Bacterial methylmercury degradation in Florida Everglades peat sediment

Environmental Science & Technology
By:  and 



Methylmercury (MeHg) degradation was investigated along an eutrophication gradient in the Florida Everglades by quantifying 14CH4 and 14CO2 production after incubation of anaerobic sediments with [14C]MeHg. Degradation rate constants (k) were consistently ≤0.1 d-1 and decreased with sediment depth. Higher k values were observed when shorter incubation times and lower MeHg amendment levels were used, and k increased 2-fold as in-situ MeHg concentrations were approached. The average floc layer k was 0.046 ± 0.023 d-1 (n = 17) for 1−2 day incubations. In-situ degradation rates were estimated to be 0.02−0.5 ng of MeHg (g of dry sediment)-1 d-1, increasing from eutrophied to pristine areas. Nitrate-respiring bacteria did not demethylate MeHg, and NO3- addition partially inhibited degradation in some cases. MeHg degradation rates were not affected by PO43- addition. 14CO2 production in all samples indicated that oxidative demethylation (OD) was an important degradation mechanism. OD occurred over 5 orders of magnitude of applied MeHg concentration, with lowest limits [1−18 ng of MeHg (g of dry sediment)-1] in the range of in-situ MeHg levels. Sulfate reducers and methanogens were the primary agents of anaerobic OD, although it is suggested that methanogens dominate degradation at in-situ MeHg concentrations. Specific pathways of OD by these two microbial groups are proposed.

Publication type Article
Publication Subtype Journal Article
Title Bacterial methylmercury degradation in Florida Everglades peat sediment
Series title Environmental Science & Technology
DOI 10.1021/es971099l
Volume 32
Issue 17
Year Published 1998
Language English
Publisher ACS
Contributing office(s) Toxic Substances Hydrology Program
Description 8 p.
First page 2556
Last page 2563
Country United State
State Florida
Other Geospatial Everglades
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