- The population of sea stars along the west coast is estimated to be in the tens of millions. With limited data, scientists don't know how many have succumbed to the disease, but estimate are it may be in the tens of thousands to the low millions.
Thank You Ocean has released a new video with recent information on the sea star die off. Please watch to learn more about the geographic extent of the event, the species involved, the research into a cause, and what may be expected in coming months.
This past summer we began hearing about a massive sea star die off along the west coast. Though we’ve seen these types of events before, the spatial extent of this one is quite alarming. Reports from folks walking along the shores were of animals that “looked like their arms had been chopped off.” Pete Raimondi, professor of ecology and evolutionary biology at UC Santa Cruz and the principal investigator on the Pacific Rocky Intertidal Monitoring Group, is hard at work trying to figure out why.
What We Know
Sea star wasting syndrome is a general description for the disease causing the die off, and impacts of this disease can be massive. Typically, the first signs of the disease are white lesions on the surface of the sea star that spread rapidly and are followed by decay of the tissue surrounding the legions. Next the animal becomes limp as the water vascular system fails. As the body structure begins to break down, signs of stretching appear between the arms, which may twist and fall off, and the animal dies within a few days. The arms may continue to crawl around for a while after being shed.
The science so far appears to indicate that species are affected differently depending on physical location. For sea star species in tide pool areas, the lesions or sores show up, followed by tissue decay, Raimondi said. Death might follow in a matter of weeks, or not at all. In underwater species with less physical structure in the environment, the results are catastrophic and quick, Raimondi said. Decay happens in hours or a day, rather than weeks.
The ultimate cause is not clear although such events are often associated with warmer than typical water temperatures as was the case for the major die off in southern California in 1983-1984 and again (on a lesser scale) in 1997-98.
Although little is known about the disease or what triggers it, Raimondi said scientists are close to identifying the cause of sea star wasting syndrome. A pathogen appears to be the most likely culprit. Other possible causes of the condition that have been suggested include high sea temperatures, oxygen depletion and low salinity due to freshwater runoff. Research suggests that high water temperatures are indeed linked to the disease, increasing its incidence and virulence. The disease also seems more prevalent in sheltered waters than in open seas with much wave movement.
What You Can Do
This is a great opportunity for all of you to participate in an important citizen science effort. Raimondi and his colleagues at the Pacific Rocky Intertidal Monitoring Group are asking people to collect spatial data on where the wasting syndrome is showing up. Early data for our part of the coast has shown occurrences at Point Cabrillo and Cantus Cove in Caspar. Educate yourself on the sign of the disease and take pictures when you see it on our coast. Note the location, and fill out the web data form offered by the lab. The more information we have on where and when we find sea star wasting syndrome, the sooner we’ll be able to figure out what’s causing it. Once we know that we can set upon determining possible prevention or treatment actions.