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Denitrification and photosynthesis in stream sediment studied with microsensor and wholecore techniques
Author(s) -
Nielsen Lars Peter,
Bondo Christensen Peter,
Revsbech Niels Peter,
Sørensen Jan
Publication year - 1990
Publication title -
limnology and oceanography
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.7
H-Index - 197
eISSN - 1939-5590
pISSN - 0024-3590
DOI - 10.4319/lo.1990.35.5.1135
Subject(s) - denitrification , photosynthesis , benthic zone , environmental chemistry , sediment , chemistry , oxygen , nitrogen , oceanography , geology , paleontology , biochemistry , organic chemistry
The effect of light on benthic photosynthesis, denitrification, and assimilation of NH 4 + and NO 3 − in stream sediments was studied with whole‐core techniques and with O 2 and N 2 O microsensors. Photosynthetic oxygen production increased the thickness of the aerobic surface layer from 1.5 mm in the dark ∼3.5 mm at a light intensity saturating photosynthesis. The O 2 flux changed concurrently from net uptake to net release and the overall rate of denitrification was reduced by 70%. Denitrification was always restricted to a narrow zone immediately below the aerobic‐anaerobic interface. Calculated NO 3 − microprofiles showed that overall denitrification was primarily dependent on the thickness of the aerobic layer which acted as a barrier for diffusion of NO 3 − from the overlying water. In the light, algal NO 3 − assimilation could exceed NO 3 − consumption by denitrification when availability of NH 4 + was low. Assimilation of NO 3 − , however, had no influence on the flux of NO 3 − to the denitrification zone, since assimilation occurred relatively close to the sediment surface.