Tracking Oysters Around the Sound

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Associate Professor Bonnie Becker uses innovative technique to track native Olympia oysters with team of local partners, students.
Associate Dean of Curriculum and Academic Initiatives and Associate Professor Bonnie BeckerAssociate Professor Bonnie Becker has received a $210,000 Washington Sea Grant award to study the Olympia oyster, or Ostrea lurida, a rare species native to Puget Sound. But, she confesses, “To be honest, and you can write this, I like the (non-native) Pacific Oysters more for taste.”
Becker’s project involves using the relatively new technique of “trace elemental fingerprinting” to track populations of Olympia oysters. Local conservation groups will use data from the experiment to determine where to focus their habitat restoration efforts. 
The two-year project began February 1, 2015. Becker and her team of students and partners will take samples around Puget Sound beginning in May and through the summer, then spend the following period analyzing the results. 
Groups like the Puget Sound Restoration Fund, a nonprofit and partner on the study, are working to restore the Olympia oysters, in large part for their habitat value. The muddy bottom of Puget Sound is difficult for many aquatic species to live on or attach to. A reef of oysters provides a habitat for anemones, seaweed and other sedentary life. “There are a lot of critters that like to live on Olympia oysters that salmon like to eat,” adds Becker.  Additionally, many environmentalists philosophically support restoring Puget Sound to its natural state, and commercially, some groups are looking to start harvesting the Olympia oysters again. 
Olympia oysters once formed a “bathtub ring around the muddy bays of Puget Sound,” Becker says. But their numbers dwindled, in large part due to overfishing and water pollution from the 1850s to 1940s. The heartier Pacific Oysters were brought in, but they became an added hurdle to the Olympia oyster population, as they pushed the Olympia oysters out.
Muddy students from one of Becker's previous research projects last summer.
The restoration groups will use data from Becker’s study to direct their work. “If they restore a site over here, they want to know, first of all, if that site is going to be able to self-persist…. Second of all, if they restore a site over here, is that going to help bring back the population next door?” says Becker.
“It’s not a theoretical question,” she adds.
Becker’s research will use trace elemental fingerprinting, a relatively new technique that creates a “fingerprint” for oysters from one location and uses it to track their movement. Oyster larvae are typically very difficult to track due to their small size and high mortality rate. Some researchers have tried to stain them, but “the numbers just don’t work out,” says Becker. “You have to stain an unbelievable number of them to catch any.” 
Instead, she and her team are “letting nature provide the tag,” Becker says. As they grow, oyster larvae form a shell of calcium carbonate that takes on some of the surrounding elements, like strontium or magnesium.  
“If you had some oysters in a bay full of lead, you’d expect some extra lead in the shell. Most of the time it’s not that straightforward,” she says. 
The team will collect “fingerprints” from all over Puget Sound, then compare samples to fingerprints found in oysters found in Dyes Inlet, on the Kitsap Peninsula, and Fidalgo Bay, near Anacortes. Both locations are already sites of Olympia oyster restoration. 
Olympia oysters can switch between being male and female. When they are males, they spit sperm into the water and females take up the sperm from the water into their shells, where fertilization occurs. "It’s not very romantic," Becker says. The females hold the resulting larvae inside their shells for several weeks, during which the research team will scrape out larval samples, taking care to keep the mothers alive.
Oyster mothers then spit out the larvae, which float around the Sound for several weeks until they settle and attach themselves to the sea floor. These “settlers” retain their larval shell as they grow, which still has the same fingerprint that they had as larvae. Becker and her team will then take samples of settled oysters, comparing the chemical signatures of these shells to their earlier samples.
This experiment builds upon Becker’s previous work; she was one of the first to use trace elemental fingerprinting on an invertebrate, when she studied mussels in San Diego Bay for her dissertation. Henry Carson, a partner on the project and fish and wildlife biologist with the Washington Department of Fish and Wildlife, had done a similar experiment afterward in San Diego on oysters.
“It’s really the bringing together of work that I’ve done in the past and my collaborators have done in the past, and bringing it together in Puget Sound,” says Becker.
Becker will work with her students in her research class during Spring Quarter and a team of a master’s student and four undergraduates over the summer. 
Ostrea Lurida
“They’re going to be doing all levels of this work, from field work to chemistry and using a laser to sample the chemistry. It’s students the whole way,” Becker says. 
The study is a collaboration with many community partners, including Puget Sound Restoration Fund, the Department of Fish and Wildlife, the UW School of Aquatic and Fishery Sciences, and the Northwest Indian College, as students from that institution will also participate in the experiment. Funding was provided by Washington Sea Grant, with matching funds provided by the Center for Urban Waters, Interdisciplinary Arts and Sciences at UW Tacoma and the Samish Indian Nation.
Becker hopes to also gain involvement from students and the Puget Sound Community. “Being part of a large-scale effort to restore a native species, I think is an important service learning opportunity… to understand the history and the future of Puget Sound,” she says.
Written by: 
Abby Rhinehart / April 24, 2015
Media contact: 

John Burkhardt, UW Tacoma Communications, 253-692-4536 or