Regulation of heterocyst frequency in Baltic Sea Aphanizomenon sp.
2014 (English)In: Journal of Plankton Research, ISSN 0142-7873, E-ISSN 1464-3774, Vol. 36, no 5, 1357-1367 p.Article in journal (Refereed) Published
Heterocyst frequencies in Baltic Sea Aphanizomenon sp. were similar along a strong nutrient gradient from the discharge point of a sewage treatment plant at the head of the Himmerfjarden bay to the open sea. Filaments lacked heterocysts in winter and for over a month after the spring bloom had depleted combined nitrogen in the surface layer. Heterocyst-free filaments in spring contained granulate structures that decreased in abundance simultaneously as colony nitrogen content decreased, but delta N-15 remained unchanged, indicative of storage of fixed nitrogen in over-wintering Aphanizomenon sp. filaments. Heterocyst formation was initiated when water temperature was sufficient to form a shallow seasonal pycnocline that allowed filaments to be exposed to enough light to initiate growth and a subsequent intracellular shortage of nitrogen. During the growth season, heterocyst frequency varied significantly with maximum values in early summer (May), lower values in mid-August that coincided with maximum temperatures and an increase in late summer. Heterocyst frequencies decreased with increased temperatures, suggesting a more efficiently functioning nitrogenase enzyme. Based on data from three seasons, filament C: P ratios did not correlate with heterocyst frequencies, neither did reduced heterocyst frequencies coincide with high dissolved inorganic nitrogen concentrations. Increased heterocyst frequencies, however, resulted in decreased C:N ratios, probably as more heterocysts likely increase nitrogen fixation.
Place, publisher, year, edition, pages
2014. Vol. 36, no 5, 1357-1367 p.
Aphanizomenon sp., heterocysts, cyanobacteria, diazotrophs, Baltic Sea proper
IdentifiersURN: urn:nbn:se:su:diva-108379DOI: 10.1093/plankt/fbu055ISI: 000342235000016OAI: oai:DiVA.org:su-108379DiVA: diva2:758095