Award: OCE-1241263

Nitrogen is an essential element for life. In the open sea, the availability of nitrogen often controls plankton growth, resulting in intense competition and unique adaptations among the plankton to acquire nitrogen. This project sought to identify how different forms of nitrogen, supplied to open ocean plankton, modified and controlled the diversity, biomass, and growth of planktonic microorganisms in the subtropical North Pacific Ocean. Using a combination of at-sea experiments, shipboard sampling, and state-of-the art laboratory methodologies, research conducted as part of this project yielded new insights into the competitive successes of plankton to different forms of nitrogen-containing nutrients. The project was highly collaborative, involving scientists at the University of California Santa Cruz, Stanford University, and University of Hawaii. We quantified how changes in the availability of nitrogenous nutrients influenced the physiologies and competitive interactions among plankton that flourish in some of Earth?s largest habitats. Among many findings deriving from this research, we found that tiny (<1 um in diameter) plankton are the major drivers of productivity and dominant plankton biomass in these ecosystems; however, when perturbed by inputs of nitrogen (e.g. in the form of nitrate or ammonium) the size and composition of these plankton communities shifts to larger, faster growing populations. Sequencing of plankton nucleic acids further revealed the types of organisms that actively respond to changes in nitrogen availability. Such results will be useful for predictive models of future changes to the ocean and how such changes might impact the ecology and cycling of elements in ocean systems. This award provided training for undergraduate and graduate students in oceanography and ecology. In addition, funding from this award created both laboratory and field-based research opportunities for professional staff and students. Results from this research have been presented at scientific meetings, disseminated in peer-reviewed scientific literature, and integrated into public lectures delivered by the project principal investigators, post-doctoral fellows, and graduate students. In addition, through collaboration with the Exploratorium in San Francisco, CA., scientists from this project contributed to the development of a program on genomic-based analyses of plankton in the oceans. Last Modified: 03/17/2017 Submitted by: Matthew Church