Macrophyte Assessment for River Ecology

Bioindication studies in selected control sections were performed using the Macrophyte Method for River Assessment (MMRA) [23 ]. The method is based on the qualitative and quantitative assessment of the species composition of macrophytes present in the water. It allows for determining the degree of degradation of the watercourse, mainly in relation to its trophic state. The research was carried out on 100-meter representative sections of the analyzed river. MMRA was assessed at five points: T1 named, Zielonka” (52°33’26.05"N, 17°06’40.76"E), T2:, Głęboczek” (52°3428.82" N, 17°06’06.92"E), T3:, Gębice” (52°36’12.46"N, 17°02’58.09"E), T4:, behind the Przebędowo reservoir” (52°35’06.55"N, 17°00’55.05"E), T5:, Mściszewo” (52°35’05.54"N, 16°58’14.95"E). The locations of the points are shown on the map in Fig 1. In the MMRA study, only macrophytes growing in water (at least rooted in water or in the so-called splash zone) were recorded. According to the methodology, macrophytes were identified to the species level or genus, in the case of algae. 189 indicator taxa are used to calculate the MRI index, including 63 monocotyledonous vascular plants, 55 dicotyledons, 5 ferns, 27 mosses, 13 liverworts, 1 water lichen (Collema), 22 macroalgae, 2 cyanobacteria and 1 colony bacterium (Sphaerotilus natans). For each taxa, the share in watercourse coverage was recorded using the following nine-point scale: 1 for <0.1%, 2 for 0.1–1%, 3 for 1–2.5%, 4 for 2.5–5%, 5 for 5–10%, 6 for 10–25%, 7 for 25–50%, 8 for 50–75% and 9 for >75%. Based on the inventory, the Macrophyte River Index (MRI) was calculated, which, when related to the reference values for a given macrophyte type, allows for the assessment of the ecological status defined by the Water Framework Directive [2 , 24 (link)].
The total number of species was assessed by direct identification in the field. Species that grew in the water or amphibious species growing on the watercourse bank, leaning towards the water, are included.
Indicator species were identified based on the list of macrophyte species used in the MMRA. The basic criterion for selecting species for the index list is the trophic level of the aquatic environment in which a given taxon occurs (from advanced trophic to oligotrophy). Additionally, the criterion is the ecological tolerance of the species (from sten- to eurotypic). Indicator plants and all other aquatic plants were identified in a 100-meter stretch of the watercourse.In addition, the degree of coverage was assessed based on all species of aquatic plants present in the riverbed.