Temperature characteristics of bacterial sulfate reduction in continental shelf and slope sediments

Abstract

Abstract. The temperature responses of sulfate-reducing microbial communities were used as community temperature characteristics for their in situ temperature adaptation, their origin, and dispersal in the deep sea. Sediments were collected from a suite of coastal, continental shelf, and slope sediments from the southwest and southeast Atlantic and permanently cold Arctic fjords from water depths ranging from the intertidal zone to 4327 m. In situ temperatures ranged from 8 • C on the shelf to −1 • C in the Arctic. Temperature characteristics of the active sulfate-reducing community were determined in short-term incubations with 35 S-sulfate in a temperature gradient block spanning a temperature range from 0 to 40 • C. An optimum temperature (T opt ) between 27 • C and 30 • C for the South Atlantic shelf sediments and for the intertidal flat sediment from Svalbard was indicative of a psychrotolerant/mesophilic sulfate-reducing community, whereas T opt ≤ 20 • C in South Atlantic slope and Arctic shelf sediments suggested a predominantly psychrophilic community. High sulfate reduction rates (20-50 %) at in situ temperatures compared to those at T opt further support this interpretation and point to the importance of the ambient temperature regime for regulating the short-term temperature response of sulfate-reducing communities. A number of cold (< 4 • C) continental slope sediments showed broad temperature optima reaching as high as 30 • C, suggesting the additional presence of apparently mesophilic sulfate-reducing bacteria. Since the temperature characteristics of these mesophiles do not fit with the permanently cold deep-sea environment, we suggest that these mesophilic microorganisms are of allochthonous origin and transported to this site. It is likely that they were deposited along with the mass-flow movement of warmer shelf-derived sediment. These data therefore suggest that temperature response profiles of bacterial carbon mineralization processes can be used as community temperature characteristics, and that mixing of bacterial communities originating from diverse locations carrying different temperature characteristics needs to be taken into account to explain temperature response profiles of bacterial carbon mineralization processes in sediments.

Impacts of Shallow Geothermal Energy Production on Redox Processes and Microbial Communities

“…Two studies on marine 53 and estuarine sediments 55 report E a values of sulfate reduction in the same range as observed for the mesophilic range in sediment Scherpenzeel (50% of E a values between 30 and 60 kJ/mol in Figure 5B). The E a for sulfate reduction in geothermal systems ( Figure 5B), however, reveals an E a range between 100 and 160 kJ/mol (50% box) suggesting a different thermodynamic behavior of thermophilic compared to mesophilic sulfate reduction.…”

Sulfur Cycling in an Iron Oxide-Dominated, Dynamic Marine Depositional System: The Argentine Continental Margin

“…Sulfide can only build up in the pore water when the rates of sulfide formation exceed those of iron-phase alteration, leading to the establishment of a sulfidic zone (Figure 3). Because of the low reactivity of the organic matter , SRR are extremely low even in the presence of abundant sulfate in the upper meters ( Figure 3A), with average rates of 5.8 pmol cm −3 d −1 -about one order of magnitude lower than rates usually found in sediments from similar water depths (e.g., Fossing et al, 2000;Sawicka et al, 2012). Thus, sulfide production is mainly restricted to the SMT.…”

Seasonal Microbial Population Shifts in a Bioremediation System Treating Metal and Sulfate-Rich Seepage

“…Thus, the sulfate-reducing bacteria found in the BCR and their close relatives also found in metal-rich or cold marine environments may share special adaptations to stressful environments. Many mesophilic sulfate-reducers are present in permanently cold environments [15,16] indicating that they are psychrotolerant and some are active at low temperatures [14]. In cold Arctic Ocean sediments, sulfate-reducers are thought to contribute to the majority of carbon cycling [52].…”