Ocean Acidification: The Influence of Ocean Acidification and Rising Temperature on Phytoplankton Proteome Composition

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In recent years, a number of studies have demonstrated significant impacts of ocean acidification on the physiology of marine phytoplankton. While the most well-known are studies that have focused on calcifying organisms, there have also been studies on noncalcifying phytoplankton, such as marine cyanobacteria and diatoms. Three particularly notable observations include: 1) increased growth and nitrogen fixation rates with acidification in marine nitrogen fixing cyanobacteria, 2) differences in response between the two most abundant marine cyanobacteria groups, Prochlorococcus and Synechococcus, where the growth of the latter responded positively to the acidification while the former did not, and 3) an increased level of iron stress in marine diatoms and a coccolithophore due to decreased iron availability upon lowered pH and the resultant shift in complexation chemistry. Together these suggest that ocean acidification has the potential for causing large shifts in: phytoplankton community composition, the sensitivity of this community to iron availability, and the marine nitrogen biogeochemical cycle. In this project, a research team at the Woods Hole Oceanographic Institution will investigate physiological mechanisms set into motion by the environmental stimuli associated with ocean acidification by quantifying changes in the proteome of four marine phytoplankton species: the abundant cyanobacteria Synechococcus and Prochlorococcus, the key nitrogen fixing cyanobacterium Crocosphaera, and an Antarctic diatom Nitzschia sp., in response to ocean acidification. In recent years, the team has adapted and developed quantitative proteomic capabilities for marine microbes using liquid chromatography mass spectrometry systems. The approach has become virtually routine and could be applied to a variety of problems related to ocean acidification. In addition, because of the climatic link between ocean acidification and global warming, the synergistic influences of increasing temperature will also be studied.Broader Impacts: This proposed study will provide mechanistic information about how the processes of ocean acidification and warming influence marine phytoplankton. In addition, a Postdoctoral Investigator and Graduate Student will be trained and supported. The project will also feature an outreach program to expose summer minority students from New Bedford, Massachusetts to oceanography and environmental science in partnership with the Eagle Eye Institute and Trustees of the Reservations.