Effects of ocean acidification on marine ecosystems and its chemistry

The climate change is more than a matter of temperature: about 30 percent of the CO2 released by human activities over the past 200 years has already been absorbed by the ocean, and much more will ultimately end up there. And all that CO2 is having an unfortunate effect: the ocean is “acidifying,” or becoming less basic. The reaction of CO2 and ocean water produces chemicals such as carbonic acid, which lowers ocean pH, and bicarbonate. On the one hand, increased amounts of carbonic acid should make it more difficult for many organisms, like snails or corals, to build their calcium carbonate shells or skeletons. On the other hand, increased amounts of bicarbonate may stimulate growth in some marine organisms, so the overall effect of rising CO2 is uncertain and may affect different organisms in varied ways. The ocean’s pH has dropped from about 8.2 in preindustrial times to around 8.05. This seemingly small change may already be affecting ocean organisms—and future CO2 emissions could lower ocean pH even further. Once dissolved in seawater, CO2 reacts with water, H2O, to form carbonic acid, H2CO3:CO2 + H2O ↔ H2CO3. Carbonic acid dissolves rapidly to form H+ ions (an acid) and bicarbonate, HCO3-(a base). Seawater is naturally saturated with another base, carbonate ion (CO3−2) that acts like an antacid to neutralize the H+, forming more bicarbonate. The net reaction looks like this: CO2 + H2O + CO3−2→ 2HCO3-.

Sharma S., Sharma E. & Sharma Y., 2016. Effects of ocean acidification on marine ecosystems and its chemistry. International Multidisciplinary Research Journal III(II):78-91. Article.

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