Starfish Are Not the Wallflowers You Think They Are
This is the time of year for wandering the beaches and studying what washes up, and starfish often figure prominently in what we find, and in our memories of summer. It’s partly because they are so strangely symmetrical—often with their hundreds of small, tube-like legs still wriggling underneath. And it’s also because they seem so vulnerable caught out in the sun, even though in their own world, beneath the waves, they are in fact great predators.
But you will probably not be seeing any starfish this summer on the U.S. East Coast. Some unknown killer has devastated populations from New Jersey to Maine. Caitlin del Sesto, a graduate student at the University of Rhode Island, was one of the first to notice it, when starfish she had collected for a study began to develop white lesions and then melt away in her aquarium. Some of the sick ones actually shed all their limbs in response to the stress.
Other researchers have since reported the same disturbing phenomenon. Divers from the Marine Biological Laboratory on Cape Cod are also finding that concentrations of starfish—or sea stars, as scientists prefer to call them—have been missing from their usual locations. Del Sesto is asking scuba divers and other members of the public to email her (email@example.com) information on any large congregations of starfish seen in Rhode Island waters, including their exact location, depth, numbers, and whether the animals appear healthy or diseased.
So far the cause of the die-off remains a mystery. “We don’t know if it’s something in the water, or something inside the starfish,” says del Sesto. She and her professor, Marta Gomez-Chiarra, are beginning experiments to isolate a possible bacterial or viral pathogen. They’ll also look at whether a rise in seawater temperature, or other environmental changes, may be a factor.
“There was a big increase in sea star numbers about three or four years ago,” says Gomez-Chiarri, “and often when you have a population explosion of any species you end up with a disease outbreak. When there’s not enough food for them all, it causes stress, and the density of animals leads to increased disease transmission.”
She worries that the disease may persist, preventing recovery of the population. “Diseases don’t just completely disappear after a massive die-off,” says Gomez-Chiarri. That matters because starfish are the original keystone species, and their absence can be devastating for the diversity of other coastal species.
The importance of starfish first became evident in the 1960s in a classic experiment by the University of Washington researcher Robert T. Paine. He was studying the rocky world between high and low tides on the Pacific Coast near Seattle, where the food chain typically consists of barnacles, limpets, chitins, anemones, and particularly mussels. The mussels normally wind up concentrated closer to the high tide line, where it’s hard for starfish, the dominant predator, to get at them.