caa a22 4500 465790283 CHVBK 20180323112022.0 cr unu---uuuuu 170327e19900101xx s 000 0 eng 10.1007/BF02015054 doi (NATIONALLICENCE)springer-10.1007/BF02015054 Denitrification and oxygen respiration in biofilms studied with a microsensor for nitrous oxide and oxygen [Elektronische Daten] [Lars Nielsen, Peter Christensen, Niels Revsbech, Jan Sørensen] Depth distributions of O2 respiration and denitrification activity were studied in 1- to 2-mm thick biofilms from nutrient-rich Danish streams. Acetylene was added to block the reduction of N2O, and micro-profiles of O2 and N2O in the biofilm were measured simultaneously with a polarographic microsensor. The specific activities of the two respiratory processes were calculated from the microprofiles using a one-dimensional diffusion-reaction model. Denitrification only occurred in layers where O2 was absent or present at low concentrations (of a fewμM). Introduction of O2 into deeper layers inhibited denitrification, but the process started immediately after anoxic conditions were reestablished. Denitrification activity was present at greater depth in the biofilm when the NO3 − concentration in the overlying water was elevated, and the deepest occurrence of denitrification was apparently determined by the depth penetration of NO3 −. The denitrification rate within each specific layer was not affected by an increase in NO3 − concentration, and the half-saturation concentration (Km) for NO3 − therefore considered to be low (<25μM). Addition of 0.2% yeast extract stimulated denitrification only in the uppermost 0.2 mm of the denitrification zone indicating a very efficient utilization of the dissolved organic matter within the upper layers of the biofilm. Springer-Verlag New York Inc., 1990 Nielsen Lars Department of Ecology and Genetics, University of Aarhus, Ny Munkegade, DK-8000, Aarhus C, Denmark aut Christensen Peter Department of Ecology and Genetics, University of Aarhus, Ny Munkegade, DK-8000, Aarhus C, Denmark aut Revsbech Niels Department of Ecology and Genetics, University of Aarhus, Ny Munkegade, DK-8000, Aarhus C, Denmark aut Sørensen Jan Department of Ecology and Genetics, University of Aarhus, Ny Munkegade, DK-8000, Aarhus C, Denmark aut Microbial Ecology Springer-Verlag 19/1(1990-01-01), 63-72 0095-3628 19:1<63 1990 19 248 https://doi.org/10.1007/BF02015054 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/BF02015054 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Nielsen Lars Department of Ecology and Genetics, University of Aarhus, Ny Munkegade, DK-8000, Aarhus C, Denmark aut NATIONALLICENCE 700 1- Christensen Peter Department of Ecology and Genetics, University of Aarhus, Ny Munkegade, DK-8000, Aarhus C, Denmark aut NATIONALLICENCE 700 1- Revsbech Niels Department of Ecology and Genetics, University of Aarhus, Ny Munkegade, DK-8000, Aarhus C, Denmark aut NATIONALLICENCE 700 1- Sørensen Jan Department of Ecology and Genetics, University of Aarhus, Ny Munkegade, DK-8000, Aarhus C, Denmark aut NATIONALLICENCE 773 0- Microbial Ecology Springer-Verlag 19/1(1990-01-01), 63-72 0095-3628 19:1<63 1990 19 248 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer