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CHARACTERIZATION OF PCB BIOACCUMULATION IN THE LAKE HARTWELL FOODWEB USING THE AQUATOX MODEL
Citation:
RASHLEIGH, B., M. C. BARBER, AND D. WALTERS. CHARACTERIZATION OF PCB BIOACCUMULATION IN THE LAKE HARTWELL FOODWEB USING THE AQUATOX MODEL. Presented at VIIth International Congress on the Biology of Fish, St. John's, NL, CANADA, July 18 - 22, 2006.
Impact/Purpose:
The overall objective is to develop watershed modeling tools for the immediate client (CVI) and their stakeholders in the Mid-Atlantic Highlands. This research continues the contributions that REVA has made to the CVI toolset and adds modeling and decision support capabilities for more general use by managers. To facilitate the prediction and analysis of fish health issues by EPA Program and Regional Offices and other environmental agencies, process-based models that describe these processes will be implemented:
1. the expected trophic dynamics of the dominant fish species
2. the spawning and recruitment dynamics of the dominant fish species
3. the bioaccumulation of organic chemicals and metals in aquatic biota
4. how physical habitat and chemical water quality impact fish feeding, reproduction, survival, and migration
To facilitate the use and application of these models, graphical user interfaces (GUI), supporting databases, and libraries of management scenarios will also be developed. Models will be linkable to integrated water quality and hydrologic models that simulate habitat characteristics (e.g., water depth, current velocity, water temperature and sediment loadings) that determine the survival, reproduction, and recruitment of fish and aquatic invertebrates. Similar to what has been achieved in REVA, frameworks based on the biogeography of fish will be developed to apply these models spatially for regional assessments of important fish health issues.
Objectives of this task between FY03 and FY05:
To provide modeling and decision support capabilities for aquatic resources compatible with existing geographic information (GIS) frameworks to evaluate effectiveness (and ultimately cost-benefit) of restoration activities planned in Region 3, initially the Mid-Atlantic Highlands region. This includes the primary interests in evaluating riparian zone restoration (using Rosgen methods) and acid mine drainage remediation.
To develop methods that explicitly link process models and spatial analysis methods across spatial and temporal scales.
To identify knowledge and information gaps in the integration of REVA and process models that enable projections of future ecosystem state.
To create a new generation of quantitative environmental assessment tools that explicitly address issues of scale, are not restricted in extent of application, and enable efficient rescaling (both spatial and temporal).
This research supports long-term goals established in ORD's multi-year research plans for Both GPRA Goal 2 (Water Quality) and Goal 8.1.1 (Sound Science/Ecological Research). This research will provide the tools to assess and diagnose impairment in aquatic ecosystems and the sources of associated stressors and to forecast the ecological, economic and human health outcomes of alternative solutions. Central to this task (as described in Goal 8) is the development and demonstration of methods to the states, tribes and local managers to: (1) assess the condition of waterbodies in a scientifically-defensible and representative way while allowing for aggregation and assessment of trends at multiple scales, (2) diagnose cause and forecast future condition in a scientifically defensible fashion to more effectively protect and restore valued ecosystems, and (3) assess current and future ecological conditions, probable causes of impairments and management alternatives.
Description:
PCBs from the Sangamo-Weston Superfund Site near Clemson, South Carolina, USA, were released into the Twelvemile Creek arm of Lake Hartwell until the early 1990s. Monitoring data have shown that while PCB concentration in sediments declined since 1995, PCB concentrations in largemouth bass have remained in the range of 5-10 ppm. The EPA aquatic ecosystem model AQUATOX was applied to this system to better understand food web dynamics and characterize bioaccumulation. The model was parameterized with available flow, nutrients, and TOC data, calibrated with observed fish biomass data, and then initialized with measured PCB values in water (0.05ug/L), sediment (5 ppm), and fish. According to model results, PCB loadings at approximately half the initial conditions were necessary to simulate fish PCB concentrations in the range of observed data over a 5-year period. The model demonstrated that contaminated detritus loaded to the system was incorporated into the food chain through direct consumption and ingestion by benthic organisms. More detritial PCB was consumed than deposited (17% vs. 4%), thereby maintaining the PCB concentrations in fish while the concentrations in the sediment declined. The model can be used to estimate the time needed for PCB concentrations in fish to be reduced to target levels for recovery (>2.0 ppm).