Can corals adapt to changing ocean temperatures and acidity?

Did you know oceans are the largest habitat in the world and support 50 percent of all species on Earth? Our oceans are home to a great diversity of plant, animal and microbial groups, many of which depend on specific water temperature and pH ranges for optimal health. How are sensitive organisms, such as coral reefs, responding to changing ocean temperatures and acidity? Can they adapt to these changes? (…)

In addition to rising water temperatures, increasing levels of atmospheric carbon dioxide are causing ocean water acidification. Sea water has the ability to absorb carbon dioxide from the atmosphere. Carbon dioxide molecules react with water, producing carbonic acid, which shifts the pH of the water. Over the last 250 years, oceans have absorbed 560 billion tons of carbon dioxide and the acidity of surface waters has increased by 30 percent. Changes in sea water temperatures and pH, especially over long periods of time, produce stress in ocean-dwelling organisms and can lead to death.

Coral reefs are the poster child for the effects of ocean warming and acidification. Since 1950, 19 percent of the world’s coral reefs have been lost and 35 percent are threatened or in critical condition. Warmer water temperatures can result in coral bleaching (corals turn completely white) when corals expel the algae living in their tissues that produce nutrients through photosynthesis. Ocean acidification also challenges corals’ ability to build their skeletons. More acidic waters diminish the concentration of aragonite, a form of calcium carbonate that is used by marine animals to build their shells and skeletons. It has been reported that other aquatic organisms such as sea butterflies have had shells dissolved by acidic waters.

Although a large portion of the world’s corals is threatened by rising temperatures and ocean acidification, scientists have discovered reefs adapted to live under harsh conditions. (…) Researchers have also found corals in Palau in the western Pacific Ocean that are bigger and more diverse in acidic waters, when compared to the average for the Pacific. Scientists are studying these corals to understand their ability to adapt and explore the possibilities for restoring declining reefs.

Earth Gauge, via WKYC, 8 July 2014. Article.

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