Research on the ecology of water mites in flowing water has focused mainly on analysis of factors directly affecting these organisms in the aquatic environment. The hypothesis of this study was that apart from factors acting within the aquatic environment, the formation of Hydrachnidia communities in lotic ecosystems may also be affected by factors acting in the terrestrial environment. The analysis was made at three different levels of organization of the environment: (1) landscape level (sub-catchments, terrestrial environment), (2) macrohabitat level (sampling sites, aquatic environment) and (3) mesohabitat level (sampling sub-sites, aquatic environment). Some correlation was noted between certain species and some sub-catchment parameters. This may indicate a link between some landscape features (terrestrial environment) and the formation of water mite assemblages in the river. The low percentage for physicochemical parameters together in explaining the variance in occurrence of species, very low correlations between species and physicochemical parameters and the discrepancy in the grouping of sites in the case of faunal data and data on the physicochemical indicates that physicochemical factors had little influence on water mites. Taking into account all three levels of organization of the environment analyzed, we can say that at the landscape level we can find only indirect relationships between environmental factors and the fauna inhabiting the aquatic environment; at the macrohabitat level the description of Hydrachnidia is more precise but still of a general nature. Only analysis at the mesohabitat level fully explains the specific character of Hydrachnidia assemblages.

Knowledge and management of aquatic ecosystems (formerly Bulletin Français de la Pèche et de la Pisciculture), an international journal on freshwater ecosystem

Rehabilitation of river beds is sometimes necessary, particularly when a substantial amount of bottom sediment causes unnaturally slow water flow. However, it is difficult to predict whether such procedures will negatively affect biodiversity and species composition of organisms inhabiting these sites. The effects of such procedures were analysed in the Krąpiel river in northwestern Poland. It was postulated that dredging would not reduce Heteroptera diversity, but would alter the habitat significantly and create lotic habitats for rheophilous species. It was also postulated that conditions would become less favourable for taxa preferring a bottom with accumulated mud and abundant vegetation. According to our results, dredging did not significantly affect species diversity of Heteroptera, but did cause an increase in abundances of several species. Dredging increased the number of available habitats, which were mainly inhabited by abundant pioneer species. Aquarius najas, Aphelocheirus aestivalis, Plea min...

Studies on the fauna of water beetles inhabiting anthropogenic water bodies were conducted on 44 clay-pit and gravel-pit ponds. A total of 125 water beetle species were identified. The dominant species were Scarodytes halensis and Laccobius minutus, representing the argillophilous component. Eurytopic, lake and riverine, and peatland species were also identified. Among the environmental factors determining the diversity of the water beetle fauna in particular types of habitats, the most significant role was played by the substratum and succession stage.

This paper presents the results of an analysis of species richness (expressed as number of species), biodiversity (the H′ index) and synecological structure of communities of aquatic beetles living in clay and gravel pits. It evaluates the analyzed habitats in terms of the influence of water physical and chemical parameters on the characteristics of beetle assemblages. The assessment of beetle communities was performed from the point of view of ecology and nature conservation. The analyzed physical and chemical parameters of water as well as the presence of certain species, mainly rheophiles, indicate very weak eutrophication of the ponds. The parameters which most significantly distinguish gravel pits from clay pits are specific conductivity, HCO₃ ⁻, SO₄ ²⁻ and Cl^–. The PCA analysis, however, suggests that the abundance and species richness as well as the biodiversity of beetles living in the analyzed ponds were most closely correlated with temperature and with NH₄-N, total N and the BOD₅ of water. The analyzed ponds proved to be very attractive habitats populated by numerous species, including rare, threatened (listed in the Polish Red Book of Species) and termophilous ones, or organisms valuable to Polish wildlife for other reasons. They include two species rare in Poland—Hydrochus ignicollis and Ochthebius hungaricus, one species fully protected in Poland—Hydrophilus aterrimus (VU), as well as Haliplus fulvicollis (VU) and Gyrinus caspius (EN). The findings are important for the preservation of biodiversity, both locally and on a scale surpassing the region, a conclusion which highlights the value of anthropogenic ponds such as clay pits and gravel pits, in the ecological landscape and implies that they deserve an adequate protection in order to sustain their function.