SS2.05 Phylogenetic and Physiologic Successions in Aquatic Bacterial Communities
Date: Thursday, June 13, 2002
Location: Poster Session - VCC
 
Vaitomaa, J, , Department of Applied Chemistry and Microbiology, Helsinki, Finland, jaana.vaitomaa@helsinki.fi
Rapala, J, , Finnish Environment Institute, Helsinki, Finland, jarkko.rapala@vyh.fi
Saari, L, , Department of Applied Chemistry and Microbiology, Helsinki, Finland, luydmila.saari@helsinki.fi
Repka, S, , Department of Applied Chemistry and Microbiology, Helsinki, Finland, sari.repka@helsinki.fi
Sivonen, K, , Department of Applied Chemistry and Microbiology, Helsinki, Finland, kaarina.sivonen@helsinki.fi
 
GROWTH OF HEPATOTOXIN PRODUCING AND NON-TOXIC MICROCYSTIS STRAINS IN VARYING PHOSPHORUS AND NITROGEN CONCENTRATIONS
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Variation in the toxin concentration of cyanobacterial bloom is due to species and strain composition, biomass, toxin production efficiency, and the condition of the toxic cells. We studied the effects of nutrients on the above mentioned. The aim was to compare growth of toxic and non-toxic Microcystis stains to understand cyanobacterial bloom dynamics and toxin concentrations. A microcystin producing strain and two non-toxic Microcystis strains were cultivated in chemostats in varying nutrient concentrations. Phosphorus (0.025 – 1.2 mg l-1) and nitrogen concentrations (2.0 – 84 mg l-1) of nine growth media were determined using Central Composite Design. Growth and toxin production was measured after a steady state was achieved. Dry weight of all the studied strains was highest with the highest nutrient concentrations. However, the dry weight production of the toxic strain was higher than that of the non-toxic strains. Total and intracellular toxin concentration was highest in the media with the highest nutrient concentration. Reduction of nutrient loading and restoration of lakes may affect bloom formation and also to the strain composition of the bloom.