A new Navicula (Bacillariophyta) species from low-elevation carbonate springs affected by anthropogenic disturbance

Diatom assemblages in carbonate spring habitats at low elevations, with low discharge, and affected by direct human impacts were studied only recently and in some geographic areas. We describe and characterize the ecology of a new Navicula species from springs with these characteristics within the basin of the River Adige in the south-eastern Alps and Alpine foothills (Province of Verona, Italy). Navicula veronensis sp. nov. is in the group of species around N. cincta but has distinct outline, size, central area, and proximal raphe endings. The availability of data on the distribution of the new species in streams of the Island of Cyprus allowed to quantitatively compare the ecological preferences, niche position, and niche breadth of Navicula veronensis sp. nov. with those of allied species. The new species was found to be characteristic of medium-high conductivity freshwaters, rich in sulphates and chloride, often nitrate enriched and affected by marked discharge fluctuations and seasonal desiccation. Niche position however differed only slightly from those of morphologically-similar species, with the exception of Navicula dealpina that was found to be characteristic of oligotrophic, calcium-bicarbonate rich environments with medium(-low) conductivity. Canonical Correspondence Analysis clearly showed that the most influential environmental variables determining the diatom assemblages of low-elevation carbonate springs affected by anthropogenic disturbance were nitrate enrichment, spring morphology alteration (in particular for water abstraction), and low discharge.