Whitmire, S.L. and S.K. Hamilton
Presented at the Campus Symposium (2001-04-19 )
Wetlands are often situated at points of groundwater recharge and discharge and hence biogeochemical processes in wetlands can affect downstream water quality. A survey was conducted along a hydrological gradient from groundwater-fed to precipitation-fed wetlands to determine the influence of hydrology on biogeochemical functions associated with anaerobic microbial processes. The 13 wetland study sites are located on glaciated terrain in southwestern Michigan. Nitrate concentrations were low or undetectable at all sites, even though groundwater inputs are often elevated in nitrate. Iron (II) was present in most wetlands, but varied among the sites. Sulfate reduction was greater in groundwater-fed wetlands than precipitation-fed wetlands, resulting in removal of sulfate and some accumulation of hydrogen sulfide. Sediment gas bubble samples usually contained at least 50% methane, indicating that methanogenesis is important in all types of wetlands. Considering the equivalent carbon mineralization rates, sulfate reduction is relatively important in the groundwater-fed wetlands, while methanogenesis is important at all sites and dominates in the precipitation-fed wetlands.
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