Interactions Between Changing pCO2, N2 Fixation, and Fe Limitation in the Marine Unicellular Cyanobacterium Crocosphaera

Authors

Fei-Xue Fu
Margaret R. Mulholland, Old Dominion UniversityFollow
Nathan S. Garcia
Aaron Beck
Mark E. Warner
Sergio A. Sañudo
David A. Hutchins

Document Type

Article

Publication Date

2008

DOI

10.4319/lo.2008.53.6.2472

Publication Title

Limnology and Oceanography

Volume

53

Issue

6

Pages

2472-2484

Abstract

We examined the physiological responses of steady-state iron (Fe)-replete and Fe-limited cultures of the biogeochemically critical marine unicellular diazotrophic cyanobacterium Crocosphaera at glacial (19 Pa; 190 ppm), current (39 Pa; 380 ppm), and projected year 2100 (76 Pa; 750 ppm) CO₂ levels. Rates of N₂ and CO₂ fixation and growth increased in step with increasing partial pressure of CO₂ (pCO₂), but only under Fe- replete conditions. N₂) and carbon fixation rates at 75 Pa CO₂ were 1.4-1.8-fold and 1.2-2.0-fold higher, respectively, relative to those at present day and glacial pCO₂ levels. In Fe-replete cultures, cellular Fe and molybdenum quotas varied threefold and were linearly related to N₂ fixation rates and to external pCO₂. However, N₂ fixation and trace metal quotas were decoupled from pCO₂ in Fe-limited Crocosphaera. Higher CO₂ and Fe concentrations both resulted in increased cellular pigment contents and affected photosynthesis vs. irradiance parameters. If these results also apply to natural Crocosphaera populations, anthropogenic CO₂ enrichment could substantially increase global oceanic N₂ and CO₂ fixation, but this effect may be tempered by Fe availability. Possible biogeochemical consequences may include elevated inputs of new nitrogen to the ocean and increased potential for Fe and/or phosphorus limitation in the future high-CO₂ ocean, and feedbacks to atmospheric pCO₂ in both the near future and over glacial to interglacial timescales.

Original Publication Citation

Fu, F.-X., Mulholland, M.R., Garcia, N.S., Beck, A., Bernhardt, P.W., Warner, M.E., . . . Hutchins, D.A. (2008). Interactions between changing pCO₂, N₂ fixation, and Fe limitation in the marine unicellular cyanobacterium Crocosphaera. Limnology and Oceanography, 53(6), 2472-2484. doi: 10.4319/lo.2008.53.6.2472

Repository Citation

Fu, Fei-Xue; Mulholland, Margaret R.; Garcia, Nathan S.; Beck, Aaron; Warner, Mark E.; Sañudo, Sergio A.; and Hutchins, David A., "Interactions Between Changing pCO2, N2 Fixation, and Fe Limitation in the Marine Unicellular Cyanobacterium Crocosphaera" (2008). OES Faculty Publications. 167.
https://digitalcommons.odu.edu/oeas_fac_pubs/167

ORCID

0000-0001-8819-189X (Mulholland)