Hydrothermal hotspots for microbial sulfate reduction in the Norwegian Sea

Ever noticed a rotten egg odor when walking through a swampy area? It is likely that you smelled the result of microbial sulfate reduction, a biological process in which oxidized sulfur (sulfate) is transformed into the reduced form of sulfur (sulfide) with its characteristic smell.

Sulfate reducers are common in areas where sulfate and organic matter are abundant, such as coastal swamps or shallow marine areas close to land. On the other hand, they tend to thrive less in deep-sea environments where organic matter – their main source of energy – is scarce or used up by other micro-organisms before it reaches the sulfate reducers. But seafloor hydrothermal vent fields seem to provide an exception to this rule.

Research by Dr. Desiree Roerdink and a team of geochemists and microbiologists in the Center for Deep Sea Research shows that deep-sea hydrothermal systems in the Norwegian Sea are hotspots for microbial sulfate reduction. Together with PhD and MSc students, Desiree injected radioactive sulfate into hydrothermal chimneys and sediments and measured how much of this sulfate was transformed into sulfide over time. They did the same in marine sediments away from the vent fields, and found a remarkable difference: microbial sulfate reduction was only detected in the hydrothermal areas.

Interestingly, the team found some of the highest activity of sulfate reducers on low-temperature hydrothermal barite chimneys that were thought to be inactive, and the measured rates suggest that microbes could add a substantial amount of sulfide to venting fluids. These findings indicate that hydrothermal systems provide a pleasant haven for sulfate reducers in a setting that otherwise seems like a dark and barren part of our planet.

The research in the article reflects the work of many PhD and MSc students in the Center for Deep Sea Research over the past years: Francesca Vulcano (BIO, PhD 2023), Karen Moltubakk (GEO, MSc 2022), Hannah Babel (BIO, MSc 2019), Jan-Kristoffer Landro (GEO, MSc 2016), as well as fruitful collaborations between the Department of Biological Sciences and Department of Earth Sciences.

Find the article here.