Concentrations of potentially toxic elements in sediments are orders of magnitude higher than concentrations of these elements in water. The ecological influences of metals and metalloids in aquatic sediments depend upon how available sediment-bound elements are to aquatic organisms and the implications of that bioavailability for effects of the elements. Development of realistic pollution regulations, in turn, depend upon understanding all processes influencing bioavailability and effects, in nature. This project involves developing tools and understanding of the processes determining metal and metalloid bioavailability. The project employs experimental studies of processes affecting metal/metalloid bioavailability, fate and effects. Long-term, intensive field studies are also used to understand processes, trends and effects of metals/metalloids in estuaries, tidal freshwater ecosystems, lakes (primarily in the San Francisco Bay-Delta and its watershed) and rivers (primarily the Clark Fork River in Montana, USA) .

Objectives of this project over the years have included: (1) study the partitioning of trace metals among the components of sediments, processes that determine the fate of contaminants within the sediment column (with sediment cores); (2) study the influence of geochemical and biogeochemical processes in sediments upon metal/metalloid uptake and metal effects in organisms which contact sediments directly; (3) study physiological characteristics of aquatic organisms that determine metal/metalloid uptake and effects; (4) improve methodology that makes use of biota and sediments as indicators of bioavailability, and better experimental ways of determining impacts of sediment bound metals/metalloids; (5) understand the trophic transfer of metals and metalloids; (6) develop protocols and models for predicting the bioavailability of metals from diet and dissolved forms; (7) understand the impacts of mine wastes in rivers and how estuarine processes influence impacts; (8) develop methods for assessing the presence of biological affects from toxic wastes in aquatic communities in nature; (9) Develop ecosystem scale models useful for constructing new ways of evaluating risk from metals/metalloids.