reefs Soul Soil
Coral reefs, once teeming with colour and marine life, are turning ghostly white — an alarming symptom of a changing ocean. Ocean acidification is one of the consequences of increasing concentrations of carbon dioxide (CO₂) gas in the atmosphere, which is then absorbed by oceans, altering their chemistry.
This change threatens coral reefs, marine biodiversity, and human livelihoods, as well as the broader economic systems that depend on the ocean. Ocean acidification, fuelled by rising CO₂ emissions, is causing widespread coral bleaching and disrupting marine ecosystems, economies, and global food security. While some corals may recover under ideal conditions, urgent global and local action is needed to protect our oceans and ourselves.
Ocean acidification is defined as the lowering of the seawater’s pH values, caused by excessive carbon dioxide gas (CO₂) from the atmosphere dissolving into the ocean. This chemical reaction forms carbonic acid, which then lowers the pH of seawater. But why are carbon dioxide levels increasing at such a rapid pace? The increase is primarily induced by human activities, namely the burning of fossil fuels and land use change.
Fossil fuels such as petroleum, coal, and natural gas are burned during transportation, manufacturing, industrial activities, and power generation. These activities release large amounts of CO₂ gas into the atmosphere. Meanwhile, land use change, including deforestation for agriculture or urban development, leads to the destruction of carbon sinks such as forests. Forests play an important role in absorbing CO₂ from the atmosphere, but when they are cleared or degraded, that function is lost. These human activities collectively break the natural balance of CO₂ in the atmosphere and lead to further acidification of the ocean.
Coral bleaching is a phenomenon caused by ocean acidification, in which corals expel the algae that live in their tissues. This results in the corals losing their vibrant colours and turning white. While they may appear to be dead, bleached corals are highly stressed and more vulnerable to disease and death. But why does this happen? Corals rely heavily on calcium carbonate to build their skeletons, but acidification reduces the concentration of carbonate ions (CO₃²⁻) in seawater, making calcification—the process where corals build their skeletons—much more difficult. This in turn leads to weaker, thinner skeletons in coral reefs.
According to the journal Nature Geoscience, a 0.1 drop in ocean pH can reduce coral growth and calcification by up to 40%. Acidic waters not only affect coral growth but also cause corals to expel their algae. Once this happens, the coral can no longer obtain food through photosynthesis or shield itself from predators and harsh environmental conditions. Without nutrients, they may be destroyed by storms or simply die off.
It is important to note that coral reefs cover less than 1% of the ocean floor, yet they support around 25% of all marine life. Their loss leads to cascading effects across entire ocean ecosystems, including fish, crustaceans, and other sea creatures that rely on the reef for shelter and food. The decline of coral reefs represents not just an ecological tragedy, but a loss of biodiversity that affects the entire ocean.
Coral reefs play a major role in our lives, even if we may not immediately realise it. Coral bleaching has economic consequences that affect fisheries, tourism, livelihoods, and food security. Coral reef-related tourism and fisheries are worth an estimated $36 billion annually, according to the World Wide Fund for Nature (WWF). People from all over the world travel to witness the splendour of underwater marine life in reef areas.
Bleaching events diminish the appeal of these destinations, resulting in reduced tourism and a direct drop in revenue for local economies. In addition to tourism, acidification affects shellfish such as mussels, oysters, and clams by weakening their calcium carbonate shells. This reduces their survival rates and affects the livelihoods of communities involved in shellfish farming and harvesting.
As coral habitats degrade, reef fish populations also decline. This has a major impact on small-scale fisheries and food supply chains. More than 500 million people around the world depend directly on coral reefs for food and income. Coastal and island communities are especially vulnerable, as seafood is often their primary source of protein.
These communities rely on the sale of seafood to local consumers, restaurants, fish markets, wholesalers, and international importers to generate income. When bleaching reduces fish populations, these communities face economic hardship, food scarcity, and even displacement. The consequences are not limited to marine ecosystems but extend far above water into human societies.
It’s often said that bleached corals are not always dead. With improved environmental conditions, they can regain their symbiotic algae and recover. Some reef systems exhibit resilience due to local factors like clean water, natural temperature variation, and conservation efforts to replenish the reef system. Local authorities, scientists, and volunteers are making notable efforts to restore coral reefs through coral nurseries, artificial reefs, and stricter environmental regulations.
These efforts have shown some success in particular areas. However, recovery is only possible under short-term and mild stress conditions. As ocean acidification and global warming increase in both frequency and intensity, the opportunity for coral recovery diminishes. While the number of volunteers and initiatives aimed at rebuilding reef systems is growing, the rate of ocean acidification and warming is still accelerating, making our efforts seem small in comparison.
According to the Global Coral Reef Monitoring Network (2011), 14% of the world’s coral reefs were lost between 2009 and 2018. While coral resilience offers a glimmer of hope, it is not sufficient to counteract the accelerating global impact of climate change and acidification.
There are a few possible solutions to coral reef bleaching and ocean acidification. First, we must reduce CO₂ emissions. This can be achieved by transitioning to renewable energy sources like solar, wind, and hydropower. Traditional industries and transportation systems powered by fossil fuels should gradually be replaced with cleaner, renewable options.
For example, using electric vehicles instead of petrol-powered ones can significantly reduce carbon emissions. Governments and environmental agencies should implement policies to encourage this shift, such as offering subsidies for the purchase of electric vehicles and installing public charging stations. Once these policies are in place, more people will be motivated to make eco-friendly choices and lend a hand in reducing carbon emissions.
In addition, protecting marine ecosystems plays a major role in reducing coral bleaching and ocean acidification. Authorities should expand Marine Protected Areas (MPAs) to reduce local stress and improve ecosystem health. Sustainable fishing laws must be enforced to prevent overfishing and protect the balance of marine life. It is also essential to reduce agricultural runoff and plastic pollution in coastal areas. This can be done through proper waste management systems and stricter laws regarding the disposal of plastic materials by both industries and individuals.
Ocean acidification and coral bleaching are urgent global problems that threaten not only marine biodiversity but also economies and food security around the world. Coral reefs may be resilient to a degree, but they cannot survive unchecked acidification and climate change.
We must act now—both globally and locally—to reduce emissions, protect ecosystems, and support scientific and community-led solutions. The future of the oceans is ultimately tied to the future of humanity. Our actions today will determine whether coral reefs continue to thrive beneath the waves—or disappear from our planet altogether.
By: Cheng E Xin
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