Temperature effects on respiration and photosynthesis in three diatom-dominated benthic communities

[摘要] ABSTRACT: Short-term temperature effects on respiration and photosynthesis were investigated in intact diatom-dominated benthic communities, collected at 2 temperate and 1 high-arctic subtidal sites. Areal rates of total (TOE) and diffusive (DOE) O₂exchange were determined from O₂-microsensor measurements in intact sediment cores in the temperature range from 0 to 24°C in darkness and at 140 µmol photons m^-2 s^-1. In darkness, theO₂ consumption increased exponentially with increasing temperature for both TOE and DOE, and no optimum temperature was observed within the applied temperature range. Q₁₀ was calculated from the linear slope in Arrhenius plotsand ranged between 1.7 and 3.3 at the respective sites. The volume-specific rate (R_dark,vol) solely representing the biological temperature response was somewhat stronger, with Q₁₀ values of 2.6 to 5.2. TheQ₁₀ values were overall not correlated to the in situ water temperature or geographical position. Accordingly, no difference in the temperature acclimation or adaptation strategy of the microbial community was observed. Slurredoxic sediment samples showed a Q₁₀ of 1.7 and were, hence, lower than estimates based on intact sediment core measurements. This can be ascribed to changes in physical and biological controls during resuspension. Gross photosynthesis wasmeasured with the light-dark shift method at the 2 temperate sites. Both areal (P_gross) and volumetric (P_gross,vol) rates increased with temperature to an optimum temperature at 12 and 15°C, with aQ₁₀ for P_gross of 2.2 and 2.6 for the 2 sites, respectively. The gross photosynthesis response could be categorised as psychrotrophic for both sites and no temperature adaptation was observed between the 2 sites. Ourmeasurements document that temperature stimulates heterotrophic activity more than gross photosynthesis, and that the benthic communities gradually become heterotrophic with increasing temperature. This has implications for C-cycling in shallow watercommunities experiencing seasonal and diel temperature fluctuations.

[学科分类] 生物科学（综合）

[关键词] Temperature;Adaptation;Benthic microphytes;Photosynthesis;Respiration;Q10;Microelectrodes;Oxygen