Program and Agenda

Abstract

SAME STAGE BUT DIFFERENT ACTORS: 20 YEARS OF CHANGE IN NITROGEN FIXATION AT STATION ALOHA

Since the early 1990’s, N2 fixation has been a focus of interest and research at Station ALOHA. Studies focused on Trichodesmium blooms, until a partial nitrogenase (nifH) gene sequence was discovered at Station ALOHA that ultimately changed the paradigm of open ocean nitrogen fixation. This sequence was from a cyanobacterium (UCYN-A) smaller than Trichodesmium, but larger than Prochlorococcus, that is now known to be missing typical metabolic features of cyanobacteria, including oxygenic photosynthesis and carbon fixation. Only recently it has been shown to be a symbiont with the prymnesiophyte Braarudosphaera bigelowii. The discovery of UCYN-A, and the subsequent characterization of its wide distribution globally has changed our view of where N2 fixation occurs, the size-fraction it is associated with, its stoichiometric (or not) coupling to carbon fixation, and its fate in microbial food webs or sedimentation. One significant change in biogeochemistry studies, is the measurement of N2 fixation rates in bulk water, rather than only in net collected Trichodesmium. New findings show that there are multiple UCYN-A strains that differ in sequence but little in genome content, providing the tantalizing hypothesis that there are UCYN-A ecotypes. The Hawai’i Ocean Time-series provided the logistics and comprehensive datasets that facilitated these important discoveries.

Authors

Zehr, J. P., University of California, Santa Cruz, USA, zehrj@ucsc.edu

Carter, B. J., University of California, Santa Cruz, USA, bjcarter@ucsc.edu

Foster, R. A., University of California, Santa Cruz, USA, rfoster@ucsc.edu

Thompson, A. W., University of California, Santa Cruz, USA, anne.w.thompson@gmail.com

Tripp, H. J., Joint Genome Institute, USA, hjtripp@lbl.gov

Details

Oral presentation

Session #:049
Date: 2/27/2014
Time: 15:00
Location: 313 B

Presentation is given by student: No