The effects of temperature on oxygen uptake and nutrient flux in sediment inhabited by molluscs

Benthic invertebrates play an important role in oxygen uptake and nutrient cycling in the benthic boundary layer. The invertebrate activity, as well as the effects of the bioturbation on biogeochemistry, is greatly influenced by temperature. The present study aimed to investigate the influence of temperature on the sediment oxygen uptake and nutrient flux across the sediment-water interface in sediment inhabited by molluscs - animals often dominating the benthic community. Microcosms were constructed using sediment, lake water, and molluscs from lake Taihu (China). The clam Corbicula fluminea (Bivalvia: Corbiculidae) and the snail Bellamya aeruginosa (Gastropoda: Viviparidae) were selected for the experiment because they dominate the benthic community in the lake. The effect of molluscs on sediment oxygen uptake and nutrient flux was simultaneously examined using 6 treatments representing a combination of temperature (15 and 25 degrees C) and biota (C. fluminea, B. aeruginosa, and none). C. fluminea significantly increased the sediment oxygen uptake and release of soluble reactive phosphorus (SRP) and ammonium from the sediment to the overlying water at both temperatures. The net sediment oxygen uptake, net SRP and ammonium fluxes caused by the clam were significantly higher at 25 degrees C than at 15 degrees C. Moreover, B. aeruginosa significantly increased the sediment oxygen uptake at both experimental temperatures, however the net sediment oxygen uptake induced by the snail did not differ significantly between 15 and 25 degrees C. B. aeruginosa also produced significantly more net SRP release at 25 degrees C than that at 15 degrees C. In contrast, the influence of B. aeruginosa on the net ammonium flux at each temperature was not statistically significant. The result indicates that temperature is an important environmental factor that influences the effect of molluscs on nutrient flux across the sediment-water interface.