Rough seas: one-third of coral reef species face extinction

“I’d like to be
under the sea,
in an octopus’s garden
in the shade.”

Or so the Beatles put it back in the good ole’ days, before things got really rough in Neptune’s realm.

Amid a host of problems for the world’s oceans, last week brought a reminder that coral reefs, the sentinel species for measuring the health of the seas, are taking a beating. One-third of all coral reef species face extinction worldwide, reports the latest study, released by Science magazine, with more species looking threatened.

“Whether corals actually go extinct this century will depend on the continued severity of climate change, the extent of other environmental disturbances, and the ability of corals to adapt,” say the study authors, led by Kent Carpenter of Old Dominion University in Norfolk, Va. Coral extinctions “will threaten the geologic structure of reefs and their coastal protection function, and have huge economic effects on food security for hundreds of millions of people dependent on reef fish,” concludes the study.

The news comes with the closing of the 11th International Coral Reef Symposium in Fort Lauderdale, a worldwide gathering of coral experts that takes place every four years. Not much of the news from the meeting was good:

  • Coral diseases, including cancer-like growths in Hawaiian and Samoan reefs, are on the increase in the Caribbean, Pacific and Indian Oceans, according to Hawaii Institute of Marine Biology research.
  • African dust linked to Caribbean coral disease contains six pesticides dangerous to humans as well as the reefs, reported U.S. Geological Survey scientists.
  • Tropical islands such as Fiji, the Marianas and American Samoa have reported less than half of the fish caught from reefs since 1950, according to a University of British Columbia project.

Nearly the only bright spot was a report of a newly-discovered reef off Brazil still teeming with marine life.

The U.S. National Oceanic and Atmospheric Administration kicked off the week by reporting that one-half of all shallow-water U.S. reefs were in fair or poor condition, with more headed away from healthy status in coming years. “Certainly the situation is just as bad or worse in most of the rest of the world,” said NOAA’s Mark Monaco in an interview.

In the Science study, researchers assessed the 845 coral-reef building species extant, and found enough data to estimate the extinction chances of 704 species. They found threats from global warming driving up sea temperatures and increasing the acidity of ocean waters. Higher temperatures can kill the algae that feed many coral, leading to “bleaching” of reefs, which in turn kills off most species of coral. Development also threatened reefs, bringing increased sewage, over fishing and dumps of fertilizer that poisoned coral. “Our results indicate that the extinction risk of corals has increased dramatically over the past decade,” says the study.

Unable to move to cooler waters, slow-growing at only inches per century and at the mercy of humankind, corals face a lot of challenges, even without the latest threat, ocean acidification. Ocean acidification occurs because higher levels of atmospheric carbon dioxide, a greenhouse gas, results in more carbonic acid in sea water. More acid waters make it harder for coral to build their calcium carbonate shells.

At the coral reef symposium, scientists debated whether a “tipping point” where corals are unable to build any shells would take place at atmospheric carbon dioxide concentrations expected by 2040 under “business as usual” prediction of greenhouse gases. Malcolm McCulloch of the ARC Centre of Excellence for Coral Reef Studies and Australian National University reported that some corals seem to “amplify” the effects of acidification.

In February, the United Nations Environment Programme (UNEP) found that between global warming, pollution and overfishing, “at least three quarters of the globe’s key fishing grounds may become seriously impacted,” in coming decades. The same report, entitled “In Dead Water,” suggested that at least 80% of coral reefs worldwide would suffer bleaching by 2080.

A big part of the problem, experts like Monaco suggest, is simply that people don’t know anything about corals besides the simple observation that they are beautiful. “Many people don’t even know coral reefs are living creatures,” Monaco says. “Some people walk on them or drop anchors without even realizing the damage they are doing.”

Coral reefs result from the work of little polyps, creatures only a few millimeters long, budded on top of one another. Over centuries, the shells of these creatures combine to form the exotic shapes of coral reefs. Tiny differences in the anatomy of each polyp species affect the shape of their shells and produce the exotic shapes of each reef.

Besides their beauty, reefs shelter the shores from storms, an effect observed in the 2005 Indian Ocean tsunami, and shelter a wide diversity of young fish, serving as the playgrounds of the seas. “They are tremendously valuable, for tourism, fisheries and other economic benefits,” says NOAA’s Jenny Waddell.

Dan Vergano, USA Today. Article.

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