The distribution of rotifers (Rotifera) within a single Myriophyllum bed

The research on the spatial distribution of rotifers between the central and border part of the Myriophyllum bed (M. verticillatum) was carried out between 1998 and 1999 in the shallow part (approx. 1 m depth) of Budzynskie Lake (Wielkopolski National Park, Poland). The comparison of both species composition and the numbers of individuals between both of the examined zones have not revealed statistically significant differences. However, a higher number of rotifer species and their higher densities, as well as increased participation of littoral species were observed in the middle of the vegetation bed. The structure of the dominating species also differed between both areas. Seven rotifer species were found to have significantly greater numbers in the central part of the Myriophyllum bed, while only one species was significantly correlated with the border part of the macrophyte stand. These differences in the behaviour of particular groups of rotifers may be dependent on the structure of their microhabitat and their position in relation to the open water zone. They may also be related to young fish predation in both habitats and better refuge conditions inside the thick macrophyte stand, as well as typical adaptation to littoral or limnetic life.