Concerned researchers are investigating the death of sea urchins in the Caribbean

SAN JUAN, Puerto Rico (AP) – Sea urchins are dying across the Caribbean at a rate that researchers say could compete with a mass death that most recently occurred in 1983, prompting many to warn that the trend could further decimate already weak coral reefs in the region.

Dive shops began reporting deaths in February, which puzzled researchers and worried government officials who are receiving a growing number of reports of dying sea urchins from islands including Antigua, St. Lucia, Dominica, Jamaica, St. Vincent, Saba and US Virgin Islands as well as Cozumel in Mexico.

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

At first, the mortality was only linked to black sea urchins – diadema antillarum – which are recognizable on their extremely long, lean backs. But two other species have since been affected, including the rock-drilling sea urchin and the Caribbean sea egg.

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

The deaths are worrying because sea urchins are herbivores known to be effective baits that remove macroalgae from coral reefs and free up space for small sea corals to attach, the two researchers said.

“They’re kind of the unsung heroes on the reef because they do so many good things,” Kramer said.

While macroalgae are an important source of food and protection for some fish, for many of them, coral reefs that are under stress can be degraded by warmer-than-average temperatures and a disease known as rocky coral tissue loss.

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, says Shamal Connell, an officer at St. Vincent and the Grenadines Fisheries Service, which oversees research.

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

The Florida-based Gulf and Caribbean Fisheries Institute and the Atlantic and Gulf Rapid Reef Assessment recently created a network to investigate deaths, analyze tissue samples and find solutions.

Kramer noted that very few populations of black sea urchins recovered from the 1983 incident that began in the Atlantic near the Panama Canal and spread north and then east over the next 13 months.

During that time, only the black sea urchin was affected, with 90% or more of the population dying, but at a much slower rate than the current event, she said.

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

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

In mid-March, the Dutch Caribbean island of Saba reported similar deaths, noting that 50% of the sea urchin population in its port was dead 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 researchers in the eastern Caribbean island are considering launching their own study to get more information about where sea urchins die and why.

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

She said that dive shops in St. Lucia and other Caribbean islands have reported that the seabed is full of sea urchins or sea urchins floating in the water when they are normally anchored to a reef via hydraulic structures called tubular feet. Divers have also found dying sea urchins with drooping backs or with their white skeletons protruding 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 Caribbean countries and territories, according to the Atlantic and Gulf Rapid Reef Assessment programs.

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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