Competition for Light between Toxic and Nontoxic Strains of the Harmful Cyanobacterium MicrocystisReversal in competitive dominance of a toxic versus non-toxic cyanobacterium in response to rising CO2Amino acid availability determines the ratio of microcystin variants in the cyanobacterium Planktothrix agardhiiPulsed nitrogen supply induces dynamic changes in the amino acid compositionand microcystin production of the harmful cyanobacterium Planktothrix agardhii