Ocean acidification plays havoc with diatoms

New study shows that these tiny algae are not the winners of the acidification game, after all.

A single diatom, magnified to 200x. Credit: Clouds Hill Imaging Ltd / Getty Images

Diatoms – single-celled algae which occupy much of the world’s water – were thought to be more resistant to acidification than some of their aquatic counterparts, with their silicon-containing shells more impervious to acid than the carbonates in shellfish and corals.

But according to research published in Nature, acidification threatens diatoms as well.

“With an overarching analysis of field experiments and observational data, we wanted to find out how ocean acidification affects diatoms on a global scale,” says first author Dr Jan Taucher, a marine biologist at the Helmholtz Centre for Ocean Research Kiel, Germany.

“Our current understanding of ecological effects of ocean change is largely based on small-scale experiments – that is, from a particular place at a particular time. These findings can be deceptive if the complexity of the Earth system is not taken into account.”

The researchers examined five experiments done in different ocean waters, from 2010 to 2014. They then designed five similar experiments, simulating ocean water from 2100.

More acidic water, the researchers found, causes the silicon shells of diatoms to thicken. This makes them sink and dissolve, meaning their silicon falls to the bottom of the ocean and becomes silica, where it can’t get into new diatoms. This causes an overall decline.

“Our study uses diatoms as an example to show how small-scale effects can lead to ocean-wide changes with unforeseen and far-reaching consequences for marine ecosystems and matter cycles,” says Taucher.

This research sits in contrast with previous studies, which assumed the main risk of ocean acidification was calcium-dependent, not silicon-dependent, organisms.

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Ellen Phiddian, COSMOS, 28 May 2022. Press release.


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