The effect of temperature on rates of sulfate reduction in marine sediments

Abstract

Rates of sulfate reduction in sediments of Long Island Sound have been determined, as a function of temperature, via the ³⁵S radiotracer method. Temperature dependence was measured either by following changes in rates in intact cores with seasonal changes in temperature, or by conducting laboratory experiments on homogenized sediments under controlled temperatures. At constant temperature, a large range of sulfate reduction rates were observed for the study sites. In both the intact cores and the laboratory experiments, sediments with lower rates of sulfate reduction exhibited a more pronounced temperature dependence. Apparent activation energies determined using the Arrhenius equation show a systematic trend with sulfate reduction rate when temperature was normalized. As the rate of sulfate reduction decreased, the apparent activation energy increased from 36 to 132 kJ/mole. Although this observation can be interpreted in a number of ways, it is suggested that susceptibility of organic matter to metabolic attack exerts an important control on the temperature dependence of sulfate reduction, as well as on the rate itself. Our findings indicate that the use of a constant temperature correction for estimating annual rates of sulfate reduction will be inaccurate.