Scientists study ecological fallout of sea star die-off
Marine scientists are studying kelp to see how starfish wasting disease is changing the ecosystem
Marine scientists with the Vancouver Aquarium were on — and under — the water in Howe Sound near West Vancouver on Monday taking a close look at how a serious decline in starfish is affecting the rest of the marine ecosystem.
Sea star wasting disease was first noticed in 2013 and has now been found in Pacific West Coast waters stretching from Alaska to Baja, California.
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"It was really striking to see the wasting sea stars. They kind of lose their internal body pressure, they develop lesions, they start to fall apart, drop their arms, so it's really quite gruesome," said Jessica Schultz, ecology and climate research manager with the aquarium's Howe Sound Research and Conservation team.
Scientists are still struggling to fully understand the mass die-off.
"It's definitely a big concern. It's been called the largest wildlife mortality event that we know about," said Schultz in an open 22-foot aluminum boat near a rocky shore, where two of her scuba diving colleagues were below the surface looking around.
But the Vancouver Aquarium's researchers weren't seeking sea stars — they were inspecting kelp, the so-called underwater forests that serve as a food source for countless marine species. They're about halfway through a two and a half year study examining the trophic cascade.
"Trophic cascade means that there's an alternating effect at each level of food chain," explained Schultz. "Sea stars decline and their prey item — which is the urchins — increase drastically, and then [we see] the subsequent decline of their food, which is the kelp."
"Kelp is important to the ecosystem in a number of different ways. It provides habitat for a number of different organisms, it's a primary producer, and it's also a way that carbon is sequestered — or stored — in the environment," said Schultz.
Schultz points out there wasn't a lot of research done on starfish before the wasting disease took hold because they weren't commercially fished.
But now, with the resulting boom in urchins and corresponding decrease in kelp, people may take notice of at least one species that relies on kelp in Howe Sound: the ever-popular spot prawn.
"People tend to care a lot about kelp because it can influence species that we're interested in," she said.
Schultz and her team, which includes marine scientists Laura Borden and Donna Gibbs, tag individual blades of kelp, and return to make measurements over time.
"At the sites where we do have the urchins and this kelp … you'll see where they've grazed them, because you'll see little cutouts, basically, where they've chomped down on that kelp," said Borden.
"In terms of the kelp, we definitely have seen it decline since sea star wasting syndrome, and we're trying to determine how resilient it is... or isn't," said Schultz.
And while the aquarium researchers follow the ecological fallout from the dramatic loss of sea stars, there's still a lot of uncertainty about whether the affected species will bounce back.
"The recovery of sea stars has been a big question mark. There's even been talk of listing some species, like the sunflower star, as endangered, because we're not sure how well they'll be able to recover," said Schultz.