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

[摘要] The temperature responses of sulfate-reducing microbial communities were usedas community temperature characteristics for their in situ temperatureadaptation, their origin, and dispersal in the deep sea. Sediments werecollected from a suite of coastal, continental shelf, and slope sedimentsfrom the southwest and southeast Atlantic and permanently cold Arctic fjordsfrom water depths ranging from the intertidal zone to 4327 m. In situtemperatures ranged from 8 °C on the shelf to −1 °C in the Arctic. Temperaturecharacteristics of the active sulfate-reducing community were determined inshort-term incubations with ³⁵S-sulfate in a temperature gradient blockspanning a temperature range from 0 to 40 °C. An optimum temperature(T_opt) between 27 °C and 30 °C for the SouthAtlantic shelf sediments and for the intertidal flat sediment from Svalbardwas indicative of a psychrotolerant/mesophilic sulfate-reducing community,whereas T_opt ≤20 °C in South Atlantic slope and Arcticshelf sediments suggested a predominantly psychrophilic community. Highsulfate reduction rates (20–50%) at in situ temperatures compared tothose at T_opt further support this interpretation and point tothe importance of the ambient temperature regime for regulating theshort-term temperature response of sulfate-reducing communities. A number ofcold (<4 °C) continental slope sediments showed broad temperatureoptima reaching as high as 30 °C, suggesting the additional presenceof apparently mesophilic sulfate-reducing bacteria. Since the temperaturecharacteristics of these mesophiles do not fit with the permanently colddeep-sea environment, we suggest that these mesophilic microorganisms are ofallochthonous origin and transported to this site. It is likely that theywere deposited along with the mass-flow movement of warmer shelf-derivedsediment. These data therefore suggest that temperature response profiles ofbacterial carbon mineralization processes can be used as communitytemperature characteristics, and that mixing of bacterial communitiesoriginating from diverse locations carrying different temperaturecharacteristics needs to be taken into account to explain temperatureresponse profiles of bacterial carbon mineralization processes in sediments.

[学科分类] 地球化学与岩石