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Spider-mediated flux of PCBs from contaminated sediments to terrestrial ecosystems and potential risks to arachnivorous birds
WALTERS, DAVID M., M. MILLS, K. M. FRITZ, AND D. RAIKOW. Spider-mediated flux of PCBs from contaminated sediments to terrestrial ecosystems and potential risks to arachnivorous birds. ENVIRONMENTAL SCIENCE & TECHNOLOGY. American Chemical Society, Washington, DC, 44(8):2849-2856, (2010).
Contaminated sediments are of interest to a broad group of programs in the agency. OERR and the Regions are interested in monitoring contaminated sediments to characterize/assess existing conditions, determine remediation alternatives, track spatial and temporal changes, and determine if post-remediation goals have been achieved. The Office of Water, Regions, and states are interested in contaminated sediments because they impact designated uses established in State water quality standards. Office of Science and Technology (OST) is interested in contaminated sediments because they have been given a charge to conduct a comprehensive national data survey regarding the quality of aquatic sediments in the United States. In response to the Water Resources Development Act of 1992, OST has evaluated sediment chemistry, tissue chemistry, and sediment toxicity data from 1983-1999, taken at the same sampling station (or site), individually and in combination using a variety of assessment methods. Because of these varied needs, a consistent approach to monitoring the chemical, physical, and biological characteristics/conditions of contaminated sediments across all of EPA's programs would be advantageous. To address the chemical, physical, and biological monitoring issues associated with contaminated sediments, collaborative efforts will be sought across ORD labs and Regions to work on sites where multiple issues can be addressed simultaneously. Various approaches, methods, and techniques can be tested in a common contaminated environment, maximizing the efficiency and comparability among the results of the proposed activities. For example, NERL, NRMRL and NHEERL have proposed to use a site based approach (e.g., Lake Hartwell) to develop and demonstrate various remote sensing and ecological tools and approaches. NERL/EERD research has focused on the use of small short-lived fish as indicators of pre- and post-remediation to determine if changes can be detected sooner in these fish than in longer-lived game or bottom dwelling fish. This research will provide OERR and OW with a valuable tool to rapidly determine the effectiveness of remedial clean up operations without having to wait to observe the effects in longer-lived or bottom dwelling fishes. Also, research will be conducted to assess the effectiveness of remediation operations by conducting pre- and post-remediation toxicity assessments, bioassessments (periphyton, macroinvertebrates and fish monitoring), and toxicogenomics assessments. Included in this proposed research effort will be the development of molecular biological methods to provide new data on the bioavailability, fate and transport of contaminants in sediments. These methods will use several water column and sediment organisms to monitor the real-time bioavailability of these contaminants and their movement between compartments. New and unique data would be integrated into the aquatic components of existing aquatic ecosystem compartmental models (NERL-RTP) to assist in the characterization of the mass balance of sediment contaminants at a collaborative ORD contaminated sediments field study site (e.g., Lake Hartwell). We propose to use an emerging tool in stream ecology, stable isotope analysis, to develop a mechanistic understanding of energy and material flux within PCB contaminated streams and lakes and their food webs. Stable isotopes techniques have been used to track biomagnification of PCBs in marine and lake food webs but similar applications in streams have not been explored. We also hypothesize that PCBs cycling in littoral (i.e., near-shore) and pelagic (i.e., open water) food webs of PCB contaminated sites may delay natural recovery. An analysis of food web dynamics and biomagnification pathways would improve our ability to forecast recovery and interpret current data on PCB levels in fishes of concern. We propose to evaluate new and existing data sets for parameterizing a food web model of Lake Hartwell.
We investigated aquatic insect utilization and PCB exposure in riparian spiders at the Lake Hartwell superfund site (Clemson, SC , USA). We sampled sediments, adult chironomids, terrestrial insects, riparian spiders (Tetragnathidae, Araneidae, and Mecynogea lemniscata), and upland spiders (Araneidae) along a sediment contamination gradient. Riparian spiders consumed large quantities of aquatic insects, whereas upland spiders did not. PCBs in chironomids were two orders of magnitude higher than terrestrial insects similar to differences between riparian and upland spiders. Riparian spider PCBs were positively correlated with sediment concentrations for all taxa. We assessed PCB exposure risks to arachnivorous birds using spider-derived wildlife values (WVs). Spider concentrations exceeded WVs for most species at heavily contaminated sites and were 14-fold higher for the most sensitive species. Spiders are abundant and ubiquitous in riparian habitats, where they depend on aquatic insect prey. These traits, along with the high degree of spatial correlation between spider and sediment concentrations we observed, suggest that they are ideal indicator species for monitoring contaminated sediment sites and assessing risks associated with contaminat flux into terrestrial ecosystems.