Sea stars, more commonly known as star fish, have littered the coastal tidal pools and sea bottoms for the past 450 million years. In recent years, sea stars have been dying due to sea star wasting disease. At this moment, researchers all over the coasts are battling to find the reasons why millions of stars are being ripped apart, losing their arms first, then eventually dying, leaving only goo behind in their wake. This phenomena is known as sea star wasting disease, and it is puzzling students, professors, researchers, and the community, as there has been no answers yet as to what causes these animals to suffer horrible mass mortalities.
This week, I had the opportunity to listen to a biology lecture from marine biologist and Western Washington University professor Ben Miner, who has been doing research on the disease for years. Last September, National Geographic wrote an article and produced a short video on the disease, interviewing Miner around Shannon Point Marine Center, Western's lab in Anacortes, Wash. Both students and professors from Western are working to understand what is causing these mass mortality events, and trying to learn about ways we can slow down, if not stop, this disease from spreading.
In 1972, the first mass mortality event of sea stars took place on the east coast of the United States, with the common sea star (Asterias rubens) being the species hit hardest. Since 1972, there have been at least six other mass mortalities, almost all in the coastal regions of the United States.
Why is this outbreak, which started in 2013, different from others that have occurred in the past? This outbreak of sea star wasting disease if affecting around 20 different species of sea stars up and down the entire West Coast. Past outbreaks have been contained in smaller areas and have been seen in only a few species of sea star at a time.
In the summer of 2013, a diver noticed some unhealthy looking sea stars on the western coast of the US. The stars had white lesions forming in their armpits, and some of the stars had an arm break off and "walk" away from the body. After the lesions form, normally an arm will break off, and the internal organs of the star will start to ooze out of the open wound. After arms break off, these lesions can occur on the abdomen, where even more organs are located that can spill out of the star.
After observations were made in the summer of 2013, divers in the fall found dead sea stars littered across the ocean floor, followed by members of the Seattle and Vancouver, B.C. aquariums noticing the death of their stars around the same time. The same deaths were also occurring down in Monterey Bay in California, creating three contained groups of affected individuals.
A year later, the Salish Sea (previously known as the Puget Sound) was hit hard. Researchers went out that summer, and when they returned about a week later, they found that all the stars that had previously been healthy were lying dead in piles of white goo.
Contaminated individuals are transformed from a fully functioning sea star into a white sludge of calcium carbonate remains. Most stars die from bacterial infections entering the body through open gashes caused by the lesions. Millions of sea stars have already died because of sea star wasting disease all the way from Alaska to Baja, Mexico. A huge diversity of sea star species are being affected, with no apparent genetic link between the species being hit.
Sunflower, mottled, ochre, giant pink, giant, morning sun, and striped sun stars, being the most common, are the most affected by the disease and have suffered the largest mortality rates. Other less common stars affected include rainbow, bat, leather, six-armed, vermilion, fragile, sand, rose, velcro, and fragile rainbow.
One species that has escaped the disease is the slime star, which produces copious amounts of colorless slime when stressed. It is believed by some that the slime could be the reason why it is not suffering in the same way as other species closely related.
Sea stars play a vital role in their ecosystems, and their deaths are causing organisms like mussels and sea urchins to increase in populations due to the absence of sea stars. In the past three years, researchers have been working hard to try and figure out what all the causes are for these deaths, and lots of progress has been made nailing down the virus, densovirus, which may be responsible for all of the deaths.
Ben Miner, along with other marine biologists, have been collecting long-term data looking at the population sizes of starfish along the West Coast, and over the years they have shown no increase in population. Western students have also been doing research on the sea stars, specifically looking to see if water temperature would stop the disease from spreading to other organisms, or even reverse the damaged stars.
The students found that by lowering the temperature of the water, the disease killed the stars at a slower rate than the warmer water. Antibiotics have been used in aquariums to try and stop the death of sea stars, but sadly the antibiotics have just slowed the process down as opposed to stopping the disease altogether.
No cure for the disease has been found, and at this point many researchers have now started to look at the impact of no starfish on the ecosystem instead of looking for a cure due to the massive number of organisms lost already. More research is being done along the coast, and community support and volunteers along with the scientific community are working towards learning more about the disease and what can be done to save the sea stars.
