OCEANS Sea star babies appear on coast Researchers: Numbers could help rebuild species lost to wasting disease By Will Houston whouston@times-standard @Will_S_Houston on Twitter With a wasting disease decimating populations of sea stars across the West Coast, local marine researchers are finding some solace in large numbers of returning juveniles making their way back to the coastline. Several recent surveys in nearby rocky intertidal zones have found a fair amount of young sea stars, Humboldt State University Marine Laboratory and Marine and Coastal Science Institute Director Brian Tissot said. “It’s too early to give an overall summary,” he said. “We’re definitely still seeing the wasting disease and seeing individuals affected, but we’re also seeing that there is still a large number of juvenile sea stars.” The highly lethal sea star wasting syndrome — which has about a 95 percent mortality rate — has become an epidemic along the West Coast and has been found on sites from Alaska to Northern Mexico. As the disease progresses, white lesions will show up on the limbs of affected individuals and eventually, the organisms start to disintegrate in a period lasting a week or less, sometimes falling apart. During the past year, local researchers have seen up to an 80 percent reduction in some sea star populations on the North Coast. Though the data has not been fully analyzed, Tissot said some surveys have shown up to 27 juveniles of varying size in a square quarter-meter area. Many of the juveniles being found are six-rayed starfish, a species of less importance on the ecological scale than the ochre sea star, which has been a hard-hit victim of the disease. Marine ecologist Joe Tyburczy of the California Sea Grant Extension said that ochre sea stars are keystone species because they consume competitively dominant mussels. If the mussel populations go unchecked by predators, they can dominate other organisms in the rocky intertidal habitats, thereby reducing biological diversity and creating an unhealthy ecosystem, Tyburczy said. “If the only thing we see are six-armed stars, then that won’t be helpful in restoring the ecosystem to its previous state,” he said. Tissot said the recruitment of juveniles landing near Trinidad is relatively small when compared to those seen near Santa Cruz. UC Santa Cruz’s Ecology and Evolutionary Biology Department Chairman Pete Raimondi said some surveys have shown a large abundance of the juvenile sea stars. “We’ve seen more babies in the last six months than we’ve seen in the last 15 years combined,” he said, citing one survey conducted at Terrace Point. The recent findings come with good and bad news. Raimondi said the good news is that a large recruitment of juveniles might lead to a faster population recovery than was anticipated. “The effects of the wasting disease will be relatively limited in terms of time as long as the babies themselves don’t get sick,” he said. “It just takes a long time for animals to reproduce, because they have to find each other and fertilization occurs in the water column. Then they have to survive in this young larval period for 30 days as little tiny things. It’s just a dangerous situation. If they’re just rare and little, it takes a long time for the population to recover.” And the bad news: “Unfortunately, we’re starting to see some of the babies with the disease.” The cause of the wasting syndrome is unknown at this time, but Raimondi said that it is likely that bacterial infections lead to the wasting symptoms of the affliction. One hypothesis that is being tested is warmer water contributing to the disease, but Raimondi said that was not the case in this past year’s outbreak as the water temperatures were cooler. The other idea researchers are testing is a viral infection. “If you have got a nasty virus, you can get debilitated and your immune system can become suppressed,” he said. “That happens in everything.” The return of juveniles is a good sign, Tyburczy said, but the full effect of what this return will mean for future sea star populations has yet to be determined. “The other possibility that remains to be investigated that one might look at is that the sea stars that are healthy to reproduce, maybe some of the ones are more resistant to the disease were able to reproduce and the returning juveniles will be more resistant as well,” he said. “Mere speculation, but it’s a possibility.” Will Houston can be reached at 707-441-0504.
Posted on: Tue, 26 Aug 2014 15:44:46 +0000
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