A method for measuring depth-integrated community metabolism in experimental planktonic-benthic ecosystems

We developed incubation chambers of clear acrylic extending the full depth of the water column to measure in situ depth-integrated community metabolis m in experimental planktonic-benthic ecosystems. A magnetic stirring appara tus at mid-depth in each chamber prevented stratification and maintained a vertical turnover time that roughly matched turnover in the experimental ec osystems. We used the chambers in light-dark experiments to partition the d epth-integrated photosynthesis and respiration occurring in the experimenta l ecosystems among water column, wall periphyton, and benthic communities. Community metabolism measured with the chambers was positively related to t he chlorophyll-a concentrations of the water column and wall periphyton com munities. We also found close agreement between the summation of partitione d community metabolism measured in the chambers and an independent measure of total ecosystem metabolism in the experimental ecosystems. Incubations i n chambers and in light-dark bottles revealed similar patterns of water col umn and wall periphyton community metabolism, but magnitudes differed. In a ddition to application in experimental ecosystems, this incubation chamber technique may provide an efficient and realistic measure of water column an d benthic metabolism and nutrient uptake in lakes and estuaries.