2001-2002 Final Report
ENVIRONMENTAL QUALITY OF WILMINGTON AND
NEW HANOVER COUNTY WATERSHEDS
2001-2002
by
Michael A. Mallin, Lawrence B. Cahoon, Martin H. Posey, Douglas C. Parsons,
Virginia L. Johnson, Troy D. Alphin and James F. Merritt
CMS Report 03-01
Center for Marine Science
University of North Carolina at Wilmington
Wilmington, N.C. 28409
February, 2003
www.uncwil.edu/cmsr/aquaticecology/tidalcreeks
Funded by:
The City of Wilmington, New Hanover County, the North Carolina Clean Water
Management Trust Fund, and the North Carolina Wetlands Restoration Program
Dedicated to:
Paul Foster, a friend of the environment
Executive Summary
This report represents combined results of Year 9 of the New Hanover County
Tidal Creeks Project and Year 5 of the Wilmington Watersheds Project. Water quality
data are presented from a watershed perspective, regardless of political boundaries. The combined programs involved 12 watersheds and 52 sampling stations. In this
summary we first present brief water quality overviews for each watershed from August
2001 – July 2002, and then discuss key results of several special studies conducted
over the past two years.
Barnards Creek – There was a fecal coliform bacterial pollution problem at all three of
the stations sampled in the Barnard’s Creek watershed, with generally higher fecal
coliform counts compared with the 2000-2001 study. Lower Barnard’s Creek at River
Road had poor water quality as judged by turbidity and fecal coliform counts, and there
was increased loading of all nitrogen species, suspended sediments, and BOD to this site compared with the 2000-2001 study.
Bradley Creek – Turbidity was not problematic during 2001-2002. Low dissolved
oxygen was an occasional problem in brackish waters of the creek during summer and
fall. Elevated nitrogen and phosphorus levels enter the creek in both the north and south branches, and one major algal bloom occurred in the south branch and one in the
creek at College Acres. Fecal coliform bacterial contamination was excessive at five of
the seven stations sampled in 2001-2002, especially at the station at College Acres,
which proved to be contaminated on 83% of the occasions sampled.
Burnt Mill Creek – A sampling station on Burnt Mill Creek at Princess Place had
substandard dissolved oxygen during 33% of the sampling trips. This station also had
poor microbiological water quality, exceeding the standard for human contact in seven
of 12 samples, and hosted two algal blooms in 2001. The effectiveness of Ann
McCrary wet detention pond on Randall Parkway as a pollution control device was improved over last year. The pond led to significant reduction in conductivity,
ammonium, orthophosphate, total phosphorus, and fecal coliform bacteria. All water
quality parameters indicated a subsequent worsening of the creek from where it exited
the pond to the downstream Princess Place sampling station. Fecal coliform bacteria
and low dissolved oxygen are the primary problems in Burnt Mill Creek.
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 and
turbidity were not problems in 2001-2002. Dissolved oxygen concentrations improved
over last year’s assessment. 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 – 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, as did station GL-2340, within the
lake proper. 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. The stream near Lakeshore Commons also maintained high nitrate and
phosphate concentrations. The lake again experienced algal blooms at times, with
several blooms exceeding 40 µg/L of chlorophyll a. Generally, nutrient loading was
highest at a station (GL-2340) located in the south end that receives several urban and
suburban inputs. Fecal coliform bacterial contamination was prevalent at all in-lake and tributary stations during 2001-2002, although this contamination was not as high as
previous years due to low runoff as a result of the drought.
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, and conductivity were all realized. However, contrary to previous years, ammonium and
fecal coliform bacteria were not reduced, likely because of construction activities
occurring along the lower pond. 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 large pond design.
Hewletts Creek – This creek received lower nutrient loading in its three upper branches
compared with last year, due to the drought, with only one algal bloom exceeding the
State standard occurring 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 was not a problem in 2001-2002. Fecal coliforms were not
sampled in Hewletts Creek in 2001-2002.
Howe Creek – Five stations were sampled in Howe Creek in 2001-2002. The lower creek maintained good water quality. In the upper creek there were a few problems
with low dissolved oxygen and occasional algal blooms. Fecal coliform bacteria counts
were low near the ICW, moderate in mid-creek, and high in the uppermost station
during 2001-2002.
Motts Creek – This creek was sampled at only one station, at River Road. Three algal
blooms occurred during this period, up from only one last year. Low dissolved oxygen
was a problem 25% of the sampling occasions in 2001-2002, and turbidity and
suspended sediments were a periodic problem. Fecal coliform pollution was a frequent
(50% of the time) problem at this station. Biochemical oxygen demand (BOD5) tripled in 2001-2002 compared with 2000-2001, and algal blooms increased as well.
Pages Creek – This creek maintained generally good water quality during 2001-2002.
Nutrient loading and phytoplankton growth was low, even at the most
anthropogenically-impacted stations. However, there was periodic low dissolved oxygen in warmer months at some stations draining Bayshore Drive. Pages Creek was
not sampled for fecal coliform bacteria during 2001-2002. This watershed has some of
the lowest development and impervious surface coverage in the New Hanover County
tidal creek system.
Smith Creek – Smith Creek had moderate water quality problems as reflected by
several parameters. Turbidity and elevated suspended sediments occurred on
occasion, and algal blooms exceeding 30 µg/L of chlorophyll a occurred twice at one
station. Fecal coliform bacteria were not sampled in 2001-2002. Low dissolved oxygen
problems occurred 25% of the time and 50% of the time at two of our Smith Creek
stations during 2001-2002.
Whiskey Creek – Whiskey Creek had relatively high nutrient loading but generally low chlorophyll a concentrations in 2001-2002. There were several incidents of low
dissolved oxygen at two of the five stations sampled this year, but high turbidity was not
a problem. Fecal coliform bacteria were not sampled in 2001-2002 in this creek.
Lower Cape Fear Watershed – Sampling was continued in the creek draining Greenfield Lake into the Cape Fear River. Fecal coliform concentrations exceeded the state standard for human contact waters on 33% of the sampling occasions during
2001-2002. Other parameters were not problematic at this station.
Water Quality Station Ratings – The NC Division of Water Quality utilizes an EPA-based system to help determine if a water body supports its designated use (described in Appendix B). We applied these numerical standards to the water bodies described in
this report, based on 2001-2002 data, and have designated each station as good, fair,
and poor accordingly. Our analysis shows that (based on fecal coliform standards for
human contact waters) all three of the Barnards Creek stations were rated poor quality. Two of the three stations in Burnt Mill Creek were rated as poor in 2001-2002, and the other was rated fair. Four of the stations in Bradley Creek were rated as poor and the
other two were rated good. Futch Creek rated good for fecal coliform bacteria,
including for shellfishing throughout the lower creek. Greenfield Lake and its tributaries
were poor microbiological water quality throughout. The one station in Hewletts Creek sampled for fecal coliforms last year was rated poor. The uppermost two stations in Howe Creek were rated poor and fair, respectively, while the lower three were rated
good. Lower Motts Creek was rated poor and both of the Smith Creek stations were
rated fair. The Lower Cape Fear station was rated poor for fecal coliforms. We also list
ratings for chlorophyll a, dissolved oxygen and turbidity in Appendix B.
Fecal coliform contamination of sediments - Sediments in the Bradley Creek watershed
were sampled for fecal coliform bacteria, and showed a variable but significant
population of fecal coliforms at all times and places sampled. In the brackish water of
BC-SB, suspension of the sediments by physical forces would have sufficed to create
water column concentrations of fecal coliforms high enough to mandate closure to shellfishing, and, in several cases, to close these waters to human body contact. Direct
body contact with sediments, such as by wading or manual disturbance of the
sediments, would likely be particularly hazardous, assuming that sediment fecal
coliform concentrations indicate pathogen presence. When one adds in the fecal
coliforms normally suspended in the overlying water as well, then disturbance of the sediments can add a significant health threat to certain water bodies.
Sediment phosphate levels are important in controlling fecal coliform bacteria
survival and growth in estuarine sediments. Phosphate loading to estuarine waters is
driven by storm water runoff and other sources that may involve fecal coliform loading. Residential use of phosphate-containing fertilizers is a major source of phosphate to
sediments in tributaries in the Bradley Creek watershed. Consequently, fecal coliform contamination of tidal creeks in New Hanover County may be driven by a complex
relationship between storm water runoff, animal sources of fecal matter, and phosphate
(and other nutrients) from fertilizers, all associated with residential land uses.
Tidal Creek Benthic Fauna - The types of benthic fauna dominating New Hanover tidal creeks are representative of communities with moderate environmental impacts,
including a mix of species characteristic of more pristine area as well as species
characteristic of more disturbed habitats. Hewletts and Howe Creeks are distinct with
respect to benthic communities compared to Pages and Bradley Creeks. Hewletts and
Howe Creeks have lower abundances of several taxa, especially juvenile clams, as well as lower numbers of species and diversity. This may reflect greater impacts to the
bottom communities in these creeks. A series of experiments showed that small
increases in local nutrient levels had little effect on the existing bottom communities.
Table of Contents
1.0 Introduction 1
1.1 Methods 1
2.0 Barnards Creek 3
3.0 Bradley Creek 8 4.0 Burnt Mill Creek 11
5.0 Futch Creek 14
6.0 Greenfield Lake 17
7.0 Hewletts Creek 22
8.0 Howe Creek 26 9.0 Motts Creek 29
10.0 Pages Creek 33
11.0 Smith Creek 35
12.0 Upper and Lower Cape Fear 38
13.0 Whiskey Creek 40 14.0 Fecal Contamination of Tidal Creek Sediments 43
15.0 Benthic Fauna of New Hanover County Tidal Creeks 51
16.0 References Cited 61
17.0 Acknowledgments 63
18.0 Appendix A: Selected N.C. water quality standards 64 19.0 Appendix B: UNCW Watershed Station Ratings Based on DWQ Chemical
Standards 65
20.0 Appendix C: GPS coordinates for the New Hanover County Tidal Creek
and Wilmington Watersheds Program sampling stations 67
21.0 Appendix D: UNCW reports and papers related to tidal creeks 69
(Cover by Heather CoVan and Virginia Johnson)
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 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). In the past four years we have produced combined Tidal Creeks –
Wilmington City Watersheds reports (Mallin et al. 1998b; 1999; 2000a; 2002). In the
present report we present results of continuing studies from August 2001 - July 2002 in the tidal creek complex and the City of Wilmington watersheds.
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. In 1999-2000 Whiskey Creek was added to
the matrix of watersheds analyzed by our combined programs.
1.1 Methods
Field parameters were measured at each site using a YSI 6920 Multiparameter
Water Quality Probe (sonde) linked to a YSI 610 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.
