Increasing levels of CO₂ in the atmosphere are leading to ocean acidification. The oceans absorb significant amounts of CO₂ from the atmosphere. When CO₂ dissolves in seawater, chemical reactions occur that lower the pH of the ocean, making it more acidic.

Here are the main points that explain this relationship:

• Dissolving CO₂: Atmospheric CO₂ dissolves in the surface waters of the ocean.
• Carbonic acid formation: Dissolved CO₂ reacts with water to form carbonic acid (H₂CO₃).
  • • Dissociation: Carbonic acid dissociates into bicarbonate ions (HCO₃-) and hydrogen ions (H+).
• Increased acidity: Increasing the concentration of hydrogen ions lowers the pH of the ocean, increasing its acidity.

The overall reaction can be represented by the equation: 2KOH+CO₂ → H₂O+K₂CO₃

This process has several important consequences:

• Decrease in carbonate ion concentration: Increasing acidity reduces the concentration of carbonate ions (CO₃²-), which are important for marine organisms such as coral reefs and mollusks, which need them to build their shells and skeletons.
• Threat to marine ecosystems: Ocean acidification can have negative impacts on marine ecosystems, including slowing coral growth, disrupting food chains, and threatening biodiversity.
• CO₂ absorption: The ocean's ability to absorb CO₂ from the atmosphere decreases as acidity increases, which may lead to an even faster increase in atmospheric CO₂ and intensify climate change.

The pH of ocean surface waters has dropped from about 8.1 to 8.05 over the past 30 years. Although this change seems small, it actually represents an increase in hydrogen ion concentration of 20 to 35 parts per million, which has a significant impact on the marine environment. Spring