Investigating eukaryotic phytoplankton in Bermuda's Sargasso Sea

Friday, Mar 9, 2012

“Day after day, day after day/ We stuck, nor breath nor motion;/ As idle as a painted ship/ Upon a painted ocean./ Water, water, every where,/ And all the boards did shrink;/ Water, water, every where,/ Nor any drop to drink.”          

—Samuel Taylor Coleridge

 

Members of the Ward and Sigman lab groups recently embarked on a four-day research cruise to the famous Bermuda Atlantic Timeseries Study (BATS) site in the Northwestern Sargasso Sea as part of a new collaborative project entitled “Functional diversity of marine eukaryotic phytoplankton and their contributions to C and N cycling.” The science party consisted of undergraduates Lija Treibergs and Owen Coyle, graduate student Sarah Fawcett, senior researcher Amal Jayakumar, and laboratory manager Alexa Weigand. The goal of this cruise was to collect a number of samples and conduct a series of experiments designed to investigate the taxonomic, genetic and functional diversity of eukaryotic phytoplankton with respect to nitrate uptake during winter mixing/spring bloom conditions in the subtropical North Atlantic. Over the next two years, these collections will be complemented with samples taken from the BATS site during the summer, a period that is biogeochemically and physically distinct from the winter, and also with samples collected on two cruises in the subarctic North Atlantic during 2013.

Sample information: Seawater was collected using a rosette of Niskin bottles (pictured) from the surface down to 4000 m for later analysis of nutrient concentrations; suspended particles, RNA, and DNA were sampled throughout the sunlit surface layer (down to ~150 m) using various techniques such as inline filtration and large volume pumping in order to assess the key players in nitrate assimilation; bacterial and phytoplankton cells were collected for later determination of community composition via microscopy and flow cytometry; zooplankton net tows were carried out at a number of different depths to collect foraminifera for later N isotope analysis; and 15N and 13C incubation experiments were conducted to quantify rates of nitrate and ammonium assimilation, as well as carbon fixation, by different phytoplankton groups.