Can sea stars make a comeback in Kachemak Bay?
Sea star wasting syndrome ,or disease as it has become known, hit Kachemak Bay hard in 2016, killing about 90 percent of sunflower and true star populations. Researchers eagerly waited for spring to roll around in hopes their numbers would rebound. As the days got longer, it quickly became apparent that wasn’t going to happen this year, but there is some hope the disease is waning.
Sea star wasting disease has been demolishing sea star populations along the West Coast for the past few years. It begins with lesions and quickly progresses to full-blown deterioration.
“Eventually the sea stars appear to be melting away and rotting away,” Katie Gavenus said.
Gavenus works with the Center for Alaskan Coastal Studies and has been monitoring sea star populations at three sites in Kachemak Bay for about four years.
The disease was first documented in the area in 2014, but populations of true stars remained relatively steady until August of last year. Gavenus then saw a significant increase in the number stars in the ladder stages of the disease, essentially melting away. Since last year, adult true stars have shown little sign of their existence in Kachemak Bay.
“I just looked back at our data from late June and what we just collected last week, and we found two true stars in one of them, zero in another,” Gavenus said of the three beaches she monitors. “So, really a significant decrease in the number of true stars that we’re seeing.”
Gavenus notes prior to the disease, 50 to 75 true stars could be seen at these sites.
Other species have also been hit hard in the bay. Brenda Konar is a professor of marine biology at the University of Alaska Fairbanks, and she has worked with Gulf Watch Alaska to monitor Kachemak Bay since 2002. Konar trains scuba divers in Kasitsna Bay near Seldovia every spring and sends trainees to survey for sunflower stars.
“This year, not a single sunflower star was seen there,” Konar explained, “which is crazy, because normally they’re everywhere.”
But, not all hope is lost. Konar’s Ph.D. student Ben Weitzman tracks sea star populations in Prince William Sound. Weitzman also works for the U.S. Geological Survey as a wildlife biologist. This year, he’s been seeing signs of a rebound.
“At some of the sites around Knight Island, we were seeing juvenile sunflower stars, the pycnopodias, about the size of your palm,” he said. “We weren’t seeing them everywhere, but it was nice to see them at least some places.”
However, Weitzman is cautiously optimistic. Locations from northern California to the coast of British Columbia have seen increases in Juvenile recruitment over the past year, but survival has been a mixed bag. Weitzman has the same questions other researches have been asking.
“Our big question is are these guys going to survive? Will this recruitment pulse that’s come in actually start to repopulate the sunflower stars in the system?” he wonders. “Maybe they don’t survive. Maybe they survive in only some of the bays, we’ll see.”
Weitzman notes other sites Gulf Watch monitors in Katmai and Kenai Fjords national parks haven’t seen the same signs of life. As to why researchers are seeing a pulse in Prince William Sound, Weitzman says that’s a complicated answer.
Starfish are satellite spawners, releasing eggs and sperm into the water column. Where their larva lands is largely depends on ocean currents.
“There could be more local retention of larva there. It could just be conditions are a little cooler or warmer, they vary in some way that allows the sunflower stars to be successful this year,” Weitzman explained.
Konar thinks conditions in Kachemak Bay could lead to a similar spike in juvenile stars in the next few years, and there are small signs that could happen. Researchers have found juvenile true stars hiding under rocks and in non-surveyed locations, but only time will tell if those signs translate into a rebound.