Responding to Ocean Acidification: The Oyster Emergency Project
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Posted byKirsten Feifel
In response to persistently low shellfish harvests from 2005-2008, the Pacific Coast Shellfish Growers Association (PCSGA) proposed the “Oyster Emergency Project,” a collaboration between regional shellfish growers, NOAA, Oregon State University, and The Nature Conservancy. The goal of the proposal was to identify short-term solutions to enhance hatchery production, establish monitoring programs in key estuaries to better understand changes in the environment, identify resilient oyster genotypes, and identify better tools to detect disease-causing bacteria. Monitoring programs and the development of commercial-scale water treatment systems have proven successful in combating impacts of ocean acidification, although significant challenges remain for Pacific Northwest oyster growers.
In 2005, shellfish growers began to encounter difficulties in rearing hatchery-produced oyster larvae and in successfully setting wild populations of oysters. Preliminary research indicated that increasingly acidic, nutrient replete, deep, upwelled waters could be the cause of the increase in oyster mortalities. The upwelled seawater may retard oyster larval development by dissolving calcium carbonate shells, exposing larvae to gas super-saturated conditions, and harboring increased concentrations of the bacterium Vibrio tubiashii.
To help shellfish growers adapt, PCSGA initiated a targeted research project to identify environmental stressors of oyster populations and to isolate genetic stocks of oysters that offer enhanced resilience. Four projects were proposed:
- Equip hatcheries to treat the chemistry of seawater and evaluate efficacy: Poor water quality caused Whiskey Creek Shellfish Hatchery and Taylor Shellfish Hatchery to have years with low production of oyster larvae. In 2008, a commercial-scale water treatment system was installed at Whiskey Creek to reduce the concentration of Vibrio tubiashii, a bacterium that is harmful to larval oysters. The water treatment system did not increase larval survival, indicating that Vibrio may not be the sole cause of oyster larvae mortality. Larval mortality coincided with periods of intense upwelling, suggesting that changes in seawater chemistry may also be correlated to low production rates. To understand water quality issues in hatcheries, PCSGA proposed to update hatchery water treatment facilities with technologies able to alter the chemistry of large quantities of seawater. Hatcheries will systematically test larval response to changes in seawater chemistry by:
- Continuously monitoring seawater quality: pH, oxidation reduction potential (ORP), temperature, salinity, and dissolved oxygen
- Monitoring water quality before and after each stage of seawater treatment to understand how each treatment step changes water properties
- Conducting simultaneous bioassays with oyster larvae to understand how changes in seawater quality affects larval survival
- Monitor seawater quality in Willapa Bay, WA and Puget Sound, WA to better understand the complexities occurring within the environment: The information gathered provides researchers with a standardized way to compare seawater properties in different estuaries. The datasets will ultimately be correlated with survival and growth rates of oyster larvae to determine those environmental parameters that largely affect oyster populations. The data to be gathered includes:
- Water chemistry (discrete samples - weekly): total alkalinity, total dissolved inorganic carbon, pCO2, pH, nutrient levels, trace elements
- Water chemistry (continuous - hourly): pH, temperature, salinity, dissolved oxygen, ORP
- Vibrio (weekly): total bacteria present, total counts of Vibrio species, assay for presence of pathogenic vibrios
- Assess condition of broodstock (during spawning season - bi-weekly)
- Assess in situ larval performance vs. hatchery larvae (weekly)
- Monitor for harmful algal blooms (weekly)
- Genetic studies to identify resistant oyster broodstocks: Preliminary results indicate that some genetic strains of oysters may be more resistant to environmental stress than others. In 2008, a year of abnormally low oyster production, one specific batch of oyster larvae exhibited lower mortality and higher growth rates at Whiskey Creek Shellfish Hatchery. The more resilient batch of oysters were from a selective breeding program, the Molluscan Broodstock Program, at Oregon State University (OSU). To identify other resilient broodstocks, PCSGA proposes to screen oyster families to isolate oyster stocks that are more resistant to adverse conditions. This project will be done in collaboration with OSU, USDA Agricultural Research Service, and commercial hatcheries. In the future, oyster stocks that are genetically more resistant to stressful environmental conditions will be made available to hatcheries.
- Develop a rapid assay for detection of Vibrio tubiashii: Vibrio tubiashii is a bacterium that can harm larval and juvenile oysters. Despite the substantial economic consequences for exposing developing oysters to Vibrio, a rapid assay for detection has not been developed. PCSGA proposes to develop an on-site, quantitative, rapid tool to detect Vibrio in seawater samples.
As of December 2009, three of the four projects had been funded: monitoring seawater, the genetic study, and developing an assay to detect Vibrio. In spring 2009, Whiskey Creek Shellfish Hatchery initiated their comprehensive water quality monitoring program and in 2011, large-scale buffering systems were installed. Based on the Whiskey Creek model, monitoring stations were quickly established at Taylor Shellfish Hatchery, the Lummi Nation Shellfish Hatchery, and three sites in Willapa Bay. Continuous monitoring systems were also installed at Whiskey Creek, Taylor Shellfish Hatchery, and in Willapa Bay, and provide real-time seawater chemistry data.
Outcomes and Conclusions
The comprehensive water quality monitoring program demonstrated clear evidence of ocean acidification impacts on larval oysters. In response to this information, managers were first able to shift timing of spawning, which resulted in immediate improvements in survival and growth of larval cohorts. Once large-scale buffering systems were installed, hatcheries shifted production cycles to earlier in the year to increase seed production. While buffering systems have greatly improved production, water chemistry issues continue to impact commercial hatcheries; treatment systems are undergoing further development and testing to combat secondary effects of acidification.
Selective breeding efforts are ongoing and, although unlikely to identify larvae totally resistant to acidification, will likely produce larvae with some tolerance. Additional strategies to combat acidification include the construction of new hatchery facilities in remote locations, with the hope that these sites will be less impacted by ocean acidification.
Feifel, K. (2021). Responding to Ocean Acidification: The Oyster Emergency Project [Case study on a project of the Pacific Coast Shellfish Growers Association]. Version 2.0. Product of EcoAdapt’s State of Adaptation Program. (Last updated August 2021)