Organic carbon mass accumulation rate regulates the flux of reduced substances from the sediments of deep lakes
The flux of reduced substances, such as methane and ammonium, from the sediment to the bottom water (<i>F</i><sub>red</sub>) is one of the major factors contributing to the consumption of oxygen in the hypolimnia of lakes and thus crucial for lake oxygen management. This s...
| Main Authors: | , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2017-07-01
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| Series: | Biogeosciences |
| Online Access: | https://www.biogeosciences.net/14/3275/2017/bg-14-3275-2017.pdf |
| Summary: | The flux of reduced substances, such as methane and ammonium, from
the sediment to the bottom water (<i>F</i><sub>red</sub>) is one of the major factors
contributing to the consumption of oxygen in the hypolimnia of lakes and thus
crucial for lake oxygen management. This study presents fluxes based on
sediment porewater measurements from different water depths of five deep
lakes of differing trophic states. In meso- to eutrophic lakes <i>F</i><sub>red</sub> was
directly proportional to the total organic carbon mass accumulation rate
(TOC-MAR) of the sediments. TOC-MAR and thus <i>F</i><sub>red</sub> in eutrophic lakes
decreased systematically with increasing mean hypolimnion depth
(<i>z</i><sub>H</sub>),
suggesting that high oxygen concentrations in the deep waters of lakes were
essential for the extent of organic matter mineralization leaving a smaller
fraction for anaerobic degradation and thus formation of reduced compounds.
Consequently, <i>F</i><sub>red</sub> was low in the 310 m deep meso-eutrophic Lake
Geneva,
with high O<sub>2</sub> concentrations in the hypolimnion. By contrast, seasonal
anoxic conditions enhanced <i>F</i><sub>red</sub> in the deep basin of oligotrophic Lake
Aegeri. As TOC-MAR and <i>z</i><sub>H</sub> are based on more readily available data,
these relationships allow estimating the areal O<sub>2</sub> consumption rate by
reduced compounds from the sediments where no direct flux measurements are
available. |
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| ISSN: | 1726-4170 1726-4189 |