CSIRO Marine and Atmospheric Research
Past Seminars

Monday 24 May 2004, 11.30 am (Tas time)

CSIRO Auditorium, Hobart

Dr Martina Doblin
Department of Ocean, Earth & Atmospheric Sciences
Old Dominion University, Norfolk, VA

Biogeochemical cycling of selenium in the San Francisco Bay and the importance of an introduced clam in determining foodweb toxicity

Chemical contamination remains a critical issue for the ecological and economic integrity of aquatic environments. One example of a significant effect on wildlife was the discovery of selenium poisoning at Kesterson Reservoir, California in 1983. Selenium, concentrated in irrigation drainage from the Central Valley of California (300 µg/L; 3.8 mM), was transported into the Kesterson National Wildlife Refuge where it was accumulated by nesting birds, resulting in a significant deformity rate in bird hatchlings. Currently, such effects may still occur in the San Francisco Bay ecosystem (connected to the Central Valley via the San Joaquin River), where some aquatic animals continue to be threatened by selenium while others are not. In order to understand selenium contamination in this system, we undertook an assessment of its biogeochemical cycling under different river flow conditions. We focused on particulate selenium, since this is the primary mode of exposure to estuarine consumers (as opposed to direct uptake from the dissolved phase). Resident animals (invertebrates and fish) were also sampled and assessed for selenium accumulation, and stable isotopes and gut content analyses were used to elucidate feeding relationships amongst consumers. The results of these investigations show that particulate selenium dynamics are important in determining the level of selenium exposure to consumers, with variability derived from different sources (e.g., resident phytoplankton, autochthonous sediments and riverine inputs). Further, an introduced clam, Potamocorbula amurensis, functions as a ‘biological pump’ in this system, accumulating relatively high amounts of selenium (due to low efflux rates), and exposing its consumers to elevated selenium concentrations.

Martina Doblin obtained her Ph.D. degree from the University of Tasmania, Australia, in 1998, and has been a Self Supporting Research Professor in the Ocean, Earth and Atmospheric Science Department at Old Dominion University (Norfolk, Virginia, USA) since 2001. Her research interests span biogeochemical cycling of trace elements, biological invasions, microbial ecology of ships’ ballast water and harmful algal blooms.

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