Determining Whether Native Eelgrass and Pacific Oysters Synergistically Enhance Their Environments

Researchers assessed whether Zostera marina and Crassostrea gigas are potential partners in a changing ocean.

Principal Investigator

Carolyn Friedman, University of Washington, School of Aquatic and Fishery Sciences

Co-Principal Investigators

Meg Chadsey, University of Washington, Washington Sea Grant

Colleen Burge, University of Maryland Baltimore County

Drew Harvell, Cornell university

Brady Blake, Washington Department of Fish and Wildlife


Eelgrass wasting disease (EGWD), which may be caused by the pathogen Labyrinthula zosterae, negatively affects eelgrass beds along the West Coast. In the Pacific Northwest, eelgrass and shellfish cultures often grow in the same place. This project focuses on a potential benefit of co-culture: filtration services of oysters to improve the health of eelgrass beds, potentially reduce pathogen loads, and improve local water quality. Different strains of Labyrinthula were analyzed for virulence and responses under different conditions (i.e. temperature, pH, and shellfish presence) were considered. The results provided the shellfish industry, tribes, resource managers, and the public with key diagnostic and genomic resources that promoted sustainable shellfish culture in Washington State.

Research Updates


Eelgrass plays a critical role in Washington’s marine ecosystems, as eelgrass beds stabilize shorelines and provide food, shelter and habitat for organisms, including juvenile salmon and herring. However, eelgrass is declining in many areas of the state, and eelgrass wasting disease (EGWD)—caused by the pathogen Labyrinthula zosterae—is a possible culprit. Washington Sea Grant-funded researchers began an investigation on the threat of EGWD to local eelgrass, how this threat may change with warmer and acidified waters, and whether shellfish living within eelgrass beds could help mitigate the situation.

Results Thus Far

Of the 14 Labyrinthula strains investigated, 4 did not produce signs of EGWD, 3 resulted in low-to-moderate infections, and 7 produced severe infections evidenced by widespread tissue damage. The researchers discovered that an individual eelgrass does not need to be in contact with another individual in order to spread the disease, suggesting the pathogen can spread through the water column. Temperature makes a difference: widespread infections occurred more quickly at 15 than at 7.5 degrees Celsius. The surveys showed EGWD prevalence levels exceeded 65 percent at all but one of the 10 sites, indicating widespread, high levels of the disease in Washington.

Project Outreach

Project investigators collaborated with science communicator Tullio Rossi of Animate Your Science on an animated short to share this exciting research with broader audiences. The 4.5 minute video Seagrass Wars: The Spots Awaken tells the story of Simon the Salmon and his intrepid oyster friends, who become alarmed when mysterious spots threaten the health of their beloved eelgrass home, and hatch a plan to fight back. Will they prevail, or will the spots gain the upper hand? Time (and research) will tell… but in the meantime, visit the Seagrass Wars webpage to learn about oyster superpowers and catch up on the latest eelgrass wasting disease science. Then take The Sequel Challenge and let us know how you think eelgrass will fare in a warming world. Learners of all ages will enjoy the interesting and inspiring content on this page, and educators will find age-appropriate resources to share with their students.