Effects of bioirrigation on the spatial and temporal dynamics of oxygen above the sediment–water interface

Abstract

AbstractBurrow ventilation by tube-dwelling benthic animals affects solute exchange between sediments and water by 2 means. Drawing of O2-rich water into the burrow increases O2 availability in the sediment and stimulates biogeochemical and microbial processes, whereas flushing of the burrow creates a 3-dimensional flow field above the burrow, which induces mixing. Previous studies have revealed the role of the diffusive boundary layer (DBL) thickness on the exchange of solutes between the sediment and overlying water. Mapping the O2 gradient within the DBL is a challenging task in the presence of benthic faunal activities. We used a novel lifetime-based laser induced fluorescence (τLIF) technique that enables unobstructed observations of spatial and temporal O2 dynamics above burrows inhabited by midge larvae (Chironomus plumosus). We observed instantaneous plumes of O2-depleted water released from the outlet of the burrows and drawdown of O2-rich water above the inlet caused by peristaltic pumping of C....