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Aquatic Microbial Ecology

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AME 14:223-233 (1998)  -  doi:10.3354/ame014223

Oxygen dynamics at the base of a biofilm studied with planar optodes

Ronnie Nøhr Glud1,2,*, Cecilia Maria Santegoeds1, Dirk De Beer1, Oliver Kohls1, Niels Birger Ramsing3

1Max Planck Institute for Marine Microbiology, Celsiusstr. 1, D-28359 Bremen, Germany
2University of Copenhagen, Marine Biological Laboratory, Strandpromenaden 5, DK-3000 Helsingør, Denmark
3University of Aarhus, Institute of Biology, Dept of Microbial Ecology, Ny Munkegade bgn. 550, DK-8000 Århus C, Denmark

The O2 dynamics at the base of biofilms was studied using planar optodes. Biofilms were grown directly on the optodes and the 2-dimensional distribution of O2 at the base of biofilms was resolved at a spatial resolution of 30 × 30 μm, using a CCD camera. The average O2 saturation at the base decreased and the heterogeneity increased as biofilms developed. In mature biofilms heterogeneous O2 distributions were caused by clusters of high biomass which had low O2 saturations surrounded by O2-rich voids and channels. The O2 distribution at the base of biofilms was highly dependent on the free flow velocity above the biofilm, e.g. in a 400 μm thick biofilm the average O2 saturation increased from 0 to 23.1% air saturation as the free flow velocity increased from 6.2 to 35.1 cm s-1. Addition of glucose to a concentration of 2 mM in the water phase at maximum flow velocity caused the O2 consumption rate to increase and the base of the biofilm to go anoxic. The insertion of an O2 microelectrode into a biofilm caused the O2 saturation at the base of the biofilm to increase by approximately 25 μM. This effect, presumably caused by hydrodynamic disturbances, typically extended several mm away from the position of the microsensor tip. The presented data show for the first time the true distribution of O2 at the basis of heterogeneous biofilms and demonstrate the great potential of planar optodes for the study of solute dynamics within biofilms at a very high spatial and temporal resolution.

Optodes · Flow · Microniches

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