The Nature Conservancy estimates that over the past decade, approximately 5.75 billion sunflower sea stars have died, largely due to climate change and warming waters along the Pacific Coast of North America, from Mexico to Alaska, over a period of three years.
The world’s second-largest sea star, the Sunflower Sea Star (Pycnopodia helianthoides), is now listed as critically threatened due to a severe disease exacerbated by climate change, with warming oceans making the impacts more critical and often deadly. According to the National Oceanic and Atmospheric Administration (NOAA), the species is at risk of future extinction and is proposed to be listed as threatened under the Endangered Species Act.
Starting in 2013, Sunflower Sea Stars have been devastated by an outbreak of Sea Star Wasting Syndrome, which is now recognized as one of the largest marine wildlife epidemics on record. This disease, originating from a lethal pathogen, has claimed over 90 percent of the species.
Sea stars that contracted the syndrome exhibited symptoms of lethargy, lesions, lost limbs and contortions, and would quickly disintegrate into gooey, jelled masses. These lesions, forming on their arms, dissolved surrounding flesh, resulting in not only the demise of this species but also impacting overall sea star populations. This condition has been detrimental to the Sunflower Sea Stars in particular, with cases where organisms have become functionally extinct (no longer serving their biological function), leading to a significantly difficult time recovering their numbers. Coinciding with this epidemic was the abnormal warming of the Pacific Ocean, known as the Blob, a major marine heat wave. Rapid temperature changes and warming waters have further contributed to the decline of the species.
Sunflower Sea Stars are Important for Maintaining a Healthy Marine Ecosystem
Before the 2013 disease outbreak, sunflower sea stars were among the most prevalent and distinctive species of sea stars along the Pacific Coast. These sea stars can span up to one meter across and can have 20-24 arms, each about three feet long, colored in beautifully vibrant hues of red, beige, or purple.
As significant marine predators, sunflower sea stars are able to play a crucial ecological role along the North Pacific Coast, controlling invasive sea urchin populations in kelp forests and other nearshore habitats. These sea urchins feed on marine vegetation essential for the survival of local marine ecosystems and especially kelp forests.
To many marine biologists, these kelp forests are considered “the lungs of the ocean.” They sustain marine biodiversity, serving as the home base for a variety of fish, invertebrates, mammals, and birds. Additionally, they help to substantially curb the amount of Carbon Dioxide (CO2) present in the water, capturing 20 times more CO2 than an overground forest could. Overall, seaweed and kelp store almost 200 million tons of carbon dioxide every year, equivalent to a year’s worth of emissions from New York State.
If the sunflower sea stars were to go extinct it would mean the total collapse of the entire California kelp forest ecosystem. Already, the significant decline in the sea star population has allowed sea urchin prey to flourish, resulting in the destructive consumption of kelp. This decline has destabilized what was once a biodiverse environment, now replaced by what is known as “urchin barrens.”
How are Scientists Combating this Problem?
Sea Star Wasting Syndrome remains a subject of ongoing research by scientists, exacerbated by detrimental temperature fluctuations and warming oceans, with the possibility of recurring outbreaks as warming persists. Despite these significant threats to their existence, there is growing optimism, and scientists have made considerable strides in helping these creatures.
In August of 2021, the Center for Biological Diversity proposed a petition to NOAA Fisheries soliciting the listing of the sunflower sea stars under the Endangered Species Act. Later in December of the same year, NOAA Fisheries resolved that the petition was valid and reviewed for the strongest scientific data and commercial information to officially determine if listing may be sanctioned. Since then, NOAA have submitted a recommendation that this species should be listed under the Endangered Species Act.
The protections afforded by the Endangered Species Act will aid in the recovery of sunflower sea stars. Scientists can pursue the species’ recovery plan by accessing available funding for further research, particularly focusing on the underlying pathogen of the wasting syndrome. Listing would also establish safeguards against and mitigate threats from water pollution, shoreline armoring, dredging, and other coastal construction projects contributing to the species’ decline.
Fortunately, the Birch Aquarium at Scripps Institution of Oceanography achieved a significant milestone earlier this year by successfully breeding three sunflower sea stars, marking progress in the restoration project. The Birch Aquarium, along with partners such as the Aquarium of the Pacific in Long Beach, Steinhart Aquarium at California Academy of Sciences, San Diego Zoo Wildlife Alliance, and the Sunflower Star Laboratory, collaborated to facilitate the reproduction and release of sunflower sea stars into the ocean.
Melissa Torres, an aquarist at the Birch Aquarium leading the project, believes that through this collaborative effort, there is an opportunity to ensure “good genetic diversity.” The Birch Aquarium currently houses five sunflower stars, serving as one of the largest populations of sunflower sea stars in captivity in California.
To reproduce the species, aquarium researchers inject hormones into the arms of the sunflower stars to stimulate a reproductive response. After a few hours, they gather sperm from the male sunflower stars and eggs from the female ones. Following this process, the genetic material is immediately cryogenically frozen.
The ultimate goal is to reproduce multiple generations of new sunflower sea stars. However, according to lead researcher Melissa Torres, further testing must be conducted before the fertilization process can be executed, to determine whether the offspring can survive diseases or parasites.
Researchers have been devotedly working across the United States to restore the population of sunflower sea stars. Their progressive research has shown increasing success, inching us closer to resolving what could be described as the sunflower sea star crisis.
Edited by Nikita Osadchiy