Microbes on ocean seafloor play a role in climate change

The Guardian reports, 6th May 2016 : Microbes are hardly the poster-children of climate change, but they have far more impact than polar bears on Earth’s carbon cycle — and therefore on our climate.

A new study published in Science Advances finds that seabed bacteria and archaea (which look like bacteria but have very different genetics and biochemistry) are sensitive to climate. Because their habitat covers 65% of the entire globe, they form a huge part of the biosphere and are important in the regulation of carbon in the deep ocean, which affects long-term climate change.

The microbes in question are packed together in the top 15 centimetres of the deep ocean seabed, like rush hour commuters in a city metro, up to a million times more abundant than in the sunless ocean water, or buried in deeper layers of seabed sediments. Their city-like crowding is fuelled by a sparse sordid snow of excrement and microscopic dead bodies from life in the upper ocean, far above them.

The scientists, led by Professor Roberto Danovaro of Polytechnic University of Marche in Ancona, Italy, collected 228 samples from various locations in the North Atlantic and Mediterranean, from a range of ocean depths (400 to 5570 meters deep) and a wide variety of ocean bottom temperatures.

They discovered that the seabed microbes thrive where water temperatures are cold, but their populations decline significantly as deep ocean waters warm. In other words, their population is limited because their food is limited. Moreover, as the microbes warm so does their metabolic rate, requiring more food to survive, so the meagre food supports fewer individual microbes.

A giant scale worm is seen on the Antarctic seabed at 645 meters (2116 feet) below the surface in Antarctic waters in January 2008.Photograph: Martin Riddle/AP

A giant scale worm is seen on the Antarctic seabed at 645 meters (2116 feet) below the surface in Antarctic waters in January 2008.
Photograph: Martin Riddle/AP

The study also discovered that archaea make up a far larger proportion (11% to 31%) of the living matter in the ocean seabed than previously thought (less than 6%), and most of that population is made up of a temperature-sensitive group known as “Marine Group I Thaumarchaeota.”

Source: The Guardian, 6th May 2016. For the full details, see http://www.theguardian.com/environment/climate-consensus-97-per-cent/2016/may/06/deep-sea-microbes-may-be-key-to-oceans-climate-change-feedback

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