Elizabeth Inman, Johns Hopkins University

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Abstract:

This study attempts to ascertain the effect of substrate addition on methanogenesis in anoxic estuarine sediments. Box cores of sediment were taken from the upper and middle Chesapeake Bay from which the top and bottom layers were collected, so that a profile of methanogenesis with changing sulfate concentration and changing or by methanogens alone ("noncompetitive"). When sulfate ion was decreased from ambient levelssalinity could be seen. The mud was slurried and assays were made of methanogenesis in the presence of added substrates that are metabolized by both methanogens and sulfate reducing bacteria ("competitive") or by methanogens alone ("noncompetitive"). When sulfate ion was decreased from ambient levels increased methane production from acetate was observed. No significant difference in methane production from methanol was noted between sulfate containing and sulfate depleted samples possible because of the high concentration of added methanol. When noncompetitive substrates were available methanogens were able to coexist with sulfate reducing bacteria in anoxic estuarine sediments. Sulfate did not inhibit methanogens from producing substantial amounts of methane from added trimethylamine dimethylamine and monomethylamine. Estuare methanogens from sulfate rich areas rapidly metabolize methylamines and appear readily able to adapt to acetate metabolism when sulfate levels decrease.