Ocean acidification is the process of lowering the pH of seawater caused by increasing concentrations of carbon dioxide (CO₂) in the atmosphere. Since the beginning of the Industrial Revolution, atmospheric CO₂ levels have increased due to human activities such as the burning of fossil fuels, deforestation, and industrial processes. The oceans absorb approximately 25–30 % of anthropogenic CO₂ emissions, leading to chemical reactions that increase the acidity of seawater.

🧪 Chemical process of acidification:

1. CO₂ absorption in the ocean:

• CO₂ from the atmosphere dissolves in the surface layers of the ocean.

2. Carbonic acid formation:

• Dissolved CO₂ reacts with water (H₂O) to form carbonic acid (H₂CO₃).

3. Dissociation of carbonic acid:

• Carbonic acid further breaks down into bicarbonate ions (HCO₃-) and hydrogen ions (H+).

4. Lowering the pH of water:

• Increased amounts of hydrogen ions (H+) cause a decrease in pH, which means the water becomes more acidic.

5. Decrease in carbonate ions:

• Hydrogen ions react with carbonate ions (CO₃²-), reducing their availability.

🐚 Impacts on marine life:

1. Threat to organisms with calcareous shells:

• Corals, bivalves, mollusks, sea urchins and some planktonic species need carbonate ions to form their shells and skeletons (calcium carbonate – CaCO₃).
• The reduced availability of carbonate ions makes it difficult for these organisms to build and maintain their shells.
• Shell erosion: More acidic water may even dissolve existing shells, leading to increased mortality.

2. Disruption of food webs:

• Planktonic organisms, the foundation of marine food chains, are under threat. Their decline can have a cascading effect on entire ecosystems.
• Fish and marine mammals dependent on these organisms may suffer from food shortages.

3. Changes in fish behavior and physiology:

• Increased acidity can affect the nervous system of fish, leading to problems with orientation, avoiding predators, and finding food.
• Reproductive success may be reduced.

4. Impact on coral reefs:

• Coral bleaching: Acidification increases corals' sensitivity to temperature stress, leading to bleaching and death.
• Biodiversity loss: Coral reefs are home to more than 25 % of all marine species; their degradation has wide-ranging ecological consequences.

5. Changes in chemical signals:

• Some marine organisms use chemical signals to communicate and find mates or food. Changing pH can disrupt these processes.

💰 Wider implications:

Economic impacts:

• Fisheries and aquaculture: The decline in marine species populations is affecting the livelihoods of millions of people who depend on the sea for food and income.
• Tourism: The loss of attractive coral reefs can negatively impact the tourism industry.

🌱 Ecosystem services:

• Oceans play a key role in the global carbon cycle and climate regulation, and acidification could impair their ability to store carbon.
• Deterioration in water quality can affect its ability to support life and provide other ecosystem services.

🥗 Food safety:

• Threats to marine food sources can increase pressure on land-based food systems and worsen global food security.

🛠️ Possible solutions and adaptation measures:

1. Reducing CO₂ emissions:

• The main solution is to reduce greenhouse gas emissions globally through a transition to renewable energy sources, increased energy efficiency, and technologies to remove carbon from the atmosphere.

2. Protection and restoration of ecosystems:

• Creating marine protected areas to reduce other stressors such as overfishing and pollution.
• Restoring mangrove forests and seagrasses, which can help store carbon and improve water quality.

3. Research and monitoring:

• Investing in research to better understand the effects of acidification on different species and ecosystems.
• Monitoring changes in pH and other chemical parameters of the oceans at a global level.

4. Adaptation strategies in fisheries:

• Developing more resilient species for aquaculture.
• Diversification of economic activities in fishing-dependent communities.

5. Education and awareness:

• Increasing public awareness of the causes and consequences of ocean acidification.
• Promoting sustainable consumer practices and reducing individuals' carbon footprint.

Ocean acidification is a serious and growing threat to marine life and the overall health of the oceans. It has the potential to disrupt fundamental ecological processes, reduce biodiversity and affect millions of people who depend on the sea for their livelihoods and food. Addressing this problem requires a coordinated global effort to reduce greenhouse gas emissions, protect marine ecosystems and support local adaptation. The oceans are an integral part of our planetary system and their protection is essential for sustaining life on Earth in its diverse forms. Spring