Explanatory variables that were not presented directly to the Kohonen artificial neural network.

Chlorophyll a (a-c), water temperature (d-f) at the Zarzęcin (a, d), Bronisławów (b, e) and Tresta (c, f) stations; water inflow to the Sulejow Reservoir (g) and time of water retention in the reservoir (h). Point–median; whiskers–interquartile range; H–statistics of the Kruskal-Wallis test (df = 5, NESp = 66, NSp = 46, NLSp/Sm = 106, NSm = 57, NHotSm = 80, NHunLSp/Sm = 57) applied in testing the differences between the SOM sub-clusters (the latter is underlined with the same line if not different at p ≤ 0.05 in post-hoc tests). An asterisk indicates SOM sub-clusters for which a significant difference between sampling stations was recorded (see Table 1 for details). Abbreviations of the sub-clusters names: 1 ESp–early spring; 2 Sp–spring; 3 Sp/Sm–spring/summer; 4 Sm–summer; 5 HotSm–hot summer; 6 HunLSp/Sm—hydrologically unstable late spring/summer.