Concerned scientists are investigating sea urchin deaths in the Caribbean

SAN JUAN, Puerto Rico (AP) – Sea urchins are dying across the Caribbean at a rate that scientists say could compete with a mass death that last occurred in 1983, alerting many who warn that the trend could further destroy already fragile coral reefs in the region.

Dive shops first began reporting the deaths in February, confusing scientists and concerned officials, who are receiving an increasing number of reports of dying sea urchins from islands including Antigua, St. Louis and more. Lucia, Dominica, Jamaica, St. Vincent, Saba and the American Virgin. Islands as well as Cozumel in Mexico.

“It’s very worrying, especially because it’s happening so fast,” said Patricia Kramer, a marine biologist and program director for the Atlantic and Gulf Rapid Reef Assessment, a scientific collaboration to improve reef conditions in the region.

In the beginning, mortality was only associated with black sea urchins – Diadema antillarum – which can be recognized by their extremely long, thin spine. But two other species have since been affected, including the rock-dwelling sea urchin and the West Indies sea egg.

The deaths worry Kramer and other scientists, including Dana Wusinich-Mendez, Atlantic-Caribbean team leader for the U.S. National Oceanic and Atmospheric Administration’s coral reef conservation program: “Losing our sea urchins would be truly devastating.”

The deaths are a cause for concern because sea urchins are herbivores known to be effective grazers that remove macroalgae from coral reefs and free up space for baby sea corals to attach, the two scientists said.

“They’re a bit of the fox’s unsung heroes because they do so many good things,” Kramer said.

While macroalgae are an important source of food and shelter for some fish, too many of them can degrade coral reefs that are under stress at warmer-than-average sea temperatures and a disease known as loss of rocky coral tissue.

Overfishing across the Caribbean had already led to a greater abundance of macroalgae, which were kept in check by sea urchins that are now dying, said Shamal Connell, an officer at St. Louis. Vincent and the Grenadines Fisheries Service, which oversees research.

“It is very urgent that we find a solution,” he said.

The Atlantic and Gulf Rapid Reef Assessment recently helped create a network to investigate deaths, analyze tissue samples and find solutions. It includes the Florida-based Gulf and Caribbean Fisheries Institute and nearly two dozen groups in the Caribbean and the United States

Kramer noted that very few black sea urchin populations recovered after the 1983 event, which began in the Atlantic Ocean near the Panama Canal and spread north and then east over the next 13 months.

During that time, only black sea urchins were affected and 90% or more of the population died, albeit at a much slower rate than the current event, she said.

“Just when we get to the point where they’re recovering, they die,” Kramer said.

The US Virgin Islands Thomas was the first to report the latest round of deaths in February, though it is unclear if that was where the event started.

In mid-March, the Dutch Caribbean island of Saba reported similar deaths, noting that 50% of the sea urchin population in its port had died a week later. Saba officials said they have about 200 sea urchins in a nursery and are gathering information about the new mortality event, adding that they are treating some with antibiotics that can cure them or prevent them from getting sick.

Meanwhile, said Monique Calderon, a fisheries biologist with the government in St. Louis. Lucia, that scientists on the eastern Caribbean island are considering launching their own study to get more details on where sea urchins die and why.

“When the last death occurred in the 1980s, sampling was not robust enough to determine what exactly the problem was, what could have caused it,” Calderon said, adding that she hopes to find an explanation with improved technology.

She said dive shops on St. Lucia and other Caribbean islands have reported seabeds filled with sea urchin ridges or sea urchins floating in the water when normally anchored to a reef via hydraulic structures known as tube feet. Divers have also found dying sea urchins with drooping spines or with their white skeletons sticking through their bodies.

The loss of sea urchins comes amid coral bleaching events due to high sea temperatures and the presence of a disease known as the loss of rocky coral tissue that has affected more than 30 coral species in nearly two dozen countries and territories in the Caribbean, according to the Atlantic and Gulf Rapid Reef Assessment program.

Coral reefs also provide protection against rising seas and storm surges generated by hurricanes that have become more powerful with global warming, and they are a key attraction for a region that is heavily dependent on tourism.

“We are concerned that a real crisis is developing in the Caribbean,” the Diadema Response Network said in a recent report on the loss of sea urchins.

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