"Researchers are restoring the Caribbean’s surprising, spiky custodians, which gobble up the algae smothering coral reefs."
"South of Tampa Bay, Florida, wedged between a quiet neighborhood and a mangrove forest, custom-designed aquariums are home to thousands of sea urchin larvae that tumble and drift through the water. Scientists with The Florida Aquarium and the University of Florida care for the little urchins, checking them daily under microscopes for signs that they’re maturing into juveniles, which look like miniature versions of the adults. Few will make it. For every one million embryos conceived in the lab, only about 100,000 become larvae. Of those, only up to 2,000 become adults.
And at this particular moment, coral reefs in the Caribbean need all the urchins they can get.
Long-spined sea urchins (Diadema antillarum) play a vital role in Caribbean coral ecosystems. While overpopulated urchins elsewhere are treated as villains—in California, for instance, divers smash purple urchins with hammers to keep them from mowing down kelp forests—Diadema are the Caribbean’s unsung heroes. Dark and rotund with spines radiating in all directions, some as long as knitting needles, the urchins eat massive amounts of algae that would otherwise smother corals or prevent coral larvae from affixing to rocks and growing into colonies.
“They’re very simple animals, but they’re very effective at what they do,” says Alex Petrosino, a biologist at The Florida Aquarium and a member of the urchin lab team. Where their radiating spines converge, urchins have delicate, bulbous skeletons with holes for wriggly tube feet and bumps where spines attach. Their mouths—equipped with limestone plates for scraping algae off hard surfaces—are in the middle of that skeleton, on the animal’s underside. Petrosino calls Diadema the janitor of the reef because it’s so efficient at cleaning reef surfaces."
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