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An evaluation of techniques for measuring periphyton metabolism in chambers

350 210 Stroud Water Research Center

Bott, T.L., J.T. Brock, A. Baattrup-Pedersen, P. Chambers, W.K. Dodds, K. Himbeault, J.R. Lawrence, D. Planas, E. Snyder, and G.M. Wolfaardt. 1997. Canadian Journal of Fisheries and Aquatic Sciences 54(3):715–725.

doi: 10.1139/f96-323

Abstract

Experiments were performed to compare 14C uptake, dissolved O2 and CO2 change, and microelectrode techniques for measuring benthic primary productivity and community metabolism at a site on the South Saskatchewan River, Saskatchewan. The highest estimates of primary productivity were obtained with O2 microelectrodes (two to four times higher than simultaneous estimates from bulk-water dissolved O2 measurements), presumably because measurements are biased toward active communities under optimal conditions for photosynthesis. In daytime experiments lasting ~1.3 and 2.4 h, estimates from 14C uptake were higher than those measured simultaneously from dissolved O2 and CO2 change, suggesting that 14C uptake measured gross primary production (GPP) in these short-term incubations. Differences in experimental water velocity ranging from 0.2 to >6.5 cm · s-1 had less of an effect than chlorophyll a concentration on metabolic rates in diel experiments with rocks taken from a site where velocities were from 5.6 to 7.8 cm · s-1. There was a potential for phosphorus and possibly NH4 limitation of metabolic activity during long-term incubations. Results highlight areas in which further research is needed when using chambers to determine periphyton metabolism.

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