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Tracking contaminant flux from aquatic to terrestrial food webs
Citation:
WALTERS, DAVID M., K. M. FRITZ, D. RAIKOW, M. MILLS, AND R. R. Otter. Tracking contaminant flux from aquatic to terrestrial food webs. Presented at 6th International Conference on Applications of Stable Isotope Techniques to Ecological Studies, Honolulu, HI, August 25 - 29, 2008.
Impact/Purpose:
The goal of this research is to develop methods and indicators that are useful for evaluating the condition of aquatic communities, for assessing the restoration of aquatic communities in response to mitigation and best management practices, and for determining the exposure of aquatic communities to different classes of stressors (i.e., pesticides, sedimentation, habitat alteration).
Description:
Aquatic insects provide a critical energy subsidy to riparian food webs, yet their role as vectors of contaminants to terrestrial ecosystems is poorly understood. We investigated aquatic resource utilization and contaminant exposure among riparian invertivores (spiders and herptiles) along a stream and reservoir contaminated with polychlorinated biphenyls (PCBs). Aquatic insect utilization varied among stream riparian predators, as predators shifted from aquatic to terrestrial prey. We sampled spiders and insects at various distances (0-30 m) from the reservoir shore to quantify the lateral extent of contaminant flux. Aquatic insect flux was limited to the first 5 m of the shore. Riparian spiders preyed heavily on aquatic insects along the shore, but switched to terrestrial prey beyond 5-10 m of the shore. PCB concentrations tracked these patterns in aquatic insect utilization and declined rapidly beyond 5 m from the shore. Persistent contaminants (e.g., PCBs) are underutilized for addressing landscape-level questions in subsidy research, but our results demonstrate that they are an ideal in situ tracer of aquatic-derived energy because they label aquatic insects over large distances. Likewise, riparian predators such as spiders have great potential as biological monitors of ecosystem condition and as assessment tools for risk management of contaminated aquatic sediments.