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Ocean Acidification

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Ocean Acidification

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Ocean Acidification

  1. 1. By: Gayatri R. Kachh
  2. 2. • The ocean absorbs a significant portion of carbon dioxide (CO2) emissions from human activities, equivalent to about onethird of the total emissions for the past 200 years from fossil fuel combustion, cement production and landusce change. • Uptake of CO2 by the ocean benefits society by moderating the rate of climate change but also causes unprecedented changes to ocean chemistry, decreasing the pH of the water and leading to a suite of chemical changes collectively known as ocean acidification. • The ocean is constantly exchanging with the atmosphere. It stores and distributes large amounts of heat around the globe via ocean currents. In this way, the ocean plays a key role for the global climate. However this regulatory mechanism is presently disturbed by global warming, consequence of the greenhouse effect.
  3. 3. • The carbon cycle involves both organic compounds such as cellulose and inorganic carbon compounds such as carbon dioxide and the carbonates. The inorganic compounds are particularly relevant when discussing ocean acidification for it includes many forms of dissolved CO2 present in the Earth's oceans.[When CO2 dissolves, it reacts with water to form a balance of ionic and non-ionic chemical species: dissolved free carbon dioxide (CO2), carbonic acid (H2CO3),bicarbonate (HCO −3 ) and carbonate (CO −2 3). The ratio of these species depends on factors such as seawater temperature and alkalinity. These different forms of dissolved inorganic carbon are transferred from an ocean's surface to its interior by the ocean's solubility pump. • The resistance of an area of ocean to absorbing atmospheric CO2 is known as the Revelle factor.
  4. 4. • Ocean acidification is rapidly changing the carbonate system of the world oceans. Past mass extinction events have been linked to ocean acidification, and the current rate of change in seawater chemistry is unprecedented. • Evidence suggests that these changes will have significant consequences for marine taxa, particularly those that build skeletons, shells, and tests of biogenic calcium carbonate. • Potential changes in species distributions and abundances could propagate through multiple trophic levels of marine food webs, though research into the long-term ecosystem impacts of ocean acidification is in its infancy. • Many marine organisms form biogenic calcium carbonate including: crustose coralline algae (the primary cementer that makes coral reef formation possible), Halimeda (macroalgae), foraminifera, coccolithophores, tropical reef-building corals, cold-water corals, bryozoans, mollusks, and echinoderms. The majority of marine calcifiers tested to date are sensitive to changes in carbonate saturation state and have shown declines in calcification rates in laboratory and mesocosm studies. Impact On Marine Ecosystem
  5. 5. • Since the beginning of the Industrial Revolution, the pH of surface ocean waters has fallen by 0.1 pH units. Since the pH scale, like the Richter scale, is logarithmic, this change represents approximately a 30 percent increase in acidity. Future predictions indicate that the oceans will continue to absorb carbon dioxide and become even more acidic. • Estimates of future carbon dioxide levels, based on business as usual emission scenarios, indicate that by the end of this century the surface waters of the ocean could be nearly 150 percent more acidic, resulting in a pH that the oceans haven’t experienced for more than 20 million years.
  6. 6. Ocean acidification is an emerging global problem. Over the last decade, there has been much focus in the ocean science community on studying the potential impacts of ocean acidification. Since sustained efforts to monitor ocean acidification worldwide are only beginning, it is currently impossible to predict exactly how ocean acidification impacts will cascade throughout the marine food chain and affect the overall structure of marine ecosystems. With the pace of ocean acidification accelerating, scientists, resource managers, and policymakers recognize the urgent need to strengthen the science as a basis for sound decision making and action.

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