Ecogenomic sensor reveals controls on N sub(2)-fixing microorganisms in the North Pacific Ocean

• Published in: The ISME Journal 2014-06, Vol.8 (6), p.1175-1185
• Main Authors: Robidart, Julie C, Church, Matthew J, Ryan, John P, Ascani, Francois, Wilson, Samuel T, Bombar, Deniz, Marin, Roman, Richards, Kelvin J, Karl, David M, Scholin, Christopher A, Zehr, Jonathan P
• Format: Article
• Language: English
• ISSN: 1751-7362
• DOI: 10.1038/ismej.2013.244

Nitrogen-fixing microorganisms (diazotrophs) are keystone species that reduce atmospheric dinitrogen (N sub(2)) gas to fixed nitrogen (N), thereby accounting for much of N-based new production annually in the oligotrophic North Pacific. However, current approaches to study N sub(2) fixation provide relatively limited spatiotemporal sampling resolution; hence, little is known about the ecological controls on these microorganisms or the scales over which they change. In the present study, we used a drifting robotic gene sensor to obtain high-resolution data on the distributions and abundances of N sub(2)-fixing populations over small spatiotemporal scales. The resulting measurements demonstrate that concentrations of N sub(2) fixers can be highly variable, changing in abundance by nearly three orders of magnitude in less than 2 days and 30 km. Concurrent shipboard measurements and long-term time-series sampling uncovered a striking and previously unrecognized correlation between phosphate, which is undergoing long-term change in the region, and N sub(2)-fixing cyanobacterial abundances. These results underscore the value of high-resolution sampling and its applications for modeling the effects of global change.