ENVIRONMENTAL ASSESSMENT OF THE LOWER CAPE FEAR RIVER SYSTEM, 1998-1999

by

Michael A. Mallin, Martin H. Posey, Mary L. Moser, Lynn A. Leonard,
Troy D. Alphin, Scott H. Ensign, Matthew R. McIver, G. Christopher Shank,
and James F. Merritt

Report Number 99-01
Center for Marine Science
University of North Carolina at Wilmington

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 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 1998-May 1999. The opinions expressed are those of UNCW scientists and do not necessarily reflect viewpoints of individual contributors to the Lower Cape Fear River Program.
    Basic water quality patterns were similar to those of previous years. Dissolved oxygen showed summer sags to hypoxic (3.2-4.9 ppm) conditions in the lower river and upper estuary. Turbidity was high in the river and estuary following upstream rain events. Inorganic nutrient concentrations were elevated in the river and decreased downstream through the estuary. Based on four years of data, summer phosphate concentrations in the lower river and estuary showed a significant increase. Inorganic nutrient and turbidity concentrations were lower in the blackwater tributaries than in the Cape Fear mainstem. Fecal coliform counts were elevated at many stations following rain events, and elevated regardless of weather at certain chronically problematic stations below point source discharges.
    Several stations were in violation of North Carolina water quality standards based on parameter averages for the sampling year. Turbidity levels were above the 25 NTU standard for estuarine waters at both NAV (34.0 NTU) and HB (27.4 NTU). Average dissolved oxygen concentrations were below the state standard of 5.0 ppm at both NC403 (3.5 ppm) and SR (3.3 ppm). Geometric mean fecal coliform concentrations exceeded 200 CFU/100 mL at PB (223 CFU/100 mL), LRC (382 CFU/100 mL), BCRR (300 CFU/100 mL) and BC117 (978 CFU/100 mL). Average copper exceeded 7.0 ppb at BC117 (8.0 ppb).
   Suspended particulate matter (SPM) data collected in the lower Cape Fear River indicate that precipitation and season interact to control the composition of material being exported to the coastal ocean. Positive correlations between rainfall in the upper watershed and the various components of SPM in the Cape Fear mainstem suggest that runoff from the Piedmont contributes to sediment loading in the estuary. The mineralogy of suspended sediments at N11 is consistent with an expected composition for Piedmont soils, suggesting a Piedmont source for the inorganic component. The low inorganic SPM concentrations and high organic percentages observed at N117 and B210 further indicate that little particulate matter enters the lower Cape Fear River from these blackwater systems. Tidal processes and seasonal variations in primary productivity, both beyond the scope of this study, appear to mediate SPM concentration and composition in the estuary. Efforts to control particulate loading in the lower Cape Fear River should begin in the upper watershed and should focus on the retention of inorganic components.
   The LCFRP examined loading of biochemical oxygen demand (BOD) into the lower river system. The stations included NC11 on the Cape Fear mainstem, B210 on the Black River, and NCF117 on the Northeast Cape Fear River. Average BOD5 load coming into NC11 was 27,842 lbs/day, while at B210 and NCF117 loads were 3,460 and 3,737 lbs/day, respectively. Inputs from International Paper and Livingston Creek combine to increase BOD5 load to the mainstem by approximately 28%. BOD5 was positively correlated with fecal coliform bacteria counts and also with turbidity. Turbidity was strongly correlated with fecal coliform counts, river flow, and BOD loading rate, indicating the importance of non-point source runoff to the BOD load. Predictive regression models are presented within that explain much of the variability in BOD load entering the lower river system. River flow alone can explain much of the variability in BOD load in the mainstem Cape Fear and Black Rivers, but a significant portion of the BOD load in the Northeast Cape Fear appears to be related to other factors, possibly point sources.
    A statistical analysis of eleven largely rural watersheds within the Cape Fear Basin found significant correlations between stream turbidity, fecal coliform counts, and the amount of rain that fell in the area in the previous 24 hours. This indicates that there is an overall non-point source runoff pollution problem in the basin. When the watersheds were examined individually, those watersheds with greater than 13.5% wetlands coverage did not show significant relationships between rainfall and the two pollution parameters. However, watersheds with less than 13% wetlands coverage demonstrated very strong correlations between rainfall, turbidity, and fecal coliform counts. Thus, the presence of extensive wetland areas within a watershed appears to buffer the effects of rainfall-induced pollution runoff, even in watersheds containing large numbers of concentrated animal operations.
    The riparian forest was logged just upstream of our Goshen Swamp site in June of 1998. This clearcutting activity led to increases in suspended solids, turbidity, total nitrogen, total phosphorus, and fecal coliform bacteria that lasted until Hurricane Bonnie in late August 1998. Following Bonnie, nitrogen, phosphorus, and fecal coliforms continued to increase until October, and subsequently declined. Dissolved oxygen showed sharp declines during this period, demonstrating near anoxia in June, and following Bonnie in September and October. Longer-term effects were reflected by high chlorophyll a concentrations, which indicated the appearance of unprecedented algal blooms in July and August of 1998 and June and August of 1999. Fecal coliforms also displayed large increases in June and July of 1999. The blooms were likely a result of the tree canopy being reduced, allowing more light penetration to the stream. The 30 ft vegetated buffer left along the stream was evidently not wide enough to prevent the water quality impacts noted above.
   For the benthic community, we have emphasized analysis of site characteristics, annual and seasonal variations in community structure, effects of Hurricane Bonnie, and correlations with selected physical parameters monitored as part of the overall Cape Fear River Program monitoring effort. These analyses are very preliminary in nature, based upon only three years of data (two of which were affected by hurricanes) and only four sampling sites. However, they provide an initial insight into biotic community structure in the lower Cape Fear River system. Basic findings for this report are:

