Why can ocean acidification threaten corals, mollusks, and marine food chains?

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Diagram illustrating Earth's environmental spheres, with labeled sections showing the geosphere (land and crust), biosphere (living things), atmosphere (air), and hydrosphere (water), each extending vertically from the Earth's surface. — Biosphere Earth's environment includes the atmosphere, the hydrosphere, the lithosphere, and the biosphere.

Ocean acidification, caused by the ocean's absorption of excess atmospheric carbon dioxide, threatens marine life by reducing the concentration of carbonate ions in seawater.1

Impact on Calcifying Organisms

Coral, shellfish, and other marine calcifiers rely on carbonate ions and aragonite to build and maintain their shells and skeletons. As acidity rises, these essential raw materials become less available, leading to:1
* Reduced Growth: Organisms grow smaller, making them more vulnerable to predators.1
* Dissolution: The shells of some species, such as pteropods, can physically dissolve in high-acid environments.1
* Physiological Stress: Increased acidity can cause acidosis in larger animals like squid and fishes, impairing their respiration, growth, and reproduction.1

Consequences for Food Chains

These physiological changes threaten the stability of marine food chains. If key species like pteropods decline, predators must switch to new food sources, potentially causing population collapses and shifting predation pressure. Furthermore, the loss of coral reefs—which serve as critical habitats—could lead to a widespread decline in biodiversity, as many organisms depend on these structures for food and shelter.1