Community structure and activity of sulfate-reducing bacteria in an intertidal surface sediment: a multi-method approach

Abstract

The community structure of sulfate-reducing bacteria (SRB) in an intertidal mud flat of the German Wadden Sea (Site Dangast, Jade Bay) was studied and related to sedimentary biogeochemical gradients and processes. Below the penetration depths of oxygen (~3 mm) and nitrate (~4 mm), the presence of dissolved iron and manganese and the absence of dissolved sulfide indicated suboxic conditions within the top 10 cm of the sediment. Moderate to high bacterial sulfate reduction rates were measured with radiotracers throughout the sediment, and dissimilatory sulfate reduction was also demonstrated by the presence of acid-volatile sulfides (AVS, essentially iron monosulfide). Stable sulfur isotope discrimination between dissolved sulfate and AVS was dominated by sulfate reduction. The diversity of SRB was studied using denaturant gradient gel electrophoresis of 16S rDNA, phospholipid fatty acid analysis and counting viable cells with the most probable number technique. Phylogenetic groups of SRB identified with these techniques were almost evenly distributed throughout the top 20 cm of the sediment. Application of fluorescence in situ hybridization, however, demonstrated a maximum of active members of the Desulfovibrio and Desulfosarcina-Desulfococcus-Desulfofrigus groups between 2 and 3 cm depth. These 2 groups encompass acetate and lactate utilizing SRB. The coincidence of this SRB maximum with a local maximum of sulfate reduction rates and the depletion of acetate and lactate reflects the microbiological processes related to sulfate reduction.

Transport and mineralization rates in North Sea sandy intertidal sediments, Sylt-Rømø Basin, Wadden Sea

“…Nutrients were determined with a Scalar autoanalyzer (Grasshoff et al 1999). Dissolved sulfate was quantified gravimetrically as BaSO 4 from pore water that was fixed in Zn acetate solution immediately after sectioning sediment cores into 1-cm slices at the field station (Llobet-Brossa et al 2002).…”

Degradation of cyanobacterial biomass in anoxic tidal-flat sediments: a microcosm study of metabolic processes and community changes

“…As long as sulfate is available, the oxidation of fermentation products is mainly coupled to sulfate reduction and not to methanogenesis (Jørgensen, 1982). The terminal processes sulfate reduction and methanogenesis are well studied (for example, Llobet-Brossa et al, 2002;Beck et al, 2011), whereas the initial fermentation processes and the involved organism are poorly understood. In most studies, molecular tools were used to investigate the terminal oxidizers.…”

Imprint of past and present environmental conditions on microbiology and biogeochemistry of coastal Quaternary sediments

“…Tidal flats are found all over the world, for example in Asia along the Korean coast, in North Africa and North America along the Atlantic coast, and in Europe in the British channel and along the North Sea coast. On a global scale, this type of landscape is of great importance due to its high primary production and organic matter remineralization rates (van Beusekom et al, 1999;Cadée and Hegeman, 2002;D'Andrea et al, 2002;de Beer et al, 2005;Loebl et al, 2007). The water column and underlying sediments are tightly coupled due to bidirectional exchange of nutrients and organic material (Huettel et al, 1998;Rusch et al, 2001;Billerbeck et al, 2006;Beck et al, 2008a).…”

“…The studies focused on surface sediments (e.g. Böttcher et al, 2000;Llobet-Brossa et al, 2002;Billerbeck et al, 2006;Al-Raei et al, 2009;Jansen et al, 2009) as well as on deeper sediment layers down to 5 m below the seafloor (mbsf) (e.g. Köpke et al, 2005;Wilms et al, 2006b;Beck et al, 2008b;Gittel et al, 2008;Røy et al, 2008).…”