Limnol. Rev., Volume 12, Issue 3 (September 2012) – 6 articles , Pages 103-157

The study describes thermal regimes of thirty selected Polish lakes in the spring season. The author used 35-year series of daily measurements of surface water temperature in the years 1961–2005 and the measurements of the vertical distribution of water temperature taken in tens of selected water bodies. The diversified pace of the increase in surface water temperature (SWT) during the spring warming period makes it possible to distinguish two thermal phases: the early and late phases of spring warming. The limits of those phases are marked by the dates of the disappearance of ice cover and the dates when the SWT stays well over the threshold values, which amount to 4 °C and 15 °C respectively. The SWT increase in the lakes (April and May) causes changes in the water’s vertical thermal structure (the formation of epi- and metalimnion) and considerable dynamics of its descriptive parameters, such as water temperature, thermal stratification coefficient, thermal gradients, heat resources, etc. Full article

The principal threat to lakes of the temperate zone is posed by factors accelerating their eutrophication and causing marked deoxygenation of the deeper layers of water, mainly the hypo- and metalimnion. Among their effects are frequent phytoplankton blooms, including those of blue-green algae, and general deterioration of water quality also affecting the abundance and health status of fish. The chief concern is a disturbed proportion between the quantity of complex chemical compounds, especially organic, and the oxygen content of lake waters. Natural processes of water oxygenation are not too intensive, because they are practically limited to the epilimnion layer, connected as they are with the activity of aquatic plants of the littoral and sublittoral zone (which tends to disappear in contaminated lakes) and wind energy (the effect of waving). In summer conditions, with a relatively great chemical activity of bottom deposits, the intensity of those processes is usually inadequate. Hence, in 1995 research was launched in the Institute of Agricultural Engineering of the Agricultural University in Poznań on an integrated lake restoration technology whose core was a self-powered aerator capable of oxygenating also the bottom layers of water (the hypolimnion) of deep lakes. The aerator uses energy obtained from a Savonius rotor mainly to diffuse gases: to release hydrogen sulphide, which usually saturates the hypolimnion water completely, and then to saturate this water with oxygen. Even early studies showed the constructed device to be highly efficient in improving oxygen conditions in the bottom zone. They also made it clear that it should be equipped with an autonomous system designed to inactivate phosphorus, one of the principal factors determining the rate of lake degradation. In 2003 the first wind-driven pulverizing aerator equipped with such a system was installed in Lake Urban in Chodzież. The aim of this work is to present the principles of operation of a wind-driven pulverizing aerator with a phosphorus inactivation system, as well as its general technical characteristics and preliminary results of a study of its performance. Full article

The character of phenomena related to freezing depends on macroscale factors and mainly on thermal conditions, but local conditions can also be of great importance in shaping the course of these phenomena. Building of ice cover can be substantially different even for neighbouring lakes as a result of different individual features such as, for example, morphometric parameters. In this study the variation in the thickness of ice cover on Lake Samołęskie (29 ha) localised in western Poland, is analysed. According to measurements performed the differences in the thickness of ice cover was significant as it varied from 20 to 33 cm. A characteristic feature was that along the west bank of the lake the ice cover was thinner and its thickness increased towards the east. Analysis of the hydrogeological data revealed that this phenomenon is related to the supply of water to the lake basin by efficient water-carrying formations. The influx of water affects the bottom layer of the ice cover. This effect is aggravated by the fact that the water is supplied under elevated pressure as evidenced by the presence of a polynia of about 10 m in diameter, over the deepest (over 20 m deep) site in the lake. The polynia is never frozen, even during the coldest winters. The specific features of the lake illustrate the influence of local geological conditions on the character of processes taking place in lakes in general. Full article

The study examined the development of pike (Esox lucius L.) roe in water containing variously concentrated coagulants PIX^®113 and PAX^®18, which are increasingly being used in Poland as a method of lake reclamation. The genital products came from spawners caught from a natural water body (Lake Przybiernów). The eggs were incubated in water taken from the same lake, and subjected to the process of phosphorus and iron precipitation with coagulants. Based on the results, it was found that the coagulants used in the experiment inhibit the embryogenesis of pike by the formation of aggregates falling to the bottom, reducing the percentage of live embryos and affecting the size and malformation of the hatching larvae. Full article

Sediments from hypereutrophic Lake Łajskie localized in northeastern Poland were examined on the basis of P-fraction. The sediments were collected at five sampling sites. In the investigated lake, the rank order of P-fractions was HCl-P > BD-P > NH₄Cl-P > NaOH-nrP. The loosely sorbed phosphorus NH₄Cl-P represented < 3% of the sedimentary inorganic phosphorus, while the reductant phosphorus (BD-P) ranged from 2 to 10%. The calcium bound phosphorus (HCl-P) showed considerable contribution (59–74%) to the sedimentary inorganic P-loads. BDP was the most reactive fraction in Lake Łajskie. Iron compounds and organic matter seem to play a significant role in regulating this labile P-budget. Full article

The article presents the results of landscape analysis of the surroundings of Lake Rzecin in Noteć Forest depicted on cartographic materials. Morphometrical analysis and analysis of changes in the water conditions of Lake Rzecin were conducted. Thanks to many cartographic data, changes in lake geometry could be observed during almost the whole of the last two centuries. The results show that the major impact on the rate of lake level decrease in the last two hundred years was due to melioration works. Two periods of rapid decrease in the lake surface can be observed during this time. The first occurred as a result of the creation of Rzecin Ditch, which probably took place in the middle of the 19th century; the second, in all likelihood, with its cleaning out; the exact date of this operation is not known but the results of map analysis suggest that it could have happened between 1958 and 1966. Due to these two events the lake surface decreased by 73.6% during the analysed period. Apart from this phenomenon the lake surface area seems to be quite stable: there were some fluctuations; however, changes did not exceed more than 5%. That is why it can be assumed that the human factor has the biggest influence on succession rate of the lake ecosystem. Analysis of the map collection shows that during the last two centuries there were no huge changes in the local landscape; however, other historical sources do not confirm this. According to them, not only man but also fires and insect gradations had an enormous influence on the Noteć Forest ecosystem. Nonetheless, land use structure within the Rzecin Ditch catchment area did not change a great deal; the most significant modification was the increment of forested areas from 74.1 up to 85.1%. Full article