The effect of a temperature rise on the sulphate reducing rates in cold marine sediments of Kongsfjorden (Svalbard, Arctic Ocean)

Abstract

Arctic Ocean is a useful sentinel for understanding the impact of climate change. Dramatic changes are occurring in this region, calling for monitoring of biogeochemical processes. The study site, Konsfjorden is a unique marine coastal system located at the north-western coast of Spitsbergen island in Svalbard (78 degrees 55’N, 11 degrees 56’E, Norway). Since 90 per cent of the sea floor has temperatures less than 4 degrees C, low environmental temperatures characterise the habitat of many bacteria living in the marine sediments. Sulfate reduction rates (SRR) in sediments of 4 sites in the Kongsfjorden area have been measured as a functionof temperature using the 35S radiotracer method. Experiments conducted with homogenised sediments amended with acetate and/or lactate at two different temperatures (0 degrees C and 4 degrees C) included suitable controls without amendments. SRR increased by almost 45 per cent with a 4 degrees C rise in temperature. This increase in sulfate respiration could imply an increase in the CO2 flux and subsequently global warming. The rate of carbon mineralised (CM) is proportional to the SRR, which in turn is influenced by salinity variations due to mixing of sea water with the fresh water from melting glaciers. Consequently, with a rise in temperature, the SRR actually tends to decrease with lowered salinities due to ice melting, thus offsetting the increase in CO2 flux that could have occurred due to the warming effect. This work is a part of the 3rd Indian Arctic Expedition to Svalbard from 14 June to 18 July 2009.