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Most of the information presented on this page was taken from
a report entitled Environmental Quality of Wilmington and New
Hanover County Watersheds 2003-2004. This report was prepared in
January, 2005 by Michael A. Mallin, Lawrence B. Cahoon, Martin
H. Posey, Douglas C. Parsons, Virginia L. Johnson, Troy D.
Alphin, Byron Toothman and James F. Merritt of the Center for Marine
Science University of North Carolina at Wilmington.
This report represents combined results of Year 10
of the New Hanover County Tidal Creeks Project and Year 6 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
2003 – July 2004, and then discuss key results of several special
studies conducted over the past two years.
To learn more about the purpose of this program,
or find water quality dating back to 1993 visit the UNCW Center for
Marine Science Tidal Creeks website visit.
Water Quality Sampling Station Results
2003-2004:
Click on any Tidal Creek or Watershed Name to view
the sampling results by individual station. Water quality analyzed
in the tidal creeks includes 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
Barnards
Creek – There was only one station sampled in this watershed during
2004, lower Barnard’s Creek at River Road. This site had no algal bloom
or BOD problems; it had fair water quality in terms of fecal
coliform counts but poor water quality as judged by excess turbidity
and low dissolved oxygen.
It also had the highest suspended solids, ammonium, total
nitrogen and total phosphorus levels among all the local
watersheds.
Bradley
Creek – Turbidity was not
problematic during 2003-2004.
Dissolved oxygen was good to fair at all sites except the
branch at College Acres (BC-CA) where it fell below 5.0 mg/L on
three occasions during summer.
Elevated nitrogen and phosphorus levels enter the creek in
both the north and south branches, one minor algal bloom occurred in
the south branch (BC-SB) and one major bloom occurred in the creek
at College Acres. Fecal
coliform bacterial counts were only sampled at BC-CA, where
contamination was excessive during six of the seven samples
collected in 2004.
Burnt Mill
Creek – A sampling station
on Burnt Mill Creek at Princess Place had no turbidity or suspended
solids problems, but substandard dissolved oxygen during all visits
from May through September.
There was one moderate algal bloom in June 2004. This station also had poor
microbiological water quality, exceeding the standard for human
contact in five of seven samples. The effectiveness of Ann
McCrary wet detention pond on Randall Parkway as a pollution control
device was poor during 2004.
While the pond led to a significant reduction in fecal
coliform bacteria and an increase in dissolved oxygen, it failed to
reduce nutrient concentrations including ammonium, nitrate, total
nitrogen, orthophosphate and total phosphorus. Several water quality
parameters indicated a subsequent worsening of the creek from where
it exited the pond to the downstream 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 2003-2004. Dissolved oxygen
concentrations periodically decreased below 5.0 mg/L in summer at
some upper creek stations, but otherwise 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. However, fecal coliform
concentrations have recently shown an increasing trend in some upper
and middle creek stations, potentially a result of increasing
development in the headwaters areas.
Greenfield
Lake
– The
three tributaries of Greenfield Lake (near Lake Branch Drive,
Jumping Run Branch, and Lakeshore Commons Apartments) all suffered
from severe low dissolved oxygen problems and the in-lake stations
(GL-2340, GL-YD, and GL-P) had low dissolved oxygen
periodically. 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.
Station GL-P, at the Park, had high fecal coliform counts on
three of the seven occasions sampled, and very low dissolved oxygen
during summer. The
stream near Lakeshore Commons also maintained high nitrate and
phosphate concentrations.
The lake again experienced algal blooms at times, with
several blooms exceeding the N.C. State Standard of 40 mg/L of chlorophyll a, and a three-month
duckweed bloom near the Park.
In general, Greenfield Lake continues to suffer from fecal
coliform bacterial contamination, algal blooms, and low dissolved
oxygen problems.
Hewletts
Creek – The
tidally-influenced stations in this watershed had generally low
turbidity levels in 2003-2004.
Two major algal blooms occurred in the north branch (NB-GLR)
in summer 2004, with dissolved oxygen concentrations generally good
to fair at tidal sites.
Fecal coliform counts were low at the lower sites, moderate
at the mid-creek sites, and high in terms of the N.C.human contact
standard of 200 CFU/100 mL at the north and middle branches, but
moderate at the south branch.
Since January 2004
five non-tidal sites have been sampled in the Hewletts Creek
watershed. One site is
PVGC-9, draining Pine Valley Country Club. This stream had no dissolved
oxygen or turbidity problems, moderate nutrient levels, and had one
severe algal bloom in summer 2004. However, six of the seven
months sampled showed excessive fecal coliform counts, a general
increase over previous years.
The other sites are being sampled to gain background
information on the water quality of streams entering (DB-1, DB-2,
DB-3) and exiting (DB-4) a proposed constructed wetland/future park
area known as the Dobo site, draining into the headwaters of
Hewletts Creek. The
input and output streams to the Dobo site had no turbidity or algal
bloom problems, but low dissolved oxygen was an issue at DB-1 and
all sites had excessive fecal coliform problems. DB-1 also had comparatively
high ammonium, total nitrogen, and total phosphorus
problems.
Howe
Creek – Five
stations were sampled in Howe Creek in 2003-2004. 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 mid-creek, and high in the uppermost two stations during
2003-2004. After
several years of improving water quality, in 2003-2004 the upper two
stations showed a doubling of fecal coliform counts from 2001-2003
levels. This is a
concern especially as Howe Creek was previously designated as an
Outstanding Resources Water by the State of North
Carolina.
Motts
Creek
– This creek was
sampled at only one station, at River Road. One major and one minor
algal bloom occurred during this sampling period. Dissolved oxygen was below
5.0 mg/L on all occasions from May through September and there were
a few instances of elevated BOD5 in 2004. Turbidity and suspended
sediments were not a problem.
