Oxygenic primary production below the oxycline and its importance for redox dynamics
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- 作者：Andreas Brand ; Hannah Bruderer ; Kirsten Oswald ; Carole Guggenheim…
- 关键词：Primary production ; Anoxic zone ; Redox cycling ; Oxygen
- 刊名：Aquatic Sciences - Research Across Boundaries
- 出版年：2016
- 出版时间：October 2016
- 年：2016
- 卷：78
- 期：4
- 页码：727-741
- 全文大小：3,036 KB
- 刊物类别：Biomedical and Life Sciences
- 刊物主题：Life Sciences
Ecology
Oceanography
Life Sciences - 出版者：Birkh盲user Basel
- ISSN：1420-9055
- 卷排序：78
文摘
We present evidence that oxygenic primary production occurs in the virtually anoxic regions (i.e. regions where no oxygen was detected) of the eutrophic, pre-alpine Lake Rot (Switzerland). Chlorophyll-a measurements in combination with phytoplankton densities indicated the presence of oxygenic primary producers throughout the water column. While Chlorophyceae were present as the main class of oxygenic phototrophs above the oxycline, which extended from 8 down to 9.2 m, the phototrophic community in and below the oxycline was dominated by cyanobacteria. In-situ incubation experiments with H14CO3− conducted in August 2013 revealed an oxygenic primary production rate of 1.0 and 0.5 mg C m−3 h−1 in 9 and 10 m depth, respectively. However, measurements with optical trace oxygen sensors showed that oxygen concentrations were below the detection limit (20 nmol l−1) during the incubation period below 9.2 m. Potential oxygen consumption rates, which were 10–20 times higher than oxygen production rates, explain this absence of free oxygen. Our data show that oxygen production in the virtually anoxic zone corresponded to approximately 8 % of the oxygen flux driven by the concentration gradient in the oxycline. This provided an important source of electron acceptors for biogeochemical processes beyond the conventional redox boundary and in the apparently oxygen depleted zone of Lake Rot. This oxygenic primary production in the virtually anoxic zone could allow growth and activity of aerobic microorganisms adapted to low oxygen supply.