Sudden bursts of carbon dioxide released into the ocean from pollution and fish farms might be enough to cause marine creatures like starfish to literally dissolve.

That is the conclusion reached in a new paper that looks at the impact of the gas on coastal coralline algae ecosystems. These creatures, not unlike a coral, are formed of red algae encased in a calcified ‘house.’

Most research looking into the impact of rising CO₂ levels on ocean life has focused on how it will affect individual plants and animals, rather than looking at ecosystems as a whole. For obvious reasons this has its limitations, as the interactions between organisms are many and varied, and often incredibly difficult to predict.

This led the team of researchers from Heriot-Watt University in Edinburgh and Glasgow University to devise a set of experiments where they can test the impact that increasing carbon dioxide levels have on entire marine ecosystems.

Over a period of four days, they pumped water enriched with CO₂ into chambers that were placed over coralline algal ecosystems in Loch Sween, off the west coast of Scotland. Measuring the health of the calcified organisms living in the loch before, during, and after the experiment, the researchers were able to ascertain exactly what impact the enriched water was having on them at an ecosystem level.

And it turns out that the plants and animals were being dissolved. Calcified organisms such as the coralline algae and starfish living on the shoreline were literally dissolving due to the increase in carbon dioxide levels. While just four days of exposure was enough to begin the breakdown of the creatures, the recovery time once levels went back to normal was much slower.

The researchers suspect that farming practices and pollution in the region are causing the levels of carbon dioxide in the sea water to suddenly spike and then drop again. “If you think of pulses of carbon dioxide being carried on the tide to a particular site, it’s like a flash flood of CO₂,” explained Dr Heidi Burdett, who co-authored the paper published in the journal Marine Progress Ecology Series.

“Our continued monitoring of the site directly after the CO₂ exposure found recovery was comparably slow, which raises concern about the ability of these systems to ‘bounce back’ after repeated acute CO₂ events,” Dr Burdett continued.

The team suspects that this impact is happening around the world in coastal regions, and is only expected to get worse as atmospheric carbon dioxide levels increase, and if fish farms and other land-based practices become more intensified.