What is Ocean Acidification?

Ocean acidification refers to the ongoing decrease in the pH of Earth’s oceans, caused primarily by the uptake of carbon dioxide (CO₂) from the atmosphere. Since the Industrial Revolution, human activities have released vast amounts of CO₂, much of which dissolves into the oceans, changing their chemistry.

Chemical Process

When CO₂ dissolves in seawater, it reacts to form carbonic acid, which then dissociates into bicarbonate and hydrogen ions:

CO₂ (atmosphere) → CO₂ (dissolved)
CO₂ + H₂O → H₂CO₃ (carbonic acid)
H₂CO₃ → HCO₃⁻ (bicarbonate) + H⁺ (hydrogen ion)

The increase in hydrogen ions lowers the pH, making the ocean more acidic.

Diagram: Ocean Acidification Process

Ocean Acidification Process

Impacts on Marine Life

  • Calcifying Organisms: Species like corals, mollusks, and some plankton build shells or skeletons from calcium carbonate (CaCO₃). Acidification reduces carbonate ions, making it harder for these organisms to form shells.
  • Food Web Disruption: Changes in plankton populations affect the entire food web, including fish and marine mammals.
  • Coral Reefs: Acidification, combined with warming, leads to coral bleaching and decreased reef resilience.

Surprising Facts

  1. Plastic Pollution in the Deepest Oceans: Microplastics have been detected in the Mariana Trench, the deepest known part of the ocean, showing that pollution reaches even the most remote environments.
  2. Ocean pH Has Dropped Significantly: Since pre-industrial times, surface ocean pH has decreased from about 8.2 to 8.1—a 30% increase in acidity.
  3. Acidification Can Affect Sound Transmission: Lower pH alters the chemistry of seawater, making it easier for sound to travel, potentially impacting marine animal communication.

Human and Economic Impacts

  • Fisheries: Shellfish industries are vulnerable, as acidification hampers shell growth and survival rates.
  • Tourism: Coral reef degradation affects tourism and coastal protection.
  • Food Security: Changes in fish populations threaten global food supplies.

Interdisciplinary Connections

  • Chemistry: Understanding acid-base reactions and carbon cycling.
  • Biology: Effects on marine organisms, ecosystems, and biodiversity.
  • Economics: Impact on fisheries, tourism, and livelihoods.
  • Technology: Development of sensors for monitoring ocean chemistry and modeling future changes.
  • Environmental Science: Links to climate change, pollution, and conservation strategies.

Technology and Ocean Acidification

  • Sensors and Monitoring: Advanced pH sensors and autonomous underwater vehicles (AUVs) track ocean chemistry changes in real-time.
  • Data Analysis: Machine learning and big data help predict acidification hotspots and biological impacts.
  • Mitigation Technologies: Research into carbon capture and storage (CCS) aims to reduce atmospheric CO₂ emissions.
  • Public Awareness Tools: Interactive maps and apps visualize acidification trends for education and policy-making.

Recent Research

A 2022 study published in Science Advances found that acidification is progressing rapidly in the Arctic Ocean, with some regions expected to become corrosive to shell-building organisms by 2030 (Qi et al., 2022). This highlights the urgent need for global action.

Glossary

  • pH: A measure of how acidic or basic water is; lower pH means more acidic.
  • Carbonate Ion (CO₃²⁻): Essential for shell-building in marine organisms.
  • Calcifying Organisms: Species that build shells or skeletons from calcium carbonate.
  • Coral Bleaching: Loss of color in corals due to stress, often from warming and acidification.
  • Autonomous Underwater Vehicle (AUV): Robot used to collect ocean data.
  • Carbon Capture and Storage (CCS): Technology to capture and store CO₂ emissions.

Connections to Other Environmental Issues

  • Plastic Pollution: Microplastics interact with chemical processes, affecting marine life and possibly exacerbating acidification.
  • Climate Change: Both phenomena are driven by fossil fuel emissions and have overlapping impacts on ocean health.
  • Biodiversity Loss: Acidification contributes to the decline of species and habitats.

Summary Table

Aspect Details
Cause Uptake of atmospheric CO₂
Main Chemical Change Lower pH, less carbonate ions
Key Impacts Harm to shell-builders, coral reefs, fisheries
Surprising Fact Microplastics in the deepest ocean trenches
Technology Role Sensors, data analysis, CCS
Recent Study Qi et al., 2022, Science Advances

Further Reading

End of Study Notes