Climate Change and the World's Ocean
Acidification and its effects on Marine Life

By Linda Hunter
Published: October 2007

Melting of arctic sea ice.

The oceans, which cover more than 70% of the earth’s surface, play a fundamental and complex role in regulating climate. The effect of climate change on the world’s ocean is irrefutable and signals a profound transformation of the fragile marine ecosystem that nurtures our world.

Scientists are beginning to understand just how vast these changes will be and how quickly they are occurring. Among them: rising ocean temperatures that lead to species migration or extinction, the melting of arctic sea ice that endangers polar bears and other species, rising sea levels that threaten our coast, significant changes in the manner in which the ocean’s currents transport water around the globe and the acidification of the ocean.

The marine sanctuary just off our shore can be seen as a microcosm of the ocean’s larger issues and so local scientists and those charged with protecting our resources are keeping a watchful eye on these changes including the effects of rising acidification.

Although the natural absorption of CO2 by the world's oceans helps mitigate the climatic effects of man-made emissions of CO2, it is believed that the resulting decrease in pH (rise in acidity) will have negative consequences, primarily for oceanic calcifying organisms such as the ones found in the rocky intertidal environments in the Gulf of the Farallones Marine Sanctuary and in the open ocean.

According to the Center for Biological Diversity, "Carbon-dioxide pollution threatens to decimate corals and other calcifying marine life. Rising levels of carbon dioxide in the ocean strip the seawater of important compounds needed for marine organisms to build shells and skeletons. Corals, crabs, starfish, sea urchins, and plankton will have difficulty building their protective shells."

Under normal conditions, calcite and aragonite are stable in surface waters since the carbonate ion is at supersaturating concentrations. However, as ocean pH falls, so does the concentration of this ion, and when carbonate becomes under-saturated, structures made of calcium carbonate are vulnerable to dissolution. Research has already found that corals, algae, foraminifera, shellfish and sea butterflies experience reduced calcification or enhanced dissolution when exposed to elevated CO2.

Aside from calcification, organisms may suffer other adverse effects, either directly as reproductive or physiological effects, or indirectly through negative impacts on food resources.

Fish and other marine animals are also at risk from living in a more acidic ocean environment. Scientists warn that stresses from ocean acidification are likely to make marine life more vulnerable to disease and less tolerant of warming waters caused by global warming.

The Farallones Marine Sanctuary Association’s monitoring programs, Beach Watch and the rocky intertidal program of LiMPETS, contribute to our knowledge base about how local marine life is affected by acidification and other ramifications of climate change.

Learn more about these programs by going to our website.