Macrophytes as bioindicators of the physicochemical characteristics of wetlands in lowland and mountain regions of the central Balkan Peninsula

• Univariate macrophyte responses were studied for the first time on the Balkan Peninsula.
• Perennial macrophytes tolerate a wide range of conditions during a growing season.
• Environmental variables showed significant seasonal variability.
• Macrophytes with narrow environmental tolerance have the highest bioindicator potential.
• Phragmites australis has regional bioindicator capacity.

The simultaneous monitoring of vegetation, water and sediments was conducted in wetlands of the central Balkan Peninsula due to the lack of available knowledge on the univariate response of macrophytes along environmental gradients. The environmental preferences and bioindicator potential of macrophytes were assessed using Huisman-Olff-Fresco (HOF) models. Bolboschoenus maritimus and Scirpus lacustris subsp. tabernaemontani are valuable bioindicators of slightly saline (electroconductivity of 2000–4000 μS cm−1 in the sediment) and alkaline habitats that are rich in SO42−. Their ecological niches are partially overlapped. Bolboschoenus maritimus prefers saltier and more alkaline habitats for optimal development. The salinity and alkalinity of habitats are decisive factors in the ecological diversification of the Boloboschoenus species. Bolboschoenus glaucus is adapted to non-saline (400–900 μS cm−1) and slightly alkaline habitats, unlike Bolboschoenus maritimus. Relatively deep, slightly acid waters which are poor in SO42− (0.30 mg/l), and sediments with low values of electroconductivity and K2O (6.8 mg/100 g sediment) are preferred by Typha angustifolia, Sparganium erectum and Typha latifolia. The abundance of Phalaris arundinacea, Scirpus lacustris, Carex riparia and Eleocharis palustris increases when there is a decrease in the amount of nutrients (NH4+, PO43− and SO42−) in the water. Phragmites australis has low indicative value and regional bioindicator potential. The data obtained in the study may serve as a basis for adjusting the existing indicator values of these species and extending indicator systems by defining the indicator values of species with respect to environmental variables which have not yet been considered.