The relationships between the physical and chemical properties of an aquatic environment and the floristic specificity of pleustonic communities in northern Poland

Abstract

A comparative phytosociological and habitat analysis of 84 pleustonic phytocoenoses in northern Poland was carried out in order to determine the scale of their floristic distinctiveness and to obtain an answer to the question whether and to what extent the floristic differentiation of pleustonic communities corresponds to the differentiation of their habitat conditions. Based on phytosociological studies, it was shown that the investigated phytocoenoses are not random groups of species, but well differentiated in terms of floristic composition and phytocoenotic structure by communities. It was shown that the studied phytocoenoses represent the following separate associations in phytosociological terms: Salvinio natantis-Spirodeletum polyrhizae, Lemno-Spirodeletum polyrhizae, Riccietum fluitantis and Ricciocarpetum natantis. Hydrochemical studies showed that the floristic distinctiveness of these communities is largely confirmed by the differentiation of properties of the water habitat. Salvinio natantis-Spirodeletum polyrhizae is characterised by the deepest waters (mainly 0.7–1.2 m), alkaline, of a low colour, rich in ions (Mg2+, Na+, Cl−) and therefore characterised by the highest electrolytic conductivity, poor in dissolved organic matter, NO3− and total iron. Lemno-Spirodeletum polyrhizae is characterised by medium deep waters (mainly 0.3–0.8 m), mostly alkaline, of a low colour, less rich in ions (Ca2+, Na+, Cl−) and relatively low in dissolved organic matter and NO3−. Riccietum fluitantis is characterised by shallow waters (mainly 0.2–0.4 m), most often slightly acidic, of a quite high colour, low in cations and Cl−, and relatively rich in total iron, NO3−, and dissolved organic matter. Ricciocarpetum natantis is characterised by the shallowest waters, (mainly < 0.3 m), most often acidic, of the highest colour, low in ions, and rich in total iron, dissolved silica, NO3− and dissolved organic matter. By demonstrating habitat distinctiveness, the studied pleustonic communities may have significance as indicators of various types of aquatic environment.