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 35S-sulfate in a temperature gradient block spanning a temperature range from 0 to 40 °C. An optimum temperature (Topt) 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 Topt ≤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 Topt 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.
Highlights
About 95 % of the seafloor is permanently cold with in situ temperatures below 4 ◦C (Levitus and Boyer, 1994)
Bacteria that grow at temperatures extending into the mesophilic range and that do not show cold adaptations were isolated from the cold deep seafloor (Ruger, 1989; Ruger and Tan, 1992; Finster and Bak, 1993; Chen et al, 2003; Aono et al, 2010)
The highest organic carbon content was measured in Namibian (4.4 % total organic carbon (TOC)) and Uruguayan (5.0 % TOC) shelf sediments, and Namibian (6.5 % TOC) slope sediment
Summary
About 95 % of the seafloor is permanently cold with in situ temperatures below 4 ◦C (Levitus and Boyer, 1994). Bacteria carrying out carbon mineralization in the cold seabed must be adapted to operate effectively under such low temperatures. As a result of such microbial adaptation to low temperature, the rate and efficiency of organic carbon mineralization in the cold may be as high as in temperate and warm habitats (Kostka et al, 1999). Bacteria that grow at temperatures extending into the mesophilic range and that do not show cold adaptations were isolated from the cold deep seafloor (Ruger, 1989; Ruger and Tan, 1992; Finster and Bak, 1993; Chen et al, 2003; Aono et al, 2010).
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
