Vardeh, David (2011) Biogeochemische Prozesse an marinen Walkadavern und Methanquellen = Biogeochemical processes at marine whale falls and methane seeps. (Diploma thesis), Christian-Albrechts-Universität zu Kiel, Kiel, 74 pp.

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Abstract

To test the "everything is everywhere" hypothesis, four marine sediment types of different origins were enriched with either whale biomass or methane. Sulphide and methane concentrations were measured for almost 200 days. After 35 days, sediments that were from sites of high organic matter input showed constant or even increasing rates of sulphate reduction. Increasing rates of methanogenesis were detected with a lag of about 100 days from onset of sulphate reduction. The sediment that had been exposed to methane in situ exhibited a low rate of anaerobic oxidation of methane (AOM) when enriched with methane. Nitrogen and organic carbon content of the whale biomass enriched sediments showed a two- to threefold increase compared to pristine sediment. No change in elemental composition was observed in methane enriched sediments. A whale vertebra sampled at an inactive whale fall site was examined for rates of sulphate reduction. Pockets of lipids were shown to be hotspots of sulphate reduction in deep layers of the bone. By measurement of citrate content, age determination was attempted. In a related experiment, fresh whale and bird vertebrae were incubated on two marine sediments in flow-through aquaria and microbial mat development and sediment appearance were monitored for six months. Bones were sampled every month and light, fluorescence and scanning electron microscopy was done on surfaces and cross-sections to determine the nature and extent of bioerosion. Microbial bioerosion was found to start rapidly after incubation and no differences were observed between bones or sediments. No bioerosion was detected in bone parts incubated below sediment. The results obtained shed an ambivalent light on the hypothesis of "everything is everywhere". Whereas some metabolic reactions in sediments were similar, others did not exhibit the same pattern. In bone incubations, mat formation and bioerosion were very similar between sediments, but identification of the actual organisms is necessary to unravel the succession and mechanism of bioerosion.

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