By Matt Axling, Yellow Island Steward
My great grandmother had a tradition of taking a daily swim in the frigid Puget Sound waters. Of all the things she saw during those swims, sea stars were her favorite. Dried sea stars adorned her little beach cabin on Bainbridge Island, and later into her life she would often wear a small sea star pendant on her necklace.
Pisaster ochraceus in the intertidal zone of Yellow Island in Puget Sound. Photo by Heather Van Steenburgh.
When I was a kid, sea stars were always on my radar, probably because of her influence. I remember seeing the pilings under the ferry terminal covered in a tangle of colorful and bumpy appendages. As an adult, I've marveled at their numbers from my kayak.
But Pisaster ochraceus, the iconic purple and orange sea star of the Pacific Northwest (as well as almost every other local sea star variety) has suffered tremendously recently. Sea star wasting disease was first seen in Howe Sound in British Columbia in 2013. Since then, it has spread down the west coast of the United States, and in some areas has killed more than 99 percent of the local sea star communities.
While marine biologists don’t fully understand sea star wasting disease, they do know that warmer temperatures in the coastal waters may have exacerbated its impact. Biologists also recognize that the sea star is a keystone species, and its presence plays a vital role in the delicate balance of the intertidal ecosystem. Without sea stars, the local populations of California mussels and sea urchins have skyrocketed. This, in turn, has negatively impacted native bull kelp forests and other intertidal seaweeds that nourish snails, limpets and bivalves.
On Aug. 10, Nature Conservancy in Washington staff members Emily Howe, Molly Bogeberg, Bryna Mills and a monitoring crew from Port Susan Bay came ashore on our Yellow Island preserve to conduct a census of sea stars in the intertidal zone. The most recent census was conducted by former Yellow Island steward Phil Green in 2009, before the onset of the wasting disease in our waters.
Our census survey on Yellow Island revealed evidence of sea star wasting and lower populations than a 2009 survey. Photo by Heather Van Steenburgh.
Our objective this summer was to compare the data, and we expected a dramatic reduction in numbers. The survey team divided the island up in quadrants and plotted the locations of sea stars within three intertidal zones, looking for Pisaster ochraceus as well as Leptasterias hexactis, a small six-rayed sea star that commonly hides under rocks .
At the end of the survey, the group found a total of 48 Pisaster ochraceus (four of which showed active signs of the disease) and 57 Leptasterias hexactis. Most of the Pisaster ochraceus were clustered together on the rocky tips of Yellow Island’s west spit, and a few were also located at the east spit. In contrast, a decade ago, Phil Green would commonly count 250 Pisaster ochraceus during the summer low tides.
Ecologist Emily Howe looks out over Puget Sound during a survey of sea star health on Yellow Island. Photo by Heather Van Steenburgh.
What does this mean? The findings on Yellow Island are consistent with the precipitous population decline in sea stars throughout the Puget Sound. Having said that, the group actually counted many more Pisaster ochraceus than I anticipated. Anecdotally, I’ve heard locals in the San Juan Islands say that sea stars “are coming back.”
Whether or not that is true remains to be seen. But for now I will hold out hope that my kids and I will be seeing those colorful clusters below the ferry docks again in the not-so-distant future.
