Overview
This lecture covers the causes, chemistry, biological impacts, and future projections of ocean acidification due to increased atmospheric carbon dioxide.
Causes and Chemistry of Ocean Acidification
- Ocean acidification is caused by increased carbon dioxide (CO₂) in the atmosphere dissolving into oceans.
- When CO₂ dissolves in seawater, it forms carbonic acid, increasing ocean acidity (lowering pH).
- Ocean chemistry is directly linked to atmospheric chemistry; more atmospheric CO₂ means higher ocean CO₂.
- Acidic ocean water disrupts the formation and maintenance of calcium carbonate (CaCO₃) shells and skeletons.
Impacts on Marine Organisms
- Organisms with calcium carbonate shells or skeletons (e.g., oysters, clams, corals, lobsters, crabs, pteropods) are especially affected.
- Increased acidity dissolves existing shells and makes it harder for organisms to build new ones.
- Coral reefs, formed by corals' calcium carbonate skeletons, may disappear if acidification continues.
- Pteropods, key food sources for juvenile fish, are highly susceptible to acidic waters, threatening marine food webs.
- Disruption in base-level organisms can impact food security, jobs, and tourism.
Demonstrations and Evidence
- Laboratory dye and dry ice show increased CO₂ lowers water pH (more acidic).
- Chalk (CaCO₃) dissolves faster in more acidic solutions, illustrating the effect on marine life.
- Video and animations show pteropod shells dissolving and projections of widespread impacts by 2100.
Future Projections and Research
- Ocean acidity has increased 30% since the Industrial Revolution—100x faster than in at least 20 million years.
- By mid-century, coral calcification rates may decline by one-third; erosion will outpace new coral growth.
- By 2100, large ocean areas will be too acidic for corals, pteropods, and similar organisms to survive.
- Ocean's ability to absorb CO₂ is decreasing due to acidification.
- Reducing atmospheric CO₂ is necessary to mitigate ocean acidification.
Key Terms & Definitions
- Ocean Acidification — Increase in ocean acidity due to absorption of atmospheric CO₂.
- Calcium Carbonate (CaCO₃) — Compound forming shells and skeletons of many marine organisms.
- pH — Scale measuring acidity; lower pH means more acidic.
- Pteropods — Small, shelled planktonic creatures essential to marine food webs.
- Coral Calcification — Process by which corals build their skeletons using calcium carbonate.
Action Items / Next Steps
- Monitor ongoing research developments on ocean acidification.
- Review any assigned readings or materials on marine chemistry and ecosystem impacts.
- Consider implications for policy and conservation efforts.