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 1.0 micrometer pore-sized 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 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 two hours, after which the material was centrifuged, leaving the solution containing
the extracted chlorophyll. Each solution 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 monthly within the Wilmington City watersheds from
August 2001 through July 2002. 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-CMS as described above, except filters were ground
using a teflon grinder prior to extraction.
For two wet detention ponds (Ann McCrary Pond on Burnt Mill Creek and Silver Stream Pond in the Greenfield Lake 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
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 Barnard’s and Mott’s Creeks. We collect data at a station located on Barnard’s Creek at River Road (BNC-RR) that drains part of
this area. The BNC-TR site in Barnard’s Creek watershed drains a wooded area and
had been considered a control site for nutrients and physical parameters. However, we
also note that the control is now near an active road and condominium construction
area on Titanium Road, or Independence Road Extension (Fig. 2.1), and this can no longer be considered a background site. Fecal coliform bacterial counts at BNC-TR
have increased considerably relative to the 1997-1998 period (Mallin et al. 1998b; 1999;
2002). The BNC-CB site is near Carolina Beach Road and drains an area hosting
construction activities. BNC-TR exceeded the state fecal coliform standard of 200
CFU/100 mL on 70% of the sampling trips and BNC-CB exceeded the standard on 50% of the trips (Table 2.1; Appendix B). Both of these sites were thus significantly impaired
by elevated fecal coliform counts during 2001-2002, and overall geometric mean fecal
coliform counts were higher than in 2000-2001 (Mallin et al. 2002). Nutrient and
chlorophyll a levels were unremarkable at these sites, and turbidity was low.
We report here water quality data from the estuarine site on River Road. BNC-RR had average salinity of 4.9 ppt with a range of 0.3-13.7 ppt. Lower Barnard’s Creek
had dissolved oxygen levels below 5 mg/L on two occasions out of 12 samples in 2001-
2002. It is notable that concentrations of all nutrient species increased over the 2000-
2001 values at this station, and ammonium and total nitrogen showed particularly
increasing trends (Figs. 2.2 and 2.3). Total suspended solids appeared to show an increasing trend from summer through fall of 2002 (Fig. 2.4). BOD5 was sampled 12
times at BNC-RR last year, yielding a median of 2.6 and a mean of 2.9 mg/L, which was
approximately three times higher than the BOD5 concentrations found in the 2000-2001
study (Mallin et al. 2002). BOD5 concentrations may be representative of an increasing
trend (Fig. 2.5). Median and mean BOD20 in 2001-2002 was 6.7 and 9.5 mg/L, respectively. Turbidity on average was moderately high (29 NTU), and exceeded the
state standard for estuarine waters of 25 NTU five times, up from three times during the
2000-2001 year. Fecal coliform counts exceeded the state standard four of 12
occasions for a 33% non-compliance rate. Thus, this station can be considered
impaired by low dissolved oxygen, turbidity and fecal coliform loading, with somewhat elevated BOD as well. The housing construction upstream of Carolina Beach Rd. may
have been related to the recent impairment of these waters.
Table 2.1. Mean and standard deviation of water quality parameters in Barnard’s Creek watershed, August 2001-July 2002. Fecal coliforms as geometric mean; N/P ratio as
median.
_____________________________________________________________________
Parameter BNC-TR BNC-CB BNC-RR
_____________________________________________________________________
DO (mg/L) 6.2 (2.0) 7.5 (1.6) 6.8 (2.3)
Turbidity (NTU) 4 (4) 5 (10) 29 (18)
TSS (mg/L) 5.3 (6.1) 3.5 (3.7) 44.7 (50.1)
Nitrate (mg/L) 0.066 (0.042) 0.088 (0.070) 0.240 (0.148) Ammon. (mg/L) 0.074 (0.088) 0.088 (0.059) 0.142 (0.105)
TN (mg/L) 0.618 (0.442) 0.680 (0.344) 0.987 (0.575)
Phosphate (mg/L) 0.015 (0.012) 0.034 (0.075) 0.108 (0.093)
TP (mg/L) 0.064 (0.061) 0.095 (0.113) 0.165 (0.147)
N/P molar ratio 23.3 20.7 6.0
Chlor. a (µg/L) 2.4 (2.9) 3.1 (2.9) 8.3 (7.1)
Fec. col.(/100 mL) 415 348 112
_____________________________________________________________________
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 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. 2000b). Seven stations were sampled in the past year, both fresh and brackish (Fig. 3.1).
As with last year, turbidity was not a problem during 2001-2002 (Table 3.1). The
standard of 25 NTU was not exceeded during our brackish water sampling (Table 3.1).
There were some problems with low dissolved oxygen (hypoxia), with BC-SB and BC-NB both having DO of less than 5.0 mg/L on two occasions and BC-CA had
substandard dissolved oxygen conditions on seven of 12 sampling occasions (Appendix
B).
Table 3.1 Parameter concentrations at Bradley Creek sampling stations, August 2001-July 2002. Data as mean (SD) / range, fecal coliform bacteria as geometric mean /
range.
_____________________________________________________________________
Station Salinity Turbidity Dissolved Oxygen Fecal coliforms
(ppt) (NTU) (mg/L) (CFU/100 mL) _____________________________________________________________________
BC-76 34.2 (1.4) 6 (4) 6.6 (1.6) 2.7
31.6-36.1 0-16 3.5-9.4 0-23
BC-SB 18.5 (13.4) 9 (7) 7.1 (2.8) 156
1.1-33.3 3-23 4.7-14.7 23-1025
BC-SBU 0.2 (0.0) 3 (2) 8.9 (2.3) 138
0.2-0.2 0-7 5.3-13.9 20-730
BC-NB 27.2 (9.0) 7 (5) 6.6 (1.8) 25
8.7-35.3 2-17 3.7-10.5 2-200
BC-NBU 0.1 (0.2) 3 (1) 7.4 (1.0) 167 0.1-0.2 1-6 5.7-9.3 26-2000
BC-CR 0.1 (0.0) 2 (4) 8.2 (1.0) 213
0.0-0.1 0-13 6.2-9.5 23-1250
BC-CA 0.1 (0.1) 9 (9) 4.1 (2.0) 1169
0.1-0.1 3-35 0.2-7.3 162-6000
_____________________________________________________________________
All stations were sampled for fecal coliform concentrations last year, with elevated counts commonly occurring at five of the seven sites (Table 3.1). The State
standard of 200 CFU/100 mL was exceeded 83% of the time at BC-CA (the creek as it
passes beneath College Acres), 60% of the time at BC-CR (creek at Clear Run), 40% at BC-SB (south branch at Wrightsville Avenue), 33% at BC-SBU (upper south branch
at Andover Road), and 30% at BC-NBU (upper north branch at Rodgersville Rd.). All of
these we consider poor water quality in terms of fecal coliform counts (Appendix B).
Nitrate concentrations were highest at stations BC-CR, BC-SBU (upper south branch) and BC-NBU. The highest orthophosphate levels were found at BC-CA, with
somewhat elevated orthophosphate levels at BC-SB, BC-SBU, and BC-76 (Table 3.2).
Ammonium was also elevated at BC-CA, and to a lesser extent at BC-SB. Bradley
Creek hosted only one algal bloom in excess of the state standard of 40 µg/L, at BC-SB
(55 µg/L, Table 3.2). Median inorganic molar N/P ratios were 5.5 for BC-76, 7.9 for BC-
SB, and 5.8 for BC-NB. This indicates that phytoplankton growth was likely nitrogen
limited at all three of these stations.
Table 3.2. Nutrient and chlorophyll a data at Bradley Creek sampling stations, August
2000-July 2001. Data as mean (SD) / range, nutrients in mg/L, chlorophyll a as µg/L.
_____________________________________________________________________
Station Nitrate Ammonium Orthophosphate Chlorophyll a
_____________________________________________________________________
BC-76 0.005 (0.003) 0.018 (0.011) 0.009 (0.004) 1.7 (1.5) 0.001-0.009 0.003-0.044 0.004-0.017 0.5-5.7
BC-SB 0.019 (0.017) 0.025 (0.028) 0.009 (0.004) 11.3 (16.5)
0.002-0.048 0.006-0.106 0.003-0.016 0.6-54.7 BC-SBU 0.089 (0.073) NA 0.010 (0.005) 4.7 (3.3)
0.002-0.234 0.002-0.019 0.9-11.7
BC-NB 0.005 (0.003) 0.016 (0.004) 0.008 (0.002) 5.3 (6.8) 0.002-0.011 0.011-0.023 0.005-0.012 0.6-20.8
BC-NBU 0.080 (0.049) NA 0.007 (0.010) 0.7 (0.4)
0.015-0.201 0.002-0.035 0.1-1.6
BC-CR 0.229 (0.054) NA 0.006 (0.006) 1.1 (1.7) 0.123-0.276 0.002-0.020 0.1-6.3
BC-CA 0.057 (0.073) 0.083 (0.065) 0.109 (0.190) 15.1 (12.2)
0.004-0.280 0.005-0.202 0.002-0.680 0.9-43.8 _____________________________________________________________________
4.0 Burnt Mill Creek
The Burnt Mill Creek watershed was sampled just upstream of Ann McCrary
Pond on Randall Parkway (AP1), 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 an 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 were low to moderate. Fecal
coliform concentrations entering Ann McCrary Pond at 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. Eight out of 12 samples at AP1 had counts exceeding 200 CFU/100 mL. There was a February 2002 algal bloom at AP1 with a chlorophyll a
concentration of 97 µg/L and a May 2002 bloom at AP3 of 72 µg/L. Additionally, there
was a bloom of 43 µg/L as chlorophyll a at Princess Place in June.
The efficiency of the pond as a pollutant removal device was mixed 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. Ammonium,
orthophosphate and total phosphorus were significantly reduced during passage
through the pond this year, but nitrate and total nitrogen were not (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 AP2 site (fig.
4.1). 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.
As in previous studies, the Princess Place location experienced several water quality problems during the sample period (Appendix B). Dissolved oxygen was
substandard on four of 12 sampling trips, for a non-compliance rate of 33%. The most
important issue, from a public health perspective, was the excessive fecal coliform
counts, which maintained a geometric mean (1169 CFU/100 mL) far 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 10 of 12 samples, or 83% of the time. It is
notable that fecal coliform, suspended solids, phosphorus and nitrogen concentrations
all increased considerably along the passage from BMC-AP3 to the Princess Place
location, while dissolved oxygen decreased (Table 4.1).
The UNCW Aquatic Ecology Lab has conducted additional sampling at various locations along Burnt Mill Creek in support of the restoration efforts of the North
Carolina Wetlands Restoration Program. These stations were BMC-KA3, which drains
the created wetland near Kerr Avenue, BMC-GS, a tributary stream entering the creek
from an apartment complex between AP3 and Princess Place, and BMC-ODC, a
branch of Burnt Mill Creek that drains an urbanized area and passes through Oakdale Cemetery before joining the main branch of the creek just before it enters Smith Creek.
