Ocean acidification describes the ongoing decrease in the pH of the Earth’s oceans. This phenomenon occurs as the ocean absorbs excess carbon dioxide (CO2) from the atmosphere, primarily a result of human activities like burning fossil fuels and deforestation. When CO2 dissolves in seawater, it forms carbonic acid, which then releases hydrogen ions, increasing the water’s acidity and lowering its pH. This chemical change has significant implications for marine ecosystems and human society.
Impacts on Marine Life
The increase in ocean acidity directly affects marine organisms, particularly those that build shells or skeletons from calcium carbonate. These calcifying organisms, such as corals, shellfish, and certain plankton, find it harder to form and maintain their structures in more acidic waters due to the reduced availability of carbonate ions, the building blocks for these shells and skeletons. For example, coral reefs, composed of calcium carbonate skeletons, weaken and can eventually die, impacting the many species that rely on them for habitat.
Ocean acidification also exacerbates other environmental stressors, such as rising water temperatures, which can lead to coral bleaching. When corals are stressed by high temperatures, they expel the algae living in their tissues, making them more vulnerable to disease. The increased acidity then hinders the corals’ ability to recover from these bleaching events, as they need calcium carbonate to rebuild. This impact extends to commercially important species like oysters and mussels, whose growth and survival are compromised, along with tiny pteropods, or “sea butterflies,” a food source for many marine animals.
Broader Ecological Consequences
The decline of key marine species due to ocean acidification creates ripple effects throughout marine ecosystems. The loss of foundational species, such as corals that form complex reef habitats, can lead to habitat destruction and a reduction in biodiversity. Reefs provide shelter and feeding grounds for many fish and invertebrate species, and their degradation can cause a collapse in local marine communities. Similarly, the reduction in pteropod populations can disrupt the marine food web, as these small organisms are a food source for fish, whales, and seabirds.
Changes in ocean chemistry can also lead to competitive imbalances, where some species might adapt or even thrive in more acidic conditions while others decline. This shift can alter the community structure of marine ecosystems, leading to the dominance of acid-tolerant species and reducing biodiversity. Such ecosystem-level changes can result in less resilient marine environments, making them more susceptible to other disturbances like pollution or disease outbreaks. The interconnectedness of marine life means that the impact on one species can cascade through the food web, affecting populations at higher trophic levels.
Economic and Human Impacts
The effects of ocean acidification extend beyond marine ecosystems, directly impacting human society and economies. Commercial fisheries and aquaculture operations face challenges due to the decline of affected species like oysters, clams, and crabs. For instance, oyster farms can experience reduced harvests and increased mortality rates in their stock, leading to economic losses. This decline in seafood availability can threaten the livelihoods of fishing communities and contribute to reduced food security for populations reliant on marine protein sources.
Beyond fisheries, ocean acidification also poses a threat to tourism and coastal protection. Coral reefs, for example, are attractions for diving and snorkeling, supporting tourism industries in many coastal regions. Their degradation due to acidification can lead to a decrease in tourist revenue and associated job losses. Structures like coral reefs and shellfish beds provide natural buffers against storm surges and coastal erosion, protecting shorelines and infrastructure. Their weakening or loss can leave coastal communities more vulnerable to the impacts of severe weather events.
Addressing Ocean Acidification
Addressing ocean acidification requires a global reduction in carbon dioxide emissions. Since the absorption of excess atmospheric CO2 is the main driver, transitioning away from fossil fuels and adopting cleaner energy sources are important actions. This involves coordinated efforts across governments, industries, and individuals to decarbonize sectors, including transport, energy, and agriculture. Reducing these emissions will slow the rate at which the ocean absorbs CO2, allowing marine ecosystems more time to adapt.
In addition to global emission reductions, local mitigation efforts can help alleviate acidification in specific areas. Reducing nutrient runoff from agriculture and wastewater treatment can improve local water quality, as excess nutrients can exacerbate local acidity. Research into the adaptation and resilience of marine species exploring ways to enhance their ability to cope with changing ocean chemistry. These combined approaches highlight the need for comprehensive action to protect marine environments for the future.