Fern Azolla filiculoides at New Sites in Oder River (Poland) — Invader or Ephemeral?

Azolla filiculoides Lam. is the second most widely distributed alien aquatic plant in Europe. A native of America, it has become — on account of human mediation — a cosmopolitan species. In Poland, it has been known so far from a few stands in ponds and old river beds. In 2016, it was recorded at six new sites in-between the groynes at the main Oder river bed between Maszewko near Krosno Odrzańskie (52°3′10.69″N, 14°57′13.56″E) and Owczary (52°28′53.59″N, 14°37′30.43″E). The assemblages containing the fern were identified as representing the association Ceratophyllo-Azolletum filiculoidis Nedelcu 1967. Azolla has also entered the phytocoenoses of other floating plant communities. Mean values of several chemical parameters of the water like conductivity, salinity, total dissolved solids and nitrate content at the fern stations were significantly higher than the mean values found in the Azolla-devoid sites while the values for hardness (Ca), pH and visibility (Secchi Disc depth) were lower at Azolla sites. In 2017, this alien fern was found to had successfully overwintered in the main bed of Oder river, and its further spread down the river was observed. The appearance of Azolla filiculoides in the Oder may be associated with an exceptionally warm winter; its emergence may also accelerate the species' invasion in Poland.

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Opracowanie rekordu w ramach umowy 509/P-DUN/2018 ze środków MNiSW przeznaczonych na działalność upowszechniającą naukę (2018).