Dataset Information

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. IMPORTANCE Crocosphaera watsonii is as a key nitrogen (N) supplier in marine ecosystems, and it has been estimated to contribute up to half of oceanic N₂ fixation. Conversely, a recent study reported that Crocosphaera can assimilate combined N and proposed that unicellular diazotrophs can be competitors with non-N₂ fixing phytoplankton for combined N. Despite its importance in nitrogen cycling, the methods by which Crocosphaera compete are not currently fully understood. Here, we present a new role of Crocosphaera as a combined-N consumer: a competitor against nondiazotrophic phytoplankton for combined N. In this study, we combined in situ microcosm experiments and an ecosystem model to quantitatively evaluate the combined-N consumption by Crocosphaera and other non-N₂ fixing phytoplankton. Our results suggest the high fitness of Crocosphaera in combined-N limiting, oligotrophic oceans and, thus, heightens its potential significance in its ecosystem and in biogeochemical cycling.

SUBMITTER: Masuda T

PROVIDER: S-EPMC9431459 | biostudies-literature | 2022 Aug

REPOSITORIES: biostudies-literature

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Crocosphaera as a Major Consumer of Fixed Nitrogen.

Masuda Takako T Inomura Keisuke K Kodama Taketoshi T Shiozaki Takuhei T Kitajima Satoshi S Armin Gabrielle G Matsui Takato T Suzuki Koji K Takeda Shigenobu S Sato Mitsuhide M Prášil Ondřej O Furuya Ken K

Microbiology spectrum 20220630 4

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 picoeukaryot ...[more]

PMID: 35770981

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Crocosphaera as a Major Consumer of Fixed Nitrogen.

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<i>Crocosphaera</i> as a Major Consumer of Fixed Nitrogen.

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