Contributions of three subsystems of a freshwater marsh to total bacterial secondary productivity.

Rates of bacterial production were measured in the water column, on the surface of plant detritus, and in the surface sediments of a freshwater marsh in the Okefenokee Swamp, Georgia, USA. Bacterioplankton production rates were not correlated with several measures of quantity and quality of dissolved organic matter, including an index of the relative importance of vascular plant derivatives. Bacterioplankton productivity was high (mean: 63 μg C liter(-1) day(-1)) compared with rates reported for other aquatic ecosystems. Somewhat paradoxically, bacterial productivity on plant detritus (mean: 13 μg C g(-1) day(-1)) and sediments (mean: 15 μg C g(-1) day(-1)) was low relative to other locations. On an a real basis, total bacterial productivity in this marsh ecosystem averaged 22 mg C m(-2) day(-1), based on sample dates in May 1990 and February 1991. Marsh sediments supported the bulk of the production, accounting for 46% (May) and 88% (February) of the total. The remainder was contributed approximately equally by bacteria in the water column and on accumulated stores of plant detritus.