The effect of nutrients on carbon and nitrogen fixation by the UCYN-A–haptophyte symbiosis
Fuchs, Bernhard M.
Amann, Rudolf I.
Kuypers, Marcel M. M.
MetadataShow full item record
Symbiotic relationships between phytoplankton and N2-fixing microorganisms play a crucial role in marine ecosystems. The abundant and widespread unicellular cyanobacteria group A (UCYN-A) has recently been found to live symbiotically with a haptophyte. Here, we investigated the effect of nitrogen (N), phosphorus (P), iron (Fe) and Saharan dust additions on nitrogen (N2) fixation and primary production by the UCYN-A-haptophyte association in the subtropical eastern North Atlantic Ocean using nifH expression analysis and stable isotope incubations combined with single cell measurements. N2 fixation by UCYN-A was stimulated by the addition of Fe and Saharan dust although this was not reflected in the nifH expression. CO2 fixation by the haptophyte was stimulated by the addition of ammonium nitrate as well as Fe and Saharan dust. Intriguingly, the single-cell analysis using nanoSIMS indicates that the increased CO2 fixation by the haptophyte in treatments without added fixed N is likely an indirect result of the positive effect of Fe and/or P on UCYN-A N2 fixation and the transfer of N2-derived N to the haptophyte. Our results reveal a direct linkage between the marine carbon and nitrogen cycles that is fuelled by the atmospheric deposition of dust. The comparison of single-cell rates suggests a tight coupling of nitrogen and carbon transfer that stays balanced even under changing nutrient regimes. However, it appears that the transfer of carbon from the haptophyte to UCYN-A requires a transfer of nitrogen from UCYN-A. This tight coupling indicates an obligate symbiosis of this globally important diazotrophic association.
Author Posting. © The Author(s), 2014. This is the author's version of the work. It is posted here by permission of Nature Publishing Group for personal use, not for redistribution. The definitive version was published in ISME Journal 9 (2015): 1635–1647, doi:10.1038/ismej.2014.253.
Showing items related by title, author, creator and subject.
Phosphate availability and the ultimate control of new nitrogen input by nitrogen fixation in the tropical Pacific Ocean Moutin, T.; Karl, David M.; Duhamel, Solange; Rimmelin, P.; Raimbault, P.; Van Mooy, Benjamin A. S.; Claustre, H. (Copernicus Publications on behalf of the European Geosciences Union, 2008-01-29)Due to the low atmospheric input of phosphate into the open ocean, it is one of the key nutrients that could ultimately control primary production and carbon export into the deep ocean. The observed trend over the last 20 ...
Sohm, Jill A.; Hilton, Jason A.; Noble, Abigail E.; Zehr, Jonathan P.; Saito, Mak A.; Webb, Eric A. (American Geophysical Union, 2011-08-27)Dinitrogen (N2) fixation is recognized as an important input of new nitrogen (N) to the open ocean gyres, contributing to the export of organic matter from surface waters. However, very little N2-fixation research has ...
Using indirect methods to constrain symbiotic nitrogen fixation rates : a case study from an Amazonian rain forest Cleveland, Cory C.; Houlton, Benjamin Z.; Neill, Christopher; Reed, Sasha C.; Townsend, Alan R.; Wang, Yingping (Springer, 2009-12-05)Human activities have profoundly altered the global nitrogen (N) cycle. Increases in anthropogenic N have had multiple effects on the atmosphere, on terrestrial, freshwater and marine ecosystems, and even on human health. ...