The shrinking of the Aral Sea represents one of the greatest ecological disasters of modern time. The data on the surviving northern part (Small Aral) is scarce and requires an update. This study aimed to analyze the chemistry, phyto- and zooplankton composition, and their relation in the waters of the Small Aral and its tributary, Syr Darya River. The chemistry of both ecosystems was significantly different. Small Aral was characterized by higher ionic concentrations, salinity, and electric conductivity and more significant spatial variation of chemical properties. The area near the river mouth was more pristine, while the ions concentration and salinity in the distant bays were much higher (>10‰). The highest concentrations of nitrates and total phosphorus in the Syr Darya were observed near Kyzylorda, indicating urban pollution. Overall, 109 phytoplankton taxa were identified in both ecosystems, with diatoms, green algae, and cyanobacteria being most abundantly represented. Oligohalobes dominated, but no polyhalobes and euhalobes algal species were identified. In total, 27 taxa of zooplankton were identified in both studied ecosystems, with the domination of rotifers over microcrustaceans. An exceptionally high level of dominance (65-91%) of rotifer Keratella cochlearis in the Syr Darya was found. The phyto- and zooplankton species richness was higher in the Syr Darya. Plankton communities of the Small Aral reflected horizontal variability of chemical properties. The total phosphorus promoted the prevalence of diatoms, rotifers, and crustaceans. Increased nitrogen concentration promoted cyanobacteria, chlorophytes, cryptophytes and chrysophytes, and rotifers Keratella cochlearis and K. quadrata. The abundance of dinophytes, diatoms Navicula cryptotenella and Cocconeis placentula, green algae Mychonastes jurisii and rotifer Keratella tecta was driven by the higher alkalinity and conductivity/salinity levels. The results represent a reference point for future monitoring of the area and add to understanding the complexity of biological transformations in the Aral Sea and its tributary.

This study was aimed at determining whether the origin, morphometry, and hydrology of post-mining lakes affect their hydrochemical and hydrobiological parameters (i.e. water quality). The investigated post-mining lakes were very young compared to glacial lakes and represent early stages of ecosystem succession. Despite their different ages and morphometries, they are all mesotrophic and have good water quality. They have not been supplied with phosphorus and nitrogen, which can cause excessive development of pelagic phytoplankton; as a result, they share low chlorophyll a (Chl a) content, low phytoplankton biomass, and relatively high water transparency. Low abundance and species richness of zooplankton indicate low trophic levels in all of the lakes. Chl a in Lakes Przykona and Bogdałów were within the range typical of mesotrophic lakes, while Lake Janiszew had very low Chl a, typical of an oligotrophic water body. The low N:P ratios (4–6), especially in summer, indicates nitrogen limitation of primary production. There is a risk that such a proportion of the major biogenic elements could lead to harmful cyanobacterial blooms. The lake basins were formed using quaternary deposits (sand, clay) at their bottoms; as a result, the lakes had a slightly alkaline pH (>8), which favors the development of aquatic organisms. Optimum depth helps establish lake stratification and ensures ecological stability. This applies to post-mining lakes as well; an optimum depth should be determined to ensure the development of thermal stratification, which affects lake processes. Diese Studie sollte ermitteln, ob der Ursprung, die Morphologie und Hydrologie von Bergbauseen Auswirkungen auf hydrochemische und hydrobiologische Parameter (z.B. Wasserqualität) haben. Im Vergleich zu glazialen Seen sind die Bergbauseen sehr jung und haben frühe Stadien der Ökosystemfolge. Trotz unterschiedlicher Alter und Morphologie sind sie alle mesotroph und haben gute Wasserqualität. Phosphor und Stickstoff wurden nicht zugeführt, welche exzessive Vermehrung von pelagischem Phytoplankton bewirken können; daraus resultiert ein niedriger Chlorophyll a-Gehalt (Chl a), eine geringe Phytoplanktonbiomasse und eine