Autecology and morphology of selected Vaucheria species (Xanthophyceae)

Abstract

In this study, the yellow-green alga Vaucheria was collected from 86 sites with different environmental characteristics. A principal component analysis of the sites revealed a model with four principal components explaining 64.7% of the total variance in the data set. The principal components were interpreted as nutrient enrichment, ions, current, and buffer capacity. In total, seven Vaucheria species were found: V. taylorii, V. debaryana, V. sessilis, V. geminata, V. terrestris, V. walzii, and V. woroniniana. V. taylorii was noted only three times, V. terrestris occured exclusively at terrestrial sites, the remaining taxa were frequent. Vaucheria seems to have its optimal growth at lower temperatures; in the cold season thick covers were observed, which exceeded the abundance in summer. A discriminant analysis revealed that growth types are highly explained by current; high flow velocity favors the development of pads. Species occurrence along artificial gradients consisting of the obtained principal components were analyzed simultaneously by means of a canonical correspondence analysis. V. sessilis occurred widely with no preferences, but three species showed a distinct pattern within the gradient analysis: V. woroniniana mainly occurred at elevated pH and total alkalinity, V. walzii was favored by increased ion contents and slow current, and V. geminata clearly preferred unpolluted sites with decreased pH and alkalinity values. This species may be used as an indicator species for unpolluted locations, however some taxonomic uncertainties remain to be first resolved.