title: The distance that contaminated aquatic subsidies extend into lake riparian zones.
abstract: 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 invertivores. 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 Lake Hartwell, (Clemson, South Carolina, USA). PCB concentrations in aquatic insects were orders of magnitude higher than in terrestrial insects. Aquatic insect consumption by spiders (as indicated by delta13C and delta15N), 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  5 m inland. Measurable, but much lower, PCBs were present in insect predators dominated by social wasps up to 30 m inland. These results illustrate the importance of emergent insects as vectors of contaminant transfer from lake sediments to riparian food webs, and that spiders are key predators in this process.
authors.affiliation: U.S. Environmental Protection Agency, National Exposure Research Laboratory, Ecological Exposure Research Division, 26 Martin Luther King Jr. Drive, Cincinnati, Ohio 45268, USA. david@raikow.com
authors.forename: David F
authors.initials: DF
authors.lastname: Raikow
authors.forename: David M
authors.initials: DM
authors.lastname: Walters
authors.forename: Ken M
authors.initials: KM
authors.lastname: Fritz
authors.forename: Marc A
authors.initials: MA
authors.lastname: Mills
mesh_terms: D000818:Animals; D004784:Environmental Monitoring; D020387:Food Chain; D005618:Fresh Water / Q000737:chemistry*; D007313:Insecta / Q000737:chemistry / Q000502:physiology*; D011078:Polychlorinated Biphenyls / Q000737:chemistry*; D011235:Predatory Behavior; D013022:South Carolina; D013112:Spiders / Q000737:chemistry / Q000502:physiology*; D014874:Water Pollutants, Chemical / Q000737:chemistry*
chemical_list: D014874:Water Pollutants, Chemical; D011078:Polychlorinated Biphenyls