Award: OPP-1142018

Phytoplankton (small, single-celled plant-like organisms) produce half of the oxygen we breathe and form the base of the global marine food web. The genus Phaeocystis is a key component of the phytoplankton community in highly productive waters over much of the globe, with Phaeocystis antarctica dominating in waters of the Southern Ocean. The aim of our project was to use field-based experimental and sampling approaches to study the physiological and genotypic adaptations of P. antarctica that make this genus so successful, as well to better understand the degree variability in these adaptations between different populations. To achieve this goal, we studied populations of P. antarctica in both sea ice and in the open ocean during cruises to the Ross Sea in 2013 and to the west Antarctic Peninsula (wAP) in 2014. This was a collaborative research project and the role of the Arrigo research team was to focus on the physiological adaptations of P. antarctica in different light environments. Our main findings were that: Colonial P. antarctica dominates the spring sea ice but is much less common in the water column along the wAP. This situation is reversed in the Ross Sea, with P. antarctica dominating open water blooms but seldom seen in the sea ice. Although phytoplankton and ice algal communities were similar in taxonomic composition, seeding of the phytoplankton blooms by ice algae appeared to be of little importance. Specific physiological responses of bloom-forming algal taxa such as P. antarctica are controlled by prior environmental conditions, such as loght history and nutrient concentrations. Physiological characteristics differ between P. antarctica populations found in sea ice and in the open ocean. P. antarctica is more negatively buoyant than other phytoplankton taxa (including diatoms), suggesting it has a higher potential to sink relative to other phytoplankton taxa. So far, the Arrigo research team has made 13 presentations at scientific meetings and has produced seven publications for peer reviewed journals based on this research. The Arrigo component of the project supported the training of four female graduate students and one female research associate. In addition, two under-represented minority high school students were trained on phytoplankton taxonomy, imaging software, the programming language R, and biological oceanography of polar regions. Last Modified: 01/03/2017 Submitted by: Kevin R Arrigo