by Cameron Douglas
Sea stars (called starfish in days gone by) are suffering a massive die-off, and for the first time it is happening in two oceans in the same year. The culprit is a mysterious, gruesome illness called sea star wasting disease, which turns its victims to mush as they decompose and disintegrate.
Sea star wasting disease is a sort of undersea flesh-eating malady. White lesions appear on the body of the sea star and spread rapidly. Then the body becomes limp as the animal’s water vascular system fails, which renders it unable to maintain its internal hydrostatic balance. The body structure breaks down and signs of stretching between the arms appear. Arms may twist and fall off, crawling about on their own for a period of time after the sea star expires. All this happens in the course of a few days.
Documentation of sea star wasting disease looks to have commenced around 1972, when common sea stars died off in large numbers along the east coast of the U.S. Six years later in the Gulf of California, the disease hit the predatory sea star Heliaster kubiniji, causing extinction in some areas, with populations still not fully recovered by the year 2000. The disappearance of this top-level predator had profound effects on the area’s ecosystem. A total of ten species of sea stars in the Channel Islands were documented as having been affected, along with three species of sea urchins, two species of brittle stars, and a sea cucumber. All these suffered significant declines in numbers during the 1978 plague.
When sea stars aren’t melting down, the spiny sea urchin seems to suffer a similar fate from time to time. Pacific Grove resident John Pearse, a Professor Emeritus from the Department of Ecology and Evolutionary Biology at UC Santa Cruz, confirms via e-mail to Cedar Street Times that there was a mass mortality of sea urchins in Santa Cruz in the 1970’s, which his department documented. Sea stars were not affected at that time. Pearse adds there was a massive die-off of sea urchins in Maine and Nova Scotia during the 1980’s, which occurred right after a mass sea urchin mortality in the Caribbean, but with no reports that it spread to sea stars.
Sea star wasting disease appeared again in July 2013 when sea star populations declined sharply along the Atlantic seaboard between New Jersey and Maine. (Worthy of note is the fact that sea star numbers in that region had increased greatly in 2010.) In September 2013, observers in British Columbia reported Pacific sea stars were in trouble. By November, others were reporting the problem up and down the west coast.
Here in Pacific Grove, Pearse reports that divers have spotted diseased sea stars in the kelp forest near Hopkins Marine Lab. “They recently told me that there are almost no stars left except bat stars that seem to be more resistant,” states Pearse.
Pearse has tracked sea star populations in three intertidal sites at Hopkins since the 1980’s: these were also the sites for a pioneering study on sea stars conducted in the 1950’s. “There has been a steady decrease in the numbers at those sites for over a decade.” While sea gull predation is a possible cause, Pearse speculates that the disease has also been a factor, slowly spreading until becoming epidemic this year. “There are almost no stars at those sites now.”
Some scientists have expressed concern that the absence of sea stars will throw off the balance of intertidal animals and cause certain species such as mussels to reproduce unabated. Pearse disagrees. “In California, at least, it is very unlikely that there will be a noticeable ecological impact, and the mussel population will not increase much if at all.”
In the face of speculation that warming waters and/or Fukashima radioactivity may be affecting our area, Pearse says no and no. “Sea temperatures off the coast of central California and north have not been going up; if anything, they have been going down slightly the past decade or two—because of global warming, which is causing increased winds on our coast and upwelling which brings up cooler water and nutrients, leading to increased productivity and all the whales we now enjoy. The mass mortality in southern California was associated with warmer sea temperatures, but that is not the case here.”
And regarding the March 2011 Fukashima nuclear power plant meltdowns: “It is my understanding that there has been little or no detectable increase in radioactivity on our coast since that disaster. Yes, some fish that swim across the ocean have detectable radionuclides (cesium-137) that almost certainly came from Fukashima, but I don’t think they have been detected in intertidal animals such as sea stars [along our coast].”
Media attention to this year’s sea star event has drawn the attention of researchers who are getting samples rapidly sent in, possibly soon enough to pinpoint the cause.
The LIMPETS citizen science program has been monitoring a site at Point Pinos in Pacific Grove. So far no diseased stars have been spotted there, but numbers have fallen off steadily for the past five years. “I was out there with a group last month and we found only one star,” says Pearse.
Reporter’s note: Professor Pearse was recently quoted in a Washington Post blog, which in turn has been posted in several other blogs concerning this year’s occurrence of sea star wasting disease. The Post quoted one sentence of Pearse’s input. We are grateful for the opportunity to share more of his expertise with our readers.
You may not see this for a while: a cluster of healthy sea stars. Image courtesy redorbit.com/