Rates of microbial processes in sediments

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Abstract
The following methods of measurement of sediment parameters are discussed: (1) rate of diffusional exchange of reactants and products across the sediment—water interface; (2) the concentration profiles of these reactants and profiles in the sediment, and (3) profiles and integrated rates of reactions in the sediment. The interaction of the processes of reaction and diffusion are illustrated using a simulation model. The effect of increasing organic loading (6.2, 37.2 and 62.0 mmol C m -2 d -1 ), with organic matter distributed in three ways: close to the sediment surface, a linear gradient downwards or evenly mixed throughout the sediment. Predictable increases in anoxic processes occurred with increasing organic loading. There were higher diffusional losses of dissolved organic matter when organic degradation occurred close to the sediment—water interface. The model predicted that degradation of organic matter at depth could have the following effects: an increase in the depth of oxygen penetration, an increase in the ratio of CO 2 /O 2 , and an increase in nitrification and denitrification.