Kreling, Julika, Bravidor, Jenny, McGinnis, Daniel, Koschorreck, Matthias and Lorke, Andreas (2014) Physical controls of oxygen fluxes at pelagic and benthic oxyclines in a lake. Limnology and Oceanography, 59 (5). pp. 1637-1650. DOI 10.4319/lo.2014.59.5.1637.

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Abstract

We compared oxygen fluxes measured simultaneously at the pelagic and benthic oxycline in a lake and analyze
their relation to hydrodynamic forcing conditions. While the mean oxygen fluxes did not differ significantly
among both sites, the fluxes were highly variable in time. Short energetic periods contributed disproportionately
to the overall oxygen flux above both the benthic and pelagic oxycline. In the pelagic region, mean fluxes across
the oxycline were limited by low diffusivities (7 3 1028 m2 s21) and were one to two orders of magnitude smaller
than fluxes above the oxycline (0.5 and 32 mmol m22 d21, respectively). A one-dimensional transport model was
used to estimate sources and sinks of oxygen potentially causing this imbalance. The model results indicate that
92% of dissolved oxygen transported into the oxycline is used by the respiration of organic material imported into
the oxycline from the epilimnion; chemical oxygen consumption associated with the upward flux of reduced
substances is negligible. Our findings indicate that under such conditions, dissolved oxygen consumption and
therewith mineralization within the oxycline can be comparable with the corresponding rates occurring in the
sediments of eutrophic lakes with an oxic hypolimnion.

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