Seasonal Biogeochemical Dynamics: Georgetown Lake, MT

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Georgetown is experiencing changes in lake biogeochemistry stemming from its shallow nature and nutrient influx due to development, deforestation and heavy recreational use. A seasonal anoxic layer near the lake bottom under ice cover has been identified along with the presence of reduced chemical species such as methane, hydrogen sulfide and ammonia.

Freshwater lakes are important resources for recreation, agricultural/industrial uses, power generation as well as being of significant environmental interest since they are very sensitive to anthropogenic activities. Lakes can be viewed as temporary water storage reservoirs and inputs such as nutrients, metals/metalloids and organics can have severe impacts on limnological processes, biological productivity and water quality. Lakes also act as important storage compartments for atmospheric carbon that is stored in sediments as organic material. Recent research has shown a positive feedback relationship between lake eutrophication and atmospheric concentrations of greenhouse gases, such as CO2, methane, and nitrous oxide. By some estimates, the global flux of methane released by lakes completely counteracts the beneficial consumption by upland soil microbes.

This presentation summarizes recent investigations at Georgetown Lake to help us gain insight into the formation and demise of the seasonal anoxic zone and the underlying chemistry and microbial dynamics.

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