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 metabolism in experimental planktonic-benthic ecosystems. A magnetic stirring apparatus at mid-depth in each chamber prevented stratification and maintained a vertical turnover time that roughly matched turnover in the experimental ecosystems. We used the chambers in light-dark experiments to partition the depth-integrated photosynthesis and respiration occurring in the experimental ecosystems among water column, wall periphyton, and benthic communities. Community metabolism measured with the chambers was positively related to the chlorophyll-a concentrations of the water column and wall periphyton communities. We also found close agreement between the summation of partitioned community metabolism measured in the chambers and an independent measure of total ecosystem metabolism in the experimental ecosystems. Incubations in chambers and in light-dark bottles revealed similar patterns of water column and wall periphyton community metabolism, but magnitudes differed. In addition to application in experimental ecosystems, this incubation chamber technique may provide an efficient and realistic measure of water column and benthic metabolism and nutrient uptake in lakes and estuaries.