Structure of the macrophyte communities of small rivers in Saratov under anthropogenic load

The article presents the results of investigations of the flora of small rivers within the city of Saratov (Yelshanka, Nazarovka, 1st Gusyolka, and 2nd Gusyolka). The species composition of aquatic plants of the streams studied is represented by 37 macrophyte species belonging to 23 genera, 17 families and three divisions (Charophyta, Polypodiophyta, and Magnoliophyta). The families Potamogetonaceae, Cyperaceae and Lemnaceae predominate by the number of represented species. The values of the Menchinik index indicate that the greatest floristic diversity is characteristic of the Yelshanka and Nazarovka rivers (3.1 and 3.4, respectively). The species composition of aquatic plants of the studied rivers within the urban area has a low similarity coefficient with the flora of rivers with relatively low anthropogenic load. Hydrophytes are the most numerous ecological group (22 species). According to the Paley–Kownacki dominance index, among the macrophytes of the studied rivers, most species are subdominant (57.28%) (Potamogeton perfoliatus, Typha angustifolia, Lemna trisulca, etc.). 37.18% (Phragmites australis, Potamogeton pectinatus, Lemna minor, Ceratophyllum demersum) belong to dominants, and the rest (11.54%) is defined as subdominants of the first order. Exceptional predominance is characteristic of Ceratophyllum demersum and Phragmites australis, which acted as dominants in all studied rivers. A significant part of the rivers is characterized by a low degree of overgrowth by hydrophilous vegetation, from slightly overgrown to not overgrown. The main types of distribution of aquatic and riparian-water vegetation are belted and fragmentary. Macrophyte communities are characterized by a simplified structure (one- or two-tiered), with absolute predominance of one plant species and the presence of two to four associated species with low values of projective coverage. The results of our calculations of indices (macrophyte index for small rivers (Sm), Indice Biologique Macrophytique in Riviere (IBMR)) based on the structural parameters of macrophytes showed that the studied rivers have a satisfactory ecological status.