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Oxygen depletion in coastal waters

A new NESSC paper by Martijn Hermans, Caroline Slomp and colleagues has been published in the journal of Environmental Science and Technology!

Human-induced climate change expresses itself in different forms. The melting of ice caps and the warming of our planet are well-known examples of direct effects of climate change. What is often overlooked is that climate change can also contribute to a depletion of oxygen in coastal waters. The loss of oxygen and  subsequent release of highly toxic hydrogen sulfide from the seafloor ultimately may lead to the loss of marine life and is therefore of critical importance. Areas in the sea where oxygen depletion occurs are referred to as “dead zones” and are growing at an alarming rate.

Recently, a novel group of bacteria was discovered that may delay the release of hydrogen sulfide from sediments in dead zones. These so-called cable bacteria mediate the transport of electrons in sediments by linking sulfide oxidation at depth to oxygen reduction near the surface sediment. They can thus detoxify the sediment. The new study by Hermans et al. shows that these cable bacteria are widespread in sediments in the Baltic Sea and that their abundance is related to the sulfide flux in the seafloor. The study further suggests that the activity of cable bacteria may explain why bottom waters in the eutrophic Gulf of Finland rarely contain sulfide in summer.

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