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Before 2013, the Pacific coast of North America was rich with sea stars – about 30 different species ranging from Dubrovnik residents to purple or ocher sea stars in the tidal zone. Then, in the summer of that year, scientists and others watched with horror one of the biggest marine extinctions in the modern history that was happening to them. From Mexico to Alaska, the starfish starved and died, and their bodies melted into the jug, leaving behind nothing but the head and the spine.
Over the next two years, as geographically diverse populations continued to fall, scientists came up with the concept of Sea Star Losers (SSWD) to refer to the inexplicable forces that caused the devastation. The SSWD has now devastated the unexplored millions of sea stars along the coast, though some areas and types are harder to hit than others. A sunflower star, a once-rich species, is now extinct locally in much of its natural range, from British Columbia to California.
Now, a new study led by Drew Harvell, ecologist and evolutionary biologist at Cornell University in Ithaca, New York, examines a complex blend of factors that seem to trigger an epidemic. For the already existing observations for coastal samples, the team added data on the biomass of marine stars collected in deep-sea brakes from 2004 to 2016 – information that includes populations before and after the outbreak. Both in the deep and coastal environment connect the marine wave of heat and the virus, called densovirus associated with the sea star, with a sudden decay of sunflower star.
"Temperature is a big deal for the disease; infectious microbes achieve a better temperature, "says Harvell. "Sea stars have no chances when it's warm."
Although ocean warming seems to play a role in the worsening of the disease, as more and more research and data continue, any neat, unique response to what each factor or combination of factors caused by SSWD has proved to be unattainable.
"When you look at some of these major epidemics we've had in the past, it takes a lot of time to reach the final answer," says Harvell. – I think there are many different opinions right now. Unfortunately, there were not many resources to investigate the cause. "
Different elements of the sea star seem to have led to the same catastrophic results. Although the virus seems to have been devastated by the sunflower star, other types of sea stars have not been affected. They are suspected that environmental factors such as drought, pollution, and bacteria have played an important role.
But massive descent clearly reveals the vital role of marine stars in maintaining balance in their ecosystems. In recent years, North California, for example, lost 90 percent of its former forests of Kelpa. As the starfish populations collapsed, the number of pink jeeps – the favorite prey of sunflower stars – increased by 60 times. As a result, biologically diverse ecosystems, dependent on sea lawns, are now replaced by lobsters, underwater spatial areas covered with pointed purple creatures.
Since the ultimate cause of the SSWD is unknown, scientists are not sure whether the starfish population will return. But given the large geographical range of epidemics and the variable mortality rate, it is likely that some populations could recover. There are already some hope in hope. The survival rate of baby starfish of many species increased dramatically along parts of the Oregon coast, for example, although it remains to be seen how many these minors will survive until maturity.
However, Harvell and her colleagues note that densovirus is still in some resilient populations, ready to jump from asymptomatic carriers to vulnerable juveniles. The general return to the abundance of sea stars before 2013 seems unlikely, says Harvell.
Despite the mass extinction and the sequel, albeit significantly reduced, the presence of SSWD, some scientists such as Marine Microbiologist Cornell Ian Hewson continue to hope that sea stars will eventually recover by adapting to new environmental conditions.
Hewson, who was not related to Harvell's team, says animals like fast-paced shark stars, often adapting to a large extent quickly adapt to environmental change.
"It's like a quote from Jurski park, "Life finds the way," he says. "That could be the case with the sea stars."
* Authors of studies include researchers at the Hakai Institute. The study also used data from the Hakai Institute monitoring project. Hakai i Magazine Hakai are part of the Tula Foundation. The journal is editorially independent of the institute and foundation.