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.

Structure of fish communities of five small water reservoirs located near the Chodelka river was investigated during the years 2002, 2008 and 2016. In the analyzed water bodies seven fish were noted, representing four families: Cyprinidae (4 species) and Esocidae, Cobitidae, Peri-cidae and Ictaluridae (1 species each). In the structure of collected fish one protected species (M. fossilis) and one alien species (C. auratus gibelio) were presented. Domination structure of ichthyofauna showed considerable differences. Among the dominant species were: R. rutilus (all five reservoir) and C. auratus. The percentage of each fish species in the biomass was slightly different in relation to the structure of domination expressed by the number of identified individuals. Regardless of the reservoir, larger share held: E. lucius, R. rutilus and C. auratus.

Dratów, Krzczeń and Tomaszne lakes are linked by means of Wieprz-Krzna Canal. On the other hand, Bikcze, Mytycze and Plotycze lakes are not included in the water system of Wieprz-Krzna Canal. However, all these lakes are regarded as biologically valuable water reser-voirs forming Łęczyńsko-Włodawskie Lakeland. They are shallow eutrophic lakes with varied water surface, different catchment area and diversified structure of catchment management. The qualitative and quantitative composition of planktonic rotifers was studied in spring, summer and autumn of 2012 and 2013. The studies revealed the presence of 67 Rotifera species with their mean density ranging from 119 ind. dm-3 in Tomaszne lake to 1441 ind. dm-3 in Bikcze lake. Dominants included few very common species of Brachionus angularis, Keratella cochlearis, Keratella cochlearis tecta, Keratella quadrata, Polyartchra vulgaris. Dominance structure and species diversity suggest a slightly higher ecological status of Mytycze lake, as compared to the remaining eutrophic reservoirs. Faunistic differences observed among rotifer assemblages inhabiting individual lakes were significantly bigger than those registered in the successive study years within the area of individual lakes. This property referred to all the reservoirs, both the ones linked with the water system of the canal and the lakes not included in the canal system. Bigger faunistic differences occurred among rotifer assemblages inhabiting the lakes of Wieprz-Krzna Canal sys-tem, as compared with the assemblages found in the lakes not included in the system.

Structure of fish communities of five small water reservoirs located near the Wieprz--Krzna Canal was investigated during the years 2002, 2008 and 2014. In the analyzed water bod-ies seven fish were noted, representing four families: Cyprinidae (5 species) and Esocidae, Cobi-tidae and Ictaluridae (1 species each). In the structure of collected fish two protected species (M. fossilis and R. sericeus amarus) and one alien species (C. auratus gibelio) were presented. Domination structure of ichthyofauna showed considerable differences. Among the dominant species were: I. nebulosus (all five reservoir), C. auratus (Jabłoń Center 2, Jabłoń Church and Jabłoń Firlej-Ostrówek), and R. rutilus (Jabłoń West and Jabłoń Firlej-Ostrówek). The percentage of each fish species in the biomass was slightly different in relation to the structure of domination expressed by the number of identified individuals. Regardless of the reservoir, larger share held: E. lucius, I. nebulosus and C. auratus Moreover, one of the purpose of the study was searching for a new stands of lake minnow. However, the species was not recorded in fish communities of any of the reservoirs, despite of the ecological state of reservoirs indicating the potential habitat for lake minnow.

Dratów, Krzczeń and Tomaszne lakes are among environmentally valuable reservoirs in Poland and Łęczyńsko-Włodawskie Lakeland. These are shallow eutrophic reservoirs of varied water surface. What they have in common is the fact that they are linked by Wieprz-Krzna Canal. The main aim of the present study was to determine the degree of faunistic similarity between planktonic rorifer assemblages inhabiting these particular lakes. The authors were interested to find out whether linking the lakes with the canal, as well as currently applied water exchange could affect the degree of faunistic similarity occurring between these lakes. Physical and chemi-cal analyses, as well as the studies of planktonic rotifers were carried out in the spring, summer and autumn of 2012 and 2013. They included determining the qualitative composition and the density of planktonic rotifers. The studies resulted in finding 50 species of Rotifera, with mean density ranging from 75 to 855 ind. dm-3. The dominants included the common species of Keratel-la cochlearis, Keratella cochlearis tecta, Keratella quadrata, Polyarthra vulgaris, Kellicottia longispina, Brachionus angularis, Ascomorpha odalis and Synchaeta pectinata. The results re-vealed high faunistic similarity among rotifer assemblages inhabiting a particular lake in different years, and high diversification occurring between the lakes compared in the work. The analyses showed that linking the lakes by Wieprz-Krzna Canal did not significantly affect the faunistic similarity of these particular lakes.

