One of the most interesting and relatively little-known water acosystems of ”Lasy Janowskie” Natural Landscape Park is its old ponds which have been in most cases excluded from intensive fisheries for many decades. Four of them were studied in 1996, 2005 and 2013, regarding their planktonic rotifer assemblages. The total of 60 rotifer taxa were observed in the plankton. The number of their species in individual reservoirs ranged from 7 to 21, while their density amounted to 33–775 ind. dm-3. As many as 21 of the species observed in individual water bodies and study periods belonged to dominants. While watching the changes occurring in the plankton during the period of 17 years , we were trying to determine which of those tiny reservoirs were inhabited by more sustainable rorifer assemblages and which ecological qualities were more closely related to such sustainability: species richness, its diversity, density, bio-mass, composition or domination structure. The results of the studies revealed slight variability of ecological properties in planktonic rotifer assemblages in the ponds composing large reservoir groups, and significantly higher variability of those qualities in ”single” ponds, not belonging to large complexes.

In two fish ponds in Lasy Janowskie Landscape Park 48 water mite species were caught. In the pond Momoty Duże, situated in the Lasy Janowskie reserve, more species (38), higher species diversity (3.88), and a larger share of lake fauna (33.2%) were observed than in Momoty Małe (33, 3.67 and 22.6% respectively). In the combined collected material small water body species were dominant (70.6%). Similarity between the Hydrachnidia assemblages of the two ponds was 50.1%. The large number of species and individuals caught and the high values for the species diversity index confirm the significant role of fish ponds as a habitat for water mites. A characteristic trait of the ponds was the very small percentage of vernal species and of tyrphobiontic and tyrphophilic species. Although more species and a larger share of lake fauna were found in the pond situated in the reserve (Momoty Duże) than in the pond outside the reserve (Momoty Małe), the differences in the structure of the fauna were slight. The lack of pronounced differences between the two ponds was due to their similar habitat characteristics and similar use.