Benthic community metabolism in three habitats in an Ozark stream

Benthic community metabolism was measured in three habitats (riffles, runs and pools) during spring (May), summer (July) and fall (October) in the Jac ks Fork River, Missouri, using an in situ chamber technique. Net community productivity (NCP) and gross community productivity (GCP) were highest in r iffles, lowest in pools and intermediate in runs. Rates of NCP and GCP duri ng spring and fall were similar for both riffles and runs, but NCP and GCP increased significantly during summer in both habitats. Pool substrates wer e always heterotrophic and exhibited no significant seasonal changes in NCP or GCP. Community respiration (CR) was highest in riffles, intermediate in runs and lowest in pools, but interhabitat differences in CR were generall y smaller than for NCP. Rates of CR during spring and fall were similar, bu t CR increased significantly during summer. Results indicate that the physi cal conditions associated with each habitat strongly affect benthic communi ty metabolism in this stream and that the relative proportions of these hab itats will influence the ratio of living algal:detrital organic matter pote ntially available for consumers.