Since sampling for this effort was designed to capture several rain events and was not
performed on a pre-set schedule, summary data will not be presented here. However,
our statistical analysis of the data has provided several insights into urban pollution.
Station BMC-ODC, at the cemetery, was characterized by excessive fecal
coliform bacterial pollution (geomean 2263 CFU/100 mL), high nitrogen and
phosphorus loading, algal blooms, low dissolved oxygen, and relatively high
concentrations of surfactants, indicators of domestic and commercial detergent usage.
BMC-GS and BMC-KA3 both had high fecal coliform counts, particularly after rain events. While the water exiting the wetland at BMC-KA3 had generally high dissolved
oxygen levels, BOD was comparatively high as well, slightly higher than at BMC-ODC.
BMC-GS and BMC-KA3 both had relatively high surfactant levels as well. BMC-KA3
had the lowest nutrient levels among the three sites and low chlorophyll as well, but the
high fecal coliform (geomean 769 CFU/100 mL) and BOD5 (median 3.9 mg/L) concentrations exiting the Kerr Avenue wetland may indicate high animal use, possibly
scavengers attracted to the dumpsters located near the pond. There are a number of
eating establishments that are in this small watershed.
Table 4.1. Mean and (standard deviation) of water quality parameters in Burnt Mill Creek, August 2001 - July 2002. Fecal coliforms as geometric mean; N/P as median.
_____________________________________________________________________
Parameter BMC-AP1 BMC-AP3 BMC-PP
_____________________________________________________________________
DO (mg/L) 5.3 (2.5) 9.3 (1.8)** 5.6 (2.3)
Cond. (µS/cm) 233 (84) 211 (52) 885 (1016)
pH 6.9 (0.3) 7.8 (0.4)** 7.3 (0.2)
Turbidity (NTU) 8 (9) 9 (9) 19 (27)
TSS (mg/L) 8.4 (8.3) 5.3 (4.3) 11.7 (14.3) Nitrate (mg/L) 0.050 (0.041) 0.029 (0.022) 0.107 (0.080)
Ammonium (mg/L) 0.114 (0.088) 0.074 (0.061)** 0.106 (0.072)
TN (mg/L) 0.641 (0.461) 0.624 (0.626) 0.733 (0.514)
Phosphate (mg/L) 0.112 (0.274) 0.064 (0.170)* 0.062 (0.067)
TP (mg/L) 0.224 (0.432) 0.108 (0.205)** 0.104 (0.083) N/P molar ratio 7.7 11.5 6.6
Fec. col. (/100 mL) 564 128** 510
Chlor. a (µg/L) 13.1 (26.9) 13.9 (19.8) 14.6 (11.3)
_____________________________________________________________________
* Indicates statistically significant difference between AP1 and AP3 at p<0.05 **Indicates statistically significant difference between AP1 and AP3 at p<0.01
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, significantly lower fecal coliform counts, and the lower creek was reopened to shellfishing (Mallin et al. 2000c). During 2001-2002, none of
the creek stations had turbidity levels exceeding the state standard of 25 NTU on any
occasion. Low dissolved oxygen, which was a problem at Futch Creek during 2000-
2001, improved during the past year (Appendix B).
Table 5.1. Physical parameters at Futch Creek sampling stations, August 2001 - July
2002. Data given as mean (SD) / range.
_____________________________________________________________________
Station Salinity (ppt) Turbidity (NTU) Dissolved oxygen (mg/L)
_____________________________________________________________________
FC-4 34.9 (2.2) 5 (3) 7.6 (1.8)
28.5-36.5 1-10 4.0-9.9
FC-6 34.2 (2.4) 6 (3) 7.7 (1.7) 27.5-36.3 1-11 4.9-10.1
FC-8 33.4 (2.8) 9 (5) 7.5 (1.9)
26.5-36.1 117 3.9-10.0
FC-13 30.9 (3.6) 9 (5) 7.3 (2.2)
23.6-35.1 3-18 4.5-10.9
FC-17 24.2 (7.7) 24 (45) 7.8 (3.4)
9.3-33.7 3-164 3.5-16.1
FOY 31.1 (4.0) 9 (7) 7.3 (2.1)
21.2-35.2 2-28 4.3-11.2
_____________________________________________________________________
Nutrient concentrations in Futch Creek remained generally low, with the
exception of periodic nitrate pulses in the upper station FC-17 (Table 5.2). The source
of these pulses has been identified as groundwater inputs entering the marsh in springs
in the area upstream of FC-17 downstream to 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 7.0 for FC-4, 10.7 for FC-
17 and 9.2 for FOY, all indicating general N 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, August
2001-July 2002. Data as mean (SD) / range, nutrients in mg/L, chlorophyll a as µg/L.
_____________________________________________________________________
Station Nitrate Ammonium Orthophosphate Chlorophyll a
_____________________________________________________________________
FC-4 0.007 (0.004) 0.019 (0.007) 0.007 (0.003) 1.4 (1.4) 0.002-0.016 0.007-0.033 0.002-0.014 0.2-4.9
FC-6 0.007 (0.006) NA 0.007 (0.003) 1.4 (1.4)
0.002-0.020 0.002-0.012 0.3-5.5
FC-8 0.010 (0.008) NA 0.009 (0.003) 1.9 (1.9)
0.002-0.027 0.003-0.013 0.3-6.9
FC-13 0.024 (0.018) NA 0.011 (0.005) 3.2 (2.8)
0.002-0.056 0.003-0.023 0.4-9.5
FC-17 0.071 (0.061) 0.054 (0.081) 0.015 (0.007) 5.5 (5.3)
0.008-0.174 0.008-0.288 0.002-0.025 0.6-15.9
FOY 0.020 (0.022) 0.022 (0.008) 0.009 (0.004) 3.1 (2.9) 0.002-0.080 0.012-0.034 0.002-0.017 0.4-9.0
_____________________________________________________________________
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 2001-2002 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 well below those of the pre-dredging period. All stations had fecal
coliform concentrations that were well within safe limits for human contact waters, with the exception of FC-17 (Appendix B).
Table 5.3. Futch Creek fecal coliform bacteria data, including percent of samples
exceeding 43 CFU per 100 mL, August 2001 - July 2002.
_____________________________________________________________________ Station FC-4 FC-6 FC-8 FC-13 FC-17 FOY ALL
Geomean (CFU/100 mL) 1 2 1 8 47 4 20
% > 43 /100ml 10 0 10 10 44 11 14 _____________________________________________________________________
6.0 Greenfield Lake Water Quality
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 were alligatorweed Alternanthera philoxeroides, pennywort
Hydrocotyle umbellate, water primrose Ludwigia leptocarpa and cattail Typha latifolia.
This pond functioned well as a nutrient removal system (Table 6.1). Statistically significant removal of nitrate (82%), orthophosphate (89%), TP (63%), and TN (73%)
was achieved, while reduction of ammonium was not statistically significant (36%).
Turbidity and TSS were generally low at both locations this past year (Table 6.1).
However, fecal coliform concentrations at SS2 were considerably higher than last year,
with no significant reduction through the pond. The elevated levels may have resulted from construction activities near the lower end of the pond during this period. Dissolved
oxygen significantly increased, because of aeration while passing through the outfall
and increased oxygenation through pond photosynthesis. There were higher
chlorophyll a concentrations exiting the pond than entering it as well (Table 6.1).
Pollutant removal efficiencies were somewhat less than last year (Mallin et al. 2002).
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 2001 – July 2002. As mean (standard deviation); geometric mean for fecal col.
_____________________________________________________________________
Parameter SS1 SS2
_____________________________________________________________________
DO (mg/L) 3.7 (1.3) 7.7 (2.0)**
Cond. (µS/cm) 331 (121) 163 (45)**
pH 6.8 (0.2) 7.0 (0.2)**
Turbidity (NTU) 3 (5) 5 (2)
TSS (mg/L) 3.5 (4.7) 3.7 (2.0)
Nitrate (mg/L) 0.315 (0.257) 0.055 (0.052)** Ammonium (mg/L) 0.228 (0.291) 0.146 (0.246)
TN (mg/L) 2.210 (4.357) 0.594 (0.439)*
Phosphate (mg/L) 0.382 (0.623) 0.043 (0.026)*
TP (mg/L) 0.700 (1.142) 0.256 (0.517)**
Chlorophyll a (µg/L) 3.4 (5.3) 11.6 (10.0)*
Fecal col. (CFU/100 mL) 381 302
_____________________________________________________________________
* indicates significant difference between input and output concentration at p<0.05
**Indicates significant difference between input and output concentration at p<0.01
Three tributaries of Greenfield Lake were sampled for physical, chemical, and biological parameters (Table 6.2, Fig. 6.1). All three tributaries suffered from extreme
hypoxia, with GL-JRB (Jumping Run Branch), GL-LB (creek at Lake Branch Drive) and
GL-LC (creek beside Lakeshore Commons) all showing average concentrations below
the state standard (DO < 5.0 mg/L). Dissolved oxygen levels were substandard 11 of
12 times at GL-JRB, nine of 12 times at GL-LC, and 10 of 12 times at GL-LB (Appendix B). Biochemical oxygen demand (BOD5) was sampled from August through November
of 2001 as part of a special project. Median values were 2.7 mg/L at GL-LB, 1.8 mg/L
at GL-LC, and 2.4 mg/L at GL-JRB. Previous studies (Mallin et al. 2002) have shown
that BOD in this lake is strongly correlated with algal bloom formation. Turbidity and
suspended solids were generally low in the tributary stations (Table 6.2). Nitrate concentrations were highest at GL-LC, and generally low at GL-JRB and GL-LB (Table
6.2). Nitrate concentrations were lower than during the previous year, this was likely
due to the drought conditions and less runoff. Ammonium concentrations were
generally similar across the three tributary stations. Orthophosphate concentrations
were highest at GL-LC, and similar 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) seven of 12 times at GL-LB, seven of 12 times at GL-LC, and four of 12 times at
GL-JRB. This represents an improvement over 2000-2001, possibly resulting from the drought conditions that subsequently reduced non-point source pollution. Chlorophyll a
levels were generally non-problematic in these streams, with the exception of one algal
bloom in GL-LB (Table 6.2).
Table 6.2. Mean and (standard deviation) of water quality parameters in tributary
stations of Greenfield Lake, August 2001 - July 2002. Fecal coliforms as geometric mean; N/P ratio as median.
