Temporal variation in the sediment permeability of an intertidal sandflat

Rapid organic matter turnover is driven by advective transport processes in sandy permeable sediments, allowing them to act as biocatalytic filters. This filtering capacity is largely defined by the permeability of the sediment, which describes the flow of water through a porous medium. However, little is known about the temporal variability of sandflat permeability under natural conditions. Therefore, the changes in sediment permeability in an intertidal sandflat were measured over a year. The results demonstrated temporal variation in permeability related to the sediment water content and concentration of extracellular polymeric substances (EPS) in the pore space. The refractory bound fraction of EPS was one of the main contributors to this variation. Proteins associated with the bound EPS fraction appeared to covary with the effect of EPS on permeability. Levels of EPS proteins were as high (415 to 2170 mu g g(-1) bovine serum albumin equivalents) as carbohydrate levels (560 to 1400 mu g g(-1) D-glucose equivalents) in this sediment. Elevated levels of EPS were observed in the summer corresponding to low permeability, which also corresponded with microphytobenthic blooms and resulting production of exudates. A powerful storm event during the experiment with associated wind-generated waves resulted in a reworking of the sediment. This cleared pore spaces, resuspended material and reduced sediment compaction, effecting an overall change in permeability from 3.6 x 10(-11) to 4.8 x 10(-11) m(2). The hypotheses that sandy sediment permeability varies with time and is influenced by EPS production were supported, and the effect of an episodic storm event was recorded.