Seawater carbonate chemistry

What is Ocean Acidification?



Pteropod Limacina Helicina. Courtesy of Russ Hopcroft, UAF.



The Chemistry



The Biological Impacts



The pteropod, or “sea butterfly”, is a tiny sea creature about the size of a small pea. Pteropods are eaten by organisms ranging in size from tiny krill to whales and are a major food source for North Pacific juvenile salmon. The photos below show what happens to a pteropod’s shell when placed in sea water with pH and carbonate levels projected for the year 2100. The shell slowly dissolves after 45 days.  Photo credit: David Liittschwager/National Geographic Stock. Used with permission. All rights reserved. National Geographic Images.

Pteropod image showing acidification results


Freshly harvested oysters from Yaquina Bay, Oregon


Photo: Freshly harvested oysters from Yaquina Bay, Oregon (Credit: NOAA)


Many marine organisms that produce calcium carbonate shells or skeletons are negatively impacted by increasing CO2 levels and decreasing pH in seawater. For example, increasing ocean acidification has been shown to significantly reduce the ability of reef-building corals to produce their skeletons. In a recent paper, coral biologists reported that ocean acidification could compromise the successful fertilization, larval settlement and survivorship of Elkhorn coral, an endangered species. These research results suggest that ocean acidification could severely impact the ability of coral reefs to recover from disturbance. Other research indicates that, by the end of this century, coral reefs may erode faster than they can be rebuilt. This could compromise the long-term viability of these ecosystems and perhaps impact the estimated one million species that depend on coral reef habitat.  For more information on the impact of ocean acidification on coral, see NOAA's Coral Reef Watch website.

Ocean Acidification: An Emerging Global Problem

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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