Inter-Research
Marine Ecology Progress Series

ABSTRACT: Although O₂ microsensors used for study of benthic photosynthesis have tip diameters of less than 10 um and stem diameters of about 150 um at a distance of 0.5 cm from the tip, they do change the local flow pattern in the overlying water and thereby reduce the thickness of the diffusive boundary layer (DBL). The reduced DBL resulted in a lower diffusional resistance towards export of O₂ from communities with a net production of O₂, and insertion of a microsensor in such a community therefore resulted in lowered O₂ concentrations. The total diffusion flux out of the photosynthetic layer was not significantly affected by the presence of the microsensor. The higher upward flux into the water phase was counterbalanced by a reduced downward flux into the sediment. The O₂ profiles and diffusion fluxes were only affected when the surface was smooth, while the effect of microsensor insertion was undetectable when the surface was made irregular by small tufts, bubbles, etc. In the investigated cyanobacteria-dominated mats, the gross photosynthetic rates as measured by the light/dark shift technique were unaffected by the presence of a microsensor.

KEY WORDS: Microelectrodes . Oxygen . Diffusive boundary layer . Benthic photosynthesis

Published in MEPS Vol. 119 (1995) on March 23
Print ISSN: 0171-8630; Online ISSN: 1616-1599. Copyright © Inter-Research, Oldendorf/Luhe, 1995