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Pacific stars disappear due to warm water, disease

Hina Alam, Canadian Press

Published on January 30, 2019 at 17:13 Pacific Time.

Last update Wednesday, January 30, 2019, 17:59 PST

VANCOUVER – Warm waters and infectious diseases have been identified as the causes of sunflower starfish extinction along the Pacific coast, a recent study says.

Sunflower starfish are among the largest starfish in the world and come in a variety of bright colors, including purple and orange. Some of them are more than a meter long and so fast that they “literally run across the seascape,” said senior study author Joseph Gaidos.

“But when this disease happens, it looks like a zombie apocalypse,” said Gaidos of the SeaDoc Society of the University of California at Davis.

“He may have 24 hands, and suddenly he walks, and his hands just fall. And suddenly, the whole body melts.

So, what used to be a “big beautiful sea star” and weighed about five kilograms reminds a pile of calcined parts in a few days, he said.

"This is just an ugly and quick disease for these starfish of the sunflower."

In 2013, scientists began to notice that species populations are declining by 80-100% in deep and shallow waters from Alaska and British Columbia all the way to California. Information about the population was collected by scuba divers and deep trawls.

Sunflower starfish are found in waters from hundreds of meters to three meters.

Diego Montechino-Latorre, co-author of the study, and also from the University of California, Davis, said scientists found a link between rising water temperatures and a decrease in the number of sea stars.

Gaidos said the rise in water temperature was not the same in all areas.

According to him, the oceans “do not look like a bath” with a constant temperature everywhere, adding that in some places in California an increase of about 4 ° C was observed, while in some places in Washington an increase of 2.5 ° C was observed.

One of the theories put forward by scientists is that the rise in temperature makes starfish more susceptible to an existing disease, especially because starfish do not have a complex immune system, he said.

Research co-author Drew Harwell, a professor of environmental and evolutionary biology at Cornell University, said that the heat wave in the oceans caused by global warming aggravates the starfish, which depletes disease and kills starfish faster.

Gaidos said that the starfish of the sunflower are insatiable predators, and when they decrease, the number of sea urchins may increase.

Such disease outbreaks can have a big impact on the entire ecosystem, he said.

“Sea urchins can mow kelp forests, and then when you lose kelp, you lose biodiversity,” he said. "Algae is a place where fish can hide, algae is food for other animals."

Kelp beds were already struggling, he added.

"Algae also do not feel very good when the temperature of the ocean rises, so it looks like one or two blows for algae."

According to Gaidos, one of the ways to help algae is a selective collection of sea urchins, which is being tested in California.

And the opportunity to help the starfish population of sunflower is captive breeding, where you can choose animals that are more resistant to the virus, he said.

Gaidos said that extinction is a wake-up call.

“It’s hard to keep track of what’s happening in the ocean, but we have to pay attention because it happened in a very short period of time,” he said. "Having the whole species almost disappeared is not good."

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