Scientists investigating the epidemic afflicting the Pisaster sea stars common in our waters met in Seattle last week to discuss the latest findings, and there wasn’t much good news to share.
“This is, if not the, certainly one of the biggest wildlife die-offs that have ever been recorded,” Dr. Martin Haulena, veterinarian with the Vancouver Aquarium told the CBC after the workshop, “and we’re not just talking marine die-offs.”
Haulena, in the CBC report, called the Pisaster a “keystone species” – a species whose presence controls the ecosystem they live in to a large degree – and said its drastic change in population, “has ramifications up and down the food chain.”
In 2014, scientists isolated the virus they are relatively certain is causing the disease, which essentially causes the sea star to disintegrate into slime, but they still don’t know what caused the outbreak, how exactly the virus gets into the animal, or why the virus – which has been found preserved in perfectly healthy sea stars for decades – is suddenly causing the scourge.
Sandra Milligan, who teaches biology here in Campbell River at North Island College and has been studying the Pisaster’s decline extensively at Willow Point Reef over the years, says it was “definitely shocking” when the mass die-off began a couple of years ago, but our area doesn’t seem to have been hit as hard as others.
“The situation here does not seem to be as bad as in the CBC report,” Milligan says, “though the numbers are quite low.”
“I’ve been out for the last few good low tides and a ball park estimate would be that we have maybe 25 to 50 per cent of the population numbers that were present three years ago.”
But she also says there is some evidence to suggest the population – at least at Willow Point Reef – is rebounding somewhat.
“We have seen quite a few juvenile Pisaster in the last few months,” she says, and at a walk with her biology class in November, they saw four juvenile Pycnopodia (the very large sunflower sea star), which she says, “were absent from the reef for all of 2014 and summer of 2015.”
So Milligan, at least, is being somewhat of an optimist about the whole situation.
“I tend to be someone who thinks about changes to the planet in terms of thousands of years, rather than year-to-year,” she says. “Two similar die-offs occurred in Oregon in the 1980s and 1990s.
“In some locations it took up to 15 years for the Pisaster to come back to original numbers,” but they did come back.
Maybe they will this time, too.
