Seaweed, or macroalgae, is thriving. Thanks to the nutrient-dense agricultural runoff and sewage that have proliferated alongside human population growth, algae of all shapes and sizes are getting some of the heartiest meals they’ve ever had. This is a win for algae but not for coral reefs, which are suffocating under the thick layers of seaweed that have taken over Florida’s coast. To help, Florida’s marine ecologists are gathering up an army of unlikely heroes: crabs.
More than 90% of Florida’s reef—the largest in the continental United States—has died off, thanks to the tissue loss disease and warming waters that have plagued the last few decades. Simply put, what remains is having a tough time. Seaweed, which has been having a great time for the reasons touched on above, is choking out living coral and forming a thick blanket on the seafloor. When coral larvae, or planulae, float through the water in search of a place to anchor, that blanket of macroalgae shrinks their odds of success significantly. Meanwhile, mature coral cannot absorb the sunlight necessary to grow when seaweed is busy functioning as a marine curtain.
Many ocean species eat macroalgae. Long-spined sea urchins comprise one such species, but they were eliminated from the Caribbean by a mysterious pathogen in the 80s. (As one might imagine, this only bolstered Florida’s seaweed population.) Thankfully, Caribbean king crabs comprise another group of enthusiastic macro algae eaters. Not only do they munch on seaweed with jaw-dropping efficiency, but the fact that they’re natives to Florida (and one of the region’s few herbivores) reduces the odds that increasing their numbers will negatively impact marine ecosystems.
They’re also relatively easy to breed. When Sarasota’s Mote Marine Laboratory and Aquarium opened its Florida Coral Reef Restoration Crab Hatchery Research Center last month, it aimed to produce 34,000 Caribbean king crabs within the following four years. Now Vox reports the nonprofit might be able to produce 29 times that quantity, or 250,000 crabs per year.
As these crabs are released into the ocean, they’ll hopefully start to consume Florida’s excess macroalgae, allowing baby coral to latch onto the seafloor and mature coral to obtain sufficient sunlight. Before that, however, the crab hatchery has to train its crustacean army to fend off predators. Because ocean mammals and octopi aren’t abundant in Mote’s tanks, the organization’s ecologists use sock puppets to spook the crabs and test their fight or flight instincts.
