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Appl. Environ. Microbiol., May 1997, 1647-1656, Vol 63, No. 5
J Lehtimaki, P Moisander, K Sivonen and K Kononen
In late summer, nitrogen-fixing cyanobacteria Nodularia spumigena and
Aphanizomenon flos-aquae form blooms in the open Baltic Sea. N. spumigena
has caused several animal poisonings, but Baltic A. flos-aquae is not known
to be toxic. In this laboratory study, performed with batch cultures, the
influences of environmental conditions on the biomass and nitrogen fixation
rate of N. spumigena and A. flos-aquae were compared and the toxin
(nodularin) concentration produced by N. spumigena was measured. Several
differences in the biomasses and nitrogen fixation rates of N. spumigena
and A. flos-aquae were observed. A. flos-aquae preferred lower irradiances,
salinities, and temperatures than N. spumigena. The biomass of both species
increased with high phosphate concentrations and with accompanying bacteria
and decreased with unnaturally high inorganic nitrogen concentrations.
Nodularin concentrations in cells and growth media, as well as nitrogen
fixation rates, were generally highest under the conditions that promoted
growth. Intracellular nodularin concentrations increased with high
temperature, high irradiance, and high phosphate concentration and
decreased with low and high salinities and high inorganic nitrogen
concentrations. Nodularin concentrations in growth media increased with
incubation time, indicating that intracellular nodularin was released when
cells lysed. The different responses of A. flos-aquae and N. spumigena to
changes in salinity, irradiance, and temperature may explain the different
spatial and temporal distribution of these species in the Baltic Sea.
According to the results, toxic N. spumigena blooms may be expected in late
summer in areas of the Baltic Sea with high phosphorus concentrations and
moderate salinity.
Copyright © 1997, American Society for Microbiology
Growth, Nitrogen Fixation, and Nodularin Production by Two Baltic Sea Cyanobacteria
Department of Applied Chemistry and Microbiology, Division of Microbiology, Biocenter Viikki, FIN-00014 Helsinki University, and Finnish Institute of Marine Research, FIN-00931 Helsinki, Finland
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