Scientists measure nutritional quality and toxicity of phytoplankton in corrosive waters
On June 6, Dr. Vera Trainer and a
team of scientists returned from a 25-day ocean acidification expedition
off the West Coast aboard the R/V Melville in an effort to measure how
changes in our ocean's acidity may affect the marine food web—starting
with phytoplankton, the base of the food chain and the "salad of the sea".
The cruise from San Francisco, CA to Seattle, WA is part of a project
funded by the National Science Foundation to help scientists study, for the
first time, how phytoplankton in the ocean responds physiologically to pH
The scientists are specifically interested in finding out what happens to
the quality of the nutrition that phytoplankton provides to the entire marine
food chain, up to the humans and other seafood consumers who eat fish
and shellfish. What happens to their nutrient supply and lipid content (think
heart-healthy omega-3s)? The lower the food quality, the less nutritional
the diet to fish and other organisms up the food chain. Will nutrient-limited
phytoplankton also become more toxic (think harmful algal blooms)?
A collaborative study
Dr. William Cochlan led a collaborative team of scientists from
Francisco State University (lead institution), NOAA-Northwest Fisheries
Science Center (Vera Trainer, Brian Bill and Kathryn Ferguson - a NOAA
NOAA-Pacific Marine Environmental Lab (Dick Feely
and Simone Alin),
University of Main, Western University (Canada)
University of Washington Northwest Association of Networked
Ocean Observing Systems,
University of Hawaii, and
University of Rhode
Island. Two Teachers-at-Sea from Texas and Tennessee also joined the
Basics of ocean acidification
The cold, nutrient-rich waters that upwell along the U.S. West Coast make
our region a natural, living laboratory for studying the effects of chemical
changes in the ocean, particularly the changes brought on by increased
atmospheric carbon dioxide.
This excess carbon dioxide is absorbed by our oceans and leads to
chemical changes that make it more acidic. Ocean acidification makes
it harder for many marine creatures to develop normally and survive,
because it disrupts the calcification process of shell-producing organisms,
such as krill, oysters, sea urchins, and corals. These changes can lead to
a ripple of effects up the marine food chain to seafood consumers like us.
The scientists aboard the R/V Melville sampled waters from the deep,
upwelled zones off our coast, since these waters naturally have a lower pH
and may be an indication of the level of ocean acidity in the future.
Sampling at sea
The research vessel traversed coastal waters that represented low pH,
upwelling zones along Point Sur and Point St. George off the California
coast, as well as higher pH, post-upwelling (relaxed) waters off Heceta
The team encountered a large bloom of Pseudo-nitzschia, the organism
that produces domoic acid that can kill sea lions, sea otters, sea birds and
humans and has closed the Washington coast razor clam fishery for a
year. Scientists will analyze the amount of domoic acid present in the cells
found at these two low pH sites to help determine if phytoplankton become
more toxic in culture with lowered pH under nutrient stress.
At the Heceta Bank, Oregon site, the team encountered two other
toxic phytoplankton species, Alexandrium, a historically toxic organism
to this region that can cause paralytic shellfish poisoning in humans, and
Dinophysis, that caused the first ever diarrhetic shellfish toxin event in
the U.S. in Sequim Bay in 2011. Here again, the scientists are trying to
determine the possibility of these cells becoming more toxic in a future, low
The data collected on this expedition will undergo further analysis and
review, but will eventually help give us a better understanding of the
effects of a future acidifying ocean on our entire marine food web-- from
phytoplankton, to fish and fisheries, to the seafood on your plate.
Stay tuned for more stories on this topic and learn more about our work by
visiting our page on Harmful Algal Blooms.