_____________________________________________________________________
Parameter GL-JRB GL-LB GL-LC
_____________________________________________________________________
DO (mg/L) 2.7 (1.6) 2.4 (2.1) 3.2 (1.8) Turbidity (NTU) 4 (4) 6 (5) 5 (6)
TSS (mg/L) 4.1 (3.0) 6.5 (3.8) 4.2 (4.3)
Nitrate (mg/L) 0.085 (0.084) 0.062 (0.066) 0.305 (0.174)
Ammonium (mg/L) 0.136 (0.104) 0.157 (0.117) 0.120 (0.107)
TN (mg/L) 0.675 (0.497) 0.653 (0.392) 0.877 (0.515) Phosphate (mg/L) 0.038 (0.018) 0.045 (0.026) 0.213 (0.543)
TP (mg/L) 0.076 (0.034) 0.112 (0.085) 0.330 (0.839)
N/P molar ratio 14.1 11.5 11.3
Fec. col. (/100 mL) 234 499 430
Chlor. a (µg/L) 9.3 (11.4) 9.5 (14.4) 5.6 (4.8)
BOD5 (mg/L) 2.0 (1.2) 2.5 (0.9) 2.1 (1.4)
_____________________________________________________________________
Three in-lake stations were sampled (Table 6.3). 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 affected GL-2340, with 58% of the samples below the state standard (Appendix B).
Median BOD5 was 3.2 mg/L at GL-2340 and 2.7 mg/l at GL-P. Turbidity and
suspended solids were moderate at the three sites. Fecal coliform concentrations were
improved over last year, although still problematic at all three stations. At GL-2340 the
state standard was exceeded on four of 12 occasions, at GL-YD it was exceeded on three of 11 occasions, and at GL-P it was exceeded on seven of 12 occasions in 2001-
2002.
Nitrate concentrations were highest at GL-2340, reflecting the proximity of three
tributary streams. Nitrate levels decreased considerably toward the park (Table 6.3). Total nitrogen, ammonium, total phosphorus and orthophosphate all were highest at
GL-YD (Table 6.3). 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 6.3),
phytoplankton growth in Greenfield Lake should be primarily nitrogen-limited. Our
previous bioassay work indicated that this was indeed the case (Mallin et al. 1999).
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.
Algal blooms exceeding the state standard of 40 µg/L occurred at GL-2340 in
September 2001, and April and June of 2002. GL-YD had blooms of 42 µg/L in
September 2001 and 89 µg/L in April 2002, and GL-P had a bloom of 53 µg/l in May
2002. Thus, Greenfield Lake proper is impaired by high fecal coliform counts, algal
blooms, and high sediment metals levels (Mallin et al. 1999); its tributary stations are
impaired by high fecal coliform counts and low dissolved oxygen. The lake in general and its tributaries were in somewhat better shape in 2001-2002 as compared with 2000-
2001 as a result of less non-point source runoff pollution from drought conditions.
Table 6.3. Mean and (standard deviation) of water quality parameters in Greenfield Lake sampling stations, August 2001 - July 2002. Fecal coliforms given as geometric
mean, N/P ratio as median.
_____________________________________________________________________
Parameter GL-2340 GL-YD GL-P
_____________________________________________________________________ DO (mg/L) 4.0 (2.0) 8.6 (3.5) 9.7 (2.7)
Turbidity (NTU) 5 (6) 5 (3) 6 (4)
TSS (mg/L) 4.4 (2.9) 5.4 (3.4) 5.1 (3.1)
Nitrate (mg/L) 0.151 (0.188) 0.069 (0.092) 0.043 (0.036)
Ammonium (mg/L) 0.127 (0.185) 0.185 (0.305) 0.152 (0.261) TN (mg/L) 0.774 (0.667) 0.864 (0.498) 0.762 (0.562)
Phosphate (mg/L) 0.197 (0.573) 0.212 (0.598) 0.033 (0.029)
TP (mg/L) 0.351 (0.974) 0.410 (1.112) 0.122 (0.144)
N/P molar ratio 19.0 9.4 12.2
Fec. col. (/100 mL) 158 46 262
Chlor. a (µg/L) 24.8 (28.6) 24.1 (25.6) 16.5 (15.3)
BOD5 (mg/L) 3.1 (1.2) NA 2.8 (0.6)
____________________________________________________________________
7.0 Hewletts Creek
Hewletts Creek was sampled at five tidally-influenced areas (HC-2, HC-3, NB-
GLR, MB-PGR and SB-PGR) and one freshwater runoff collection area draining Pine
Valley Country Club (PVGC-9 - Fig. 7.1). Physical data indicated that turbidity was well
within State standards except for two occasions at NB-GLR and one occasion at SB-PGR (Tables 7.1 and 7.2). In contrast to last year, there were no incidents of hypoxia
seen in our 2001-2002 sampling. 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). However, nitrate concentrations in
general were lower than 2000-2001, likely a result of the drought leading to lower non-point source runoff pollution. This was also reflected by the lower median N/P molar
ratios seen at the tidally influenced stations. The chlorophyll a data (Table 7.1) showed
that Hewletts Creek continues to host periodic algal blooms at SB-PGR, as it has in the
past (Mallin et al. 1998a; 1999; 2002a). Fecal coliform bacterial counts were not
performed for the tidally influenced stations in 2001-2002.
Phosphate and nitrate were elevated leaving the golf course at PVGC-9 relative
to the other stations (Tables 7.1 and 7.2). Fecal coliform bacteria counts exceeded
State standards 50% of the time in 2001-2002 at PVGC-9, less than 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. The highest monthly count (5,800 CFU/100 mL) occurred in August
2001. A collaborative effort among Pine Valley Country Club, New Hanover County,
Cape Fear Resource Conservation and Development, the Clean Water Management
Trust Fund, the New Hanover County Tidal Creeks Program, the N.C. State
Cooperative Extension Service at North Carolina State University, the City of Wilmington and UNCW is continuing restoration work on the course that is expected to
improve downstream water quality in upcoming years.
Table 7.1. Selected water quality parameters at lower creek stations in Hewletts Creek watershed as mean (standard deviation) / range, August 2001-July 2002.
_____________________________________________________________________
Parameter HC-2 HC-3
_____________________________________________________________________
Salinity 34.8 (1.5) 32.7 (3.2)
(ppt) 32.1-36.6 26.3-36.5
Turbidity 4 (2) 6 (3)
(NTU) 2-9 2-12
DO 7.7 (1.2) 7.6 (1.3)
(mg/L) 6.2-10.0 5.9-10.3
Nitrate 0.004 (0.004) 0.004 (0.002) (mg/L) 0.002-0.005 0.002-0.009
Ammonium 0.013 (0.007) NA
(mg/L) 0.003-0.027
Phosphate 0.007 (0.003) 0.007 (0.002)
(mg/L) 0.002-0.011 0.004-0.011
Mean N/P 5.7 NA
Median 4.7
Chlor a 1.3 (0.6) 2.2 (1.6)
(ug/L) 0.6-2.8 0.5-4.8
_____________________________________________________________________
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 2001-July 2002.
_____________________________________________________________________
Parameter NB-GLR SB-PGR MB-PGR PVGC-9
_____________________________________________________________________
Salinity 15.7 (11.6) 22.7 (10.2) 0.8 (1.4) 0.1 (0.0)
(ppt) 1.8-32.7 4.9-34.3 0.1-4.1 0.1-0.1
Turbidity 15 (10) 12 (8) 2 (1) 3 (2) (NTU) 4-37 4-26 1-4 1-6
DO 8.2 (2.4) 7.9 (2.0) 7.0 (1.0) 6.2 (1.5)
(mg/L) 5.4-11.5 5.2-10.9 5.9-8.9 3.6-9.1
Nitrate 0.025 (0.024) 0.010 (0.015) 0.157 (0.046) 0.283 (0.208)
(mg/L) 0.004-0.094 0.002-0.055 0.096-0.225 0.010-0.543
Ammonium 0.037 (0.049) 0.021 (0.008) 0.032 (0.026) 0.164 (0.237)
(mg/L) 0.008-0.190 0.011-0.040 0.007-0.086 0.005-0.720
Phosphate 0.015 (0.011) 0.010 (0.007) 0.017 (0.008) 0.184 (0.519)
(mg/L) 0.006-0.050 0.005-0.016 0.009-0.031 0.001-1.827
Mean N/P ratio 8.5 7.6 28.7 130.6 Median 8.1 7.1 25.0 40.6
Chlor a 10.3 (9.8) 11.9 (16.1) 1.2 (1.8) 2.5 (1.6)
(ug/L) 0.9-27.1 0.8-51.3 0.3-6.7 0.9-5.0
Fecal coliforms NA NA NA 244 CFU/100 mL 36-5800
_____________________________________________________________________
8.0 Howe Creek Water Quality
Howe Creek was sampled for physical parameters, nutrients, chlorophyll a , and
fecal coliform bacteria at five locations during 2001-2002 (HW-M, HW-FP, HW-GC,
HW-GP and HW-DT, Fig. 8.1). Turbidity was low near the ICW and exceeded North
Carolina water quality standards on only one occasion at HW-GP (Table 8.1; Appendix
B). Dissolved oxygen concentrations were generally good in Howe Creek, with HW-GP and HW-DT below the standard of 5.0 mg/L on two occasions each (Appendix B).
Fecal coliform bacteria abundances were low near the Intracoastal Waterway,
moderate in mid-creek, and high in the uppermost stations (Table 8.1). HW-GP
exceeded the North Carolina human contact standard on two of twelve occasions, and
HW-DT exceeded the standard on six of twelve occasions (Appendix B). Nutrient levels were generally low in 2001-2002 (Table 8.2). Nitrate levels were lower than during
2000-2001, probably as a result of less runoff due to the drought. Median inorganic
molar N/P ratios were low, reflecting low nitrate levels, and, indicating that nitrogen was
probably the principal limiting nutrient at all stations. There was one algal bloom of 56
µg/L as chlorophyll a at HW-DT, and a lesser bloom of 38 µg/l at HW-GP.
Table 8.1. Water quality summary statistics for Howe Creek, August 2001-July 2002,
as mean (st. dev.) / range.
Salinity Diss. oxygen Turbidity Chlor a Fecal coliforms
(ppt) (mg/L) (NTU) (µg/L) CFU/100 mL _____________________________________________________________________
HW-M 35.6 (0.8) 7.3 (1.2) 6 (3) 1.3 (0.9) 1
34.2-36.9 5.2-9.3 1-11 0.1-3.3 0-20
HW-FP 35.4 (0.9) 7.4 (1.5) 6 (3) 1.1 (0.7) 1 34.0-37.0 5.0-10.0 1-11 0.1-2.2 0-26
HW-GC 34.0 (2.3) 7.2 (1.7) 7 (3) 1.6 (1.4) 8
28.5-36.8 4.7-10.5 1-12 0.1-4.6 0-102 HW-GP 25.4 (10.1) 6.9 (1.7) 11 (8) 6.4 (10.8) 81
2.6-36.1 4.4-10.3 4-27 0.1-38.3 21-525
HW-DT 13.4 (11.50 7.7 (3.7) 11 (7) 10.4 (16.3) 214 1.1-32.8 4.7-18.1 2-22 0.1-56.0 57-865
Table 8.2. Nutrient concentration summary statistics for Howe Creek, August 2001-July 2002, as mean (st. dev.) / range, N/P ratio as mean / median.
