The ocean absorbs roughly a quarter of all anthropogenic carbon dioxide emissions. This vital service acts as a massive climate buffer, but it comes at a steep cost: ocean acidification. As CO2 dissolves in seawater, it forms carbonic acid, lowering the pH and depleting the concentration of carbonate ions.
For deep-water corals, which build their intricate, slow-growing skeletons in cold, dark environments, these carbonate ions are essential. Unlike their shallow-water cousins, they do not rely on symbiotic algae for energy, making them entirely dependent on capturing organic matter in an increasingly hostile chemical environment.
Recent deep-sea surveys indicate that the aragonite saturation horizon—the depth below which calcium carbonate structures begin to dissolve—is rising. If this trend continues, these ancient, diverse ecosystems, some of which are thousands of years old, face total collapse before they are even fully explored.