Diffusive and total oxygen uptake of deep-sea sediments in the eastern South Atlantic Ocean:in situ and laboratory measurements |
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| Authors: | Ronnie Nhr Glud Jens K Gundersen Bo Barker Jrgensen Niels Peter Revsbech Horst D Schulz |
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| Institution: | Ronnie Nøhr Glud, Jens K. Gundersen, Bo Barker Jørgensen, Niels Peter Revsbech,Horst D. Schulz |
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| Abstract: | Total O2 uptake rates were measured by the benthic flux chamber lander ELINOR, and O2 microprofiles were measured by the profiling lander PROFILUR in the eastern South Atlantic. Diffusive O2 fluxes through the diffusive boundary layer and the depth distribution of O2 consumption rates within the sediment were calculated from the obtained microprofiles. The depth integrated O2 consumption rate agreed closely with the diffusive O2 uptake at all stations. Total O2 uptake was 1.2–4.2 times the diffusive O2 uptake, and the difference correlated with the abundance of macrofauna in the sediment. Diffusive O2 uptake and O2-penetration depths correlated with the organic content of the sediments and exhibited an inverse correlation with water depth. Total and diffusive rates of in situ O2 uptake were higher than previously published data for shelf and abyssal sediments in the Atlantic, but were comparable to rates from upwelling areas in the eastern Pacific. Laboratory measurements on recovered sediment cores showed lower O2 penetration depths and higher diffusive uptake rates than in situ measurements. The differences increased with increasing water depth. We primarily ascribe this compression of O2 profiles to a transiently increased temperature during recovery and enhanced microbial activity in decompressed sediment cores. Total O2 uptake rates measured in the laboratory on macrofauna-rich stations were, in contrast, lower than those measured in situ because of underrepresentation and disturbance of the macrofauna. |
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