Millennium Post

In hot waters!

A study shows that inordinate rise in CO2 levels and global temperatures would favour the growth of some species of nitrogen-fixing marine cyanobacteria but threaten the survival of other such species.

Blue-green cyanobacteria are the foundation of the food chain in oceans. They obtain energy through photosynthesis and fix unusable atmospheric nitrogen by converting it into organic and usable forms such as ammonia, a process crucial for the survival of most other marine creatures. Therefore, the implications of rising atmospheric CO2 levels on these bacteria could create a vortex of instability in our oceans.

The study, carried out by David A Hutchins, a professor of biological sciences at the University of South California in the US, shows how different strains of cyanobacteria would adapt to grow and fix nitrogen at CO2 concentrations estimated for the year 2100. For the study, published in Nature Geoscience on 30 June, the researchers grew single cell marine cyanobacteria, like Trichodesmium and Crocosphaera, at different CO2 concentrations in the lab. It was found that those strains of these cyanobacteria that live closer to shore, like T thierythraeum, were able to survive high CO2 concentrations while the strains from open ocean, like T thiebautii, could not. This suggests future oceans, with high CO2 concentrations, would be dominated by cyanobacteria species presently existing near shores while species inhabiting open ocean waters may perish. Earlier studies have shown that all types of these cyanobacteria would be able to thrive in warmer and more acidified oceans of the future.

What does this mean for marine ecosystems? ‘We don’t know for sure yet, but we do know anytime you change the very base of a food chain, you can expect major ramifications for all the other organisms above that,’ says Hutchins. He says we urgently need to determine what these impacts will be because these food chains ultimately produce important resources like fish.

On arrangement with Down to Earth magazine

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