Oyster Restoration and Algae Blooms Under Study at Penrose State Park

Pierce County, the University of Washington Tacoma, Harbor WildWatch, Coastal Conservation Association and the Washington Department of Fish and Wildlife are all working together at Penrose State Park to study restoration of native Olympia oysters in Puget Sound to improve habitat. The work also includes studying the impact of blue-green algae blooms from nearby Bay Lake.

Jeff Barney, watershed planner for Pierce County Planning and Public Works Floodplain and Watershed Services, is managing the pilot project. “We created a lab at Penrose. The partnerships have been amazing,” he said.

The team selected five sites along the shore north of the Penrose spit. In September 2020 each 10-by-10 foot site was covered with a cubic yard of oyster shells. Twelve hundred juvenile oysters were laid on top and the site was monitored to evaluate oyster survival and the status of the oyster shell substrate.

Mike Behrens, professor of biology at Pacific Lutheran University, is the lead for the project.

“People walk the beaches, see oysters growing here and think everything is great,” Behrens said. But most of those oysters are nonnative Pacifics, imported from Asia many years ago. A hot summer in 2015 made the water warm enough to allow Pacific larvae to survive, attach to substrate on local beaches, and grow.

The Olympia, the only native oyster in Washington, is a rarity. They were wiped out by overfishing in the late 1800s. Behrens said that Gold Rush miners in San Francisco, eager to show off their wealth, ate the diminutive bivalve mollusks by the dozens. “It takes a lot of Olympias to make a Hangtown Fry,” he said.

The purpose of Olympia restoration is to improve the health of the Puget Sound ecosystem rather than growing oysters to harvest, Behrens said. Olympias grow much more slowly than Pacifics, rarely reaching the 3-inch size required for harvesting. But healthy beds filter the water, serve as habitat and provide foraging opportunities for other species, including salmon.

There have been a number of oyster restoration projects, but Barney said this is one of the few that focus on studying what happens over time when oysters are planted, and that further study would be helpful.

Behrens expected that the number of oysters surviving would be small but that the loss would be gradual due to desiccation from exposure and temperature. The main predators would typically be sea stars, but that population has been devastated by a wasting disease, he said. What he did not account for was the number of red rock crabs that have moved in — a possible increase in population as a result of closing crabbing in the area for the last two years.

In the first month, between 85% and 95% of the oysters were gone, and by the fourth month the best bed had only 6% survival.

Behrens said mixing the juvenile oysters into the substrate shells could have a protective effect. The two most successful sites had better shell substrate stability. Water flow from tide and wave action dispersed the shells, and they sank into the sand. A site that is somewhat protected and has a rockier beach will likely be more successful.

In addition to the oyster restoration project, Behrens is studying oyster recruitment. Stacks of oyster shells are held in place with dowels at seven sites along the shore. Every two weeks his team evaluates them to see if oyster larvae — either Olympia or Pacific — have attached to the shells. Recruitment so far has been minimal, he said.

Behrens also said that having an adult population of Olympias may increase recruitment and survival, possibly from chemical interactions comparable to pheromone action. He said a restoration project in Fidalgo Bay showed slow growth for years and then suddenly took off.

In 2013, Harbor WildWatch established a community science program to monitor a swath of beach at the Penrose spit. Twice a year people go to observe changes in marine life and the beach slope. “We joke that our volunteers range from 8 to 80,” said Behrens, who is one them.

“The project bolsters the work that Harbor WildWatch does with their community science program,” Barney said. “The (pilot project) grant is not huge, but it included small stipends to pay for student projects.”

Finally, in conjunction with the Tacoma-Pierce County Health Department, Barney is working to understand the impact of blue-green algae blooms from Bay Lake. TPCHD monitors Bay Lake weekly for the toxic algae from Memorial Day through Labor Day. If a toxic bloom is identified TPCHD will collect water samples weekly at Mayo Creek and Mayo Cove and collect tissue samples from mussels growing in cages in Mayo Cove. Barney said there were no blooms last year, and TPCHD has not reported any this season.