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Climate Change & Coastal Processes

    Saltmarsh ecosystems, which sequester carbon dioxide (CO2) through the formation of carbon-rich peat, are threatened by sea level rise [1]. Increased inundation will likely affect saltmarsh carbon cycling and accretion rates. Because mercury readily binds to organic carbon [2,3], these systems may play an important role in coastal mercury dynamics, and their degradation could affect mercury loading to coastal waters. We are therefore quantifying the distribution and transport of mercury species in saltmarsh systems in Massachusetts, an area of accelerated sea level rise [4]. Data suggest mercury in saltmarsh peat porewater is complexed with dissolved organic carbon. While the concentration of porewater mercury is similar to other coastal environments (~3 pM), ~50% of the mercury occurs as monomethylmercury (CH3Hg+), indicating enhanced production of this more toxic bioavailable form [5]. We will couple these results to a hydrodynamic model to quantify mercury import and export rates associated with overland flow and to derive a mercury budget for saltmarsh systems. Because mercury-carbon interactions influence mercury speciation and mobility, the diagnostic tools we develop will be readily transferable to other natural systems, such as coastal lagoons and terrestrial watersheds.
[1]  FitzGerald, D.M., M.S. Fenster, B.A. Argow, and I.V. Buynevich, Coastal impacts due to sea-level rise. Annu. Rev. Earth Planet. 
Sci., 2008. 36: p. 601-647.
[2]  Dittman, J.A., J.B. Shanley, C.T. Driscoll, G.R. Aiken, A.T. Chalmers, and J.E. Towse, Ultraviolet absorbance as a proxy for total dissolved mercury in streams. Environmental Pollution, 2009. 157(6): p. 1953-1956.
[3]  Bergamaschi, B.A., D.P. Krabbenhoft, G.R. Aiken, E. Patino, D.G. Rumbold, and W.H. Orem, Tidally driven export of dissolved organic carbon, total mercury, and methylmercury from a mangrove-dominated estuary. Environmental science & technology, 2012. 46(3): p. 1371-1378.
[4]  Sallenger Jr, A.H., K.S. Doran, and P.A. Howd, Hotspot of accelerated sea-level rise on the Atlantic coast of North America. Nature Climate Change, 2012. 2(12): p. 884-888.
[5]  Ganguli, P.M., M.E. Gonneea, C.H. Lamborg, K.D. Kroeger, G. Swarr, K.J. Vadman, S. Baldwin, B.W. Brooks, and A. Green, Mercury cycling in salt marsh pond ecosystems: Cape Cod, MA, in AGU Fall Meeting2014: San Francisco, USA.