Ocean Acidification Effects

Ocean acidification, resulting from the increased acidity of the ocean, is one of the lesser known implications of climate change, but it has the capacity to completely alter the marine ecosystem. Scientists have previously neglected ocean acidification because it was thought that rivers contained a sufficient amount of dissolved chemical from rocks to stabilize the ocean’s pH. However, in recent years, scientists have become aware of the effects that the increased anthropogenic CO2 has on the ocean. Since the beginning of the industrial era, the ocean has taken in roughly 525 billion tons of carbon dioxide from the atmosphere.1 The ocean takes in approximately 24% to 33% of CO2 emissions produced by human activity. CO2 molecules dissolve easily

The increasing amount of CO2 produced by human activity over the years has increased the average ocean temperature by 0.74, it has increased the sea level by 17 cm, it has depleted seawater carbonate concentrations by ∼30 μmol kg and decreased ocean pH by 0.1 unit from 8.2 to 8.1, increasing the acidity of the ocean.3 Studies predict a drop from a pre-industrial pH of 8.2 to about 7.8 by the end of this century, increasing the surface ocean’s acidity by roughly 150%.4 Figure 1 demonstrates the expected pH decrease of the ocean’s surface pH based on the total anthropogenic CO2 emissions and release

Corals use calcium carbonate to forms complex coral reefs which house coral animals and serve as a habitat to many other organisms. Notably, since corals are vital to the marine ecosystem, decreased rates of coral calcification harm thousands of organisms relying on the structural complexity of the calcareous corals. Figure 2 demonstrates the chemical process through which the ocean absorbs the CO2 and the chemical reactions causing the ocean to become increasingly acidic, thus, slowing coral calcification.5 When the pre-industrial CO2 emissions double, coral calcification and growth decreases by at most 40% because aragonite cannot form and carbonate-ion concentrations decrease.4 In response to the decreased calcification, coral colonies will have decreased skeletal density or preserve density and use more energy to calcify.8 Both responses are harmful for coral reefs because decreased skeletal density will make corals more susceptible to erosion, diminishing the coral reefs’ structural complexity which will in turn decrease the habitat quality and diversity for the organisms taking residence in the reefs. If corals also