Due to the significant role of macrophytes in the functioning of lake ecosystems studies have been undertaken to examine whether mutual dependence is present within emergent, floating-leaved, and submerged aquatic macrophytes. The study included 5 small lakes from Polesie Lubelskie region. The research included: qualitative analysis of macrophytes (area occupied by macrophytes, composition, range of individual plant groups of occurrence), quantitative analysis of macrophytes (biomass of macrophytes inhabiting the lake), analysis of distribution as well as characteristics diversity of shoreline and surrounding land use. Because of differences in the environmental conditions, mostly light availability, usage of buffer zone, among the three macrophyte groups, changes in biomass were analyzed in this work suggests that complementarity not competition drive the community. This phenomenon seems to occur only in macrophyte lakes where all three groups are present and the surrounding buffer zones remain natural. In lakes where one of the three groups of macrophytes were missing, it is likely that the ecological roles are fulfilled by other plant groups, such as phytoplankton. The studied lakes represent both phytoplanton and macrophyte type of lakes.

The paper presents the analysis of structure of fish communities in five small postexcavation reservoirs situated in Tyśmienica valley (Polesie Lubelskie). Special attention was paid to the quality of population of lake minnow Eupallasella percnurus. By the time the extensive drainage works were done in the 60s and 70s of the 20th century, Polesie Lubelskie was rich in small water reservoirs. As a result of drainage of wetlands, many of them disappeared. Among those which still exist, most of them are located in the Tyśmienica valley. The study revealed that the studied reservoir inhabited seven fish species representing two families. It was also found that structure of dominance and biomass structure is very diverse. In each reservoir the dominant species was different. The lake minnow E. percnurus was determined in three reservoires.

The aim of this study was to analyze the influence of water movement on both qualita-tive and quantitative occurrence of macrophytes in lakes. We studied four lakes differentiated in respect of water supply (two flow and two inflow).The investigation included: determination of the buffer zones of lakes, analysis of land use forms and layout of the buffer zone, floristic charac-teristic of lakes littoral, characteristic of phytolittoral types, analysis of physical and chemical parameters of lakes. The buffer zone of the flow lakes was dominated by farmland, but there was no land meadow. In the inflow lakes co-dominated fields and forests in the buffer zone. The in-flow lakes characterized by greater species diversity, density and biomass of emergent macro-phytes. In all investigated lakes, in the zone of water supply, analyzed features of macrophytes, and selected chemical parameters of water, reached the highest value.

The study included mesotrophic Lake Piaseczno, located in the Łęczna-Włodawa Lake District. The aim of the study was to evaluate changes of water vegetation of a mesotrophic lake subjected to strong recreational pressure. Specifically we sought to better understand which natu-ral landscapes and anthropogenic developments stimulate or impede macrophyte development and spread. The study was conducted in July in 1997, 2007 and 2017 in three transects: the peat-bog (northern part of the lake), the recreational area (southeast part) and the agricultural area (east). The phytolittoral zone was analyzed from the shoreline to the maximum range of macrophytes occurrence. The study included all groups of macrophytes. Macrophytes in the mesotrophic Lake Piaseczno are still subjected to successive changes. Clearly increased diversity among emergent macrophytes, while a group of submerged macrophytes decreased. The largest changes among analyzed groups of macrophytes occurred in recreational and agricultural transects. Macrophytes have increased the range of occurrence, which may be due to hydrological changes associated with raising the overall water level, thus with increasing the area of the littoral. Impoverishment of diversity among elodeids shows the processes associated with the increase in Lake trophy.