Ocean Acidification

Ocean acidification refers to the process by which the oceans become more acidic due to increased levels of carbon dioxide (CO2) in the atmosphere. Normally, our oceans play a crucial role in absorbing CO2—about a quarter of what is emitted each year by human activities like burning fossil fuels, deforestation, and cement production. When CO2 dissolves in seawater, it reacts to form carbonic acid, which then breaks down into bicarbonate and hydrogen ions. This increase in hydrogen ions causes the ocean’s pH to drop, making the water more acidic. Over the past two centuries, the ocean’s average pH has dropped from about 8.2 to 8.1, a significant change in terms of chemistry because the pH scale is logarithmic; even small shifts mean much higher acidity.

This process may seem gradual, but it causes profound changes in marine ecosystems. Many organisms have evolved to live in fairly stable conditions, and acidification disrupts the delicate balance crucial for life. One of the most conspicuous problems is for shell-building animals—like corals, oysters, mussels, and certain plankton. They rely on carbonate ions in the water to build their shells and skeletons. As acidification increases, carbonate ions become scarcer, making it harder for these species to grow or maintain their shells. Young shellfish are especially vulnerable, with lower survival rates and stunted growth.

Coral reefs, vital hotbeds of biodiversity, face severer threats. Not only does acidification slow down their growth, but it also weakens the structure of the reefs themselves, increasing the risk of erosion. Healthy reefs support and shelter thousands of marine species, provide food for local communities, and buffer coastlines from storms. Losing reefs means losing these essential functions, with knock-on effects for fisheries, tourism, and coastal protection.

Beyond shell builders, ocean acidification threatens many kinds of marine life. Fish, for example, can suffer from changes in behavior, sensory abilities, and reproductive success. Some lose their ability to detect predators or find suitable habitats, threatening their chances of survival. At the microscopic level, acidification impacts phytoplankton and zooplankton, which form the backbone of marine food webs. Any disruption here has the potential to cascade up, affecting larger animals—including those humans depend on for food.

The economic impacts are substantial. Fisheries and aquaculture industries rely on healthy marine organisms. If populations of shellfish and fish decline, so do the livelihoods of those who depend on them, from commercial fishermen to seafood processors. Countries whose economies are heavily based on marine resources could see job losses and reduced food security. Meanwhile, the cost to repair or adapt to damaged coastal infrastructure, cope with declining water quality, or replace lost ecosystem services would rise.

If ocean acidification is not tackled soon, we risk irreversible damage to marine biodiversity, food webs, and coastal economies. Species extinction may become more common, leading to diminished resilience of entire ecosystems. This not only affects ocean life but also disrupts the global carbon cycle, potentially accelerating climate change. Communities dependent on the ocean for food and income would see their resources dwindle, while loss of tourism and reef protection could leave coastal areas exposed to damaging storms and erosion.

Addressing ocean acidification requires swift, coordinated action to reduce CO2 emissions, transition to renewable energy sources, and protect vulnerable marine habitats. By doing so, we could slow the pace of acidification, buy time for adaptation, and preserve the health of our oceans for future generations.