sea star wasting disease

Serious Concern for Sunflower Sea Stars

By Bob Friel

Science usually happens a millimeter at a time. When looking at an animal population, for example, changes in abundance are often revealed in the data as a slight trend line amid cyclical ups and downs. But then there’s what’s happened to our sunflower sea stars.

Sea Star Wasting Disease (SSWD) has taken its deadly toll on at least 20 species of echinoderms. First noticed here in the Salish Sea in 2013, this current epidemic has since devastated starfish from Mexico to Alaska. In our region—a world-renowned hotspot for sea star diversity—the virus affects blood stars, giant pinks, morning sun stars, the beloved ochre sea star, and many others. None, though, have been hit as hard as the sunflower sea star.

When over 8,000 citizen-scuba diver surveys collected by REEF (Reef Environmental Education Foundation) were graphed to show sunflower counts, it didn’t show a shallow descending trend line. It literally traced the path of a falling star.

Actual 2006-15 and projected 2014-15 abundance for sunflower stars in 5 basins of the Salish Sea and the Outer Coast. Grey line marks the epidemic onset. Note: Figure taken from  Dr. Diego Montecino-Latorre’s paper  (2016)

Actual 2006-15 and projected 2014-15 abundance for sunflower stars in 5 basins of the Salish Sea and the Outer Coast. Grey line marks the epidemic onset. Note: Figure taken from Dr. Diego Montecino-Latorre’s paper (2016)

The hope that deep waters below the divers’ range still held healthy populations that could act as a genetic reservoir was dashed when the Washington Department of Fish and Wildlife’s (WDFW) annual deepwater sampling trawls came up with similar results: the “near extirpation” of sunflower sea stars throughout the state’s inland waters.

The inescapable fact is that what was once the most commonly seen invertebrate in the Salish Sea has almost disappeared in just a few years.

Sunflowers are the magnificent beasts of the sea star world, with as many as 24 arms that from tip to tip can measure up to the size of a nine-year-old child. And they use those arms to chase down sea urchins as enthusiastically as a nine-year-old chasing down an ice cream truck on a hot summer day. Sunflower predation is such an important control on urchin populations (which left unchecked can raze kelp forests) that the sea stars are considered ecosystem engineers. Remove them from the picture and we’re likely facing a domino effect of negative outcomes for all kinds of plant and animal species. Evidence of such a “trophic cascade” is already being found by researchers in British Columbia.

SeaDoc and our partners at REEF, WDFW, Cornell University, Vancouver Aquarium, and the Seattle Aquarium, which brought together experts for an emergency scientific summit on SSWD a year ago, have been at ground zero of this epidemic from the start. And with such startlingly clear results from the science and such alarming potential for further damage to the ecosystem, we feel there’s no time to lose in moving forward quickly with sunflower sea star conservation.

Wasting sunflower sea star / Ed Gullekson
Wasting sunflower sea star / Ed Gullekson

Consequently, SeaDoc lead scientist Joe Gaydos, with help from multiple collaborators like REEF, WDFW, Cornell, SR3 Sealife Response, Rehabilitation and Research, and others, have submitted a proposal to NOAA National Marine Fisheries Service to list the sunflower sea star as a US Federal "species of concern.” This is NOAA’s proactive protection program, with the aim of evaluating threats and identifying research priorities for at-risk species in the hope they can be saved before having to be listed as threatened or endangered under the US Endangered Species Act.

The proposal for listing is currently being reviewed while SeaDoc and other scientists continue to try and understand the workings of sea star wasting disease, including studying how this massive marine disease outbreak will ultimately change the Salish Sea and other coastal marine ecosystems. Thanks to your support, SeaDoc is on the case.

 

 

Banner photo: wasting sunflower sea star. Photo courtesy of Jenn Collins.

Sea Star Troubles Run Deep

By Bob Friel

One of the largest marine wildlife disease epidemics ever known to science —Sea Star Wasting Disease (SSWD)—has not spared the Salish Sea. While the most visible effect of the epidemic so far has been the loss of thousands of ochre stars, the Crayola-colored shallow-water species that turn our tide pools into works of purple and orange art, SeaDoc has discovered that great ecological damage is happening in deeper water too.

Drawing on data from more than 8,000 REEF (Reef Environmental Education Foundation) surveys by trained scuba diving citizen scientists along with precise transect studies completed by certified scientific divers, we found that SSWD has decimated populations of the once abundant sunflower sea stars to the point they’re considered virtually extirpated throughout our inland sea.

The Salish Sea hosts a great galaxy of sea stars encompassing a remarkably diverse collection of species. Among those, the sunflower (Pycnopodia helianthoides) holds a special place. Familiar to crabbers who often found them stuffed inside their pots eating their bait, and to divers who commonly swam over bottoms literally crawling with them, before the epidemic began in 2013, sunflowers were the most abundant sea star found below the low-tide mark.

Wasting spiny pink sea star
Wasting spiny pink sea star

The majority of our sea stars are predators, but the sunflower is a carnivore on a whole other level of dominance. Huge, relatively fast, and with three octopuses’ worth of hydraulic-powered arms, it’s the sucker-footed Starasaurus rex of the subtidal kingdom. While most marine life—as well as drysuited divers—steer well clear of sea urchins and their long, prickly spines, the sunflower stars gobble them like candy and then spit out the spiky bits. It’s the loss of such a voracious urchin-eater that’s particularly disturbing when we consider SSWD’s effects on our local ecosystem.

Herbivorous urchins graze on algae. A previous marine epidemic that killed off urchin populations in Florida and the Caribbean allowed algae to overgrow corals and severely damage tropical reefs. In our temperate waters, the concern is the reverse happening: with fewer sea star predators around, the urchin numbers can explode like underwater locusts and decimate the algae, mowing down our vital kelp forests, leaving behind what are known as urchin barrens.

With kelp such a crucial source of food and habitat for so many other creatures, the worry is that the loss of sunflower sea stars, which we’ve learned are particularly susceptible to SSWD, could start a trophic cascade that negatively alters the Salish Sea ecosystem.

SeaDoc and our partners remain on the case as this epidemic continues to affect our waters. We’re continuing the basic critter-counting science that alerts us to changes in the environment, investigating the virus linked to SSWD, and trying to determine whether other environmental factors played a part in the outbreak. If it turns out that intervention is necessary, we’ll be there to provide the science critical to inform the decision-making.