The world’s oceans are nearing critical acidity levels, threatening marine life and their role in climate stabilisation, according to a new report by the Potsdam Institute for Climate Impact Research (PIK).

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Key Findings of the report

• Six out of nine planetary boundaries, including climate change, species loss, habitat destruction, freshwater depletion, and pollution, have already been exceeded.
• Ocean acidification is set to become the seventh breached boundary due to increasing CO2 emissions.
• Breaching these limits disrupts ecosystems, food supplies, and the oceans’ ability to absorb CO2.
• All nine boundaries are interconnected, meaning addressing one issue can positively impact others, as highlighted by efforts to limit global warming.

About Ocean Acidification

• Reduction in the pH of the ocean over an extended period of time caused primarily by the uptake of carbon dioxide (CO2) from the atmosphere.
• CO2 Absorption :Ocean absorbs about 30 percent of the CO2 released in the atmosphere increasing levels of Oceanic CO2 and acidification.
  • Positive: Mitigate the effects of global warming by absorbing some of the carbon dioxide gas (CO2) released into the atmosphere. 
  • Negative: Uptake of anthropogenic CO2 causes acidification which can harm marine ecosystems.
• Ocean Acidification Process : When CO2 is absorbed by seawater, a series of chemical reactions occur resulting in the increased concentration of hydrogen ions.
  • Carbon dioxide dissolves into seawater and forms carbonic acid (H2CO3), a weak acid that breaks into hydrogen ions (H+) and bicarbonate ions (HCO3-).
  • This increase in H+ causes the seawater to become more acidic and causes carbonate ions to be relatively less abundant.

Impact of Climate Change on Acidification rate

• Impact of CO2 Concentration: Rising atmospheric CO2 increases ocean temperatures and acidification, which harm marine ecosystems.
• Impact on polar region: Polar regions absorb more CO2 due to cooler waters, causing faster acidification than in warmer areas.
• Rise in temperature accelerating Acidification:Melting sea ice accelerates ocean acidification in the Arctic Ocean.
  • As sea ice melts, more water is exposed to the atmosphere, which lowers the pH of the surface water.
  • In the Central Arctic Ocean, the pH can decrease by about 0.1 unit per decade, which is much faster than other oceans.
• Changing Ocean Circulation: Ocean circulation upwell nutrient-rich, acidic deep waters which  intensifies acidification in some regions.
• Impact in tropical sea: rising surface temperatures slow CO2 exchange between deep and surface waters, reducing absorption.
  • Warmer waters lead to stratification, limiting CO2 uptake and causing deoxygenation in deeper layer

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Acidification can have several negative effects

• Drop in the pH of the ocean water which can make it difficult for certain species of coastal life to create their exoskeletons, which is essential for their survival. 
• Ocean acidification contributes to a loss of biodiversity.
• It reduces the amount of carbonate, a key building block in seawater. 
  • Makes it more difficult for marine organisms, such as coral and some plankton, to form their shells and skeletons, and existing shells may begin to dissolve.