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NSF Postdoctoral Fellowship in Biology FY 2018


This action funds an NSF Postdoctoral Research Fellowship in Biology for FY 2018, Research Using Biological Collections. The fellowship supports research and training of the fellow that will utilize biological collections in innovative ways. The development of methods to quantify mercury stable isotopes provides new insights into sources of pollution in ecosystems. This powerful tracer reveals whether mercury accumulated in fish tissues was derived from local weather sources, long-distance atmospheric sources, or regional human activities. To date, use of mercury isotopes in fish has been restricted solely to near present-day samples. The remarkable archives of fish tissues preserved in museums can expand the size and the time-scale for analyzing mercury in fish. However, these archives have never been used for large-scale assessment of mercury contamination. This proposal will be one of the first to assess mercury contamination in multiple different collections of fish. Recognition of mercury as a global threat, due to neurotoxic effects in humans and wildlife, has led to efforts to reduce mercury contamination in many nations. The data from this proposal can help to better understand where these levels of mercury are coming from, which can help to inform mercury management and mitigation efforts.<br/><br/>This project includes three core elements: 1) A rigorous experimental test of how chemical preservation affects the concentration and isotope ratios of mercury in fish. 2) Comparing recent and historical collections from Africa?s Lake Victoria (where erosion, gold mining, and aquaculture have increased mercury) and Lake Tanganyika (where anthropogenic inputs of mercury are minimal) to reconstruct changes in mercury sources and concentrations in these massive lacustrine fisheries. 3) Quantifying pollution through time for major riverine fisheries worldwide. These approaches will use archived specimens to reveal the spatiotemporal evolution of global contamination of freshwater fisheries. After developing correction factors for interpreting results from preserved tissues, we will resolve the impact of human activities relative to natural geogenic inputs of mercury. Using fish rather than sediment cores to infer temporal shifts in mercury bioaccumulation will sidestep assumptions about bioavailability that have complicated previous approaches. Coupling mercury concentrations and isotope data will give insight to sources of intensive pollution, and the resulting geography of health threat. Findings will be conveyed to national fishery management authorities and the United Nations Global Mercury Program, to develop targeted mitigation strategies. The information can also motivate local education efforts to make subsistence anglers aware of the threat to their family's health.<br/><br/>This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

Ryan Lepak
University of Wisconsin - Madison
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