Assessment of the dinitrogen released as ammonium and dissolved organic nitrogen by unicellular and filamentous marine diazotrophic cyanobacteria grown in culture

摘要: The dinitrogen (N2) released as dissolved nitrogen (DN) has been compared in batch cultures of four marine diazotrophic cyanobacteria: the colony forming Trichodesmium IMS101 and unicellular strains Cyanothece ATCC51142, Crocosphaera watsonii WH8501 WH0003. Two approaches were conducted for this purpose. first approach consisted comparison total accumulation fixed N2 culture (both particulate pools) with net fixation rates (i. e. incorporated only fraction after 15N2 incubation). difference between two measures accounted DN. second direct measure 15N-enrichment ammonium (NH4+) organic N (DON) following incubations. DN ~0 - 20 % ~1 24 h approach, respectively. We show that recent methodological improvements determination applied study tend to reconcile formerly led contrasted values. However, large analytical uncertainties limit its reliability. Thus, pool remains best tool assess pool, particular it allows shorter incubation times. There no clear patterns detected filamentous strains, neither terms amount nor proportion NH4+ relative DON. This suggests release processes are shared among free living diazotrophs.