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

Differential effects of nitrate, ammonium, and urea as N sources for microbial communities in the North Pacific Ocean: N effects on microbial communities
Differential effects of nitrate, ammonium, and urea as N sources for microbial communities in the North Pacific Ocean: N effects on microbial communities
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.
0024-3590
2550-2574
Shilova, I. N.
5d9ef464-1ab1-4a87-b7ea-5e550ae1ea27
Mills, M. M.
8af819e3-0bd3-4a94-95e5-3201a0732e86
Robidart, J. C.
1d72ac92-7dca-49a0-9f9e-26798387e66b
Turk-kubo, K. A.
25eb3e4c-7080-4841-b795-28ac70efbdb9
Björkman, K. M.
b4b0ec50-4acb-44d0-a61a-4739ba295596
Kolber, Z.
84300b66-0904-47b5-92ea-1bc79db1bc80
Rapp, I.
acd4e6c1-eeb1-44d8-873c-50520280ed09
Van Dijken, G. L.
44ced99c-e398-4e84-bdd1-60c66957f6ac
Church, M. J.
dad189d5-866e-4ae1-b005-0d87f74282b8
Arrigo, K. R.
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Achterberg, E. P.
685ce961-8c45-4503-9f03-50f6561202b9
Zehr, J. P.
df07e726-0814-4247-8a74-942c07bd23e2
Shilova, I. N.
5d9ef464-1ab1-4a87-b7ea-5e550ae1ea27
Mills, M. M.
8af819e3-0bd3-4a94-95e5-3201a0732e86
Robidart, J. C.
1d72ac92-7dca-49a0-9f9e-26798387e66b
Turk-kubo, K. A.
25eb3e4c-7080-4841-b795-28ac70efbdb9
Björkman, K. M.
b4b0ec50-4acb-44d0-a61a-4739ba295596
Kolber, Z.
84300b66-0904-47b5-92ea-1bc79db1bc80
Rapp, I.
acd4e6c1-eeb1-44d8-873c-50520280ed09
Van Dijken, G. L.
44ced99c-e398-4e84-bdd1-60c66957f6ac
Church, M. J.
dad189d5-866e-4ae1-b005-0d87f74282b8
Arrigo, K. R.
15f4f6af-4f20-4028-940a-b3233d4d8cd5
Achterberg, E. P.
685ce961-8c45-4503-9f03-50f6561202b9
Zehr, J. P.
df07e726-0814-4247-8a74-942c07bd23e2

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

Record type: Article

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.

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More information

Accepted/In Press date: 1 January 2017
e-pub ahead of print date: 13 June 2017
Published date: 1 November 2017

Identifiers

Local EPrints ID: 418260
URI: https://eprints.soton.ac.uk/id/eprint/418260
ISSN: 0024-3590
PURE UUID: bd87e464-0039-4552-8d6a-db98ace5ca41

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Date deposited: 27 Feb 2018 17:30
Last modified: 12 Jul 2019 17:47

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