The expansion and decline of charophyte communities in lakes within the Sejny Lake District (north-eastern Poland) and changes in water chemistry

AbstractOver the last 25 years, considerable changes have been observed in the littoral vegetation of 11 lakes within the Sejny Lake District. In eight lakes (Dowcień, Jurkowo, Kunis, Miałkie, Pilwie, Płaskie, Wiłkokuk, Zelwa) where Chara species dominated, their communities declined or disappeared completely. In four of these lakes (Dowcień, Jurkowo, Kunis and Miałkie), charophytes were replaced by communities of the class Potametea (mainly Nupharo-Nymphaeetum albae and Ceratophylletum demersi). In three other lakes (Pilwie, Płaskie and Wiłkokuk), the area covered by charophyte communities decreased. In Lake Zelwa, Charetum rudis and Charetum jubatae disappeared while Charetum tomentosae and Charetum fragilis expanded. A total area of charophyte communities remained approximately the same. A considerable increase in the water total hardness and PO43- concentration was noted in each of the eight lakes. In most of them increased levels of dissolved organic matter (measured as COD-KMnO4) and pH were detected as well. However, the increase in the PO43- concentration was smaller in Lakes Wiłkokuk and Zelwa in which only slight changes in the vegetation were observed. In the above two lakes, the concentration of dissolved organic matter decreased and low water colour values are now noted. In three lakes (Długie, Dmitrowo and Gajlik), the charophyte communities tended to expand under the condition of moderate or high (Lake Długie) PO43- concentration, while dissolved organic matter concentrations were low. These lakes are also characterized by low values of colour. Charophyte communities may persist in lakes for a long period of time even when there is a moderate increase in PO43- concentration until the colour of water distinctly increases (>20mgPtL−1)

Aneuploids in the shrub birch Betula humilis populations in Poland

Shrub birch (Betula humilis Schrk.) is endangered glacial relict growing in natural and drained fens and transitional mires. At present study we examined karyotypes of 103 individuals of B. humilis, collected in six populations from eastern and northeastern Poland. We found 60% of diploid individuals with 2n = 28. The rest of studied plants were aneuploids with 26, 27, 29, 30 and 31 chromosomes in their karyotypes. High frequencies of aneuploids in Polish populations of B. humilis could be a consequence of: (i) hybridization with congeneric species, (ii) stress resulting from range fragmentation, (iii) karyotype instability of individuals with 2n ≠ 28, or (iv) vegetative reproduction

Aquatic vegetation as an indicator of littoral habitats and various stages of lake aging in north-eastern Poland

The habitats of 356 phytocoenoses dominated by 15 species of aquatic plants were investigated. Among the properties of water, Na+, pH, total Fe, Ca2+, NO3−, SO42−, hardness and COD-KMnO4 were the most important in differentiating the habitats of the phytocoenoses studied. Considerable physicochemical differences were found between the waters of the phytocoenoses of Ranunculus circinatus (hard waters rich in Na+), Nuphar pumila (soft waters with high levels of total Fe), Elodea canadensis, Ceratophyllum demersum (alkaline waters) and Stratiotes aloides (waters containing high concentrations of Ca2+ and SO42−). The substrate properties that best differentiated the habitats compared were PO43−, hydration, organic matter content, total N, dissolved SiO2, Ca2+, Na+ and pH. Patches of R. circinatus inhabited substrates containing the highest levels of PO43−. Those of S. aloides were associated with substrates poor in PO43−. Patches of C. demersum were confined to substrates rich in total N. Phytocoenoses of R. circinatus were associated with large lakes, whereas those of N. pumila were restricted mostly to smaller lakes. The deepest parts of lakes were inhabited by Potamogeton lucens. Phytocoenoses of S. aloides occurred mostly in shallow waters, on thick sediments. The investigated phytocoenoses also represent different stages of succession. The phytocoenoses of Potamogeton perfoliatus, R. circinatus, Myriophyllum spicatum and Polygonum amphibium, which develop on mineral substrates, initiate the process of succession, whereas those of Myriophyllum verticillatum, Nymphaea candida, Nymphaea alba, N. pumila and S. aloides, which inhabit highly hydrated organic substrates, are characteristic of the late stages of succession

State of the Population of Gladiolus imbricatus L. in a Molinia Meadow after Extensive Management and Abandonment

The abandonment of seminatural Molinia meadows observed in Central and Eastern Europe during the 20th century started the secondary succession and threatened the state and persistence of populations of numerous meadow species. Considering this, the aims of the presented investigations were to study the abundance and selected traits of individuals of Gladiolus imbricatus L. in extensively used (EM) and unmanaged for at least 15 years (UM) Molinia meadows (Southern Poland, Central Europe). Altogether, 125 juvenile individuals, 21 vegetative individuals, and 119 generative individuals of Gladiolus imbricatus were investigated. The field studies showed positive correlation among the height of shoots and other traits of generative individuals in both study patches. Moreover, the greater abundance of population of Gladiolus imbricatus (especially the greater number of juveniles), as well as the greater dimensions of leaf blades, shoots, inflorescence, and number of capsules in the patch UM, indicates the appropriate state of the population. These data indicate a positive influence of abandonment and evolving secondary succession on the Gladiolus imbricatus population within the Molinia meadows

The Use of Time-Frequency Moments as Inputs of LSTM Network for ECG Signal Classification

This paper refers to the method of using the deep neural long-short-term memory (LSTM) network for the problem of electrocardiogram (ECG) signal classification. ECG signals contain a lot of subtle information analyzed by doctors to determine the type of heart dysfunction. Due to the large number of signal features that are difficult to identify, raw ECG data is usually not suitable for use in machine learning. The article presents how to transform individual ECG time series into spectral images for which two characteristics are determined, which are instantaneous frequency and spectral entropy. Feature extraction consists of converting the ECG signal into a series of spectral images using short-term Fourier transformation. Then the images were converted using Fourier transform again to two signals, which includes instantaneous frequency and spectral entropy. The data set transformed in this way was used to train the LSTM network. During the experiments, the LSTM networks were trained for both raw and spectrally transformed data. Then, the LSTM networks trained in this way were compared with each other. The obtained results prove that the transformation of input signals into images can be an effective method of improving the quality of classifiers based on deep learning