal coliform counts increased. The geometric mean was 259 CFU/100 mL for the past year, in excess of the state standard of 200 CFU/100 mL. Drainage from the Lower CFR was sampled from the stream draining Greenfield Lake (Fig. 11.2). Processing within the lake served to keep concentrations of most constituents relatively low (Table 11.1). Average fecal coliforms, turbidity, and chlorophyll a were all below state water quality standards during the sampling period. Table 11.1. Water quality summary statistics (mean (standard deviation) / range) for Wilmington Upper (UCF) and Lower (LCF) Cape Fear Watersheds. _____________________________________________________________________ Station DO (mg/L) Turbidity (NTU) TSS (mg/L) Fecal col (CFU/100 mL) _____________________________________________________________________ UCF 8.0 (0.8) 3.4 (3.7) 1.5 (0.7) 259 6.9-9.3 0.1-12.2 0.5-3.0 30-1280 LCF 8.4 (2.5) 4.5 (4.4) 3.5 (2.6) 71 4.2-13.5 1.2-13.1 1.5-11.0 25-205 _____________________________________________________________________ Nitrate (mg/L) Ammonium (mg/L) Orthophosphate (mg/L) _____________________________________________________________________ UCF 2.227 (0.617) 0.017 (0.016) 0.030(0.013) 1.400-3.400 0.005-0.050 0.005-0.050 LCF 0.011 (0.016) 0.036 (0.047) 0.031 (0.020) 0.005-0.060 0.005-0.150 0.005-0.070 _____________________________________________________________________ 16.0 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, E.C. Esham, J.J. Manock, J.F. Merritt, M.H. Posey, T.D. Alphin, R.K. Sizemore and K. Williams. 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. 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., M.H. Posey, M.L. Moser, L.A. Leonard, T.D. Alphin, S.H. Ensign, M.R. McIver, G.C. Shank and J.F. Merritt. 1999. Environmental Assessment of the Lower Cape Fear River system, 1998-1999. CMSR Report No. 99-01. 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 (In press). 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 (In press). 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. Welschmeyer, N.A. 1994. Fluorometric analysis of chlorophyll a in the presence of chlorophyll b and phaeopigments. Limnology and Oceanography 39:1985-1993. 17.0 Acknowledgments Funding for this research was provided by New Hanover County, the Northeast New Hanover Conservancy, the City of Wilmington and the University of North Carolina at Wilmington. For project facilitation and helpful information we thank Paul Foster, Dexter Hayes, Patrick Lowe, David Mayes, Rick Shiver and Dave Weaver. For field and laboratory assistance we thank Jesse Cook, Virginia Johnson, Matt McIver, Christian Preziosi, Chris Shank, Brad Schroeder, Ashley Skeen and Tracey Wheeler. 18.0 Appendix A. Guideline values for sediment metals concentrations (ppm, dry wt.) potentially harmful to aquatic life (Long et al. 1995). _____________________________________________________________________ ERL (Effects range low) concentrations below ERL are those in which harmful effects are rarely observed. ERM (Effects range median) concentrations above ERM are those in which harmful effects would frequently occur. Concentrations between ERL and ERM are those in which harmful effects would occasionally occur. Chemical 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 19.0 Appendix B. 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 (µg/L) _____________________________________________________________________ CFU = colony-forming units mg/L = milligrams per liter = parts per million µg/L = micrograms per liter = parts per billion 20.0 Appendix C. Use support of Class C surface waters in Wilmington and New Hanover County watersheds based on November 1997 – November 1999 data (where available) for dissolved oxygen, turbidity, and fecal coliform North Carolina state standards. _____________________________________________________________________ FS (fully supporting) – state standard exceeded in < 10% of the measurements PS (partially supporting) – state standard exceeded in 11-25% of the measurements NS (non supporting) – state standard exceeded in >25% of the measurements _____________________________________________________________________ Watershed Station Dissolved oxygen Turbidity Fecal coliforms* Barnard’s Creek BNC-TR PS FS PS BNC-CB PS FS NS BNC-EF PS FS PS BNC-AW PS FS PS BNC-RR PS FS NS Bradley Creek BC-CA NS PS NS BC-CR FS FS NS BC-SB PS PS NS BC-SBU NS FS NS BC-NB PS PS NS BC-NBU FS PS NS BC-76 PS FS FS Burnt Mill Creek BMC-AP1 FS PS NS BMC-AP2 FS FS PS BMC-AP3 FS FS PS BMC-PP NS FS NS Futch Creek FC-2 FS FS FS FC-4 PS FS FS FC-6 PS FS FS FC-8 PS FS FS FC-13 PS PS FS FC-17 PS FS FS FC-20 PS FS PS FOY PS FS FS Greenfield Lake GL-SS1 NS FS NS GL-SS2 FS FS NS GL-LC NS FS NS GL-JRB NS FS NS GL-LB NS FS NS GL-2340 PS FS NS GL-YD PS FS PS GL-P FS FS NS Hewletts Creek PVGC-9 FS FS NS MB-PGR FS FS -** NB-GLR PS PS - SB-PGR PS PS - HC-2 FS FS - Howe Creek HW-DT PS PS NS HW-GP PS PS NS HW-GC PS FS FS HW-FP PS FS FS HW-M PS FS FS Motts Creek MOT-RR PS NS NS Pages Creek PC-BDUS NS FS - PC-BDDS PS FS - PC-M PS FS - Smith Creek SC-GT FS PS NS SC-23 FS PS NS SC-CH NS PS NS Upper and Lower UCF-PS FS FS NS Cape Fear LCF-GO PS FS PS _____________________________________________________________________ * 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. ** no recent data available for parameter 21.0 Appendix D. University of North Carolina at Wilmington reports concerning New Hanover County’s tidal creeks. 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. 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. 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., 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. 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.