Lija Treibergs, 2011, Geosciences

My project involved studying the stable isotope fractionation of nitrogen during nitrate uptake and assimilation in both a lab grown diatom culture and in a field experiment from nitrate limited water of the Sargasso Sea. The lab culture was grown in order to model an isotope fractionation curve typical of nitrate uptake in a nitrate limited system. The field experiments and samples, which were taken during a seven-day research cruise out of the Bermuda Institute of Ocean Sciences (BIOS), will be analyzed to give insight to the nitrate sources in the Sargasso Sea. Nitrate, which is a vital nutrient to the photosynthetic plankton living in the surface ocean, is quickly used up in the subtropical Sargasso Sea due to the abundance of sunlight and therefore high levels of photosynthesis and is one of the limiting factors to photosynthetic production in this region. Nitrogen cycling and sources have been studied in the Sargasso Sea, but my project aimed to study this cycling in further detail by sorting the bulk phytoplankton biomass by species via flow cytometry and looking at the individual species’ sources of nitrate