Scientists propose listing of sunflower sea stars under endangered species act after more than 97% vanish off western shores

Federal scientists are recommending that giant sunflower sea stars — key players in maintaining ecological balance in kelp forests off the West Coast — be listed as threatened under the Endangered Species Act after determining that more than 90% have recently perished from the shores off North America.

The culprit? Sea Star wasting syndrome, a mysterious pandemic that spread widely among sea star species beginning in 2013 but which affected the huge pycnopodia helianthoides with particular severity.

An estimated 5.75 billion died between 2013 and 2017, the apparent victims of a virus-sized pathogen that causes the sea stars to develop lesions, lose their appendages and dissolve.

The International Union for Conservation of Nature listed the sunflower sea star as “critically endangered” in 2020. The Center for Biological Diversity petitioned the National Oceanic and Atmospheric Administration for listing as threatened or endangered under the Endangered Species Act a year later.

NOAA Fisheries scientists have since determined that 95% to 99% of the sea stars are estimated to have died from the Washington coast south to Mexico in what the agency says is the largest marine wildlife disease outbreak on record.

The result has been catastrophic. The multiarmed sea stars can grow to more than three feet across. They have few predators, but they voraciously consume all types of marine life, especially sea urchins.

As the sea stars disappeared, sea urchins flourished, particularly small purple ones that exploded in population, decimating the kelp forests and starving out other creatures, like the red abalone that once drew thousands of divers and rock hunters to the North Coast. The abalone fishery, a springtime ritual and passion for many, has been closed since 2018.

Little is understood about the sea stars, their life cycle and the pathogen that led to their downfall. Scientists hope federal listing may steer more resources toward monitoring and research needed to learn more about them and how the survival of the estimated 600 million still remaining in the ocean can be ensured, NOAA Fisheries representatives told reporters Wednesday.

Among the efforts already underway is a captive breeding study at the Friday Harbor Labs at the University of Washington, though this kind of work is still relatively young, said Dayv Lowry, senior marine biologist with NOAA Fisheries’ Protected Resources Division.

“There’s a lot of work to be done, but a lot of really promising work to be done,” Lowry said.

Marine biologists with the California Department of Fish and Wildlife first hinted at the sea star’s crash in 2016, saying “a perfect storm” of large scale ecological impacts had drastically altered the marine ecosystem. The factors included widespread sea star wasting disease beginning in 2013, a “warm blob” of higher than usual ocean temperatures along the west coast in 2014, and an ensuing El Niño that kept water temperatures high.

Kelp, already stressed by the warm water, was soon grazed down by purple urchins that grew to more than 60 times their historic numbers and outcompeted the abalone, which died in high numbers. The urchins, meanwhile, managed to survive despite the disappearance of available plant food, earning the name “zombie urchins.”

About 95% of the bull kelp off of Sonoma and Mendocino counties died off in those first few years, and though there have been signs of regrowth in a few areas, the underwater landscape is nowhere near what it once was.

Lowry said other factors — the historic loss of sea otters, which also consume urchins — contributed to the cascading shift in the marine ecology.

Scientists still don’t know exactly what causes sea star wasting but say it appears to be exacerbated by warm water, as well as any change in temperature, even if it’s warm to cold.

They said the worst sea star losses last decade were in southern California near Baja and generally off the mainland United States. Some areas around the Aleutian Islands, for example, were not hit as hard, Lowry said.

But because the Endangered Species Act requires listing decisions for marine invertebrates to be based on species-wide assessments, without consideration for differences in local geographic areas, NOAA scientists could not petition for an “endangered” status, despite dangerously low population numbers in the southernmost part of the sea star’s range, said Sadie Wright, with NOAA Fisheries’ Alaska Region.

Wright said recovery efforts could be developed and targeted geographically, however.

The proposed rule listing the species as threatened is to appear Thursday in the Federal Register and will be subject to public comment for 60 days.

NOAA Fisheries has a year from Thursday to make a final ruling on the listing, said Lisa Manning, national listing coordinator with the Fisheries Service Office of Protected Resources.

The Canadian government is going through a similar process, Lowry said, though the species’ condition off the Canadian coast was taken into account during the U.S. status review.

You can reach Staff Writer Mary Callahan (she/her) at 707-521-5249 or mary.callahan@pressdemocrat.com. On Twitter @MaryCallahanB.