Differential effects of nitrate, ammonium, and urea as N sources for microbial communities in the North Pacific Ocean.

Shilova, I. N., Mills, M. M., Robidart, J. C., Turk-Kubo, K. A., Björkman, K. M., Kolber, Z., Rapp, Insa, van Dijken, G. L., Church, M. J., Arrigo, K. R., Achterberg, Eric P. and Zehr, J. P. (2017) Differential effects of nitrate, ammonium, and urea as N sources for microbial communities in the North Pacific Ocean. Limnology and Oceanography, 62 (6). pp. 2550-2574. DOI 10.1002/lno.10590.

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Supplementary data:

Abstract

Nitrogen (N) is the major limiting nutrient for phytoplankton growth and productivity in large parts of the world's oceans. Differential preferences for specific N substrates may be important in controlling phytoplankton community composition. To date, there is limited information on how specific N substrates influence the composition of naturally occurring microbial communities. We investigated the effect of nitrate ( math formula), ammonium ( math formula), and urea on microbial and phytoplankton community composition (cell abundances and 16S rRNA gene profiling) and functioning (photosynthetic activity, carbon fixation rates) in the oligotrophic waters of the North Pacific Ocean. All N substrates tested significantly stimulated phytoplankton growth and productivity. Urea resulted in the greatest (>300%) increases in chlorophyll a (<0.06 μg L−1 and ∼0.19 μg L−1 in the control and urea addition, respectively) and productivity (<0.4 μmol C L−1 d−1 and ∼1.4 μmol C L−1 d−1 in the control and urea addition, respectively) at two experimental stations, largely due to increased abundances of Prochlorococcus (Cyanobacteria). Two abundant clades of Prochlorococcus, High Light I and II, demonstrated similar responses to urea, suggesting this substrate is likely an important N source for natural Prochlorococcus populations. In contrast, the heterotrophic community composition changed most in response to math formula. Finally, the time and magnitude of response to N amendments varied with geographic location, likely due to differences in microbial community composition and their nutrient status. Our results provide support for the hypothesis that changes in N supply would likely favor specific populations of phytoplankton in different oceanic regions and thus, affect both biogeochemical cycles and ecological processes.

Document Type: Article
Keywords: Nitrogen, nutrient, microbial communities, North Pacific Ocean, R/V New Horizon
Research affiliation: OceanRep > SFB 754
OceanRep > GEOMAR > FB2 Marine Biogeochemistry > FB2-CH Chemical Oceanography
Refereed: Yes
Open Access Journal?: No
DOI etc.: 10.1002/lno.10590
ISSN: 0024-3590
Projects: SFB754, Dimensions in Biodiversity
Date Deposited: 26 Jun 2017 09:03
Last Modified: 01 Feb 2019 15:02
URI: http://oceanrep.geomar.de/id/eprint/38511

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