PARENT SESSION
Organized Oral Session 5: Mercury cycles: Sources, mass balances, bioaccumulation, and options to manage affected systems
Organizer(s): EPH Best, JG Wiener, and D Planas
Monday, August 8, 8:00 AM - 11:30 AM, Meeting Room 511 C, Level 5, Palais des congrès de Montréal

Influence of the characteristics of individual species on community structure in metal-contaminated aquatic environments.

Luoma, Samuel ¹, ¹ U. S. Geological Survey, Menlo Park, CA, USA

ABSTRACT- Chemical contamination can be an influential variable in aquatic ecosystems. But diagnostic concepts are needed to help us understand the specific influences of chemicals (in this case metals and metalloids) compared to other forces that affect community structure. Examples of metal/metalloid effects in river and estuarine ecosystems suggest the simplest, first order effect of metal contamination is to eliminate vulnerable species. Several processes affect which species are eliminated. The physiological processes governing bioaccumulation, and capabilities for detoxification, combine to determine effective internal exposure. Bioaccumulation varies by seven orders of magnitude among species and metals; and detoxification strategies vary widely as well. Net spinning caddisflies are common in metal-contaminated streams because they accumulate metals slowly and have strong detoxification capabilities. Some species of mayflies disappear from contaminated streams. In the Clark Fork River, MT, the vulnerable mayflies are the ones that rapidly accumulate high concentrations of metals, and/or have reduced detoxification capabilities. A second important factor is trophic transfer. Selenium is biomagnified through molluscan-based food webs much more strongly than through food webs with crustacean consumers at the base. Molluscs lose Se slowly, bioaccumulate it strongly and propogate that body burden up the food web. Sturgeon and Sacramento splittail in San Francisco Bay are particularly vulnerable to Se contamination because of their dependence on bivalves as food. Life history also influences exposures. Brooding species thrived while species that laid eggs in sediments disappeared from a contaminated mudflat in the Bay. Adult bivalves were present at the site during the contaminated era because of immigration by a mobile larval stage. Resident bivalves were incapable of reproduction. Metal-specific transfer characteristics, feeding habits, physiology and life history determine what species inhabit a contaminated community, and set the stage for other ecological influences.

Key words: metals, bioaccumulation, detoxification, life history