Volume 15 (2015): Edizione 3 (September 2015)

This paper presents the results of Cladocera subfossil analysis using material obtained from five paleolakes of the Eemian Interglacial located in central and north-eastern Poland. Analyses of Cladocera subfossils in Poland and other parts of the world have revealed detailed results covering the last 13,000 years. Cladocera subfossils from sediments older than the last glaciation have been analysed occasionally. The first analyses of older sediments were conducted in Denmark by Frey in 1962. In Poland, the first analyses of this type were conducted on material obtained in Konin. The Eemian lakes subject to the study were formed at the end of the Warta Glaciation in tunnel and kettle holes. A continuous record of environmental changes throughout the Eemian Interglacial until the early Vistulian Glaciation has been preserved in lake sediments. The bottom part of the profile consists of sands and silts, followed by gyttja and peat. The upper part of the profile contains peat and organic shales. Cladocera subfossils found in Eemian sediments were thinner and their structure was more damaged. The low degree of subfossil preservation forced a change in the method of preparation of subfossils for microscopic analysis as required by IGCP Project 158. Cladocera species determined within the studied paleolakes correspond to the present-day species inhabiting the area of Poland and Europe. The species composition and the variability in the frequency of Cladocera specimens made it possible to distinguish discrete phases of lake development associated with changes in temperature and water level, trophic state and the presence of macrophytes. The results of Cladocera analysis are well correlated with data obtained in pollen analyses.

Various factors influence the spatial and temporal patterns of land cover and land use in lakeland landscapes. Land use/cover change (LUCC) is one of the crucial factors influencing both natural processes that occur in lakelands and lakes and anthropogenic processes, which intensify these changes. Therefore, LUCC at a local and regional scale may be treated as an important geoindicator for the functioning of the lakeland landscape. Nowadays, LUCC mostly depends on different human decisions. In the existing literature, the consequences of negative changes have already been widely recognized. Conversely, in this paper, we focus on the possible positive effects of LUCC. To that end, we built an agent-based model to show how selected human decisions may positively influence lakeland landscapes and lakes. We apply the model to the Gniezno Lakeland, Poland. Based on the environmental decisions of farmers, the model demonstrates how the LUCC pattern may change in time and space and how those changes may influence freshwater quality in four individual lake catchments of the Gniezno Lakeland.

The main research problem of the paper is aimed at determining the proper functioning of Lake Gardno within the period 2012-2014 considered as hydrological years in reference to the physiochemical properties of its waters, water balance, thermal regime and water overturn. Lake Gardno is a representative of non-run-off lake geo-eco-systems; it is situated within the Southern Baltic Sea Coastland at the cliff shore of Wolin Island. The paper analyses how weather conditions affect the specifics of water supplies provided to the lake and seasonal dynamics of its waters, their chemical, thermal and aerobic properties. It also specifies their overturn and balance with a particular emphasis on their supplies together with fog deposits.

The aim of this study is to determine the factors affecting the spatial variation of the chemical composition of lake waters in the Tatra Mountains. In most cases, the lake waters are acidic and very dilute, with a low ionic content and low conductivity values. In general, HCO₃^- is the predominant anion and Ca²⁺ is the predominant cation in the chemical composition of the analysed water samples. Among nutrients, NO₃^- is the dominant form of nitrogen, but also NH₄⁺ may be found in lake waters. By using principal component analysis (PCA) two factors have been identified that explain 63.6% of the variation in the chemical composition of water. Factor 1, which explains 43.2% of the total variability, is associated with Ca²⁺, SO₄^2-, HCO₃^-, Na⁺, pH and lake area and is related to weathering and atmospheric deposition. Factor 2 explains 20.4% of the total variability and is associated with Mg²⁺, K⁺, Cl^- and with lake altitude. In terms of chemical composition, based on the projection of cases of the first and second factor, the lakes in the Tatra Mountains may be divided into four groups, representing the following: lakes situated within the subalpine forest at the lowest altitude (<1300 m a.s.l.), characterized by medium mineralization (~14 mg dm^-3) and the highest concentration of NH₄⁺ and Cl^- (Group I, 8 lakes); slightly alkaline lakes, with the lowest average acidification, medium mineralization (~31 mg dm^-3) and the highest concentrations of Ca²⁺, Mg²⁺, Na⁺, K⁺, HCO₃^-, SO₄^2-, and low concentrations of NO₃^- (Group II, 2 lakes); small lakes (<0.01 ha) located within the alpine meadow and the nival zones at high elevations with the lowest mean mineralization (~4.3 mg dm^-3), with the highest ammonium contribution to the sum of ions among all lakes and the largest sensitivity to acidification (Group III, 13 lakes); large lakes with high mineralization and slightly acidic pH (Group IV, 26 lakes) and medium mineralization (~31 mg dm^-3).

The landslide in Huta Polańska (Beskid Niski/Lower Beskids) is an example of a particular lake geoecosystem. The largest inter-colluvial depression forms a lake basin constantly filled with water, with a natural outflow in the form of a watercourse. Three drainless sink-holes constituting places of periodical accumulation of water and organic-mineral sediments were localized within the landslide. The direction of the landslide movement and its wedge-like shape are determined primarily by the fault surface located in its south-western part. It also forces the linear course of the streams and the cascade location of depressions between colluvial ramparts, seasonally or permanently filled with water. The inventory of minor tectonic structures and the morphotectonic analysis indicate tectonic conditions of this landslide lake geoecosystem. The structures located within the fault surfaces are indicative of shear stresses and their orientation determines the direction of rock movement (Zuchiewicz, 1997a; Szczęsny, 2003). The morphological analysis and correlation of landslide forms indicate the combined rotational-translational motion. It was ended by mud and debris flow which divided the valley longitudinal axis and damming the waters of the Hucianka stream. The result is a landslide dam lake, whose effects are visible within the floodplain above the former landslide dam. In order to formulate the final conclusions regarding the morphotectonic analysis and the slope transformation phases, laser scanning photos were also used.