1. Effects of ocean acidification on the early life stages of
the krill, Euphausia pacifica
Tiffany Barber1, Julie Keister2, Anna McLaskey2, Brady Olson3, Paul McElhany4
1 California State University, Monterey Bay
2 University of Washington, School of Oceanography
3 Western Washington University, Shannon Point Marine Center
4 NOAA Northwest Fisheries Science Center (NWFSC)
We found that CO2 seems to have a strong effect on the development rates
and survival of these early life stages of krill. Waters with 1200 µatm pCO2
(pH 7.6) are occasionally upwelled along the west coast of North America
and develop seasonally in Hood Canal, WA (Feely et al. 2010). This means
that E. pacifica populations may already be occasionally exposed to these
pH levels. As waters with decreased pH expand, krill may be more
susceptible to mortality at early life stages.
Fabry, Victoria J., Seibel, Brad A., Feely, Richard A., Orr, James C. (2008): Impacts of ocean acidification on marine
fauna and ecosystem processes. ICES J. Mar. Sci., 65(3), doi: 10.1093/icesjms/fsn048, 414–432.
Feely, Richard A; Sabine, Christopher L; Hernandez-Ayon, J. Martin; Ianson, Debby; Hales, Burke (2008): Evidence for
upwelling of corrosive "acidified" water onto the Continental Shelf. Science, 320(5882), doi: 10.1126/science.1155676,
1490–1492.
Feely, Richard A; Alin, Simone R; Newton, Jan; Sabine, Christopher L; Warner, Mark; et al. 2 (2010): The combined
effects of ocean acidification, mixing, and respiration on pH and carbonate saturation in an urbanized estuary. Estuar.
Coast. Shelf Sci., 88, doi: 10.1016/j.ecss.2010.05.004, 442–449.
Guinotte, John M., Fabry, Victoria J. (2008): Ocean acidification and its potential effects on marine ecosytsems. New
York Academy of Science, 1134: 320-342, doi:10.1196/annals.1439.013
Ocean acidification (OA) is the decrease in the pH of the Earth's oceans caused by increased levels of carbon dioxide (CO2) in the atmosphere (Feely, et
al. 2008). Previous studies have shown that ocean acidification has negative impacts on growth and development of marine life (Fabry, et al. 2008,
Guinotte, et al. 2008). The early life stages of crustaceans may be particularly vulnerable to this stressor because of the large metamorphoses they must
undergo during their growth to adults. We are studying euphausiids (krill) because they are a primary prey resource for fish (including commercially
important species such as herring, anchovy, and salmon), whales, and sea birds.
Hypothesis Results
Conclusions
References
Methods
Early Life Stages of E. pacifica
 We hypothesized that in a higher CO2 level environment, Euphausia
pacifica will have decreased growth rates and survival compared to krill
raised in current CO2 conditions.
Acknowledgements
We thank the NOAA Office of Education EPP Scholarship for funding and logistic support;
CSU Monterey Bay Undergraduate Research Opportunities Center for logistical support; the
NOAA National Marine Fisheries Services (NWFSC), University of Washington School of
Oceanography, and Western Washington University Shannon Point Marine Center for use of
facilities; and A. Winans, R. Wilborn, E. Bohaboy, and L. Baum for technical support.
 We collected female krill from Puget Sound, WA using a 100 cm diameter
ring net with 2000 µm mesh, towed obliquely in surface waters at night.
 We set up 3 acrylic glass boxes in the 12°C cold
room at Shannon Point with circulating CO2 at:
1) 400 µatm pCO2 (current surface waters)
2) 800 µatm pCO2 (current pycnocline)
3)1200 µatm pCO2 (predicted pycnocline for 2100)
 Each female was placed in a 500 mL jar filled with filtered seawater that
had been conditioned to the correct CO2 for each treatment level.
 We removed females that spawned and counted the eggs in the 12°C cold
room using microscopes and laboratory counters.
 On Day 5, we moved nauplii into petri dishes to a final concentration of 1
larva/20 mL. We changed the water every other day.
 We fed krill Heterocapsa triquetra, at a concentration of 150 mg carbon/L.
 We tracked krill hatching and development to the first feeding stage,
calyptopis 1 (C1), and second feeding stage, calyptopis 2 (C2).
 We tested for the effect of CO2 on hatching and development rate by
statistically analyzing the proportion of eggs that hatched and larvae which
had reached stages C1 by Day 7 and C2 by Day 16.
 We ran 3 trials, each trial for a length of two weeks.
 We used a generalized linear mixed effects model on three response
variables: 1) hatching success, 2) proportion of larvae that developed to
stage C1 & C2, and 3) mortality. Effects included the fixed effect (CO2
treatment) and random effects (jar and trials).
400 800 1200
(8.0) (7.7) (7.6)
pCO2 (µatm)
(pH)
400 800 1200
(8.0) (7.7) (7.6)
pCO2 (µatm)
(pH)
400 800 1200
(8.0) (7.7) (7.6)
pCO2 (µatm)
(pH)
400 800 1200
(8.0) (7.7) (7.6)
P CO2 (µatm)
(pH)
400 800 1200
(8.0) (7.7 ) (7.6)
pCO2 (µatm)
(pH)
By Day 7, mortality was significantly
higher under 1200 µatm pCO2 than at
400 µatm pCO2.
Female Krill Eggs Meta nauplius
Calyptopis 2 Calyptopis 1
By Day 16, mortality
was significantly
lower under 400
µatm pCO2 than at
1200 µatm pCO2.
C1 DevelopmentHatching
Euphausia mortality
C2 Development
Euphausia mortality
As larvae reached the C2
stage, we removed them
from the experiment.
Nauplius1 Nauplius2
Hatching tended to be lower at 400
µatm pCO2 than at 800 and 1200
µatm pCO2.
By Day 7, development was
significantly slower under 1200 µatm
pCO2 than at 400 µatm pCO2.
By Day 16,
development was
significantly higher
under 400 µatm
pCO2 than at 1200
µatm pCO2.