Tidal flat sediments are characterised by a high input of organic matter. Most of it is rapidly remineralised in the upper few centimetres of the sediment by microorganisms employing a variety of electron acceptors. Thus, compared to open ocean sites tidal flat sediments show vertically compressed biogeochemical gradients and moreover, may harbour typical deep subsurface communities within a few meters depth (Wilms et al., 2006).
Dissimilatory sulfate reduction is the major terminal anaerobic degradation process accounting for up to half of the total organic carbon remineralisation in marine sediments (J°rgensen, 1982). So, sulfate-reducing (SRB) significantly contribute to biogeochemical processes, even though they do not belong to the most abundant bacterial groups in marine sediments (Böttcher et al., 2000; Llobet-Brossa et al., 2002).
Previous studies on tidal surface sediments in the German Wadden Sea have shown that highest sulfate reduction rates occur in near-surface layers where microbial activity is not limited by the availability of easily degradable electron donors. In contrast, deeper sediment layers are thought to be less active due to the increase in the recalcitrance of organic matter.
However, the dynamical structure of tidal flats allows for pore water transport between corresponding permeable sediment layers and may therefore lead to an influx of nutrients into greater depths (Billerbeck et al., 2006). So, our project addresses the question how this special environmental setting influences the activity and structure of the sulfate-reducing community.
Poster VAAM Jena 2006
Poster ISME Vienna 2006
Henrik Sass (Cardiff, Wales)
Marc Mußmann (MPI, Bremen)
Nicole Dubilier (MPI, Bremen)
Biogeochemistry of Tidal flats (DFG research group)
Gittel, Antje (2007) Community, structure, activity and ecophysiology of sulfate-reducing bacteria in deep tidal flat sediments = Struktur, Aktivität und Ökophysiologie sulfatreduzierender Bakteriengemeinschaften in tiefen Sedimenten des Deutschen Wattenmeeres
Gittel A, Mußmann M, Sass H, Cypionka H, Könneke M (2008) Identity and abundance of active sulfate-reducing bacteria in deep tidal flat sediments determined by directed cultivation and CARD-FISH analysis. Environ Microbiol 10:2645-2658
Billerbeck, M., Werner, U., Polerecky, L., , Walpersdorf, E., de Beer, D. and Huettel, M. (2006) Surficial and deep pore water circularion governs spatial and temporal scales of nutrient recycling in intertidal sand flat sediment. Mar Ecol Prog Ser 326: 61-76.
Wilms, R., K÷pke, B., Chang, T. S., Sass, H., Cypionka, H., and Engelen, B. (2006) Deep-biosphere related bacteria within the subsurface of tidal flat sediments. Environ Microbiol 8: 709-719.
Böttcher, M. E., Hespenheide, B., Llobett-Brossa. E., Beardsley, C. et al. (2000) The biogeochemistry, stable isotope geochemistry, and microbial community structure of a temperate intertidal mudfalt: an integrated study. Cont Shelf Res 20: 1749-1769.
Llobet-Brossa, E., Rabus, R., Böttcher, M. E., Könneke, M., Finke, N., Schramm, A., Meyer, R. L., Grötzschel, S., Rossello-Mora, R., and Amann, R. (2002) Community structure and activity of sulfate-reducing bacteria in an intertidal surface sediment: a multimethod approach. Aquat Microb Ecol 29: 211-226.
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J°rgensen, B. B. (1982) Mineralization of organic matter in the sea bed: the role of sulphate reduction. Nature 296: 643-645.