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The distance that contaminated aquatic subsidies extend into lake riparian zones
Citation:
RAIKOW, D., D. WALTERS, K. M. FRITZ, AND M. MILLS. The distance that contaminated aquatic subsidies extend into lake riparian zones. ECOLOGICAL APPLICATIONS. Ecological Society of America, Ithaca, NY, 21(3):983-990, (2011).
Impact/Purpose:
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.
Description:
Consumption of emergent aquatic insects by terrestrial invertebrates is a poorly resolved, but potentially important, mechanism of contaminant flux across ecosystem borders leading to contaminant exposure in terrestrial invertevores. We characterized the spatial extent and magnitude of contaminant transfer from aquatic sediments to terrestrial invertebrate predators by examining riparian araneid spiders, terrestrial insects, and emergent aquatic insects for stable isotopes and polychlorinated biphenyls (PCBs, sum of 141 congeners) at a superfund site. PCB concentrations in aquatic insects were orders of magnitude higher than in terrestrial insects. Aquatic insect comsumption by spiders, PCB concentrations in spiders, and aquatic prey availability were greatest at the shoreline and declined inland, while terrestrial prey availability was invariant with distance. These patterns indicate PCB transfer to spiders through consumption of emergent aquatic insects extending to a distance of approximately 5m inland. Measurable, but much lower, PCBs were present in insect predators dominated by social wasps up to 30m inland. Prior hypotheses that wind advection and high secondary production could result in subsidies extending greater distances into the riparian zones of large, downstream aquatic ecosystems were not supported.