For the first time in decades, scientists have observed a massive die-off of sea urchins in the Caribbean, which could serve as another devastating blow to coral reefs. Widespread deaths of at least three species of sea urchins—the West Indian sea egg, rock boring, and black sea urchins—have been observed in Caribbean islands including the US Virgin Islands, Antigua, Dominica, St. Lucia, and Jamaica; the first report of deaths of long-spined black sea urchins occurred in St. Thomas in February, per NBC News and the AP.
"It's very concerning, particularly because it's happening so quickly," says Patricia Kramer, a program director with the Atlantic and Gulf Rapid Reef Assessment, which monitors coral reefs in the western Atlantic Ocean and Gulf of Mexico. In affected areas, "we're looking at around 90 to 95% mortality rates," Joshua Patterson, an associate professor of fisheries and aquatic sciences at the University of Florida, tells NBC. Such extensive sea urchin deaths haven't been observed in the region since 1983. That event, affecting only black sea urchins, "is recognized as one of the main contributors to the decline of coral reefs throughout the region that we've observed since that time," says Patterson.
Sea urchins are "kind of the unsung heroes of the reefs," as they feed on harmful algae found there, says Kramer. She adds few populations recovered from the 1983 event of unknown cause, which developed over 13 months. This event appears to be spreading much more rapidly. Again, the causes aren't known, though Patterson speculates that "a parasite, a virus or bacteria in the marine environment may be to blame." Stress triggered by warming ocean temperatures is another theory. Nearly two dozen groups in the US and Caribbean are now tracking the deaths, collecting samples, and exploring potential treatment options. (Read more sea urchins stories.)