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Title: Dissolved organic nitrogen and carbon release by a marine unicellular diazotrophic cyanobacterium
Authors: Benavides, Mar
Agawin, Nona S. R.
Aristegui, Javier 
Peene, Jan
Stal, Lucas J.
Keywords: N-15 Tracer Method
N-2 Fixation
Picoplankton Organisms, et al
Issue Date: 2013
Publisher: 0948-3055
Journal: Aquatic Microbial Ecology 
Abstract: Dinitrogen (N-2) fixation rates may be underestimated when recently fixed N2 is released as dissolved organic nitrogen (DON). DON release (DONr) is substantial in the filamentous cyanobacterium Trichodesmium but has never been reported in unicellular diazotrophic cyanobacteria. We used axenic cultures of the marine unicellular diazotroph Cyanothece sp. Miami BG 043511 to measure dissolved organic matter release under N-2-fixing conditions. DONr was measured as the transfer of N-15(2) from the culture medium to the extracellular DON pool. On average, the DON released represented similar to 1% of the total N-2 fixed. The average release of dissolved organic carbon, as determined by C-14, represented similar to 2% of the total carbon fixed. These results suggest that cultured populations of unicellular diazotrophs do not release much dissolved organic matter, but it cannot be excluded that DONr is important in the field when grazers and bacteria are present, or when the organism is exposed to environmental stresses such as turbulence, excess light, temperature changes, or nutrient limitation.
ISSN: 0948-3055
DOI: 10.3354/ame01621
Source: Aquatic Microbial Ecology[ISSN 0948-3055],v. 69 (1), p. 69-80
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