_____________________________________________________________________
Nitrate Ammonium Phosphate Molar N/P ratio
(mg/L) (mg/L) (mg/L)
_____________________________________________________________________
HW-M 0.003 (0.002) 0.015 (0.009) 0.007 (0.007) 6.1
0.002-0.007 0.006-0.035 0.002-0.012 5.0
HW-FP 0.003 (0.002) 0.019 (0.010) 0.008 (0.002) 5.9 0.002-0.006 0.006-0.035 0.003-0.011 5.3
HW-GC 0.004 (0.002) NA 0.008 (0.003) NA
0.002-0.006 0.003-0.014
HW-GP 0.006 (0.006) 0.020 (0.011) 0.010 (0.003) 5.8
0.002-0.023 0.008-0.045 0.006-0.014 6.0
HW-DT 0.011 (0.015) 0.021 (0.015) 0.011 (0.006) 6.9
0.002-0.048 0.003-0.051 0.004-0.019 4.7 ____________________________________________________________________
9.0 Motts Creek
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. UNCW scientists sampled Mott’s
Creek at the River Road bridge (Fig. 9.1). A large residential development is scheduled
for construction upstream of the sampling site and between Mott’s and Barnard’s
Creeks. Recently, extensive commercial development has occurred along Carolina
Beach Road near its junction with Highway 421.
Dissolved oxygen concentrations were below 5.0 mg/L on 25% of the occasions
sampled, the same as during the 2000-2001 sampling (Mallin et al.2002). Turbidity was
occasionally a problem, exceeding the state brackish water standard of 25 NTU on two
of twelve occasions. This station also maintained some of the higher suspended solids levels in the system. Fecal coliform contamination was a problem in Mott’s Creek, with
the geometric mean of 300 CFU/100 mL well exceeding the state standard of 200
CFU/100 mL, and monthly samples exceeding this standard on six of twelve occasions
(Appendix B). Nutrient levels showed no major change from the previous year’s study,
but chlorophyll a concentrations showed three blooms in 2002 (Table 9.1) as compared with one during the previous year’s study (Fig. 9.2). BOD5 was sampled on 12
occasions in 2001-2002, yielding a mean value of 3.5 mg/L and a median value of 2.7
mg/L, which was 3X higher than the results of the six samples collected last year (Mallin
et al. 2002). Thus, this creek is showing some water quality problems, with algal
blooms and BOD potentially increasing (Figs. 9.2 and 9.3). The commercial development activities near the headwaters upstream may have contributed to the
decrease in water quality in the creek at River Road.
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)
/ range, August 2001-July 2002. Fecal coliforms as geometric mean / range.
_____________________________________________________________________
Parameter MOT-RR
_____________________________________________________________________
Salinity (ppt) 2.6 (3.8)
0.1-13.3
TSS (mg/L) 22.8 (31.0) 3.2-119.0
Turbidity (NTU) 28 (41)
9-155
DO (mg/L) 6.6 (2.0)
4.1-11.4
Nitrate (mg/L) 0.120 (0.107)
0.006-0.320
Ammonium (mg/L) 0.080 (0.065)
0.004-0.229
Total nitrogen (mg/L) 0.755 (0.351) 0.180-1.421
Phosphate (mg/L) 0.061 (0.066)
0.001-0.254
Total phosphorus (mg/L) 0.101 (0.082)
0.036-0.339
Mean N/P ratio 17.2
Median 4.8
Chlor a (µg/L) 23.0 (36.2)
1.3-115.3
Fecal coliforms (CFU/100 mL) 300 74-3100
_____________________________________________________________________
10.0 Pages Creek
Pages Creek was sampled at three stations, two of which receive drainage from
developed areas (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 2001 and 2002, two each at the stations draining Bayshore Drive (Appendix B). Fecal
coliform bacteria were not sampled at this creek during the past year. Nutrient
concentrations were normally low, and phytoplankton biomass was low with no algal
blooms noted (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 tidal creeks in New Hanover County.
Table 10.1. Selected water quality parameters in lower Pages Creek as mean (standard deviation) / range, August 2001-July 2002.
_____________________________________________________________________
Parameter PC-M PC-BDDS PC-BDUS
_____________________________________________________________________
Salinity (ppt) 35.1 (1.3) 30.3 (4.8) 21.0 (8.3)
33.1-37.0 17.2-34.9 2.5-29.7
Turbidity (NTU) 6 (4) 9 (5) 12 (6)
0-15 1-18 3-22
DO (mg/L) 7.4 (1.4) 6.6 (1.8) 6.1 (1.4)
5.7-9.7 3.8-10.0 3.8-8.8
Nitrate (mg/L) 0.004(0.002) 0.011(0.012) 0.009(0.007) 0.002-0.008 0.002-0.044 0.002-0.022
Ammonium (mg/L) 0.016(0.004) 0.026(0.012) 0.062(0.049)
0.009-0.024 0.008-0.042 0.016-0.200
Phosphate (mg/L) 0.009(0.007) 0.012(0.005) 0.017(0.007)
0.002-0.028 0.002-0.020 0.004-0.032
Mean N/P Ratio 5.5 6.9 12.2
median 5.7 6.4 8.2
Chlor a (µg/L) 2.2 (2.8) 6.4 (6.4) 5.4 (6.3)
0.2-10.2 0.7-23.1 0.2-20.1
_____________________________________________________________________
11.0 Smith Creek
Two estuarine sites on Smith Creek proper, SC-23 and SC-CH (Fig. 11.1) were
sampled. Dissolved oxygen concentrations were below 5.0 mg/L on three of 12
occasions at both SC-CH and SC-23. Thus, low dissolved oxygen continued to be a
periodic water quality problem in Smith Creek. The North Carolina turbidity standard for estuarine waters (25 NTU) was exceeded on two of 12 occasions at SC-CH and one of
12 occasions at SC-23, a decrease over last year. These two stations also maintained
some of the higher suspended solids concentrations in the Wilmington watersheds
system.
Nitrate concentrations increased slightly over last year, but total nitrogen
concentrations increased considerably (Table 11.1). Median inorganic N/P ratios
indicate that nitrogen was generally the limiting nutrient for phytoplankton production in
2001-2002. Algal blooms of 41.4 µg/L and 42.9 µg/L of chlorophyll a occurred at SC-
23 in May and June 2002, respectively, and average chlorophyll a concentration at both stations was considerably higher than in 2000-2001 (Mallin et al. 2002). Fecal coliform bacteria levels exceeded the North Carolina standard for human contact waters (200
CFU/100 mL) three times at SC-23 and three times at SC-CH during the twelve sample
trips; thus, fecal coliform pollution continues to be a problem in Smith Creek (Appendix
B). The geometric mean fecal coliform concentration was below the human contact standard at both stations but well above the shellfishing standard (14 CFU/100 mL) in the estuarine portion of the creek (Table 11.1). The highest monthly counts occurred in
August 2001, when Station SC-23 yielded 1,900 CFU/100 mL. BOD5 was sampled on
12 occasions in 2001-2002 at SC-CH, with a mean value of 2.9 mg/L and a median
value of 2.6 mg/L, an increase over last year. Smith Creek was included for study by the North Carolina Wetlands Restoration
Program, and an additional UNCW sampling effort funded by the WRP was initiated in
summer 2001 and concluded in spring 2002. This included sampling the north and
south branches of upper Smith Creek (SC-KAN and SC-KAS) and two tributaries entering the lower creek at Smith Creek Parkway (SC-PW1 and SC-PW2). Since sampling for this effort was designed to capture several rain events and was not
performed on a pre-set schedule, summary data will not be presented here. However,
our statistical analysis of the data has provided several insights into urban pollution.
For pollutant parameters, SC-KAS had highest geometric mean fecal coliform counts at 990 CFU/100 mL, followed by SC-KAN (585), SC-PW2 (388), and SC-PW1
(264). Median BOD5 and BOD20 were highest at PW-2 (2.8 and 10.4 mg/L,
respectively). No chlorophyll a blooms exceeded 37 µg/L at any of the four sites. Low
dissolved oxygen was not a problem except at PW2, where it fell below 5.0 mg/L five out of 12 times. Suspended solids and turbidity were generally highest at PW2, but
turbidity only exceeded the State standard of 50 NTU on two occasions. Grease and oil
were highest at PW1, with a median level of 61.0 mg/L. Total phosphorus and
orthophosphate were likewise highest at PW1 (median 0.142 mg/L and 0.085 mg/L,
respectively), median nitrate was highest at KAN (0.168 mg/L), median TN was highest at KAS (0.500 mg/L), and median ammonium was 0.050 mg/L at all sites.
Table 11.1. Selected water quality parameters in Smith Creek watershed as mean (standard deviation) / range. August 2001 - July 2002.
_____________________________________________________________________
Parameter SC-23 SC-CH
_____________________________________________________________________
Salinity (ppt) 0.5 (0.6) 1.8 (2.7)
0.1-1.9 0.1-7.4
Dissolved oxygen (mg/L) 6.7 (2.1) 6.9 (2.0)
4.2-10.4 4.2-11.1
Turbidity (NTU) 18 (22) 19 (7)
7-86 11-36
TSS (mg/L) 14.0 (8.3) 20.0 (7.8) 6.6-36.0 8.0-32.0
Nitrate (mg/L) 0.102 (0.114) 0.212 (0.182)
0.010-0.400 0.005-0.510
Ammonium (mg/L) 0.070 (0.053) 0.087 (0.062)
0.005-0.180 0.005-0.180
Total nitrogen (mg/L) 0.741 (0.598) 1.121 (1.136)
0.220-2.510 0.190-4.405
Phosphate (mg/L) 0.042 (0.030) 0.067 (0.027)
0.001-0.097 0.019-0.130
Total phosphorus (mg/L) 0.079 (0.040) 0.097 (0.033) 0.022-0.150 0.049-0.180
Mean N/P ratio 30.6 6.9
Median 6.6 7.0
Chlor. a (µg/L) 19.2 (11.9) 12.8 (9.9)
5.3-42.9 2.9-32.4
Fecal col. /100 mL 93 89
(geomean / range) 28-1900 18-1110
BOD5 (mg/L) 2.9 (1.3) NA
1.3-5.5
_____________________________________________________________________
12.0 Upper and Lower Cape Fear
During previous studies the Wilmington City 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 had been sampled behind the
Wilmington Police Station between 2nd and 3rd Streets (Fig. 12.1), but sampling at that location was discontinued in fall 2001.
