The technological properties of raw fish are influenced by the changes in protein structure under heating, which determines the texture and quality of the product. The aim of the study was to examine the protein denaturation temperature and the rheological properties of Baltic herring muscle tissue. The thermal properties were determined by the differential scanning calorimetry (DSC) method and the rheological properties were determined using dynamic oscillatory tests. DSC showed four peaks associated with denaturing transformations of myosin (39.59 °C), sarcoplasm (51.67 °C), connective tissue (63.16 °C), and actin (74.40 °C). Analysis showed that not all transformations occurred according to the same kinetic model. The first two and the last peak are described by 1st order kinetics, while peak 3 is described by 2nd order kinetics. Correlating the changes in fish tissue structure during heating with the rheological characteristics provides more information. The obtained kinetics models correlated very strongly with the results of model testing. Rheological changes of the G’ and G” values had two inflexion points and demonstrate a high degree of convergence with the DSC changes of herring muscle tissue from 20 to 85 °C.

This study presents the directions and the rate of changes occurring in the coastal lakes Jamno and Bukowo, located in northern Poland. Based on the cartographic materials and aerial photographs of those water bodies, it was established that in 1909–2012, the area of the lakes decreased by 183.6 ha (7.7%) and 250.7 ha (13.6%) for Jamno and Bukowo, respectively. Another component of lake disappearance — shallowing of lake basins — was analyzed using bathymetric plans. It turned out that water supplies of Jamno during more than 100 years decreased by 2.4 million m³ (5.9%), while in the case of Bukowo, it was 5.9 million (17.5%). Unfavorable location (inflow of pollutants from the basin) and morphometry of both lakes should be considered as the main causes of such major changes. The lakes are polymictic with a considerable area of the shallowest zone (1 m depth). This favors the vegetation succession and, consequently, shallowing of the lake basins. Moreover, direct connection with the Baltic Sea contributes to the fact that the materials of marine origin deposited in the form of a reverse delta also contribute to a decrease in the open water surface area.

Bathymetric measurements of Morskie Oko LakeThe aim of this study was to gather and summarize bathymetric measurements of Morskie Oko Lake which have been carried out up to now. Apart from the two existing plans from 1909 and 1934, a plan presenting the arrangement of isobaths in 1879 was worked out on the basis of numerical data. Moreover, after field investigation with an echo sounder in 2011, a new bathymetric plan was created. All four plans were used to calculate the basic morphometric parameters of Morskie Oko. Bathygraphic curves were determined from the volume of water found by measuring the areas between consecutive isobaths. The least accurate data come from 1879 while there is a considerable resemblance between the plans dated to 1934 and 2011. In case of the most recent plan, the measurements were for the first time related to the average, multi-annual (1963-2010) water level. Thus, the greatest depth found in 2011 can be regarded as the maximum depth. Further bathymetric studies could help to determine the rate of shallowing of Morskie Oko lake caused by weathered rock material, transported for instance by avalanches.

This paper presents an analysis of the variability of short-term water temperature amplitudes in Lake Morskie Oko, situated in the Tatra Mountains National Park, which makes the human impact on the lake very limited. The objective of the study was to determine to what extent an increase in depth contributes to suppressing daily water temperature amplitudes. It was shown, among other things, that water temperature amplitudes were the lowest in the period of occurrence of the ice cover, higher in the period of occurrence of other (than ice cover) ice phenomena, and the highest in the case of their lack. The analysis of profiles of water temperature amplitudes (in the case of lack of ice phenomena) resulted in determination of their six types. A strong correlation was observed in which the effect of mean daily air temperature and the effect of wind on water level amplitudes are considerably lower during the occurrence of ice phenomena in comparison to the period when the water surface is free from such phenomena. It was demonstrated that the near-bottom waters in Lake Morskie Oko are very stable in terms of temperature. The short transition period from ice cover to free water surface was determined to be very important, because it constitutes a threshold in the effect of air temperature and wind on changes in thermal dynamics of water (in this case expressed in amplitude values). Finally, proposals are presented for future expansion of the scope of research on water temperature amplitudes. This work is important, because the amplitudes were investigated not only at the surface of the lake, but also at its bottom, and also during the ice cover period, when the lake was isolated from the atmospheric influences. This study may contribute to better understanding of the lake water temperature responses to climate change and thus to more accurate prediction these patterns in lake globally. Moreover, understanding of changes in water temperature is closely related to the variability of its heat resources, and these in the future may be used on a large scale. In the case of a mountain lake such as Morskie Oko, the heat of water may be used, for example, for heating tourist shelters.