Nitrogen fixation by Baltic cyanobacteria is adapted to the prevailing photon flux density |
| |
| Authors: | A. M. EVANS,J. R. GALLON,A. JONES,M. STAAL,L. J. STAL,M. VILLBRANDT,& T. J. WALTON |
| |
| Affiliation: | Biochemistry Research Group, School of Biological Sciences, University of Wales, Swansea, Singleton Park, Swansea SA2 8PP, UK; Netherlands Institute for Ecology, Centre for Estuarine and Coastal Ecology, PO Box 140, NL-4400 AC Yerseke, The Netherlands; University of Bremen, Faculty 2, Leobener Strasse/NW2, D-28359 Bremen, Germany; Author for correspondence (fax +44 1792 295447;e-mail ). |
| |
| Abstract: | N2 fixation, measured as acetylene reduction, was studied in laboratory cultures and in natural assemblages (both as a mixed population and as individually picked colonies) of the heterocystous cyanobacteria Aphanizomenon sp. and Nodularia spp. from the Baltic Sea. During a diurnal cycle of alternating light and darkness, these organisms reduced acetylene predominantly during the period of illumination, although considerable activity was also observed during the dark period. In both laboratory cultures and natural populations N2 fixation was saturated below a photon flux density of 600 μm−2 s−1. In cyanobacterial blooms in the Baltic Sea, nitrogenase activity was mostly confined to the surface layers. Samples collected from greater depths did not possess the same capacity for acetylene reduction as samples from the surface itself, even when incubated at the photon flux density prevailing in surface waters. This suggests that, with respect to N2 fixation, Baltic cyanobacteria are adapted to the intensity of illumination that they are currently experiencing. |
| |
| Keywords: | Baltic cyanobacteria N2 fixation Aphanizomenon Nodularia |
|
|
