PH13 Metals in the Environment: Dietary Concerns in Aquatic Systems
Exhibit Hall
8:00 AM - ALL DAYS
(PH151) Dietary metal accumulation in predatory stonefly larvae: Phylogeny & Physiology.
Buchwalter, D1, Cain, D1, Fend, S1, Luoma, S1, 1 USGS Water Resources Division, Menlo Park, CA, USA
ABSTRACT- Bioassessment procedures using aquatic insects ignore physiological differences between taxa. Field-based generalizations of sensitivity/tolerance differences among and between taxonomic groups are largely untested. Physiological generalizations are needed to explain why species differ in the sensitivity to metals. In heavy metal contaminated streams, insects accumulate metals from both aqueous and dietary sources. We have previously demonstrated that aquatic insect species differ by orders of magnitude in their rates of dissolved metal accumulation. Metal efflux rates can also differ widely (after dissolved exposures). Additionally, we have observed large inter-specific differences in how dissolved metals are partitioned subcellularly, detoxified and stored. Our current work examines dietary metal exposures in predatory stonefly species. Specifically, we are exploring the extent to which predatory Plecopterans (stoneflies) differ in their assimilation efficiencies of cadmium from their prey, and how widely their post-assimilation efflux rates vary. We also are comparing subcellular distributions of Cd from aqueous versus dietary sources, and are exploring these differences in a phylogenetic context, working with closely related species belonging to the families Perlidae, Perlodidae, and Chloroperlidae. By mapping the results of our experiments onto phylogenies, we examine whether metal accumulation (and ultimately, sensitivity) differences between species are predictable based on phylogeny. We also test whether order-, family- or genus-level generalizations about sensitivities are appropriate for diagnosing effects of heavy metal pollution.
Key words: cadmium, aquatic insects, diet, bioaccumulation