The ecological state of the Aral Sea remains an important issue affecting the overall state of the ecosystem in the region. Despite the fact that the state of the northern part of the sea or the Small Aral Sea can be described as stable, the southern part of the former sea continues to degrade. The area of degraded ecosystems around the Small Aral Sea is significant, and huge salt reserves remain the cause of further degradation of terrestrial ecosystems in the Aral Sea region. This study includes the results of geobotanical investigations researches of the dried bottom around the Small Aral Sea area. Five types of landscape-geomorphological formations of the dried-up sea were identified during the research. The creation of the formations took place during different periods of drying and depended on the element’s of sea relief. The vegetation of these landscapes is represented exclusively by salt-tolerant species of xerophytic flora. In this case, the number of plant species in the plant communities of these landscapes is directly proportional to the concentration of salt in the soil.
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In Europe the monitoring of lakes with regard to benthic diatoms is still conducted in line with the European Water Framework Directive. Ribbon lakes are a special case as extremely steep slopes of the lake basin cause their littoral zone to be narrow. The Durowskie ribbon lake was chosen as a model for the assessment of the ecological status of waters based on its Diatom Index. Given its use in recreation, it is under heavy anthropogenic pressure. Physicochemical and biological parameters were monitored in the peak of the vegetational season (July, August) between 2010 and 2018 at 12 varied littoral sites across the full length of the shoreline. This long-term analysis of the Diatom Index, despite showing an improvement in the quality of water, demonstrated the ecological state of Lake Durowskie to be weak (southern, deep part) to moderate (north, shallow part). The taxonomic structure of diatoms (referral and indicator taxa) in phytobenthos communities allowed to show the changes in physicochemical parameters of the environment such as pH, oxygen dissolved in water and its trophic status. Research results are shown in relation to the anthropogenic changes to the lake’s direct catchment area and the results of the physicochemical monitoring of waters.
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The examination of the composition and dynamics of periphytic communities took place in three lakes of similar morphometry . Lake Wielkowiejskie, Budzyńskie and Dębiniec, situated in the Wielkopolska region, (Western Poland). These lakes are typical macrophyte-dominated, shallow and polymictic water bodies. Periphyton was collected from two macrophyte-covered stations, including the rush vegetation station (Typha angustifolia L.) and the stonewort stand (Chara tomentosa L.) in each examined lake. The material was sampled three times in 2003, including the spring (April), summer (July) and autumn (September) seasons, from the same parts of the lakes.The aim of the study was to find out whether there is an influence of particular macrophyte species, differing spatially and morphologically and representing two different ecological types of aquatic vegetation, on the development of particular periphytic species. There was also an attempt at answering the question of what is more important in the structuring of the periphytic communities - the specific architecture of the macrophyte substratum or the physical-chemical features of a particular lake? The concentrations of chlorophyll a, TN, TP and TOC in water were higher in the Chara beds compared with theTypha stations in most cases. The Shannon-Weaver biodiversity index of periphytic algae revealed very high values in all lakes and amounted in the Typha and Chara stands to the mean values 4.68 and 3.87 respectively in Wielkowiejskie Lake, 3.32 and 4.39 in Budzyńskie Lake and 3.08 and 3.91 in Dębiniec Lake. Furthermore, the standardized index of evenness exhibited the greatest differentiation in the Typha station with the highest (0.76) in Wielkowiejskie and the lowest (0.52) in Dębiniec Lake The analysis of the growth-forms of periphytic communities showed slightly higher diversity of slowly moving and stalked diatoms in most cases at the Chara stations of all studied lakes. The similarity between periphytic communities in the Typha and Chara stands of the examined lakes, compared using the Ward method and Euclidean distance measure, revealed a stronger relationship within a particular habitat but not a lake. The clearest pattern of similarity grouping a particular habitat was obtained for the summer period, when macrophytes reached their optimum. The Jaccard similarity index confirmed the differentiation of both examined habitats, reaching the mean value of 0.34. Based on the biomass of single periphytic species, habitat selectivity for seven species was found. Significantly higher biomass was obtained in the case of the rush zone for only one algae species - Eunotia lunaris (Ehr.) Grun. In the Chara bed six species revealed significantly higher biomasses - Cosmarium regnelli Wille, Oocystis marssonii Lemm., Ulotrix zonata (Weber et Moor) Kutz., Scenedesmus acuminatus (Lagerh.) Chod., Merismopedia elegans A. Braun and Phacus orbicularis Hubner. The habitat preference of periphytic communities to different macrophyte species may be due to the environmental factors, including the specific architecture of a particular macrophyte substrate such as density or texture of the plant surface. Furthermore, seasonality, as well as physical-chemical parameters may structure periphytic communities within the littoral zone of lakes.
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