Drainage from the Lower CFR was sampled from the stream draining Greenfield
Lake (Fig. 12.1). Processing within the lake served to keep concentrations of most
constituents relatively low (Table 12.1). Most parameters were below state water quality standards during the sampling period. Major algal blooms within the lake did not
get transported over the dam to the river through this station, and turbidities were lower
than last year as well (Table 12.1; Appendix B). Fecal coliform counts exceeded the
state standard 33% of the time sampled, slightly more than last year's 17% (Appendix
B).
Table 12.1. Water quality summary statistics (mean (standard deviation) / range) for
Wilmington Lower (LCF) Cape Fear Watershed, August 2001 - July 2002.
_____________________________________________________________________
Station DO (mg/L) Turbidity (NTU) TSS (mg/L) Fecal col (CFU/100 mL)
_____________________________________________________________________
LCF 8.3 (1.0) 5 (3) 4.7 (2.4) 140
7.2-10.6 1-12 1.3-8.0 16-950 _____________________________________________________________________
Nitrate (mg/L) Ammonium (mg/L) Phosphate (mg/L) Chlor a (µg/L)
_____________________________________________________________________
LCF 0.058 (0.042) 0.089 (0.061) 0.026 (0.023) 13.2 (11.1)
0.007-0.150 0.005-0.200 0.005-0.070 3.0-35.7
_____________________________________________________________________
13.0 Whiskey Creek
Sampling of Whiskey Creek began in August 1999. Five stations were chosen;
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. 13.1). Dissolved oxygen
concentrations were below the State standard 50% of the time at WC-NB, and 25% of
the time at WC-MLR in 2001-2002 (Table 13.1). Turbidity was within state standards
for tidal waters on all sampling occasions (Appendix B). There were no algal blooms
during this period; chlorophyll a concentrations were usually low (Table 13.1). Nitrate
concentrations were highest upstream at WC-NB, followed by WC-SB (Table 13.2), similar to previous years. Ammonium levels were highest at WC-SB and WC-NB, and
these levels were the highest among all of the tidal creek stations sampled. Phosphate
concentrations were highest in the middle of the creek at WC-MLR and WC-AB.
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 Whiskey Creek during this period.
Table 13.1. Water quality summary statistics for Whiskey Creek, August 2001-July
2002, as mean (st. dev.) / range.
Salinity Dissolved oxygen Turbidity Chlor a
(ppt) (mg/L) (NTU) (µg/L) _____________________________________________________________________
WC-MB 33.7 (1.9) 6.6 (1.3) 7 (4) 2.0 (1.3)
30.3-36.1 5.0-8.8 2-13 0.4-4.8 WC-AB 32.2 (2.4) 6.5 (1.5) 10 (4) 2.6 (2.0)
28.0-35.4 4.2-9.1 4-15 0.6-7.2
WC-MLR 30.9 (2.9) 6.1 (1.6) 11 (5) 3.6 (2.6) 25.9-34.9 3.6-9.0 4-18 0.9-9.4
WC-SB 0.1 (0.0) 6.9 (1.3) 5 (3) 0.6 (0.6)
0.0-0.2 3.8-8.7 2-10 0.2-2.2
WC-NB 0.2 (0.0) 4.8 (1.5) 6 (3) 0.5 (0.4) 0.1-0.2 2.3-7.0 2-13 0.2-1.4
Table 13.2. Nutrient concentration summary statistics for Whiskey Creek, August 2001-July 2002, as mean (st. dev.) / range, N/P ratio as mean / median.
_____________________________________________________________________
Nitrate Ammonium Phosphate Molar N/P ratio
(mg/L) (mg/L) (mg/L)
_____________________________________________________________________
WC-MB 0.008 (0.007) 0.030 (0.010) 0.010 (0.004) 9.3
0.002-0.025 0.016-0.054 0.002-0.015 8.2
WC-AB 0.012 (0.011) NA 0.013 (0.004) NA 0.002-0.043 0.008-0.022
WC-MLR 0.013 (0.010) 0.037 (0.017) 0.016 (0.007) 7.8
0.002-0.039 0.011-0.077 0.008-0.031 6.1
WC-SB 0.082 (0.076) 0.106 (0.019) 0.007 (0.014) 109.5
0.022-0.290 0.063-0.127 0.002-0.049 105.8
WC-NB 0.142 (0.082) 0.090 (0.069) 0.005 (0.006) 113.7
0.021-0.330 0.026-0.261 0.002-0.021 105.6 _____________________________________________________________________
14.0 Fecal contamination of tidal creek sediments
Lawrence B. Cahoon
Cassandra O’lenick
Department of Biological Sciences
University of North Carolina at Wilmington
910-962-3706, Cahoon@uncw.edu
14.1 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 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). Much of the
developed area of New Hanover County is served by a central sewage system that has
been relatively well tested and refined since its installation, so animal wastes in storm
water runoff are probably the most common cause of fecal contamination in tidal creek waters. However, fecal coliform contamination even in the absence of storm events and
their immediate runoff argues for persistence of these bacteria in tidal creek
ecosystems.
Studies of fecal coliform bacteria in coastal ecosystems have shown that levels of these indicator bacteria in sediments may reach very high concentrations, and are
apparently maintained by favorable conditions (Rittenberg et al., 1958 ; Dale, 1974;
Hood and Ness, 1982; Chamroux and Guichaou, 1987; Davies et al., 1995). Our
preliminary data from the Bradley Creek drainage showed fecal coliform levels on the
order of 106 CFU m-2 of sediment. 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).
Clearly, if such a source of fecal bacterial contamination is prevalent in our coastal
ecosystems, restoration of full use of these waters will be very difficult.
The study we conducted focused on questions raised by observations of high
fecal coliform levels in aquatic sediments: How do concentrations of fecal coliform
bacteria in sediments vary seasonally and through a drainage basin? Are sediment-associated fecal coliform bacteria a potential source of contamination sufficiently
concentrated to close local shellfishing waters?
14.2 Methods
We sampled sediments at six locations in one tidal creek basin (Bradley
Creek; Fig. 14.1), including headwaters, tributary stream channels, and estuarine
waters, thirteen times during the period June 2001 to January 2002. 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. Following methods developed by Rowland (2002), each sample was then 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 then 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 bacteria, method 9.222 (APHA, 1998). 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 then 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 was
counted as one colony-forming unit (CFU). 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.
___________________________________________________________________ Figure 14.1. Map showing sampling locations in the Bradley Creek watershed,
named as streets crossed by or nearest to tributaries. A=Andover (BC-SBU),
CR=Clear Run (BC-CA), E=Eastwood (BC-NBU), M=Mallard (BC-CR), S=Softwind
(BC-SB), W=Wrightsville (BC-NB).
_____________________________________________________________________
14.3 Results
Sediment fecal coliform concentrations were highly variable within replicate
samples and among sampling locations and dates (Table 14.1). The average coefficient
of variation (standard deviation/mean) for all samples (n=25) was 49%. Mean fecal coliform concentrations ranged from 17.5 CFU cm-2 to 927 CFU cm-2 and averaged 194
CFU cm-2 (+ 240) for the entire data set. The ranges of values for each sampling
location overlapped and the sampling design for this labor-intensive work prevented
sampling at all locations at all sampling times, so differences among sites, if any, could
not be evaluated. However, there was a decline in fecal coliform concentrations during the sampling period, with lower values noted in the winter months.
_____________________________________________________________________ Table 14.1. Sediment fecal coliform bacteria concentrations at sampling locations in the
Bradley Creek basin, New Hanover County, NC, June 2001-January 2002. Values are
means of three replicates (+ one std. dev.).
Date Andover Clear Run Eastwood Mallard Softwind Wrightsville
BC-SBU BC-CA BC-NBU BC-CR BC-SB BC-NB
6/21/01 377 (293) 6/28/01 67 (17) 67 (17)
8/30/01 927 (649) 146 (61) 29 (22) 9/7/01 827 (67) 336 (192)
9/15/01 137 (40) 9/21/01 368 (157) 9/29/01 219 (138) 447 (158) 67 (34)
10/19/01 184 (192) 10/27/01 44 (12) 96 (62)
11/3/01 120 (27) 67 (18) 47 (27) 12/1/01 18 (12) 111 (77) 12/8/01 53 (26) 53 (26)
1/19/02 20 (8)
The significance of fecal coliform concentrations in the sediments was evaluated
by determining the volume of overlying water that would be contaminated to the NC standard for shellfishing (“SA”) waters (14 CFU/100 ml) if the observed quantities of
fecal coliform bacteria were suspended into the water column. For example, 14 CFU
cm-2 would, if suspended, raise the concentration of fecal coliforms to 14 CFU/100 ml in
a water column one-meter deep (1 cm2 x 100 cm = 100 ml), given that average depths
in the Bradley Creek basin are on the order of 1 meter (factoring in tidal variation). Thus, a “concentration factor” was applied to each mean value of sediment fecal
coliform bacteria found in this study that was equal to the average depth (one meter) of
the water column, and put into perspective of NC standards for human contact (200
CFU/100 ml) and for SA waters (14 CFU/100 ml) if those bacteria were suspended.
Results of this analysis were plotted in Fig. 14.2, and show that seven of the 24 samples would, if mixed into the overlying one meter of water, yield sufficient fecal
coliforms to exceed the NC human contact standard. Values were sometimes very high
in the warmer months, but declined with colder temperatures.
_____________________________________________________________________ Figure 14.2. Plot of concentration of fecal coliforms if sediment coliforms were suspended
in a 1 m deep water column vs. sampling date (June 21 2001 to January 19 2002). Lines
at concentrations = 200 and 14 CFU/100 ml denote NC standards for human contact and
shellfishing, respectively.
_____________________________________________________________________
14.4 Discussion
Fecal coliform contamination of coastal waters must be reconsidered in light of
the data presented here. Sediments in the Bradley Creek watershed supported a
variable but significant population of fecal coliform bacteria at all times and places sampled. In the brackish water of BC-SB, suspension of the sediments by physical
forces would have sufficed to create water column concentrations of fecal coliforms
high enough to mandate closure to shellfishing, and, in several cases, to close these
waters to human body contact. Direct body contact with sediments, such as by wading
or manual disturbance of the sediments, would likely be particularly hazardous, assuming that sediment fecal coliform concentrations indicate pathogen presence.
When one adds in the fecal coliforms suspended in the overlying water as well (see
Table 3.1 and Appendix B) then disturbance of the sediments can add a significant
health threat to certain water bodies.
The degree to which sediments support survival by fecal coliforms that recruit to
the sediments by various physical mechanisms (Rusch and Huettel, 2000) or support
actual growth of a colonizing population remains unclear. Fecal coliform bacteria are
ultimately produced in the guts of warm-blooded animals, entering estuarine waters by
direct deposition, e.g., wading birds, storm water runoff, or leaks from waste treatment systems. Inputs of fecal coliform bacteria to New Hanover County tidal creeks are well
documented (Mallin et al., 2000, 2001), and likely derive mostly from animal wastes.
