In 2013, a sea star wasting disease decimated sea star populations along the west coast. The Sunflower Sea Star is one of the largest sea stars in the world and suffered a loss of over five billion individuals. Scientists have come together to create a ‘Roadmap to Recovery’ to initiate and accelerate the recovery of this species. Steve Rumrill is the shellfish program leader with ODFW and an author of the roadmap. He joins us to share what sea star populations are looking like now and what should be done to aid them.
The following transcript was created by a computer and edited by a volunteer:
Dave Miller: From the Gert Boyle Studio at OPB, this is Think Out Loud. I’m Dave Miller. The Sunflower Sea Star is a dinner-plate sized starfish that’s native to North America’s Pacific Coast. Since 2013, their numbers have plummeted. Now a group of scientists and researchers have come together to create a recovery roadmap for this sea star. Steve Rumrill is one of the members of the team. He is a shellfish program leader with the Oregon Department of Fish and Wildlife and he joins us now. Steve Rumrill, welcome.
Steve Rumrill: Thanks so much for having me on your program today. Appreciate it.
Miller: So this roadmap is focused on the Sunflower Sea Star. Can you describe this particular species?
Rumrill: The Sunflower Sea Star is a very large starfish or sea star – I’m going to use that term sea star. It’s thought to be the second largest in the world. [It] occurs along our coastline, primarily in the really deep intertidal zone, only accessible at the lowest tides and down into the subtidal area, all the way from the Aleutian Islands down through the outer coast of Alaska and British Columbia, Oregon, Washington, California down into Baja Mexico. It’s a very large sea star. It can be dinner plate size, but can also get up to the size of 2.5-3 feet across. We think of the largest adults being the size of a garbage can lid. And they’re very fast. They have multiple rays, anywhere from 15 to 24 arms, and they’re voracious predators in the marine environment.
Miller: What do they eat?
Rumrill: They’re generalist predators and they eat a variety of different foods, including clams and snails, chitons – another kind of weird mollusk - sea urchins, sea cucumbers, other sea stars. It’s thought that they’re also cannibalistic. They prey upon sand dollars and can even track down and capture and consume small crab.
Miller: Anything they can get their hands on . . . or star ends [laughing].
Rumrill: One really interesting thing I mentioned, they can prey upon clams. Many of the clams are burrowing and they burrow down into permanent holes in the soft sand or soft mud. And these Sunflower Sea Stars are so determined, that they can hone in on and sense the presence of a clam. And then just literally grain by grain, using their dense tube feet, they can remove and excavate a hole and dig out a clam. The clam really doesn’t have anywhere to go but to retract down and hide out in that hole. It may take a month for them to dig a big hole and finally catch and consume that clam.
Miller: But this is just one of a number of sea star species that are native to the eastern Pacific Coast, right?
Rumrill: Yes, that’s correct. The eastern Pacific Coast is recognized as a hotspot for the biodiversity of sea stars in the world. We’ve got a large number of different species, great diversity in the intertidal zone and in the subtidal zone here, and we’ve suffered a catastrophic loss of many of the species. Our roadmap for recovery, that we’ll talk about a little bit later, is focused specifically on the problems faced by this Sunflower Sea Star. But no question about it,
the sea star wasting syndrome and mass mortality event has affected up to 20, maybe more species out of our diverse community.
Miller: This is something that we’ve talked about in the past when it was first happening in the mid 2010s, but it’s been a little while since we focused specifically on sea stars. What have scientists been able to figure out in terms of what at one point was a big mystery – what was killing the sea stars? What are the answers?
Rumrill: Over the past decade, we’ve recognized just the extent and magnitude of this marine disease event. By some accountings, it’s the largest marine disease event ever recorded in the world . . .
Miller: Meaning, there’s no other specific event or mortality event that’s been bigger, in terms of population decline, than what these sea stars have been experiencing off the Pacific Coast just in the last couple of years?
Rumrill: We’re right up there with that. There have been some very large marine mass mortality events in the past: the catastrophic loss of corals, loss of abalone, loss of sea urchins, and now this mass mortality of sea stars. But putting all those together by some accounting, we’ve experienced one of the greatest, if not the greatest in the world.
You asked me what have scientists learned? So we’ve learned about the extent and magnitude of the disease. There’s also a very detailed work going on to try to figure out the causative agents and the actual cause of sea star wasting has not been definitively determined at this point. There’s competing research that has pointed to a marine virus, a densovirus, a parvovirus-type virus, that is affecting these individuals and carried through the water from one to another [so] that they could infect each other. There’s also research that points to a disruption of the dissolved oxygen right at the layer of the sea star’s skin, their epidermis. And so in essence they suffocate and die out that way. Sea stars have an autoimmune, they can cast off rays, they can cut off part of their body that’s diseased, and when they are infected by either a virus or the loss of oxygen at particular parts, then they just take themselves apart and literally melt out and just dissolve away.
