Ocean Acidification

The Hercules robot explores a forest of corals and sponges off the coast of British Columbia, in 2018.

Around the world, coral reefs are in decline due to anthropogenic CO2 emissions. Cold-water corals, such as those found off British Columbia, attract less public attention. Yet they are as threatened by global warming as their tropical counterparts.

Off Vancouver Island, underwater mountain ranges rise in the depths of the ocean peaceful. These remains of volcanoes are home to ecosystems of phenomenal diversity, says Robert Rangeley, scientific director of the ocean protection organization, Oceana Canada.

There are huge forests, of different types of corals, such as red tree corals or bamboo. They can be several meters high. There are also glass sponges, false starfish, octopuses, tons and tons of fish, describes the researcher, who participated in an expedition to explore 13 of these seamounts in 2018.

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CO2 is also naturally captured by the oceans, where it dissolves in water to form carbonic acid. When CO2 concentrations are too high, however, it lowers the pH of the water and thus increases its acidity. The hotter the water, the more this cycle is accelerated, argues Gabriel Reygondeau.

Ocean acidification alters the calcification process of corals, which build their skeleton on limestone, explains Gabriel Reygondeau. Some of their vital growth and reproduction functions are also affected.

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Saxon, 12 March 2023. Full article.