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Source Identification of Florida Bay's Methylmercury Problem: Mainland Runoff Versus Atmospheric Deposition and In situ Production

Darren G. Rumbold, David W. Evans, Sharon Niemczyk, Larry E. Fink, Krysten A. Laine, Nicole Howard, David P. Krabbenhoft, Mark Zucker

Estuaries and Coasts (2011) 34:494-513. DOI 10.1007/s12237-010-9290-5. © Coastal and Estuarine Research Federation 2010. Posted here with permission.

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Study Area and Methods
Results and Discussion
Figures and Tables

The first advisory to limit consumption of Florida Bay fish due to mercury was issued in 1995. Studies done by others in the late 1990s found elevated water column concentrations of both total Hg (THg) and methylmercury (MeHg) in creeks discharging from the Everglades, which had its own recognized mercury problem. To investigate the significance of allochthonous MeHg discharging from the upstream freshwater Everglades, we collected surface water and sediment along two transects from 2000 to 2002. Concentrations of THg and MeHg, ranging from 0.36 ng THg/L to 5.98 ng THg/L and from <0.02 ng MeHg/L to 1.79 ng MeHg/L, were elevated in the mangrove transition zone when compared both to upstream canals and the open waters of Florida Bay. Sediment concentrations ranged from 5.8 ng THg/g to 145.6 ng THg/g and from 0.05 ng MeHg/g to 5.4 ng MeHg/g, with MeHg as a percentage of THg occasionally elevated in the open bay. Methylation assays indicated that sediments from Florida Bay have the potential to methylate Hg. Assessment of mass loading suggests that canals delivering stormwater from the northern Everglades are not as large a source as direct atmospheric deposition and in situ methylation, especially within the mangrove transition zone.

Keywords Florida Bay. Everglades . Methylmercury . Surface water . Sediment

Introduction >

Received: 20 December 2009 / Revised: 8 February 2010 / Accepted: 23 March 2010 / Published online: 22 April 2010

D. G. Rumbold . S. Niemczyk . L. E. Fink . N. Howard
South Florida Water Management District,
West Palm Beach, FL, USA

D. G. Rumbold (*)
Florida Gulf Coast University,
10501 FGCU Blvd. South,
Ft. Myers, FL 33965, USA

D. W. Evans
National Oceanic and Atmospheric Administration,
Beaufort, NC, USA

S. Niemczyk
The Abaco Group, LLC,
Boynton Beach, FL, USA

K. A. Laine
East Bay Municipal Utility District,
Oakland, CA, USA

D. P. Krabbenhoft
U.S. Geological Survey,
Middleton, WI, USA

M. Zucker
U.S. Geological Survey,
Ft. Lauderdale, FL, USA

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