Comparison of gastrotrich fauna on elodeids and in bottom sediments of lakes of different trophic status (the region Polesie Lubelskie, Eastern Poland)

Species diversity of gastrotrich communities on elodeids and in bottom sediments of lakes of different trophic status was compared. Thirty-eight species of Gastrotricha (34 in bottom sediment and 21 on elodeids) were found, which belong to the only family of Chaetonotidae Zelinka, 1889. Species diversity of both habitats was reflected in the diversity indices ranging from 2.02 (a dystrophic lake) to 2.67 (a strongly eutrophic lake) for bottom sediment, and from 2.01 (a mesotrophic lake) to 2.54 (a strongly eutrophic lake) for elodeids. The similarity of gastrotrich fauna from the two habitats was low, and varied from 17% (a mesotrophic lake) to 38% (a strongly eutrophic lake). Low similarity of elodeid fauna from lakes of different trophic status was also found, in spite of similar plant species composition. The lowest similarity in elodeid fauna (23%) was recorded for dystrophic and mesotrophic lakes, whereas the highest one (68%) was observed for eutrophic and strongly eutrophic lakes. That allows to conclude that the diversity of epiphytic fauna is affected by trophic status rather than by vegetation type. The comparison of the gastrotrich fauna from elodeids and bottom sediments in lakes of different trophic status provides additional autoecological characteristics of Heterolepidoderma ocellatum (Mečnikow, 1865) and allows to recognize this species as belonging to a group of species closely related to macrophytes.