New Approaches and Analytical Tools for Studying Mercury in the Gulf of Mexico: Sources and Transformations

Author(s): Cizdziel, J.; Bussan, D.

Monomethylmercury (MMHg), a neurotoxin produced primarily by sulfate reducing bacteria in aquatic sediments, readily biomagnifies up the marine food chain. Consumption of fish containing high levels of MMHg can lead to adverse health effects in both humans and wildlife. This is of particular concern in the northern Gulf of Mexico (GoM) because, on average, residents of the Gulf Coast consume more marine fish than other U.S. residents, and because GoM fish tend to have higher levels MMHg than fish from other coastlines.1,2 Moreover, because the economy of the Gulf coast states is intricately linked to the GoM through fishing (both commercial and recreational), understanding the distribution, levels and cycling of MMHg is vital to the long-term health and stability of the region. Whereas there has been much progress on understanding the fate, transport and transformation of mercury in aquatic and terrestrial environments, there remains a major gap in understanding of the sources and pathways of MMHg entry into food webs in the northern GoM. Recent advances in analytical techniques now offer an opportunity to answer fundamental questions such as where in the GoM is MMHg produced from inorganic mercury, and where is MMHg most bioavailable. Recent work demonstrates the potential of the use of enriched stable isotopes to simultaneously determine methylation and demethylation rates in sediments,3 and for stable isotopes to serve as probes for reaction pathways and to evaluate the source/history of mercury in samples.4 In this talk and associated poster, we will introduce these techniques and show how they can be used to advance our understanding of mercury cycling and transformation in the GoM. We will include recent results from our own research utilizing these techniques to study sediment from wetlands from the Mississippi Delta and from the cold seeps in the northern GoM.
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