Darcie Ryan, 2010, Geosciences

I investigated the effects of ocean acidification on trichodesmium, a diazotrophic cyanobacteria that lives in the subtropical and tropical Pacific, Atlantic, and Indian Oceans. Because they fix nitrogen and contribute to the ocean carbon pump, the future heartiness and behavior of Trichodesmium as average surface ocean acidity increases are important environmental variables.

With assistance from Professors Francois Morel and Mike Lomas, and Princeton graduate student Dalin Shi, I collected Trichodesmium thiebautii field samples from the North Atlantic Ocean.  Bacterial colonies then incubated in three discrete pH levels: 8.1 (contemporary average surface ocean pH), 7.8 (estimated pH for 2100), and 8.4 (pre-industrial scenario).  The experiment was repeated throughout June, July, and August.  After incubation, samples were analyzed for particulate nitrogen, particulate carbon, particulate phosphate, nitrogen fixation rate, carbon fixation rate, and chlorophyll a concentration per colony.