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Title: Crocosphaera as a Major Consumer of Fixed Nitrogen
ABSTRACT Crocosphaera watsonii (hereafter referred to as Crocosphaera) is a key nitrogen (N) fixer in the ocean, but its ability to consume combined-N sources is still unclear. Using in situ microcosm incubations with an ecological model, we show that Crocosphaera has high competitive capability both under low and moderately high combined-N concentrations. In field incubations, Crocosphaera accounted for the highest consumption of ammonium and nitrate, followed by picoeukaryotes. The model analysis shows that cells have a high ammonium uptake rate (~7 mol N [mol N]^−1 d^−1 at the maximum), which allows them to compete against picoeukaryotes and nondiazotrophic cyanobacteria when combined N is sufficiently available. Even when combined N is depleted, their capability of nitrogen fixation allows higher growth rates compared to potential competitors. These results suggest the high fitness of Crocosphaera in combined-N limiting, oligotrophic oceans heightening its potential significance in its ecosystem and in biogeochemical cycling.  more » « less
Award ID(s):
1655221
PAR ID:
10340605
Author(s) / Creator(s):
; ; ; ; ; ; ; ; ; ; ; ; ;
Editor(s):
Gralnick, Jeffrey A.
Date Published:
Journal Name:
Microbiology Spectrum
ISSN:
2165-0497
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
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