• The Northeast Cape Fear River and Cape Fear River oligohaline sites (NCF6 and NAV) exhibit fundamentally different benthic community structures. The NCF6 site is characterized by high numbers of species, very low abundances, and minimal seasonality. In contrast, the NAV site is characterized by fewer numbers of species, high abundances, and strong seasonality. Such differences indicate fundamentally different processes controlling these communities.
• Lower estuarine sites (M54 and M31) are characterized by moderate species richness (number of species) and faunal abundances. They are dominated by taxa typical of other river-dominated mid Atlantic and southeastern estuaries, though clams are much less common than reported in many other studies.
• Hurricane Bonnie was associated with severe declines in faunal abundances. After the hurricane, three of the four sites had total infaunal densities lower than any previously recorded during our three years of monitoring.
• Significant correlations between certain physical parameters and abundances of specific faunal groups were observed. However, most of these correlations appear to reflect concordant seasonality in faunal abundances and water conditions rather than indicating any specific problem area. When seasonal variation in water conditions is taken into account, no single physical measure had an overriding influence on the infaunal community.

    In 1998-1999 we completed a second year of baseline data collection for evaluation of epibenthic community stability and seasonal patterns. Epibenthic taxa consisted primarily of decapod crustaceans, amphipods, isopods, and juvenile fish. Highest abundances were recorded in the summer and fall of 1997 and 1998, a time period when many fishery species are present in the system. Abundances of early stage juvenile blue crabs, although common in the estuary, showed an interesting trend toward greater utilization of low salinity areas.
   Comparing fish monitoring results in this year to those of previous years resulted in some interesting differences, and similarities. The effects of Hurricane Bonnie (August 1998) on the fish community were less pronounced than those we documented in the aftermath of Hurricane Fran in 1996. However, fish populations in the Northeast Cape Fear River were impacted more than those in the Cape Fear River by both storms. Northeast Cape Fear River fish populations did not fully recover for almost a year following Hurricane Fran, but fish diversity and abundance rebounded in just a few months following the passage of Hurricane Bonnie. The history of storm events and the less widespread hypoxia following Hurricane Bonnie probably both contributed to the relatively rapid recovery of the fish community. Although overall disease incidence remained low (1.3%), there has been a persistent trend toward higher incidence of disease among fish collected in the upper Cape Fear River stations, as compared to upper Northeast Cape Fear or estuarine stations. This may indicate degraded water quality or environmental stressors in the upper Cape Fear River. Non-native species continue to dominate the gillnet collections. In addition, we documented the occurrence of a parasitic nematode in the swim bladder of American eels we collected throughout the drainage. This is the first time that this non-indigenous parasite has been found in North Carolina and it may have significant adverse effects on the eel population in this system.
    Hurricane Bonnie led to severe environmental impacts on water quality and the benthic communities of the LCFR system. Heavy rain brought large amounts of low dissolved-oxygen swamp water into the main channels. Large quantities of untreated or incompletely treated human sewage were rerouted into streams and rivers due to power outages. Additionally, a swine waste lagoon was inundated along the Northeast Cape Fear River, and there was extensive spraying of lagoon waste onto rain-saturated spray fields along the upper Northeast Cape Fear River. The human and swine waste caused high concentrations of fecal coliform bacteria in several areas, especially the Northeast Cape Fear River, the upper estuary, and several stream stations. Highest BOD levels were found below the swine spray fields and in streams draining watersheds rich in swine farms. There were near-anoxic waters in the Northeast Cape Fear for over three weeks, and a massive fish kill of a broad variety of species. Recovery of dissolved oxygen to normal was fastest in the mainstem Cape Fear (about two weeks), then the Black River (about one month), then the Northeast Cape Fear (two months).

Table of Contents

 

1.0 Introduction 1 Site Description

2.0 Physical, Chemical, and Biological Characteristics of the Lower Cape Fear River and Estuary 1 Introduction 2 Materials and Methods 3 Results and Discussion 4 References Cites Tables and Figures

3.0 Suspended Particulate Matter Characteristics in the Lower Cape Fear River System 1 Background 2 Methodology 3 Results and Discussion 4 Summary 5 References Tables and Figures

4.0 Rainfall, Runoff, and BOD Loading to the Lower Cape Fear River and Estuary 1 Introduction 2 Materials and Methods 3 Results and Discussion 4 Acknowledgments 5 References Cited Tables and Figures

5.0 Effects of Timber Harvesting on Water Quality of the Goshen Swamp 1 Introduction 2 Site Description 3 Methods 4 Results and Discussion 5 Conclusions 6 Acknowledgments 7 Literature Cited Tables and Figures

6.0 Benthic Communities in the Cape Fear Estuary 1 Summary 2 Background 3 Methodology 4 Results and Discussion 5 Literature Cited Tables and Figures

7.0 Epibenthic Sampling in the Cape Fear Estuary 1 Introduction 2 Methods 3 Results and Discussion 4 Literature Cited Tables and Figures

8.0 Fisheries Studies in the Lower Cape Fear River System 1 Introduction 2 Methods 3 Results and Discussion 4 Acknowledgments 5 Executive Summary 6 Literature Cited Tables and Figures

9.0 Impacts of Hurricane Bonnie on Water Quality and Benthos in the Cape Fear Watershed 1 Introduction 2 Methods 3 Results 4 Discussion 5 Acknowledgments 6 References Cited Tables and Figures

**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**