Ocean acidification is a worldwide decrease in the pH of seawater because of the oceans absorbing large amounts of carbon dioxide (CO2). The burning of fossil fuels causes ocean acidification. When there is increasing amount of carbon dioxide in the atmosphere, the amount of carbon dioxide absorbed by the ocean increases. Carbonic acid ( H2CO3) is formed as carbon dioxide is dissolved into the sea water. There is dissociation of some of the carbonic acid molecules into a bicarbonate ion and a hydrogen ion, thus the ocean’s acidity is increased ( H+ ion concentration) ( H2CO3) ( Wikipedia Foundation, 2022). After remaining constant for millions of years, the pH of surface seawater has dropped from 8.2 to 8.1 (neutral pH is 7) in just a few hundred years. A drop of.1 pH unit may not seem like much, but it translates to a 30% increase in acidity on the logarithmic scale of pH. If carbon dioxide levels reach 800 ppm by 2100 as projected by the Intergovernmental Panel on Climate Change, seawater pH will drop another.3 to.4 units, raising hydrogen ion, H +, levels by 100 to 150 percent (Orr et al., 2005). The chemistry of the oceans could take "tens of thousands of years" to return to pre-industrial levels (Quiroz, 2022).
Figure 2: Burning of Fossil Fuels
How Does This affect Marine Life? Ocean acidification has the potential to harm marine life by causing calcium carbonate shells and skeletons to dissolve. To survive, animals that produce calcium carbonate structures must expend extra energy either repairing or thickening their shells. Utilizing energy for this could have an impact on the animals' ability to reproduce and grow. Coral reefs are also in danger of extinction because of rising CO2 levels in the atmosphere. Breakable, slow-growing coral reefs erode more quickly than they accrete. Reefs may perish, and entire species may perish as a result. Animals that can survive and reproduce in more acidic waters are likely to shrink in size, posing a threat to the food chain that depends on them. (Natural History Museum, 2022). Furthermore, life cycles of many marine fish and invertebrates are complicated. They spend their early lives as larvae, developing and dispersing across the ocean on currents. Because larvae are so small, they are particularly vulnerable to increased acidity. When acidity levels rise, sea urchin and oyster larvae, for example, will not develop properly. Fish larvae, for example, lose their ability to smell and thus cannot avoid predators. Because larvae are vulnerable, even if organisms can reproduce, their offspring may not reach adulthood (United States environmental agency, 2021).
Effect of Ocean acidification:
By Safia Juman