Limnol. Rev., Volume 18, Issue 2 (June 2018) – 4 articles , Pages 47-89

The unicellular flagellates of the genus Phacotus, which form a solid calcite lorica by extracellular precipitation of calcium carbonate are some of the nanoplankters quite frequently occurring in hardwater ecosystems of the temperate zone. The aim of this study was to describe seasonal changes of Phacotus lenticularis populations in several types of water bodies (a glacial lake, small and shallow ponds, and a lowland river) in relation to some environmental parameters. All the water bodies are subject to multiple human pressure: recreation, fishing, agriculture, and urbanization. P. lenticularis individuals preserved in Lugol’s solution were counted under an inverted microscope (after sedimentation in 14 or 9 mL chambers), including both empty and filled loricae. Its populations differed both between seasons and between waters. High P. lenticularis abundance was mainly limited to the summer months. It was observed at temperatures above 19 °C and pH values above 7.8, in water characterized by quite high electrolytic conductivity (>500 μS cm⁻¹). Statistical analysis reveals two significant relationships between physicochemical parameters and the abundance of P. lenticularis. This suggests that in the investigated waters the biotic factors and processes are probably more important regulators of changes in the density of its population than nutrients. Full article

This article presents the hydrographic and hydrochemical characteristics of this lake. Lake Jazerske is located in the Western Carpathians (Spiš Magura) in northern Slovakia. It occupies a depression that was formed at the foot of the main scarp of a landslide. Below the lake, there are small intercolluvial depressions that have been transformed into wetlands (peat bogs). The studied lake is very small. Its area is 3600 m² and its length is 85 m. The maximum depth of the lake is 7.2 m and its capacity is 17,000 m³. The lake is supplied by an inflow of groundwater via fractured aquifers. During periods of heavy rainfall and snow melting, the lake is also supplied by the water from surface runoff. On the main slope of the landslides, traces of ephemeral courses were also found. During the periods of increased supply (spring snow melting, summer rainfall), the outflow of water from the lake occurs both on the surface and underground. In terms of its hydrochemistry, the lake water represents the four-ion type–bicarbonate-sulphate-calcium-magnesium. The concentrations of various ions is characteristic of the shallow groundwater of the Carpathian flysch. The predominant cation, the average concentration of which is 52 mg dm⁻³, is calcium. The dominant anion is carbohydrates with an average concentration of 163 mg dm⁻³. What is interesting is the very low levels of chlorides, which do not exceed 2 mg dm⁻³. The electrolytic conductivity of the water flowing out of the lake ranged from 290 to 328 μS cm⁻¹. Full article

The paper presents analysis results concerning changes in the range of areas of surface and transitional retention, here corresponding with wetlands, in two small lake catchments in the western part of West Polesie. The cartometric research was performed on maps covering the period from the 19th to the early 21st century. The analyses were referred to the modern state of investigation recorded on orthophotomaps in data bases disclosed in Geoportal Krajowy and in the Google Earth Pro application. Lake surface retention showed no substantial changes, and the differences result from the scale of maps used in the study, and therefore from the degree of detail of the presented objects. In the catchment of Lake Czarne Gościnieckie it occupied from 13.61 to 15.64% of its area, and in the catchment of Lake Brzeziczno from 0.96 to 1.28%. The greatest discrepancies in the area of wetlands result from the cartographic method of presentation, and generalisation of maps. In the catchment of Lake Czarne Gościnieckie, areas of transitional retention could be identified on 11 out of 13 maps, and in the catchment of Lake Brzeziczno on 12. In the case of the former catchment, transitional retention occupies from 17.35 to 34.00% of its area, and in the catchment of Brzeziczno from 4.81 to 24.00%. Such different surface areas of wetlands measured on maps, however, do not signify evident tendencies for change. Over the last 200 years, no substantial changes occurred in the studied catchments regarding the range of surface waters and wetlands, as confirmed by field research conducted in the years 2006–2012. The quantity and quality of maps and the variability of their scales encourage a careful interpretation of obtained information. In such a case, it is necessary to supplement cartographic analyses with investigating procedures of map preparation, and also to collect written documents concerning the entire area. Full article

The article concerns the study of the influence of river reservoirs of Belarus on the evolution of river channels in their downstream pools. On the basis of observational data from the Republican Hydrometeorological Center of the Republic of Belarus (RHMC), as well as own field observations a quantitative evaluation of the change of the main channel formation factors, the direction, horizontal and vertical parameters of deformation of the riverbeds below dams has been performed. Changes in the type of channel processes for the regulated parts of rivers have also been assessed. It has been found that the investigated reservoirs accumulate up to 65% of the sediment transported by the river in a suspended state. Restoration of the water turbidity to values close to the natural regime occurs at a distance of 20 km downstream from a dam of small reservoirs, and up to 50 km downstream from a dam in the case of medium-sized reservoirs. The degree of the riverbed deformations downstream from a reservoir is defined by the geological and lithologic structure of the channel bottom deposits. If there are easily washed sand deposits at the bottom, then the dominant process is deep erosion. If sediments are more heterogenic with increased admixture of gravel-pebble material the development of directed deep erosion is reduced. The change of the existing type of channel processes of regulated rivers is due to the imbalance between the main factors of channel formation in the initial period of the operation of new water-engineering systems (5–7 years). The observed changes are typical of rivers with sandy riverbed. Full article