ENVIRONMENTAL ASSESSMENT OF THE LOWER CAPE FEAR RIVER SYSTEM, 2000-2001

by

Michael A. Mallin, Martin H. Posey, Thomas E. Lankford, Matthew R. McIver, 
Scott H. Ensign, Troy D. Alphin, Michael S. Williams, Mary L. Moser,
and James F. Merritt

CMS Report Number 01-01
Center for Marine Science
University of North Carolina at Wilmington
Wilmington, N.C. 28409
October 2001

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Executive Summary

            Multiparameter water sampling for the Lower Cape Fear River Program (LCFRP) has been ongoing since June 1995.  The LCFRP currently encompasses 35 water sampling stations throughout the Cape Fear, Black, and Northeast Cape Fear River watersheds.  The LCFRP sampling program includes physical, chemical, and biological water quality measurements, analyses of the benthic and epibenthic macroinvertebrate communities, and assessment of the fish communities.  Principal conclusions of the UNCW researchers conducting these analyses are presented below, with emphasis on the period June 2000-June 2001.  The opinions expressed are those of UNCW scientists and do not necessarily reflect viewpoints of individual contributors to the Lower Cape Fear River Program.  

            The mainstem lower Cape Fear River is characterized by reasonably turbid water containing high levels of inorganic nutrients.  It is fed by two large blackwater rivers (the Black and Northeast Cape Fear Rivers) that have low levels of turbidity, but highly colored water, with less inorganic nutrient content than the mainstem.  While nutrients are reasonably high in the river channels, algal blooms are rare because light is attenuated by water color or turbidity, and flushing is high.  Periodic algal blooms are seen in the tributary stream stations, some of which are impacted by point source discharges.  Below some point sources, nutrient loading can be high and fecal coliform contamination occurs.  Other stream stations drain blackwater swamps or agricultural areas, some of which periodically show elevated pollutant loads or effects.

            Several stations were in violation of North Carolina water quality standards based on percent of samples in violation during the year June 2000 – June 2001.  Definitions used in part by the North Carolina Division of Water Quality for use support consider a water body non-supporting (NS) of its designated use if the water quality standard for a given parameter is in violation > 25% of the time, and partially supporting (PS) if the standard is in violation between 11 and 25% of the time.  Based on this, stations that can be considered non-supporting for dissolved oxygen (4.0 in blackwater stations and 5.0 in estuarine stations) were NAV, ANC, NC403, PB and SR.  Stations considered partially supporting for dissolved oxygen include HB, BRR, M61, M54, M42, NCF117, GS, BCRR and GCO.  Stations in which fecal coliform concentrations exceeded 200 CFU/100 mL  >25% of the time (NS) were LRC, ROC, BC117, BCRR and HAM.  Those considered PS for fecal coliforms include NAV, HB, LVC, SAR, NC403, PB, 6RC, SR, and COL.  Copper was the only problematic waterborne metal, with Stations M61, M42, M23, M18 and BC117 rated NS and NAV, M54 and M35 rated PS.

With five full years of data we have attempted to ascertain whether or not water quality in the system is getting better or worse, based on some common parameters that have North Carolina water quality standards.  The results (Table A) show no clear pattern at this point.  Low dissolved oxygen is a well-known problem in this system, with every year showing greater than one third of the sampling sites as impacted.  It is also strongly influenced by the presence of hurricanes, as hurricane years showed 46-65% of stations impacted while non-hurricane years showed 35-40% of stations impacted.  In contrast, yearly fecal coliform bacterial abundances appear unrelated to hurricane presence, ranging from 15-63% of stations impacted during hurricane years.  Our previous research has demonstrated that maximum fecal coliform numbers following hurricanes are seen in the first seven days after landfall, with a subsequent decrease in numbers.  However, since non-hurricane years show 35-37% of stations impacted, this tells us that fecal coliform pollution is widespread in the lower Cape Fear system, from both point and non-point sources. 

            Turbidity also appears to be relatively uninfluenced by hurricanes.  Most of the impacts are in the mainstem Cape Fear River and the estuary, and are likely due to rainfall variation in the Piedmont and upper Coastal Plain.  Copper impacts were highest in 1996-1997, due to an industrial waste treatment plant on Little Rockfish Creek, which has undergone subsequent improvement.  There are still copper violations below the Burgaw wastewater treatment plant and in the river and estuary proper.  To summarize, the water quality situation in the Lower Cape Fear system appears to be getting neither better nor worse in terms of annual standard violations by these four indicator parameters.

Biochemical oxygen demand (BOD) and streamflow were sampled in several rural stream stations during the period May 2000 – May 2001.  These were non-storm event samples; thus largely representing base flow.  Results showed that there was little difference among sites in terms of BOD.  Most sites averaged around 1.0 mg/L as BOD5.  BOD loading from the individual streams appeared to be largely dependent upon the amount of stream flow.  Details are presented in Chapter 3.  These studies lead us to suggest that samples collected during runoff events will present a more definitive picture of rural non-point source BOD loading to the system.

Benthic studies for the 2000-2001 period emphasized analysis of site characteristics, annual and seasonal variations in community structure (numerically dominant species) at each site, and long-term trends in species richness, diversity and faunal abundance. Basic findings for this report are:

·        The Northeast Cape Fear River and Cape Fear River oligohaline sites (NCF6 and NAV) exhibit fundamentally different community structures. The NCF6 site is characterized by moderate numbers of species, low abundances, and some variability in dominant species among seasons and years. In contrast, the NAV site is characterized by high abundances, domination by relatively few taxa and consistent patterns of dominance across seasons and years. Such differences indicate fundamentally different processes controlling these communities.

·        There is a general gradient in dominance from oligochaetes and insect larvae in the upper sites, along with the polychaete Marenzellaria on some dates, to exclusive domination by polychaetes in the most downstream, saline site. The mid site, M54, has a mix of these taxa along with peaks in densities of 2 amphipod species.

·        NAV and M31 showed persistent patterns of dominant species among years and seasons. There was somewhat more variability in the identity of dominant species at NCF6 and M54, possibly reflecting salinity fluctuations, but even these sites were dominated by a small subset of the 250 total taxa that have been identified from this monitoring effort.

·        Relative faunal density and diversity patterns were consistent among years with the exception of 1999. In 1999, there were relatively higher densities at NCF6 and higher diversity at NAV.

·        All of the sites are dominated by relatively opportunistic taxa, suggesting possible community resilience to certain short-duration disturbances.

To summarize the Lower Cape Fear River Program fisheries studies, monitoring efforts during 2000-2001 revealed several encouraging trends evident at both the community and species level.  Overall species richness and total abundance (indexed as catch per unit effort - CPUE) increased during spring 2001 to levels exceeding those for previous years.  A total of 49 species were captured during spring 2001 compared to 43 species in spring 1999 and 36 species in the spring 1998.  Total CPUE was also higher for all gear types during spring 2001 than for any previous spring period.  Increased abundance was driven by increased catches of spot, striped mullet, and southern flounder in 2001.  The incidence of disease during spring 2001 (1.2%) was also lower than observed during previous spring periods.  Collectively, increases in richness and abundance combined with slightly lower disease rates suggest that fish communities in the Cape Fear River are recovering from hurricane impacts experienced during 1996, 1998 and 1999.
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Table of Contents

**Any tables or figures not included on this site are available in hard copy from the Center for Marine Science at the University of North Carolina at Wilmington**