Recent research has shown that not all estuarine sediments support dense
populations of fecal coliform bacteria, so some factor(s) in addition to recruitment must
act to control the actual fecal coliform content of estuarine sediments (Dale, 1974;
Hood and Ness, 1982; Chamroux and Guichaou, 1987; Davies et al., 1995). Rowland
(2002) found that sediment phosphate levels were important in controlling fecal coliform bacteria survival and growth in estuarine sediments. Phosphate loading to estuarine
waters is driven by storm water runoff and other sources that covary with fecal coliform
loading. Cahoon (2002) showed that residential use of phosphate-containing fertilizers
was a major source of phosphate to sediments in tributaries in the Bradley Creek
watershed. Consequently, fecal coliform contamination of tidal creeks in New Hanover County may be driven by a complex relationship between storm water runoff, animal
sources of fecal matter, and phosphate (and other nutrients) from fertilizers, all
associated with residential land uses.
Acknowledgments: We thank Kevin Rowland for assistance with sediment fecal
coliform analyses. This work was supported by the New Hanover County Tidal Creeks
Program, with special thanks to Dr. Michael Mallin.
14.5 Literature Cited
APHA. 1998. Standard methods for the examination of water and waste water, 20th ed.
American Public Health Association. Washington, D.C., A.E. Greenberg, ed.
Cahoon, L.B. 2002. Residential land use, fertilizer, and soil phosphorus as a phosphorus source to surface drainages in New Hanover County, North Carolina. Journal of the
N.C. Academy of Science 118(3):156-166.
Chamroux, S. and C. Guichaou. 1987. The role of sediment in maintaining the
presence of pollution in coastal waters. Ecological Management Of The Sea 14:45-49.
Dale, N.G. 1974. Bacteria in intertidal sediments: factors related to their distribution.
Limnol. Oceanogr. 19:509-518
Davies, C.M., J.A. Long, M. Donald, and N.J. Ashbolt. 1995. Survival of fecal
microorganisms in marine and freshwater sediments. Applied and Environmental
Microbiology 61:1888-1896.
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, and Soil Pollution 25:133-144.
Henis, Y, ed. 1987. Survival and dormancy of microorganisms. New York: John
Wiley and Sons. Pp.1-35.
Hood, M.A., and G.E. Ness. 1982. Survival of Vibrio cholerae and Escherichia coli in
estuarine waters and sediments. Applied and Environmental Microbiology 43:578-
584.
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., 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., 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. Canadian Journal of Civil Engineering 15:450-455.
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 Research 30:2517-2521.
Rittenberg, S.C., T. Mittwer, and O. Ivier. 1958. Coliform bacteria in sediments around three marine sewage outfalls. Limnology and Oceanography 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.
Rusch, A., and M. Huettel. 2000. Advective particle transport into permeable sediments-
evidence from experiments in an intertidal sandflat. Limnology and Oceanography
45:525-533.
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.
Struck, P.H. 1988. Relationship between sediment and fecal coliform levels in a Puget Sound Estuary. Journal of Environmental Health 50:403-407.
Tate, R.L., III. 1978. Cultural and environment factors affecting the longevity of
Escherichia coli in Histosols. Applied and Environmental Microbiology 35:925-929.
15.0 BENTHIC FAUNA OF NEW HANOVER COUNTY TIDAL CREEKS
By
Troy Alphin and Martin Posey
Center for Marine Science
University of North Carolina at Wilmington Wilmington, NC 28409
SUMMARY
1. The types of benthic fauna dominating New Hanover tidal creeks are
representative of communities with moderate environmental impacts, including a
mix of species characteristic of more pristine area as well as species
characteristic of more disturbed habitats.
2. Hewletts and Howe Creeks are distinct with respect to benthic communities compared to Pages and Bradley Creeks. Hewletts and Howe Creeks have lower
abundances of several taxa, especially juvenile clams, as well as lower numbers
of species and diversity. This may reflect greater impacts to the bottom
communities in these creeks.
3. Small experimental increases in local nutrient levels had little effect on the existing bottom communities.
BACKGROUND
Benthic organisms (benthos) are those organisms living in or on the bottom. In estuarine systems, the benthic community is dominated primarily by species that
burrow into the sediments (infauna), often living within tubes or burrow systems.
Animals dominating the infauna in most estuaries include small worms (polychaetes
[bristleworms] and oligochaetes [earthworms and related animals]), amphipod
crustaceans (small shrimp-like animals), clams, and insect larvae, depending on the region of the estuary and salinity range. Benthos may also include larger animals such
as rock crabs and blue crabs. These smaller organisms living in the sands and muds
form the basis for many estuarine food webs. They represent an important linkage
between producers, both decomposers that break down dead plant material (detritus)
and primary producers (visible aquatic plants and microscopic algae), and higher trophic levels including fish, shrimp, and crabs. As benthic animals consume detrital or
planktonic food, they are in turn prey for larger fish, shrimp and crabs. In many
estuarine systems there is a strong link between timing of fish recruitment and their
benthic prey, making this group a crucial link to support and manage fisheries.
Benthic fauna also are considered important indicators of general water quality
conditions. They are used in a variety of monitoring programs to assess overall
estuarine health and long-term trends in estuarine communities, especially related to
anthropogenic impacts (Boesch et al. 1976, Holland et al. 1987; Aschan and Skullerod
1990, Simboura et al. 1995, Hyland et al. 1996). From a monitoring perspective,
benthos offer 3 positive features: 1) they are relatively sedentary and long-lived (1-2 years), 2) they occupy an important intermediate trophic position, and 3) many of the
taxonomic groups in this community respond differentially to varying environmental
conditions. After settlement, most benthos live their entire lives within a relatively
constrained area, often their movements cover less than 5 m2 during their entire adult
lives. Thus, unlike many other biotic or chemical measures, benthos reflect conditions at a specific location. Although a few opportunistic species may live for only a few
weeks, most benthic animals have lifespans ranging from months to a year (although
some taxa may live as long as five years), leading to a community structure that reflects
average physical conditions over a time period of months.
However, benthos vary greatly in their responses to changes in water quality.
Some taxa are relatively tolerant of organic enrichment and low dissolved oxygen while
others are quickly eliminated under low DO conditions (Boesch et al. 1976, Simboura et
al. 1995). Increased nutrient inputs can strongly affect abundances of some species,
through indirect and direct influences on food availability and sediment conditions, while not affecting others. Similarly, there is a wide variation in tolerance to pesticides and
metal contaminants such as mercury and cadmium. In general, sediment type (clays,
silts, sands, etc.), organic content, deposition rates of sediments (from upstream
erosion), dissolved oxygen, salinity and temperature are considered most important in
determining abundances and types of animals in bottom communities. This intimate relationship between the benthos and the physical and chemical environment in which
they live provides us with an extraordinary tool for evaluating estuarine systems and
changes in these systems, especially those related to development practices and
potential anthropogenic impacts within the watershed. By examining shifts in the
benthic community over time (years), one can gain an understanding of the major environmental processes affecting the local biota (Hyland et al. 1996).
A variety of indices have been developed to quantify the health of estuarine
systems based on the relative proportions of species tolerant or susceptible to specific
water quality parameters (e.g.; EPA Benthic Index; Ampelisca toxicity tests; suspension
feeder: deposit feeder ratios; deep burrower : shallow burrower ratios; the Chandler Score, and the BMWP Score Index) (Whitehurst and Lindsey 1990). However,
application of most indices requires long-term monitoring sufficient in duration to
separate seasonal or annual variations from variations due to changes in water quality.
Benthic community studies are a major component of the national EPA Environmental
Monitoring and Assessment Program for estuaries (EMAP) as well as regional monitoring efforts, such as in Chesapeake Bay, Florida Bay, Long Island Sound,
Pamlico Sound, and Tampa Bay.
We sampled the benthic community in 4 of New Hanover County’s tidal creek
estuaries to characterize the communities present, determine if there are differences among the creeks, and examine whether the benthic community is likely to change with
moderate increases in nutrient levels. This information provides both a comparison of
the creek communities as well as insight into potential responses of the creeks to
moderate changes in water quality conditions.
METHODOLOGY
The mid intertidal infaunal community was sampled in the lower portions of
Pages, Howe, Bradley and Hewletts Creek. Paired samples were taken during summer
1995 and summer 1996 at 7 replicate sites within each creek system. Paired replicate
samples were also taken at 7 replicate sites in Bradley and Pages Creek during winter
1997. Fauna were sampled with standard 10 cm diameter X 15 cm deep cores. Cores were preserved in 10% formalin with rose bengal dye added and were subsequently
sieved through a 0.5 mm screen and all retained organisms transferred to 50%
isoproponal for later sorting and identification. Sorting, identification and statistical
analysis of samples was completed over the past 2 years. Because of variability in the
species present between years and the high diversity encountered among the tidal creeks (over 200 infaunal species collected), we compared infaunal communities
among the various tidal creek estuaries based on functional group type. Functional
analyses involve grouping species by selected lifestyle characteristics (living position
and feeding type) that are representative of important impacts and function in the
community. We used two parallel ways of classifying infaunal functional type: feeding type and lifestyle type. Feeding type is classified as deposit feeder (consuming detrital
material), suspension feeder (consuming phytoplankton), grazer (consuming
macroalgae or benthic microalgae) and other (mainly predator). Feeding type is often
used as the most sensitive classification for understanding water quality effects.
Nutrient additions, turbidity and suspended particulates in the water column can strongly affect relative proportions of different feeding types because of the indirect
effect of these variables on various plant and algal food sources and the direct effect of
these factors on feeding efficiency. For example, a decline in suspension feeders and
grazers and an increase in deposit feeders has been suggested to occur with organic
enrichment or nutrient pollution.
Lifestyle functional classifications divide infauna into near surface animals (those
predominantly living within 1 cm of the sediment surface), sedentary organisms/tube
dwellers, and deep burrowers (predominantly found deeper than 2 cm into the
sediment). Infauna provide a critical food source for many fish and crabs and lifestyle distinctions indicate how their availability to these predators may vary, with deep
burrowers being less available as a food source compared to near surface species or
tube dwellers. A shift from deep burrowers and sedentary taxa to near-surface taxa or
small tube builders has been demonstrated under certain pollution regimes.
Abundances of each functional group were compared among the 4 tidal creeks using Analysis of Variance on log-transformed data (Posey et al. 2002).
