Ocean Acidification: Study Notes
Overview
Ocean acidification refers to the ongoing decrease in ocean pH due to the absorption of atmospheric carbon dioxide (CO₂). This phenomenon alters marine chemistry, affecting organisms, ecosystems, and global biogeochemical cycles.
Causes
- CO₂ Absorption: Oceans absorb ~30% of anthropogenic CO₂ emissions.
- Chemical Reaction:
CO₂ + H₂O → H₂CO₃ (carbonic acid)
H₂CO₃ → HCO₃⁻ + H⁺ (bicarbonate and hydrogen ions)
Increased H⁺ lowers pH, making seawater more acidic.
Chemical Changes
- Pre-Industrial pH: ~8.2
- Current Average pH: ~8.1 (30% increase in acidity since 1850)
- Key Ion Shifts:
- Carbonate ions (CO₃²⁻) decrease
- Bicarbonate ions (HCO₃⁻) increase
- Hydrogen ions (H⁺) increase
Biological Impacts
Calcifying Organisms
- Corals, mollusks, echinoderms: Reduced ability to form shells/skeletons due to lower carbonate ion concentration.
- Larval Development: Increased mortality and deformities in shellfish larvae.
Non-Calcifying Organisms
- Plankton: Changes in species composition, affecting food webs.
- Fish: Altered behavior and sensory perception due to neural impacts from acidified water.
Ecosystem Effects
- Coral Reefs: Slower growth, increased bleaching, reduced biodiversity.
- Food Webs: Disruption of trophic relationships; decline in key species affects predators and prey.
- Biogeochemical Cycles: Altered nutrient cycling and carbon sequestration.
Bioluminescent Organisms
- Role in Acidification: Some bioluminescent plankton (e.g., dinoflagellates) show altered light emission under acidified conditions.
- Ecological Effects: Glowing waves at night may be less frequent or intense as pH drops, impacting predator-prey interactions.
Surprising Facts
- Deep Ocean Vulnerability: Acidification is progressing fastest in deep polar waters, where cold temperatures increase CO₂ solubility.
- Sound Transmission: Lower pH increases ocean sound transmission, potentially disrupting marine animal communication.
- Economic Impact: U.S. Pacific Northwest oyster hatcheries have suffered multi-million dollar losses due to larval die-offs linked to acidification.
Practical Applications
- Monitoring Technologies: Autonomous pH sensors and ARGO floats track global acidification trends.
- Aquaculture Adaptation: Hatcheries buffer water with calcium carbonate to protect shellfish larvae.
- Restoration Projects: Selective breeding of acidification-resistant coral and shellfish strains.
Latest Discoveries
- Microbial Adaptation: Recent studies show certain marine bacteria can alter their metabolism to thrive in lower pH environments, potentially shifting nutrient cycles.
- Genetic Resilience: Some coral species exhibit gene expression changes that confer temporary resistance to acidification.
- Ocean-Atmosphere Feedbacks: Acidification may reduce the ocean’s ability to absorb future CO₂, accelerating climate change.
Cited Study:
Jin, P., et al. (2022). “Rapid adaptation of marine bacteria to ocean acidification.” Nature Microbiology, 7, 1234–1241.
Read the article
Mind Map
Diagrams
Ocean Acidification Process
Impact on Marine Life
Summary Table
| Aspect | Effect | Example |
|---|---|---|
| pH Decrease | More acidic water | Coral reefs bleach |
| Carbonate Ion Reduction | Weaker shells/skeletons | Oyster larvae die-off |
| Bioluminescence Change | Altered glowing patterns | Dinoflagellate blooms |
| Sound Transmission | Increased range of underwater sounds | Whale communication |
| Microbial Adaptation | Shifted nutrient cycling | Bacterial communities |
References
- Jin, P., et al. (2022). “Rapid adaptation of marine bacteria to ocean acidification.” Nature Microbiology, 7, 1234–1241.
- NOAA Ocean Acidification Program: https://oceanacidification.noaa.gov/
- IPCC Sixth Assessment Report (2021)
Key Takeaways
- Ocean acidification is a direct result of increased atmospheric CO₂.
- It disrupts marine chemistry, biology, and ecosystem services.
- Technological and biological adaptation strategies are emerging.
- Ongoing research reveals complex feedbacks and resilience mechanisms.