Oxygenic primary production below the oxycline and its importance for redox dynamics

摘要: We present evidence that oxygenic primary production occurs in the virtually anoxic regions (i.e. where no oxygen was detected) of eutrophic, pre-alpine Lake Rot (Switzerland). Chlorophyll-a measurements combination with phytoplankton densities indicated presence producers throughout water column. While Chlorophyceae were as main class phototrophs above oxycline, which extended from 8 down to 9.2 m, phototrophic community and below oxycline dominated by cyanobacteria. In-situ incubation experiments H14CO3 − conducted August 2013 revealed an rate 1.0 0.5 mg C m−3 h−1 9 10 m depth, respectively. However, optical trace sensors showed concentrations detection limit (20 nmol l−1) during period 9.2 m. Potential consumption rates, 10–20 times higher than explain this absence free oxygen. Our data show zone corresponded approximately 8 % flux driven concentration gradient oxycline. This provided important source electron acceptors for biogeochemical processes beyond conventional redox boundary apparently depleted Rot. could allow growth activity aerobic microorganisms adapted low supply.