Understanding Ocean Acidification
Ocean acidification describes the ongoing decrease in the pH of the Earth's oceans, caused by the uptake of excess carbon dioxide (CO2) from the atmosphere. Since the Industrial Revolution, the ocean has absorbed a significant portion of anthropogenic CO2 emissions, acting as a critical carbon sink.
The Chemical Process Behind Acidification
When CO2 dissolves in seawater, it forms carbonic acid (H2CO3), which then dissociates into bicarbonate ions (HCO3-) and hydrogen ions (H+). The increase in H+ ions reduces the ocean's pH, making it more acidic. This process also reduces the concentration of carbonate ions (CO32-), which are essential for many marine organisms.
Impacts on Marine Organisms
The reduction in available carbonate ions makes it difficult for marine calcifiers, such as corals, shellfish, and plankton (e.g., pteropods), to build and maintain their shells and skeletons. This "shell-building" problem can weaken structures, hinder growth, and even lead to dissolution, particularly in colder, deeper waters.
Broader Ecological and Economic Consequences
Ocean acidification poses a severe threat to marine ecosystems, disrupting food webs and reducing biodiversity. Coral reefs, vital habitats for countless species, are especially vulnerable. The economic impacts are significant, affecting fisheries, aquaculture, and tourism industries that rely on healthy marine environments.