Miller: If there is some debate about the actual causes of this syndrome, then how do you go about boosting the numbers? If scientists don’t know exactly what’s causing these sea stars to die, then how do you prevent them from dying?
Rumrill: In the roadmap for recovery, this unique group has come together quickly to help plot out the steps and actions to help facilitate the recovery. There’s a very strong emphasis on continued research to figure out the causative agent, research on the disease, how it propagates through the natural world, and how it can propagate from individual to individual and to see really what it is. So no question about it, that’s super important.
Miller: So let’s turn to other aspects of this roadmap. What are some of the short term elements, things that can be done within a year or two, to help the recovery of this species?
Rumrill: We organized the roadmap into seven specific objectives and those cover near term and longer term goals. On the near term side, first is just to develop the recovery goals themselves. Keep in mind that this roadmap for recovery is addressing the full biogeographic range of the Sunflower Sea Star, extending from the Aleutian Islands all the way down into Baja Mexico. So, as you can imagine, coming together on a statement of the overall goals for recovery, for research, for dealing with permitting and captive rearing, translocation possibly and outplanting, public outreach amongst all of those different nations and federal governments, state, county-level provinces, coastal tribes, all the public trust agencies and the very talented and motivated group of academic scientists, who are also focused on this issue, that’s no easy task. So an immediate issue is simply to develop and articulate the goals for recovery and thresholds for when action should be taken.
Other immediate steps, of course, are to initiate and continue the monitoring, keeping eyes and ears on the ground, keeping a pulse on the population so that we know where we have major problems. There’s a latitudinal gradient, so not all the Sunflower Sea Stars are gone. There are individuals and some subpopulations up in Alaska and upper parts of British Columbia where we still have some strongholds. But as you sweep further south, we’ve got major disappearance off the coast of Washington, Oregon, California. So monitoring efforts need to keep an eye on the places where the individuals are still present and also on the sites where they have largely disappeared.
Miller: One of the components of this roadmap is public outreach. What do you want the public to know about these sea stars?
Rumrill: Great question. We really appreciate the opportunity simply to spread information and raise public awareness about the decline in these sea stars. And not only the species, but also to let people know that other species have also declined. In the aftermath of sea star wasting, the most commonly observed sea star along our coastline are Ochre stars, the commonly seen orange and purple sea stars that we see in the rocky intertidal tide pools. Many of those populations have come back and people are celebrating that and saying, “wow, I’m so glad to see these sea stars come back.” That’s one of the few species that has made a substantial recovery. But we really want the public to be aware that the sea star wasting mass mortality event is continuing, it’s affected multiple sea stars in the intertidal zone in the shallow subtidal zone, and that they have an opportunity to contribute their knowledge and observations. There’s a Citizen Scientist network that’s been set up so people can really put in their own observations and contribute in a meaningful way to understanding the geographic location and abundance of sea stars along our coast.
Miller: Just briefly, in addition to this particular species itself, what are the broader ecological impacts of the decline of sea stars?
Rumrill: I mentioned earlier that these particular sea stars and others are generalist predators and thought to be so important that we can consider them as ecological engineers in their habitats. The Sunflower Sea Stars prey upon this diversity of different shellfish in the subtidal zone. And it’s thought that the decline in Sunflower stars has really contributed to an overall shift in the habitats that have gone through this process – the warming of sea water, the marine heatwave that we experienced, contributed to the Sunflower Sea Star’s decline through this mass mortality event. Somehow their decline allowed the numbers of sea urchins, which the Sunflower stars prey upon, to increase. That puts an increase on grazing pressure. Sea urchins graze on kelp and understory seaweeds, so that there has been a very large, broad decline in kelp and seaweeds and that’s caused problems for other animals that rely on grazing and drift algae, like abalone. So we’re seeing a decline in Sunflower Sea Stars, a decline in kelp, an increase in sea urchins, and a decline in abalone. Now, that’s a working hypothesis at this point. But the loss of these big predators in the marine ecosystem, just like in the terrestrial ecosystem, can have these cascading trophic effects throughout their food webs.
Miller: Steve Rumrill, thanks very much.
Rumrill: Yeah, thanks for having me on.
Miller: Steve Rumrill is the shellfish program leader with the Oregon Department of Fish and Wildlife, talking to us about the huge decline in Sunflower Sea Stars populations off the Pacific Coast and the efforts to reverse those losses.
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