Fecal coliform counts exceeded 200 CFU/100 mL on five of the
seven sampling occasions in 2004.
Pages
Creek – This creek
maintained generally good water quality during 2003-2004. Nutrient loading was low and
algal blooms were not found, even at the most human-impacted
stations. 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 2003-2004. This
watershed has some of the lowest development and impervious surface
coverage in the New Hanover County tidal creek
system.
Smith
Creek – Smith
Creek (sampled at SC-CH, at Castle Hayne road) had moderate water
quality problems as reflected by several parameters. Turbidity and elevated
suspended sediments occurred on occasion, but algal blooms or high
BOD were not problematic. Excessive fecal coliform bacteria counts
occurred on two of seven sampling occasions in 2004. Low dissolved oxygen
problems occurred during most summer months.
Whiskey
Creek – Whiskey
Creek had relatively high nutrient loading but generally low
chlorophyll a
concentrations in 2003-2004.
There were a few 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 2003-2004 in this creek.
Phytoplanton,
productivity in Futch and Hewletts Creeks
– Phytoplankton are microscopic plants
found in marine, estuarine and freshwater ecosystems. Phytoplankton, like other
plants, utilize sunlight to convert carbon dioxide into high-energy
carbohydrates and release oxygen during the process of
photosynthesis. The
rate at which these processes take place is known as primary
production.
Collectively, phytoplankton are the foundation of food webs
in water systems, providing a nutritional base for zooplankton and
commercially important shellfish and finfish. Phytoplankton production in
these tidal creeks is greatest in summer and lowest in winter,
showing that light and temperature control the basic seasonal
patterns. Productivity
is higher at low tide than high tide, and higher upstream than
downstream. Also,
productivity was higher in Hewletts Creek than Futch Creek,
demonstrating that the greater nutrient inputs from the more highly
developed watershed cause higher phytoplankton productivity
rates.
Our experiments also demonstrate
that phytoplankton production in Futch and Hewletts Creeks is high,
equal to or greater than that of large eutrophic estuaries such as
the Neuse and Pamlico River Estuaries. However, these tidal creeks have not
suffered from the major algal bloom problems, toxic blooms, and fish
kills that those larger systems have had. Phytoplankton biomass and
productivity can be greatly reduced due to grazing by zooplankton,
shellfish and other predators.
We suspect that intense grazing by invertebrates such as
oysters have helped to control excessive growth of algae in these
creeks, especially in summer months when phytoplankton
production is highest.
This tells us that these creeks are habitats where there is
intense food chain activity, supporting the larval and juvenile
stages of many species of finfish and shellfish, a major reason why
these creeks are considered primary nursery areas for marine
life.
Fecal
Coliform Contamination of Sediments
- Sediments in the Bradley Creek drainage frequently
harbored high numbers of potentially-pathogenic microbes including
fecal coliform, streptococcus, and enterococcus bacteria,
particularly during the warmer times of the year when children are
most likely to play in these waters. As other studies have shown,
fecal indicator bacteria concentrations in sediments correlate with
the presence of other fecal pathogens. It is important to consider
the public health risk associated with this poorly known reservoir
of contaminants. Many water-borne diseases are not properly tracked
to their sources, so a significant problem may be occurring without
real awareness of its cause. Human contact with these contaminated
sediments must be considered as a serious problem for heavily
developed coastal areas, such as the Bradley Creek watershed.
Given the
attributes of the Bradley Creek watershed, it is likely that
animals, both wild and domestic, were the most important fecal
contamination sources. One conclusion, therefore, is that pet waste
management should be addressed for all residential areas in coastal
watersheds, not just beach communities. Moreover, a significant
population of “wildlife” that actually associates with human
communities, eating human garbage and unsecured pet foods, such as
raccoons and opossums, likely lives in this watershed and
contributes to the fecal contamination problem. Educational efforts
can reduce this problem as well. It is important to note that animal
wastes can be as dangerous a source of pathogens to humans as human
waste, particularly because some animal-derived pathogens, such as
infectious protozoans, can cause infections that are difficult to
diagnose and treat.
Tidal Creek
Benthic Fauna
- Settlement
and survivorship of oyster spat are the two most important factors
determining the development and stability of oyster reefs within any
system. When reefs are
constructed of shell hash with low relief high numbers of spat
settle on them, because predators like crabs will avoid these open
areas to avoid getting eaten by larger fish. As reefs grow and their
architecture becomes more complex, many other species inhabit them
and a complex food web develops. The habitat function of
oyster reefs is critical especially in shallow estuarine
environments where oysters may represent one of the few structural
habitats available. As
oyster reefs develop the number of crevices and the amount of
internal space within the oyster matrix increases. These areas are colonized
very quickly by small crabs and shrimp that may in turn prey on
newly settled oyster spat.
Thus as oyster reefs begin to provide a more complex refuge
the overall survivorship of oyster spat may decline on that reef to
a stable level. This
provides an excellent example of biological controls and illustrates
how a healthy ecosystem operates. As the oyster reefs develop
they provide more habitat allowing a greater number of species of
epifauna (such as crabs and shrimp), these species in turn provide
food for many of the commercially and recreationally important
finfish, such as drum, blue fish, spots and croaker among
others.
Thus, if rapid
recolonization of an area by oysters is desired, construction of low
reefs of shell hash is likely to provide a boost in oyster
colonization and reef expansion. If the additional benefit of
increased habitat for the whole creek community is desired, reefs of
mixed complexity show a great deal of potential for the development
of oyster reef for habitat restoration and
mitigation. |
