Factors influencing respiration data in freshwater sediment

Abstract

Sediment respiration (oxygen consumption and CO2 evolution) was measured in freshwater sediment samples using both flask- and core-microcosms, and the estimates were compared. Oxygen consumption data were also compared in flask-microcosms constructed with sediment samples of different masses, sediment: water ratios, and storage times. Furthermore, sediment respiration was examined under different incubation conditions of temperature and agitation. O2 consumption was markedly higher in flask-microcosms than in sediment core-microcosms, when compared on a per g dry weight basis. However, when the results were expressed as O2 consumed per unit surface area, the values were more similar. CO2 evolution was less dependent on surface area as evidenced by similar CO2 values per g sediment in both microcosms. In addition, the effect of sediment mass on O2 consumption and CO2 evolution was examined. Both O2 consumption and CO2 evolution (expressed as µmole g−1 dry weight sediment) decreased significantly with increasing sediment mass between 3 and 12 g dry weight. Maximum O2 consumption per unit headspace was measured when a wet sediment mass between 10.0 and 20.0 g was used in the flask-microcosms. It was also shown that the sediment: water ratio, agitation, incubation temperature, and previous storage time of sediment all affected the respiration estimates. Initial O2 consumption and CO2 evolution in flasks were significantly higher in flasks with a decreased sediment: water ratio (1:1 versus 1:2), increased flask agitation, and increased incubation temperature (15 °C versus 5 °C). Also, respiration decreased significantly over the first 100 days of storage at 4 °C.