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Aquatic Microbial Ecology

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AME 10:181-194 (1996)  -  doi:10.3354/ame010181

Impact of the soft-shell clam Mya arenaria on sulfate reduction in an intertidal sediment

Hansen K, King GM, Kristensen E

Sulfate reduction and various parameters related to the sulfur cycle were examined at mm to cm scales around burrows of the soft-shell clam Mya arenaria in an intertidal sediment (Lowes Cove, Maine, USA). Sulfate reduction rates were 1.5 to 2 times higher in the inner 1 to 5 mm region surrounding the burrow than in ambient sediment. In contrast, pools of reduced sulfur increased with the distance from the burrow wall to values ca 1.5 times higher in ambient sediment. The highest numbers of sulfate-reducing bacteria (estimated using a most-probable-number technique) and microbial biomass (estimated from phospholipid phosphorous content) relative to ambient sediment were found in the innermost zone around burrows. Results from an artificial burrow experiment showed that artificial burrow irrigation suppressed sulfate reduction in the innermost zone around burrows, while radial profiles of reduced sulfur resembled those from M. arenaria burrows, indicating loss of reduced sulfur from the burrow wall. M. arenaria burrows are thus sites of enhanced microbial activity and a dynamic sulfur cycle, with turnover times of reduced sulfur compounds increasing with distance from the burrow wall. Enhanced sulfate reduction rates near burrows are likely caused by substrate enrichment, perhaps due to organic excretions from M. arenaria. The pattern of reduced sulfur turnover likely results from periodic oxygen inputs during burrow irrigation.

Bioturbation . Marine sediment . Sulfate reduction . Sulfate-reducing bacteria . Mya arenaria

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