Sulphur switch in algae new route to marine cloud geoengineering?

Marine bacteria produce two types of sulphur compounds as they eat dead algae biomass. The one, methanethiol, or MeSH, is cycled downwater into the food chain. The other forms a liquid aerosol, dimethylsulfide, or DMS. The latter plays an important role in ‘natural marine cloud seeding,’ which makes climate-focused minds wonder: could we increase the DMS/MeSH ratio – and thereby cool the planet?

We might one day, new research by University of Georgia scientists, published in last week’s edition of Nature shows.

The microbiologists have identified a pathway that different bacteria use to convert the dimethylsulfonioproprionate (DMSP) formed by the algae, via methylmercaptopropionate (MMPA) and two newly discovered coenzymes, into MeSH. Using this information the responsible genes in the bacteria have also been found – and genes, well, we could alter, blocking the pathway and leaving more of the raw DMSP for DMS production – and cloud formation.

Many more miles from geoengineering practice

Natural marine aerosol behaviour is tough science in itself that we slowly learn to understand, with small steps. Adding a geoengineering intention won’t help to simplify matters, as for instance we recently learned some previously desired marine aerosols may actually increase warming.

We also would not want any extra emitted DMS* to compete with aerosols already present in the marine clouds – and helping to create sunny blue skies over our oceans. Or actually, even on that level what we would really want isn’t exactly clear yet.

*) In the marine atmosphere part of the DMS converts to sulphuric acid. The sulphuric acid creates new aerosols and these aerosols are the actual condensation nuclei, influencing cloud formation.

© Rolf Schuttenhelm |

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