2024-08-31 06:00:04
The ocean depths, well below 4,000 meters, hide a worrying phenomenon linked to climate change. At these extreme depths, high pressure and low temperatures cause calcium carbonate, essential for the formation of marine animal shells, to dissolve. A little-known but expanding process, with potentially devastating consequences for the biodiversity marine.
This critical zone is called the carbonate compensation depth. While much has been written about surface water acidification, the situation at depth is All also worrying. Indeed, the increase in carbon dioxide dissolved in theocean lowers the pH of theeaumaking this area increasingly corrosive for the carbonate de calciumcausing a rapid expansion of this corrosive region. This expansion is manifested by a rise in the lysocline, the transition zone where calcium carbonate becomes unstable and begins to dissolve. A rise of a few meters in this zone can cause a considerable increase in the carbonate unsaturated zones, making the sediments unstable and subject to dissolution.
This increase in carbonate compensation depth not only transforms the chemical composition of the sediments but also the ecosystems that live there. Species that depend on calcium carbonate for their structure, such as soft corals and starfish, are being replaced by species such as sea anemones and sea cucumbers that can survive in more acidic waters.
These maps show changes in ocean areas exposed to corrosive deep waters in 17 different regions.
Crédit: Mark John Costello et Peter Townsend Harris, CC BY-SA
Moreover, this increasing acidification affects nations unevenly. Island states are particularly vulnerable, such as Bermuda, where a 300-metre rise in this critical depth corresponds to 68% of their exclusive economic zone. In contrast, countries such as the United States and Russia, with wider continental shelves, see a smaller proportion of their territory affected.
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