AME 57:175-189 (2009)  -  DOI: https://doi.org/10.3354/ame01343

ABSTRACT: Diel variations of N₂ and C fixation rates, as well as subsequent release of total dissolved N (TDN) and dissolved organic carbon (DOC) were determined for Trichodemsium erythreum and Nodularia spumigena. A circadian rhythm of N₂ and C fixation, as well as a periodicity in the calculated release of dissolved compounds, was observed. From the amounts of N and inorganic C fixed by T. erythreum during the light period of the experiment, 71 and 50% were released as TDN and DOC, respectively; for N. spumigena we found a release of 89 and 53%, respectively, during the light period. Additionally, 2 controlling factors (light and nutrient concentrations) for the release of TDN and DOC were studied. The data suggest that rapid shifts towards higher light intensity lead to a pronounced exudation of TDN and DOC. On a short-term basis (first 30 min after exposure), the exudation of NH₄⁺ and DON consumed up to 52% of electrons harvested by the cells in the same time interval. Thus TDN release serves as a potential electron sink and protects cells from photodestruction. On the other hand, there was no clear effect of phosphorus concentration on the release of TDN and DOC. Our results indicate that uptake and subsequent exudation of TDN and DOC might be induced by abiotic parameters, besides being regulated endogenously by multiple feedback loops.

KEY WORDS: N₂ fixation · C fixation · DON · DOC · DFAA · Diazotroph · Cyanobacteria

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Cite this article as: Wannicke N, Koch BP, Voss M (2009) Release of fixed N2 and C as dissolved compounds by Trichodesmium erythreum and Nodularia spumigena under the influence of high light and high nutrient (P). Aquat Microb Ecol 57:175-189. https://doi.org/10.3354/ame01343 Export citation Share:    Facebook - - linkedIn