A physical copy of the article
Before 2013, the Pacific coast of North America was rich in ocean stars – about 30 different species, from deepwater inhabitants to the purple or ocher sea stars of the intertidal zone. Then, in the summer of that year, scientists and others watched horrified as one of the greatest deadly mortals in modern history who played before them. From Mexico to Alaska, the stars of the sea have dried up and died, their bodies melting into mush, so nothing but ass and thorns remain.
Over the next two years, when geographically diverse populations continue to crash, scientists have created the term "Sea Star Destroyer Disease" (SSWD), which refers to the unexplained forces that caused devastation. SSWD now leaves wasting untold millions of sea stars along the coast, although some areas and species have been heavily hit by others. Sunflower star, a once abundant species, is now extinct locally for most of its natural range, from British Columbia to California.
Now a new study led by Drew Harvel, an ecologist and evolutionary biologist at Cornell University in Ithaca, New York, examines the complexity of factors that seem to cause an epidemic. For existing coastal survey observations, he added data on marine star biomass collected by deep-sea trawl conducted between 2004 and 2016 – information on the occurrence of the population before and after the outbreak. For both deep and coastal environments, the hot sea wave connects the virus and the virus, called the sea star denziries, with the sudden destruction of sunflower stars.
"The temperature is great for this disease, and infectious microbes are healing at warmer temperatures," says Harvell. "Sea stars do not have a chance when it's hot."
Although ocean warming seems to play a role in worsening the disease, as more and more research and data comes, every tidy and unified response to the single factor or combination of factors caused by SSWD has proven to be unclear.
"When you look at some of these big outbreaks we had in the past, it takes a long time before we get to the final answer," Harvell says. "I think there are many opinions right now, but unfortunately there was not enough money to investigate the causative agent."
For different species of sea stars, it seems that the different elements have led to the same catastrophic results. Although the virus seems to have spelled the doom for sunflowers stars, other sea stars are not affected by it. For them, environmental suspects such as drought, pollution and bacteria are suspected.
But the masses die clearly reveals the vital role of the sea star while maintaining balance in their ecosystems. In recent years, for example, North California has lost 90 percent of its once-giant kelp forests. As the sea star population collapsed, the number of algal purple hedgehogs – a popular prey of sunflower stars – increased 60 times. As a result, biosexual algae-dependent ecosystems are now replaced by infertile infertile waterways, underwater areas covered with pointed purple creatures.
Since the highest cause of SSWD is not known, scientists are not sure whether the sea star population will eventually return. Due to the large geographical range of the epidemic and the varying rates of mortality, it is likely that some populations may recover. There are already some promising flashes. Survival rates for children's marine stars of many species have risen dramatically along parts of the Oregon coast, although it has to be seen how many of these juveniles survive to maturity.
However, Harvell and her colleagues note that denzoviruses are still lurking in some flexible populations prepared to leap from asymptomatic carriers to susceptible teenagers. The total return to Starfleet's abundance before 2013 is unlikely, says Harvell.
Despite the massive death and continuing, though significantly reduced presence of SSWD, some scientists, such as Cornell University Marine Coroner Ian Hewson, continue to hope that sea stars can eventually recover by adapting to new environmental conditions.
Hewson, not associated with Harvel's team, says that animals such as sea stars, which are rapidly reproducing and having large amounts, are rapidly adapting to environmental changes.
"It's like the quote Jurassic Park"Life finds a way," he says. "That might be the case for sea stars."
* The authors of the study include researchers with the Hakai Institute. Data from the Hakai Institute monitoring projects were also used in the study. Institut Hakai a Hakai Magazine are both components of the Tula Foundation. The journal is independent from the Institute and the Foundation.