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Carbon and nitrogen fluxes associated with the cyanobacterium Aphanizomenon sp. in the Baltic Sea
Stockholm University, Faculty of Science, Department of Botany.
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2010 (English)In: The ISME journal, ISSN 1751-7362, Vol. 4, no 9, 1215-1223 p.Article in journal (Refereed) Published
Abstract [en]

Carbon and nitrogen fluxes in Aphanizomenon sp. colonies in the Baltic Sea were measured using a combination of microsensors, stable isotopes, mass spectrometry, and nanoscale secondary ion mass spectrometry (nanoSIMS). Cell numbers varied between 956 and 33 000 in colonies ranging in volume between 1.4 x 10(-4) and 230 x 10(-4) mm(-3). The high cell content and their productivity resulted in steep O-2 gradients at the colony-water interface as measured with an O-2 microsensor. Colonies were highly autotrophic communities with few heterotrophic bacteria attached to the filaments. Volumetric gross photosynthesis in colonies was 78 nmol O-2 mm(-3) h(-1). Net photosynthesis was 64 nmol O-2 mm(-3) h(-1), and dark respiration was on average 15 nmol O-2 mm(-3) h(-1) or 16% of gross photosynthesis. These volumetric photosynthesis rates belong to the highest measured in aquatic systems. The average cell-specific net carbon-fixation rate was 38 and 40 fmol C cell(-1) h(-1) measured by microsensors and by using stable isotopes in combination with mass spectrometry and nanoSIMS, respectively. In light, the net C:N fixation ratio of individual cells was 7.3 +/- 3.4. Transfer of fixed N-2 from heterocysts to vegetative cells was fast, but up to 35% of the gross N-2 fixation in light was released as ammonium into the surrounding water. Calculations based on a daily cycle showed a net C: N fixation ratio of 5.3. Only 16% of the bulk N-2 fixation in dark was detected in Aphanizomenon sp. Hence, other organisms appeared to dominate N-2 fixation and NH4+ release during darkness.

Place, publisher, year, edition, pages
2010. Vol. 4, no 9, 1215-1223 p.
Keyword [en]
Aphanizomenon, nitrogen fixation, ammonium release, photosynthesis, respiration
National Category
Natural Sciences
URN: urn:nbn:se:su:diva-50520DOI: 10.1038/ismej.2010.53ISI: 000281663700019OAI: diva2:381637
authorCount :8Available from: 2010-12-28 Created: 2010-12-28 Last updated: 2010-12-28Bibliographically approved

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Ploug, HelleBergman, Birgitta
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