Microorganisms in coastal mud can cool the warming climate

Microorganisms in coastal mud can cool the warming climate. New research from the University of East Anglia (UEA) shows that bacteria and microorganisms found in muddy marshes and coastal sediment effectively cool the warming coastal climate.

A nutrient known as dimethylsulfoniopropionate (DMSP) is constantly produced by marine phytoplankton, seaweed, corals, and bacteria, and is then broken down by marine microorganisms found in coastal sediment. When these microorganisms break down DMSP, they also release a climate-cooling gas called dimethylsulfide (DMS).

“DMS is produced when microorganisms break down DMSP, and it is important because it affects atmospheric chemistry, cloud formation and potentially climate – by increasing cloud droplets that in turn reduce the amount of sunlight reaching the ocean’s surface, said lead researcher Professor Jonathan Todd, from UEA’s School of Biological Sciences. 

“Across the world’s oceans, seas and coasts, tens of millions of tonnes of DMS are released annually by microbes that live in these environments,” he continued. “These same clouds are vital in the movement of large amounts of sulfur from the oceans to land, making the production of DMSP and DMS a critical step in the global sulfur cycle.”

The research team studied sediment from the North Norfolk coast at the Stiffkey and Cley salt marches, and each environment produces huge quantities of DMSP and DMS. It was previously thought that these compounds were produced by the marsh grasses, called Spartina, but the study has proved differently.

“Working on these coastal sediments we found that DMSP levels and DMSP and DMS synthesis rates were far higher in the surface sediment than in surface seawater,” said Dr. Beth Williams, also from UEA’s School of Biological Sciences. 

“We also found that these high DMSP levels were not dependent on the presence of Spartina, with similar levels being detected at the Yarmouth Estuary, where the plant doesn’t grow,” she continued. “Amazingly we discovered that there were as much as 100 million DMSP-producing bacteria per gram of salt marsh sediment. This supports our theory that bacteria play a very significant role in DMSP production in the sediment.”

“Our findings could mean that scientists have been significantly underestimating both the production of this molecule and the effect it is having in the environment,” Dr. Williams concluded.

This study is published in Nature Microbiology.

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By Olivia Harvey, Earth.com Staff Writer

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