Flow-induced flushing of relict tube structures in the central Skagerrak (Norway)

Measurements of the O-2 microdistribution around relict tubes of the polychaete Spiochaetopterus bergensis revealed an intense passive flushing of the tube structure if exposed to ambient flow. Flushing induced plumes, several microliters large, Of O-2-undersaturated water that spread downstream in a flow-dependent manner. The plume induced a very irregular interstitial O-2 distribution around the tubes, with suboxic microniches. Mass balance calculations based on the measured exchange rates estimated the flushing rate of the relict tubes to be on the order of 5-11 mul tube(-1) min(-1) at the applied flow rates; this strongly enhanced the benthic solute exchange in the area. Given the high density of several thousand tubes per square meter in the central Skagerrak, this flushing rate has profound effects on the biogeochemistry of the otherwise impermeable sediment, which is unique in the sense that benthic diagenesis is completely dominated by manganese oxidation.