Within the next century, Eastern Boundary Current upwelling systems, which are home to some of the major fisheries that support humans worldwide, are expected to undergo extreme acidification (pH falling to 7.3 or lower) because of increasing atmospheric CO2. Impacts on trace metal (especially iron) and nitrogen bioavailability are likely, and consequently changes in phytoplankton species composition and physiology are also to be expected. One understudied aspect of ocean acidification is its impact on the production of phytoplankton lipids and polyunsaturated fatty acids (PUFA) such as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) and other essential fatty acids (EFA) upon which higher trophic levels depend.
In this project a research team from San Francisco State University, University of Hawaii, and University of Maine will study the effect of extreme ocean acidification (OA) under iron replete and deplete upwelling conditions in regard to changes in species composition, total lipid production, and the specific production of PUFAs. There are two guiding hypotheses: (1) Extreme ocean acidification will increase lipid synthesis and EFA production in phytoplankton through the imbalance between carbon uptake and decreased nitrogen uptake; and (2) Extreme ocean acidification in natural upwelling regions will change the amount and composition of PUFA and EFA produced due either the direct effects of acidified seawater on cell physiology or to marked shifts in phytoplankton community composition. Current Fe-replete and Fe-deplete upwelling zones in the California upwelling region will be investigated to illustrate these impacts. The team will use controlled laboratory monoclonal, semi-continuous culture experiments to subject representative coastal phytoplankton isolates to varying pH and Fe availability to characterize tolerance/success under extreme pH environmental conditions and to quantify cellular physiological response to the combined stressors. In the third year of the project, community-level responses to the same set of stressors will be studied.
Broader Impacts: Because of the global importance of marine fisheries and the as-yet modest understanding of the potential threats of ocean acidification, the topic of this study spans a variety of disciplinary, institutional, academic-government, and national boundaries. Researchers at all three participating institution will lead a variety of public educational outreach activities for the benefit of K-12 students and for society at-large. Graduate and undergraduate students will also be an important part of the research effort.