Research Interests
Many metals have elevated concentrations in aquatic environments as a result of anthropogenic activities. One of the major goals of my research is to distinguish metals that are pollutants- that is to say, they have measurable deleterious impacts on organisms- from metals that are merely contaminants. To pose a risk to organisms, metals must be accumulated in aquatic food chains. Accordingly, my research looks at how water chemistry affects metal bioavailability. I often work with phytoplankton because they are the link between the water and the food chain. Moreover, accumulation of metals by phytoplankton can often be understood in terms of metal chemistry and mechanistic, process-oriented studies.
My current research is based in the San Francisco Bay and Delta, an estuary where there are elevated concentrations of many metals, including mercury. Mercury, in the form of methylmercury, can biomagnify up food chains, reaching concentrations in fish that can be a million times higher than in the water. The fish acquire their methylmercury from dietary exposure, not aqueous uptake. And that dietary exposure begins when phytoplankton, at the base of the food chain, accumulate methylmercury from surrounding waters.
I am currently working on a project to examine the role of dissolved organic matter in methylmercury accumulation by phytoplankton. To approach this problem, I am combining a variety of approaches, including radiotracer techniques in Nicholas FisherÕs lab (Stony Brook University) and characterization of organic matter with Brian Bergamaschi (USGS in Sacramento). This is an exciting project and the results will be relevant to managing the mercury problem in the San Francisco Estuary.
Publications
Luengen, A. C., and A. R. Flegal. 2009. Role of phytoplankton in mercury cycling in the San Francisco Bay estuary. Limnology and Oceanography 54: 23-40.
Luengen, A. C., P. T. Raimondi, and A. R. Flegal. 2007. Contrasting biogeochemistry of six trace metals during the rise and decay of a spring phytoplankton bloom in San Francisco Bay. Limnology and Oceanography 52: 1112-1130.
Luengen, A. C., C. S. Friedman, P. T. Raimondi, and A. R. Flegal. 2004. Evaluation of mussel immune responses as indicators of contamination in San Francisco Bay. Marine Environmental Research 57: 197-212.
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