NanoSIMS single cell analyses reveal the contrasting nitrogen sources for small phytoplankton

Nitrogen (N) is a limiting nutrient in vast regions of the world's oceans, yet the sources of N available to various phytoplankton groups remain poorly understood. In this study, we investigated inorganic carbon (C) fixation rates and nitrate (NO ), ammonium (NH ) and urea uptake rates at the s...

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Bibliographic Details
Published in:The ISME Journal 2019-03, Vol.13 (3), p.651-662
Main Authors: Berthelot, Hugo, Duhamel, Solange, L'Helguen, Stéphane, Maguer, Jean-Francois, Wang, Seaver, Cetinić, Ivona, Cassar, Nicolas
Format: Article
Language:English
Subjects:
Ammonium
Ammonium Compounds - metabolism
Biodiversity and Ecology
Biogeography
California
Carbon - metabolism
Carbon Cycle
Continental interfaces, environment
Cyanobacteria
Earth Sciences
Environmental Sciences
Eukaryotes
Fixation
Flow Cytometry
Growth rate
Heterogeneity
Inorganic carbon
Nitrates - metabolism
Nitrogen
Nitrogen - metabolism
Nitrogen sources
Nutrient sources
Ocean, Atmosphere
Oceanography
Oceans
Pacific Ocean
Photosynthesis
Phytoplankton
Phytoplankton - growth & development
Phytoplankton - metabolism
Picoplankton
Plankton
Prochlorococcus
Prochlorococcus - growth & development
Prochlorococcus - metabolism
Sciences of the Universe
Single-Cell Analysis
Spectrometry, Mass, Secondary Ion - methods
Synechococcus
Synechococcus - growth & development
Synechococcus - metabolism
Urea
Urea - metabolism
Variation
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Summary:Nitrogen (N) is a limiting nutrient in vast regions of the world's oceans, yet the sources of N available to various phytoplankton groups remain poorly understood. In this study, we investigated inorganic carbon (C) fixation rates and nitrate (NO ), ammonium (NH ) and urea uptake rates at the single cell level in photosynthetic pico-eukaryotes (PPE) and the cyanobacteria Prochlorococcus and Synechococcus. To that end, we used dual N and C-labeled incubation assays coupled to flow cytometry cell sorting and nanoSIMS analysis on samples collected in the North Pacific Subtropical Gyre (NPSG) and in the California Current System (CCS). Based on these analyses, we found that photosynthetic growth rates (based on C fixation) of PPE were higher in the CCS than in the NSPG, while the opposite was observed for Prochlorococcus. Reduced forms of N (NH and urea) accounted for the majority of N acquisition for all the groups studied. NO represented a reduced fraction of total N uptake in all groups but was higher in PPE (17.4 ± 11.2% on average) than in Prochlorococcus and Synechococcus (4.5 ± 6.5 and 2.9 ± 2.1% on average, respectively). This may in part explain the contrasting biogeography of these picoplankton groups. Moreover, single cell analyses reveal that cell-to-cell heterogeneity within picoplankton groups was significantly greater for NO uptake than for C fixation and NH uptake. We hypothesize that cellular heterogeneity in NO uptake within groups facilitates adaptation to the fluctuating availability of NO in the environment.
ISSN:1751-7362
1751-7370
DOI:10.1038/s41396-018-0285-8