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Nitrogen fixation by Baltic cyanobacteria is adapted to the prevailing photon flux density
Author(s) -
EVANS A. M.,
GALLON J. R.,
JONES A.,
STAAL M.,
STAL L. J.,
VILLBRANDT M.,
WALTON T. J.
Publication year - 2000
Publication title -
new phytologist
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.742
H-Index - 244
eISSN - 1469-8137
pISSN - 0028-646X
DOI - 10.1046/j.1469-8137.2000.00696.x
Subject(s) - cyanobacteria , aphanizomenon , nitrogen fixation , nitrogenase , population , population density , darkness , biology , baltic sea , environmental chemistry , botany , ecology , environmental science , oceanography , chemistry , anabaena , bacteria , geology , genetics , demography , sociology
N 2 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 N 2 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 N 2 fixation, Baltic cyanobacteria are adapted to the intensity of illumination that they are currently experiencing.