Sulfate reduction in Black Sea sediments: in situ and laboratory radiotracer measurements from the shelf to 2000 m depth |
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| Institution: | 1. UMR 7138 Evolution Paris-Seine, Equipe Biologie de la Mangrove, Université des Antilles, UFR des Sciences Exactes et Naturelles, Département de Biologie, BP 592, 97 159 Pointe-à-Pitre, Guadeloupe, France;2. NIOZ Royal Netherlands Institute for Sea Research, Department of Marine Microbiology, 4400 AC, Yerseke, The Netherlands;1. College of Environment, Zhejiang University of Technology, Hangzhou, China;2. Key Laboratory of Microbial Technology for Industrial Pollution Control of Zhejiang Province, Zhejiang University of Technology, Hangzhou, China;3. Geomicrobiology Group, School of Life Sciences, University of Dundee, Dundee DD1 5EH, Scotland, UK |
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| Abstract: | Sulfate reduction rate measurements by the 35SO42? core injection method were carried out in situ with a benthic lander, LUISE, and in parallel by shipboard incubations in sediments of the Black Sea. Eight stations were studied along a transect from the Romanian shelf to the deep western anoxic basin. The highest rates measured on an areal basis for the upper 0–15 cm were 1.97 mmol m?2 d?1 on the shelf and 1.54 mmol m?2 d?1 at 181 m water depth just below the chemocline. At all stations sulfate reduction rates decreased to values <3 nmol cm?3 d?1 below 15 cm depth in the sediment. The importance of sulfate reduction relative to the total mineralization of organic matter was very low, 6%, on the inner shelf, which was paved with mussels, and increased to 47% on the outer shelf at 100 m depth. Where the oxic–anoxic interface of the water column impinged on the sea floor at around 150 m depth, the contribution of sulfate reduction increased from >50% just above the chemocline to 100% just below. In the deep sea, mean sulfate reduction rates were 0.6 mmol m?2 d?1 corresponding to an organic carbon oxidation of 1.3 mmol m?2 d?1. This is close to the mean sedimentation rate of organic carbon over the year in the western basin. A comparison with published data on sulfate reduction in Black Sea sediments showed that the present results tend to be higher in shelf sediments and lower in the deep-sea than most other data. Based on the present water column H2S inventory and the H2S flux out of the sediment, the calculated turnover time of H2S below the chemocline is 2100 years. |
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