An in situ instrument for planar O-2 optode measurements at benthic interfaces

A new in situ instrument for two-dimensional mapping of oxygen in coastal sediments is presented. The measuring principle is described, and potential mechanical disturbances, solute and particle smearing associated with the measurements, and calibration routines are evaluated. The first in situ measurements obtained in two different benthic communities are presented. In a shallow photosynthetic sediment (1 m of water depth), an extensive horizontal and temporal variation in the O-2 distribution caused by benthic photosynthesis and irrigating fauna was resolved. Repetitive planar optode measurements performed along a transect in central Oresund, Denmark (17 in of water depth) revealed a positive correlation between the apparent O-2 penetration depths (OP) measured with a lateral distance