Planktonic interactions in a changing ocean: Biological responses of Emiliania huxleyi to elevated pCO2 and their effects on microzooplankton

Western Washington University, Bellingham WA

Investigators

Abstract

The calcifying Haptophyte Emiliania huxleyi appears to be acutely sensitive to the rising concentration of ocean pCO2. Documented responses by E. huxleyi to elevated pCO2 include modifications to their calcification rate and cell size, malformation of coccoliths, elevated growth rates, increased organic carbon production, lowering of PIC:POC ratios, and elevated production of the active climate gas DMS. Changes in these parameters are mechanisms known to elicit alterations in grazing behavior by microzooplankton, the oceans dominant grazer functional group. The investigators hypothesize that modifications to the physiology and biochemistry of calcifying and non-calcifying Haptophyte Emiliania huxleyi in response to elevated pCO2 will precipitate alterations in microzooplankton grazing dynamics. To test this hypothesis, they will conduct controlled laboratory experiments where several strains of E. huxleyi are grown at several CO2 concentrations. After careful characterization of the biochemical and physiological responses of the E. huxleyi strains to elevated pCO2, they will provide these strains as food to several ecologically-important microzooplankton and document grazing dynamics. E. huxleyi is an ideal organism for the study of phytoplankton and microzooplankton responses to rising anthropogenic CO2, the effects of which in the marine environment are called ocean acidification; E. huxleyi is biogeochemically important, is well studied, numerous strains are in culture that exhibit variation in the parameters described above, and they are readily fed upon by ecologically important microzooplankton. Intellectual Merit The implications of changes in microzooplankton grazing for carbon cycling, specifically CaCO3 export, DMS production, nutrient regeneration in surface waters, and carbon transfer between trophic levels are profound, as this grazing, to a large degree, regulates all these processes. E. huxleyi is a model prey organism because it is one of the most biogeochemically influential global phytoplankton. It forms massive seasonal blooms, contributes significantly to marine inorganic and organic carbon cycles, is a large producer of the climatically active gas DMS, and is a source of organic matter for trophic levels both above and below itself. The planned controlled study will increase our knowledge of the mechanisms that drive patterns of change between trophic levels, thus providing a wider array of tools necessary to understand the complex nature of ocean acidification field studies, where competing variables can confound precise interpretation. Broader Impacts This research project will provide support for two early-career scientists, a graduate student, and numerous undergraduate students. Undergraduate student involvement will come largely from SPMCs long-standing two resident programs: the award-winning Multicultural Initiative in the Marine Sciences: Undergraduate Participation (MIMSUP) and Research Experience for Undergraduates (REU). The mission statement of the MIMSUP program is to increase diversity within the next generation of marine scientists through coursework and research. Students participating in MIMSUP conduct independent research projects, present at national and international meetings, and conduct community outreach. The REU program provides the portal for our research to reach a nation-wide audience;just last year SPMC received 118 REU applications representing 90 different universities. Undergraduates from WWUs Biology and Environmental Science departments will also participate in this research through courses taught by the project PIs. Finally, SPMC has received funding to hire a K-12 outreach coordinator who will develop a series of workshops, public lectures and presentations, and contributions to K-12 curriculum. Findings from this research will be incorporated into all of these outreach efforts.