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Benthic Habitat Mapping
Contaminants Mapping in the Southern California BightThe "Bight '98" regional monitoring program was a collaborative, interdisciplinary study to quantitatively describe the health of coastal and embayment areas along the Southern California Bight (SCB), from Point Conception south to Baja California. The goal of the program was to provide an integrated assessment of the ecological condition of the SCB. This effort was initiated to determine whether legislative mandates were being met, if conditions within the SCB were improving, and whether sediment quality and toxicity trends could be used as a basis for assessing relationships between contaminant exposures and effects in the region.During the study, sediment samples were collected at 290 sites representing shallow, mid-depth, and deep shelf areas; harbors; ports; marinas; and river mouths. The diversity of sample areas provided a unique data set for evaluating sources, pathways, and sinks of anthropogenic (human-generated) contaminants. Grab samplers collected the top few centimeters of the seafloor sediment, representing recently deposited sediments. These samples were analyzed for several metals, organochlorines, and polycyclic aromatic hydrocarbons (PAH), as well as for acute toxicity experiments and analyses of benthic community health. Cluster analysis and principal components analysis (PCA) were performed to identify sites with similar contaminant signatures and distribution patterns. These results allowed researchers to interpret the relationships between larger-scale spatial patterns and possible input sources and pathways. Due to the large area represented by this study, these data also provide a regional framework for interpreting past, present, and future sediment toxicity and biological community data. What was the spatial distribution of sample sites? Cluster analysis results divided samples into five groups with different chemical and grain size characteristics. Two of the cluster groups (Groups 1 and 2 on the map) represent non-contaminated (clean) sites; the remaining three groups contain contaminated sediments. Clean sites accounted for 96 percent of the study area; contaminated sites accounted for only 4 percent of the study area. The highest levels of contaminants and most severe toxicity were found within bays, harbors, and near river mouths. Sediments in open coastal and shelf areas had low contaminant concentrations. Regional assessments of sediment quality, such as the "Bight '98" study, are necessary for regulators and resource managers to understand the impacts of pollution beyond the areas immediately adjacent to point sources. Mapping these data allow for comparisons of contaminated sediment patterns with biological community distributions, providing insight into the relationships between sediment quality indicators and benthic habitat quality. In addition, sediment contamination maps from the "Bight '98" project provide a basis for comparison with subsequent data sets to determine how distributions of contaminants change over time in response to specific remediation and management actions.
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