Algae continue to release methane even after death

(ORDO NEWS) — Seaweeds emit huge amounts of methane, which appears after the processing of their methylated compounds by marine archaea. This process can continue for decades after the death of the algae and poses a threat to the climate system.

Algae meadows cover shallow coastal regions of temperate and tropical seas around the world. They form the basis of an ecosystem inhabited by a variety of animal species.

In addition, algae protect coasts from erosion and absorb carbon dioxide from the atmosphere. However, they emit other greenhouse gases, including methane, which has a stronger effect on the climate than carbon dioxide.

Scientists from the Max Planck Institute for Marine Microbiology (Germany) and their colleagues for the first time tried to understand what is the exact process of methane formation in seaweed meadows. The results of the study are published in the journal Proceedings of the National Academy of Sciences.

Many land plants decompose and form peat deposits, from which methane is released. The researchers expected to see a similar process in seagrass meadows.

However, to their surprise, they found that methane is formed from methylated compounds that live algae produce. These substances are converted into methane by methanogenic archaea present on the seabed.

Since such microorganisms have unlimited access to methylated compounds and can use them directly, methane production in grasslands is highly efficient and resistant to environmental changes.

Another difference from terrestrial ecosystems is that the release of methane into the water column occurs quite quickly. Since algal meadows form in shallow water, the microorganisms in the water column do not have time to consume the methane before it enters the atmosphere.

When scientists examined samples of already dead algae, they were faced with another surprise. The rate of methane production by dead algae was as high as in a living sea meadow. Probably, methylated compounds persist in tissues for a long period of time. Scientists were able to detect them in algae that had died off more than two decades ago.

The global extinction of marine grasslands observed today is destroying coastal ecosystems. The authors of the work warn that the death of algae will increase the content of carbon dioxide in the atmosphere and at the same time will not affect the release of methane.

Scientists emphasize the importance of preserving sea grasslands, as coastal areas are highly susceptible to climate change. In the future, they plan to study methanogenic archaea in more detail, since this diverse group of microorganisms is still extremely poorly understood.

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