Theresa Presser

Theresa Presser is a Emeritus Research Chemist with the Earth System Processes Division of the USGS Water Resources Mission Area in Menlo Park, California. Her expertise is the environmental science of selenium. Selenium is a reproductive toxin that bioaccumulates through food webs to affect top predator species. Her field studies and body of site knowledge of Se-impacted areas document and analyze the connection of anthropogenic activities (e.g., agricultural drainage, oil refining, and mining of phosphate, coal, copper, and uranium) to aquatic environments. Her research conceptualizes, quantifies, and models the variables that determine how selenium is processed from geologic sources through ecosystems. Ecosystem-scale selenium modeling, developed in collaboration with Samuel Luoma, provides a new quantitative tool to predict the ecological effects of selenium and, thus, understand the management of selenium in the environment. The model frames a site-specific occurrence of selenium; quantifies exposure of predators through dietary selenium biodynamics (i.e., species-specific physiological parameters); and connects to the base of the food web using a metric that describes the partitioning of selenium between particulate material and dissolved phases. The initial basis for the methodology used data from a set of common aquatic settings and food webs to illustrate that an environmentally safe dissolved selenium concentration will differ among ecosystems depending on the biogeochemical conditions and ecological pathways in those systems. Thus, model development narrows uncertainties for ecosystem protection through integration of a site-specific system’s ecology, biochemistry, and hydrology and inhabiting species’ life-cycle and ecotoxicology. A cooperative U.S. Geological Survey and U.S. Fish and Wildlife website entitled Linking Selenium Sources to Ecosystems: Local and Global Perspectives is available at: https://www.usgs.gov/mission-areas/water-resources/science/linking-selenium-sources-ecosystems-local-and-global

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