Morphometric variability of the genus Nodularia (Cyanobacteria) in Baltic natural communities

Morphometric variability of the filamentous diazotroph Nodularia was determined in natural, mixed-species samples during a summer cyanobacterial bloom in the Central Baltic Sea using epifluorescence microscopy coupled with image analysis. A total of 1350 cyanobacterial filament images were acquired and a number of morphometric parameters measured for individual trichomes present in the samples and used to distinguish Nodularia from Aphanizomenon and Anabaena. The approach allowed automatic estimates of linear dimensions of Nodularia, Aphanizomenon and Anabaena, enabling us to evaluate their biovolume and vertical distribution, and to observe a high degree of morphometric variability in Nodularia filaments. We statistically analyzed this phenotypic diversity using previously collected datasets and adding further measurements. The data obtained were used to assess the variability in Nodularia trichome width and morphology and to establish the possible existence of 3 Nodularia 'morphotypes' by discriminant analysis.