In addition to comparing faunal communities across the 4 tidal creek estuaries,
we also examined the influence of nutrient additions on community composition and
abundances. This involved a series of blocked nutrient addition and predator exclusion experiments using fertilizer spikes to increase local nutrient concentrations in standard
N : P ratios (Posey et al. 2002). These experiments were conducted in Bradley and
Pages Creeks during both summers and winter. Responses to nutrient additions were
determined by treatment comparisons using Analysis of Variance. This was part of a
larger N.C. Sea Grant funded project examining food webs in these tidal creeks and only influences of nutrient increases are presented here because of potential concerns
with nitrogen and phosphorus inputs from runoff into New Hanover County tidal creeks.
A complete description of this experiment is provided in Posey et al. (2002).
RESULTS AND DISCUSSION
Unlike many estuarine communities, the benthic faunal assemblage in the New
Hanover tidal creeks is characterized by a high diversity of species, with over 200 taxa identified from the 3 sampling periods and 31 taxa comprising 97% of the individuals
collected (Table 1). These taxa include a mix of opportunistic species – species
capable of living in disturbed or anthropogenically impacted areas (e.g. Streblospio,
Mediomastus, Capitella) – as well as species more characteristic of stable
environments (e.g. Prionospio, Terrebelidae, Spiophanes). The community is
dominated primarily by polychaete worms with oligochaetes (earthworm relatives) and
certain clams being secondarily common. The diversity and types of infauna present, as compared to estuaries with greater eutrophication and human impacts (e.g. Charleston
Harbor) and those considered relatively pristine (e.g. North Inlet, SC), indicate only
moderate levels of overall impact to the bottom community in the four New Hanover
County tidal creeks examined.
Despite these overall patterns, fauna differed among creeks and years. Highest
abundances of most functional groups occurred in 1996 compared to 1995 (Figure 1).
However, while there were strong among-year differences in densities of each
functional group, the relative numbers of each functional group remained consistent
across years. This indicates that changes in ratios of functional type may be a conservative measure of community responses to disturbances. Among creeks,
Hewletts and Howe Creeks demonstrated fundamentally different community patterns
compared to Bradley and Pages Creeks. Densities of all functional groups were
greatest in either Pages or Bradley Creeks across both years. Conversely, lowest
densities occurred in Hewletts Creek for all groups in 1995 and functional groups were generally least abundant in either Hewletts or Howe Creek (with the exception of deep
burrowers) in 1996. Howe and Hewletts Creeks were especially characterized by low
abundances of small clams (mostly juveniles), as indicated by low numbers of filter
feeders. Small clams are particularly susceptible to siltation effects and their low
numbers may reflect higher levels of suspended solids and/or historic sedimentation in those systems.
The difference between Hewletts Creek/Howe Creek and Bradley Creek/Pages
Creek is indicated not only by comparison of abundances for functional groups among
creeks but also with cluster analysis of individual species patterns among creeks and years (Figure 2). These analyses (principal component and cluster analysis) look for
similarity among individual species densities and indicate groupings of samples with
similar faunal patterns. The results show groupings by both year (greater numbers in
1996) and creek type (greater numbers in Bradley and Pages Creeks relative to
Hewletts and Howe Creeks). The differences between Hewletts/Howe Creeks compared to Bradley/Pages Creeks mirror similar differences reported for oyster
community patterns in those creeks (2001/2002 Tidal Creeks Report), where Pages
and Bradley Creeks had higher proportions of living oysters on reefs while Hewletts and
Howe Creeks had greater proportions of shell hash and lower oyster densities. These
patterns taken together indicate that lower Howe and Hewletts Creeks have more
impacted benthic communities compared to lower Pages and Bradley Creeks, possibly reflecting local anthropogenic effects, circulation or landscape factors. Specific factors
that should receive further attention as possible explanations for creek differences
include silt loading and sedimentation during the mid-late 1990’s as well as the degree
of organic and nitrogen inputs. Depending on their rate of input, these factors may have
negative effects on faunal abundances in certain situations. Small clams, the group showing greatest proportional difference, are particularly harmed by increased
suspended sediment load, turbidity and siltation rates. Further sampling of benthos over
the next several years is warranted to determine whether changing land use practices
have altered these creek differences.
Nutrient addition experiments examined the effect of local nutrient additions (on
the scale of meters) on faunal densities. The results indicated mixed responses to
moderate additions of nitrogen and phosphorus (Figure 3). During summer, few groups
responded to local nutrient additions, and those were primarily grazers that were
enhanced. However, in winter several groups exhibited a negative response to nutrient enhancement, possibly reflecting indirect effects on macroalgal growth that may inhibit
benthic fauna.
ACKNOWLEDGEMENTS
This report represents part of a larger project funded by North Carolina Sea Grant
(#R/MER-33) conducted in collaboration with Lawrence Cahoon, Michael Mallin,
Meredith Nevers and David Lindquist. This research would not have been possible
without help from many people, including Christopher Powell, Alex Paen, Joe Griffitt,
Daniel Sigmon, Crystal Tilton, Scott Ensign, Matthew McIver, Doug Parsons, and Erica Hubertz.
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1994 EMAP - Estuaries Demonstration Project in the Carolinian Province. NOAA
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Posey, M.H., T.D. Alphin, L.B. Cahoon, D.G. Lindquist, M.A. Mallin and M.B. Nevers. 2002. Top-down versus bottom-up limitation in benthic communities: direct and
indirect effects. Estuaries. 25: 999-1014.
Simboura, N., A. Zenetus, P. Panayotides and A. Makra. 1995. Changes in benthic
community structure along an environmental pollution gradient. Mar. Poll. Bull. 30:470-474.
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Table 1: Dominant infauna and guild classifications. G=grazers, D=deposit feeders, F=filter feeders, O=other (predators), DB=deep burrowers, NS=near surface burrowers,
ST=sedentary/tube dwellers.
Overall Mean
Abundance* Feeding Motility/Living
Taxa (no./cm2) Guild Position Guild Polychaetes
Aricidea spp. 0.059 (0.004) G DB
Armandia maculata 0.017 (0.003) D NS
Capitella spp. 0.003 (0.0004 D DB
Hemipodus roseus 0.003 (0.0004 O DB
Laeonereis culveri 0.083 (0.008) G NS
Leitoscoloplos robustus 0.02 (0.002) G DB
Lumbrineris sp. 0.016 (0.001) G DB
Mediomastus spp. 0.021 (0.002) D DB
Nereis falsa 0.032 (0.005) G NS
Nereis succinea 0.01 (0.001) G NS Notomastus sp. 0.002 (0.0003) D DB
Polydora socialis 0.002 (0.002) D ST
Prionospio heterobranchia 0.009 (0.001) D ST
Spiophanes bombyx 0.001 (0.0008) D ST
Streblospio benedicti 0.260 (0.021) D ST
Syllid spp. 0.095 (0.012) O NS
Tharyx (annulosus) 0.168 (0.012) D NS
Terrebelid sp. 0.011 (0.002) D ST
Bivalves Gemma gemma 0.059 (0.005) F ST
Solen viridis# 0.0008 (0.0002) F ST
Tagelus plebeius# 0.018 (0.001) F ST
Tellina aequistriata# 0.011 (0.002) F/D ST
Gastropods
Acteocina caniculata 0.002 (0.0004) G NS
Ilyanassa obsoleta 0.008 (0.001) D NS
Other
Saccoglossus 0.004 (0.0004) D DB
Diptera larvae 0.005 (0.0008) G NS
Idotea 0.002 (0.0004) G NS
Oligochaeta 0.023 (0.002) D DB Nematostella 0.011 (0.002) O ST
Phoronida 0.009 (0.002) F ST
Turbularia 0.083 (0.014) O DB
*n=288, 1 SE indicated in parentheses; #predominantly juveniles
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Figure 1: Abundances of major functional groups across the 4 estuarine systems during
June 1995 and June 1996. Bars represent mean per cm2 per creek and lines above
bars indicate 1 SE.
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Figure 2: Biplot of 1st and 2nd principal components for abundances of common taxa.
Clusters are identified from subsequent cluster analysis of individual samples. A=all
1995 Hewletts and all 1995 Howe Creek samples, B=all 1996 Hewletts and all 1996
Howe Creek samples, C=all 1996 Pages and all 1996 Bradley Creek samples, and D=all 1995 Pages and all 1995 Bradley Creek samples.
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Figure 3: Proportional difference between nutrient addition and non addition (control) treatments. Numbers represent the average difference among treatments standardized
to control densities ({+nutrients-control}/control). Significant differences between
nutrient addition and open treatments are indicated by ‘*’. Actual densities and F-values
given in Posey et al. 2002.
16.0 References Cited
APHA. 1995. Standard Methods for the Examination of Water and Wastewater, 19th
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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.
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.
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 City of
Wilmington, the North Carolina Clean Water Management Trust Fund, the North
Carolina Wetlands Restoration Program, and the University of North Carolina at
Wilmington. For project facilitation and helpful information we thank Bonnie Duncan, Paul Foster, Dexter Hayes, Matt Hayes, David Mayes, Chris O’Keefe, Rick Shiver
and Dave Weaver. For field and laboratory assistance we thank Heather CoVan,
Scott Ensign, Matt McIver, Tara MacPherson and Kevin Rowland.
18.0 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 (µg/L)
_____________________________________________________________________
CFU = colony-forming units
mg/L = milligrams per liter = parts per million
µg/L = micrograms per liter = parts per billion
19.0 Appendix B. UNCW ratings of sampling stations in Wilmington and New Hanover County watersheds based on August 2001 – July 2002 data, 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-TR G F G P
BNC-CB G G G P BNC-RR G F P P
Bradley Creek BC-CA G P G P
BC-CR G G G P
BC-SB F F G P BC-SBU G G G P
BC-NB G F G G
BC-NBU G G G P
BC-76 G G G G
Burnt Mill Creek BMC-AP1 G P G P
BMC-AP3 G G G F
BMC-PP G 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 F G G
FC-17 G F G F
FOY G G G G
Greenfield Lake GL-SS1 G P G P
GL-SS2 G G G P
GL-LC G P G P
GL-JRB G P G P GL-LB G P G P GL-2340 P P G P
GL-YD F F G P
GL-P G G G P
Hewletts Creek PVGC-9 G G G P HC-M G G G -
HC-2 G G G -
HC-3 G G G -
HC-NWB G G G -
NB-GLR G G F - MB-PGR G G G -
SB-PGR G G G -
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 F G P
Motts Creek MOT-RR F F F P
Pages Creek PC-M G G G -
PC-BDDS G F G -
PC-BDUS G F G -
Smith Creek SC-23 F F G F
SC-CH G F F F
Lower Cape Fear LCF-GO G G G P
Whiskey Creek WC-NB G P G -
WC-SB G G G -
WC-MLR G F 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.
20.0 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-AP1 N 34.22927 W 77.86658
BMC-AP2 N 34.22927 W 77.89792
BMC-AP3 N 34.22927 W 77.90143 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
Hewletts Creek PVGC-9 N 34.19165 W 77.89175
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
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
_____________________________________________________________________
21.0 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,
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.
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.