Ocean Acidification: Causes, Impacts, and Solutions

Ocean acidification refers to the ongoing reduction in ocean pH levels due to the absorption of carbon dioxide (CO2) from the atmosphere. As human activities, particularly fossil fuel combustion, release increasing amounts of CO2, the oceans absorb around 30% of it, resulting in higher acidity. Since the Industrial Revolution, ocean surface waters have seen a pH drop of 0.1 units, with further declines anticipated. This shift in ocean chemistry disrupts marine ecosystems, affecting both calcifying organisms like corals and oysters and non-calcifying species. Combating ocean acidification requires reducing CO2 emissions and preserving marine ecosystems.

What is Ocean Acidification?

Ocean acidification refers to the gradual decrease in ocean pH levels due to the absorption of CO2, primarily driven by fossil fuel emissions. Since pre-industrial times, atmospheric CO2 has increased from 280 ppm to nearly 400 ppm, with oceans absorbing around 25% of these emissions. This process alters seawater chemistry, which impacts marine life and biodiversity. While oceans have helped mitigate climate change by storing excess CO2, this capacity is now strained, posing significant environmental and socio-economic risks.

Causes of Ocean Acidification

The primary driver of ocean acidification is the increased CO2 emissions from human activities such as burning fossil fuels. Other contributing factors include:

• Natural Processes: Organic material on seabeds decomposes, releasing CO2, contributing to acidification. Chemical reactions on the seabed also elevate hydrogen ion concentrations, lowering pH.
  
• Chemical Reactions: CO2 dissolves in seawater, forming carbonic acid, which dissociates into hydrogen ions and bicarbonate ions. The increase in hydrogen ions reduces the availability of carbonate ions, essential for marine calcifying organisms.
  
• CO2 Absorption: Oceans absorb about 30% of atmospheric CO2, but this leads to higher CO2 levels in the water and increased acidity.
  
• Rising CO2 Levels: Human activities such as fossil fuel burning and deforestation have caused a dramatic rise in CO2 emissions.
  
• Waste Disposal and Eutrophication: Industrial and domestic waste dumping lowers ocean pH, while nutrient-rich runoff triggers plankton blooms, further contributing to acidification.
  

Factors Influencing Ocean Acidification

Various environmental factors influence the extent of ocean acidification:

• Sea Surface Temperature: Warmer waters accelerate CO2 absorption, worsening acidification.
  
• Salinity: Higher salinity reduces CO2 solubility, slightly mitigating acidification.
  
• Organic and Inorganic Carbon: Higher levels of particulate organic carbon help bind CO2, mitigating acidification, while higher particulate inorganic carbon exacerbates it.
  
• Dissolved Oxygen: A decrease in oxygen levels can destabilize carbonate compounds, worsening acidification.
  

Impacts of Ocean Acidification

Ocean acidification has already lowered ocean pH from 8.2 pre-industrially to 8.1 today, and it is projected to decline further by 0.3–0.4 units by 2100. This seemingly small change reflects a 30% increase in acidity, disrupting marine life and vital processes.

• Ocean as a Carbon Sink: Oceans absorb one-third of human-caused CO2 emissions, but this rate is now exceeding the natural buffering capacity of marine ecosystems.
  
• Sulphur Cycle and Clouds: Ocean acidification can reduce DMS (dimethylsulphide) production by phytoplankton, which may decrease cloud formation and global temperature regulation.
  
• Biodiversity: Shell-forming organisms like corals, oysters, and plankton struggle to survive in more acidic waters, while algae and seagrasses may benefit from increased CO2.
  
• Food Webs and Fisheries: Disruptions in marine food webs, especially at the planktonic level, can lead to food shortages, particularly affecting fisheries. The decline of mollusks, for instance, could cost over $100 billion annually by 2100.
  
• Tourism: Damage to ecosystems, such as coral reefs, can significantly reduce tourism revenue, as seen with the Great Barrier Reef.
  

Ocean Acidification in the Indian Ocean

The Indian Ocean is particularly vulnerable to ocean acidification due to its unique geographical and ecological conditions. The Arabian Sea, for example, experiences high CO2 absorption, exacerbating acidification, while pollutants from nearby regions further lower pH. In the Bay of Bengal, pollutant deposition during winter increases acidity, with studies indicating a decline in phytoplankton populations, which are vital to the marine food web.

Global and Local Initiatives to Combat Ocean Acidification

To address ocean acidification and achieve the UN’s Sustainable Development Goal (SDG) 14, which promotes the sustainable use of oceans, several initiatives have been launched:

• Rio+20 Summit (2012): Identified ocean acidification as a critical threat and included oceans in sustainable development discussions.
  
• Intergovernmental Oceanographic Commission (IOC) of UNESCO: Coordinates global efforts to mitigate ocean acidification through initiatives like the Global Ocean Acidification Observing Network (GOA-ON).
  
• International Atomic Energy Agency (IAEA): Established the Ocean Acidification International Coordination Centre (OA-ICC) to advance science and policy solutions.
  
• High Seas Treaty: Aims to protect vast marine areas, ensuring the sustainable use of ocean resources and safeguarding biodiversity.
  

The Way Forward

To mitigate the impacts of ocean acidification, a comprehensive approach is necessary:

• Reducing CO2 Emissions: Transitioning to renewable energy sources like solar and wind, and promoting carbon-neutral technologies.
  
• Carbon Capture and Storage (CCS): Investing in technologies to capture CO2 emissions from industrial processes before they enter the atmosphere.
  
• Raising Awareness: Educating the public on the significance of ocean acidification and its effects on ecosystems and livelihoods.
  
• Sustainable Development: Supporting scientific research to understand acidification trends and fostering international collaboration, particularly through initiatives like Blue Carbon, GOA-ON, and IOC.
  

Ocean acidification represents a serious challenge to marine ecosystems, global food security, and economies dependent on marine resources. Addressing it requires concerted global action and sustained efforts to reduce emissions, protect marine ecosystems, and promote sustainable practices.