Over the past two years, millions of sea stars along North America’s Pacific coast met a grisly end when a virus rotted their bodies into lumps of white goo. Now that so many of these echinoderms have died, scientists fear that greater consequences of this “wasting disease” are already at play. And the sickness may be spreading even further, as evidenced by the sea stars’ spikey cousin: the urchin.
In central and northern California, where high levels of sea star wasting disease have been observed at 87 percent of surveyed sites, portions of the seafloor have become carpeted in what look like pink and purple pincushions. Here, ecologists believe the sea stars’ demise has translated into a sea urchin boom, because the wasting disease has all but wiped out the sunflower star, one of the urchins’ main predators. And, since sea urchins eat kelp, ecologists think the urchin boom could mean the deforestation of central California’s giant kelp forests.
In southern California, however, the wasting disease has affected sea urchins quite differently. South of Point Conception – a landmark that divides very different oceanic conditions, where warmer waters begin – ecologists worry that the sea urchins could now be catching the same ailment.
So far, urchin die-offs have been observed and documented at four sites along the 200 miles between Point Conception and Santa Catalina Island, and at a fifth site off Baja California. Most are purple urchins, Raimondi says, and there are reports of mass mortalities. Some scientists think another species, the green sea urchin, which lives along the north coast, could be next.
“There are particular signs that point to this being a wasting event, the way the animals are dying,” [University of California, Santa Cruz ecology professor Peter] Raimondi says. The most common kinds of California urchins – purple, red, and white – are losing their spines, and the leading edge of spine loss is often discolored pink or white.
This wouldn’t be the first time that populations of both sea stars and urchins have died off at nearly the same time. In the past, however, this was linked to warmer ocean temperatures due to El Niño events. “[N]o one can say for sure whether the newly discovered urchin wasting is linked to sea star wasting,” Leslie Willoughby writes for National Geographic.
There is one thing, however, we can say with fair certainty: no species lives in a glass bubble. Afflict one of them, and there will likely be changes to others, too—whether we fully understand these changes, or not.