Acidification effects on crustacean zooplankton

Effects of Ocean Acidification on Trophically Important Crustacean Zooplankton of Washington State

Researchers quantified the differential growth and survival rates in acidified waters of zooplankton species that are fundamental to the marine food web. Throughout the project, the team engaged hundreds of citizens, journalists, teachers, legislators, and schoolchildren in the issue of ocean acidification.

Principal Investigator

Julie Keister, University of Washington, School of Oceanography

Co-Principal Investigator

Paul McElhany, NOAA/NMFS Northwest Region


Washington Sea Grant-supported research combined laboratory experiments and local field observations to investigate acidification’s effects on the early growth, survival, and vertical distribution of two important zooplankton species, the copepod Calanus pacificus and krill Euphausia pacifica. Species-response information from experiments is being used to inform existing regional food web models.

Research Updates


Crustacean zooplankton are the prey base for most fish, but little is known about how they will be affected by ocean acidification. Research to date has revealed mixed, highly species-specific responses; nothing has been published on effects in the acidification-impacted waters of Puget Sound. Quantifying these effects is critical to fisheries management and predictive ecosystem modeling. At the same time, motivating changes in thinking and behavior that will lead to effective policies that address the underlying problem requires public education about this and other impacts.


Calanus pacificus’s hatching success declined significantly in high-CO2 water, but its growth was not significantly affected. Euphausia pacifica showed robust hatching across a wide pH range, but its early development slowed significantly at CO2 levels that occur in Puget Sound’s bottom waters during summer. Because these species and their congeners are important in food webs worldwide, the data have broad significance. Researchers engaged legislators, journalists, teachers, and the general public through activities that included speaking at public and private events, involving citizens in the research, and hosting science displays.


Keister J (2013) “Lightning Talks: Julie Keister – The effects of ocean acidification on the Puget Sound ecosystem.” March 31, 2013.

Keister JE, McLaskey A, Raatikainen L, Winans A, Herrmann B (2013) Species diversity in zooplankton responses to hypoxia and elevated pCO2. Oral presentation at the North Pacific Marine Science Organization, PICES 2013 Annual Meeting, Nanaimo, British Columbia, Oct. 11-20, 2013.

Keister JE, McLaskey A, Raatikainen L, Busch S, Winans A, McElhany P (2012) Oxygen and pH conditions experienced by zooplankton in a North Pacific fjord: Impacts on taxonomic composition, distributions, and growth. Oral presentation at the North Pacific Marine Science Organization, PICES 2012 Annual Meeting, Hiroshima, Japan, October 12-21.