Ocean Acidification Effects on Calcifiers 

Effects of Ocean Acidification on Declining Puget Sound Calcifiers

Examining five ecologically and economically important bivalves, researchers found these species exhibit different susceptibility to increasing CO2 levels. Under the conditions tested, clams were relative winners and oysters losers.

Principal Investigator

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

Co-Principal Investigators

Simone Alin, NOAA Pacific Marine Environmental Laboratory

Jonathan Davis, Taylor Shellfish Farms, Inc.

Ralph Elston, Aquatechnics, Inc.

Richard Feely, NOAA Pacific Marine Environmental Laboratory

Steven Roberts, University of Washington, School of Aquatic and Fishery Sciences

Brent Vadopalas, University of Washington, School of Aquatic and Fishery Sciences



Washington Sea Grant-funded laboratory experiments examined the responses of five bivalve species (Olympia oyster, Pacific oyster, pinto abalone, geoduck clam, and Manila clam) to combinations of three stresses: dissolved carbon dioxide, elevated water temperature, and exposure to the bacterium Vibrio tubiashii. Researchers also used their work as the basis for a high school biology curriculum on acidification.

Research Updates


Ocean acidification has arrived in the Pacific Northwest at levels surpassing end-of-century predictions. Understanding its effects on ecologically and economically important marine shell-builders is imperative, especially in vulnerable early life stages, during adult reproduction, and carry-over effects from parent to offspring.


As dissolved CO2 levels were increased, V. tubiashii reached pathogenic bloom levels faster but did not show greater pathogenicity. Larval and juvenile Manila clams and juvenile geoducks did not show any adverse effects from increased CO2in the range tested. Exposed adult Olympia oysters saw delayed larval release and reduced fecundity. When broodstock were conditioned and held at the same CO2 levels as their parents, they suffered no effects on survival, growth, or shell morphology. However, a measurable change in gene expression suggests that growing up in more acidic environments may be energetically costly. Larval Pacific oysters and pinto abalone fared worst when matured under low CO2 but exposed to high-CO2 upwelling events; such events may be more stressful than gradual increases in CO2.


Dorfmeier EM (2012) Ocean acidification and disease: How will a changing climate impact Vibrio tubiashii growth and pathogenicity to Pacific oyster larvae? MS thesis, University of Washington, Seattle, WA.

Metzger DCH (2012) Characterizing the effects of ocean acidification in larval and juvenile Manila clam, Ruditapes philippinarum, using a transcriptomic approach. MS thesis, University of Washington, Seattle, WA.

Ocean Acidification. Research notes from the School of Aquatic and Fishery Sciences. Friedman C (ed). University of Washington School of Aquatic and Fishery Sciences. http://safsoa.wordpress.com/. Created November 2011.

Timmins-Schiffman EB, Friedman CS, Metzger DC, White SJ, and Roberts SB (2013) Genomic resource development for shellfish conservation concern. Molecular Ecology Resources, 13(2):295–305.

Timmins-Schiffman EB, O’Donnell MJ, Friedman CS, Roberts SB (2013) Elevated pCO2 causes developmental delay in early larval Pacific oysters, Crassostrea gigas. Marine Biology, 160(8):1973-1982.