Five years after a mysterious disease began killing millions of
starfish and turning their tissues to mush, the decimated
population has yet to recover. Meanwhile, researchers continue to
struggle to identify a cause for the disease, which appears to have
uncertain ties to viruses and possibly environmental
conditions.
In Puget Sound, it’s not as easy as it once was to find a
diseased sea star, which seems to be a promising sign until you
consider how many have died. As I learned last week during an
outing to Lofall in North Kitsap, the total number of starfish
remains low compared to four years ago, and recovery has been
minimal, if at all.
Under the Lofall dock,
volunteers have observed that the number of sea stars is still low,
but sick ones are no longer common.
Photo: Christopher Dunagan
Local volunteers have been observing sea stars at Lofall since
the beginning of 2014. I first visited the site the following
summer with three retired women who lead the monitoring effort
there. (See
Water Ways , June 17, 2014.) They are still making regular
trips at low tide, counting and measuring the starfish and looking
for signs of disease.
“The numbers are way down,” noted volunteer Barb Erickson as we
stood beneath the Lofall dock last Friday, “but we haven’t seen
many sick ones. We also aren’t seeing the little ones.”
“Still no babies,” commented Peg Tillery, as we arrived at the
Lofall dock in North Kitsap in search of sea stars clinging to
pilings under the dock.
Barb Erickson examines sea
stars at the base of a pier in Lofall on Hood Canal.
Photo: Christopher Dunagan
“They say there’s a comeback of the little ones,” noted Barb
Erickson, “but I’m not seeing any of them.”
Peg and Barb are two of three retired volunteers who first
brought me to this site two years ago to explain their ongoing
investigation into the mysterious “sea star wasting disease.” Since
our first trip, researchers have identified the virus that attacks
sea stars, causes their arms to fall off and turns their bodies to
a gooey mush.
I first witnessed the devastation in June of 2014, when starfish
were dying by the millions up and down the West Coast (Water
Ways, June 17, 2014). Lofall, a community on Hood Canal, was
just one location where the stars seemed to be barely clinging to
life. Now, just a fraction of the population still survives in many
locations.
Bruce Menge of Oregon State University recently reported an
upsurge in the number of baby starfish on the Oregon Coast,
something not seen since the beginning of the epidemic.
“When we looked at the settlement of the larval sea stars on
rocks in 2014 during the epidemic, it was the same or maybe even a
bit lower than previous years,” said Menge in a
news release from OSU. “But a few months later, the number of
juveniles was off the charts — higher than we’d ever seen — as much
as 300 times normal.”
As Peg and Barb pointed out, the recovery at Lofall has been hit
or miss during more than two years of monitoring the site. I became
hopeful on my return trip to the dock in January of 2015, when I
noticed a mix of healthy adult and juvenile sea stars (Water
Ways, Jan. 20,2015).
This week, the young ones were nowhere in sight. Clusters of
healthy adult ochre stars were piled on top of each other at the
bottom of the piers, waiting for the tide to come back in. I was
not sure what to make of it.
Sea stars clusters on two
adjacent piers at Lofall dock.
Photo: Christopher Dunagan
“it could be worse,” Barb said. “I think it is neutral news.”
Peg agreed, saying, “It could be totally worse.”
Summer has been the period of reckoning in past years, and we
should soon know if we are in for another round of disease, which
could kill off more of the surviving sea stars, or if the disease
is finally on the wane.
Linda Martin, who normally compiles the data, was not along on
this week’s trip to Lofall, but other volunteers filled in for
her.
“It is an interesting ride,” Barb told me, referring to her
experience as a so-called citizen scientist. “It connects you to
the larger picture, and you realize that everything is
connected.”
It is nice for people in the community to know that this
volunteer work is taking place, Barb said, and that someone is
watching for changes in the environment.
“People will come up and ask me if there is anything new, people
who couldn’t have cared less before,” she said.
For those interested in this kind of volunteer work, a good
place to start is Kitsap Beach Naturalists. One can contact Renee
Johnson, program coordinator, at rkjohnson@co.kitsap.wa.us.
Meanwhile, the cause of sea star wasting disease remains
somewhat of a mystery even after its connection to the densovirus,
which is associated with dead sea stars but also has been found in
some that are free of disease.
A laboratory study
led by Morgan Eisenlord of Cornell University found that the
disease progressed faster when adult sea stars were exposed to
higher temperatures and that adult mortality was 18 percent higher
when water temperatures reached 66 degrees F. Temperature was
documented as a likely factor in the spread of disease through the
San Juan Islands.
But temperatures are not the sole controlling factor, because
the spread of the disease has been out of sync with temperature
change in numerous locations.
“The sea temperatures were warmer when the outbreak first
began,” Menge said, “but Oregon wasn’t affected as early as other
parts of the West Coast, and the outbreak reached its peak here
when the sea temperature plummeted and was actually cooler than
normal.”
Could there be another trigger that increases the virulence of
the densovirus?
“Ocean acidification is one possibility, and we’re looking at
that now,” Menge said. “Ultimately, the cause seems likely to be
multi-faceted.”