relativ hohe Transparenz des Wassers. Eine geringe Menge und Artenarmut von Zooplankton indizieren in allen Seen geringe Nährstoffgehalte. Chl a in den Przykona und Bogdałów Seen war in der gewöhnlichen Bandbreite mesotropher Seen, während der Janiszewsee sehr wenig Chl a enthielt, typisch für ein oligotrophes Gewässer. Niedrige N:P Verhältnisse (4–6), besonders im Sommer, zeigen an, daß die primäre Produktion N-limitiert ist. Dieses Verhältnis der wichtigsten biogenen Elemente bedeutet ein Risiko der Entstehung schädlicher Blüten von Cyanobakterien. Die Böden der Seebecken wurden aus quartärem Material (Sand, Ton) hergestellt; deshalb haben die Seen leicht alkalischen pH (>8), was die Entwicklung aquatischer Organismen fördert. Eine optimale Tiefe fördert eine Stratifikation der Wasserkörper und garantiert ökologische Stabilität. Das gilt auch für Bergbauseen; die optimale Tiefe sollte erkundet werden, um die Entwicklung einer thermalen Stratifikation zu sichern, welche limnische Prozesse steuert. Este estudio fue realizado para determinar si el origen, morfometría e hidrología de los lagos postminería afectan sus parámetros hidroquímicos e hidrobiológicos (i.e. calidad del agua). Los lagos postminería investigados fueron muy recientes comparados con lagos glaciales y representan estados tempranos del desarrollo sucesivo dentro del ecosistema. Independientemente de sus diferentes edades y morfometrías, ambos tipos de lagos son mesotróficos y tienen una buena calidad de agua. En general, no poseen fósforo y nitrógeno que podría causar un excesivo desarrollo de fitoplancton pelágico; debido a eso, comparten bajo contenido de clorofila a (Chl a), baja biomasa de fitoplancton y relativamente alta transparencia del agua. La baja abundancia y riqueza de especies de zooplancton indican bajos niveles tróficos en todos los lagos. La Chl a en los lagos Przykona y Bogdałów estuvieron dentro del rango típico de los lagos mesotróficos mientras que el lago Janiszew tenía muy baja cantidad de Chl a, típico de un cuerpo de agua oligotrófico. La baja relación N:P (4-6), especialmente en verano, indica limitación de nitrógeno para la producción primaria. Hay cierto riesgo de que tal proporción de los principales elementos biogénicos pudieran generar floraciones de cianobacterias nocivas. Las cuencas del lago fueron formadas con depósitos cuaternarios (arena, arcilla) en el fondo; como un resultado de ello, los lagos tenían un pH ligeramente alcalino (> 8), lo que favorece el desarrollo de organismos acuáticos. La profundidad óptima ayuda el establecimiento de la estratificación del lago y asegura la estabilidad ecológica. Esto aplica también a lagos formados luego de la actividad minera; una profundidad óptima debería ser determinada para asegurar el desarrollo de la estratificación termal que afecta los procesos en el lago. Open image in new window

Despite ubiquitous warming, the lower Oder River typically freezes over almost every year. Ice jams may occur during freeze-up and ice cover breakup phases, particularly in the middle and lower reaches of the river, with weirs and piers. The slush ice and ice blocks may accumulate to form ice jams, leading to backwater effects and substantial water level rise. The small bottom slope of the lower Oder and the tidal backflow from the Baltic Sea enhance the formation of ice jams during cold weather conditions, jeopardizing the dikes. Therefore, development of an ice jam flood forecasting system for the Oder River is much needed. This commentary presents selected results from an international workshop that took place in Wrocław (Poland) on 26–27 November 2018 that brought together an international team of experts to explore the requirements and research opportunities in the field of ice jam flood forecasting and risk assessment for the Oder River section along the German–Polish border. The workshop launched a platform for collaboration amongst Canadian, German and Polish scientists, government officials and water managers to pave a way forward for joint research focused on achieving the long-term goal of forecasting, assessing and mitigating ice jam impacts along the lower Oder. German and Polish government agencies are in need of new tools to forecast ice jams and assess their subsequent consequences and risks to communities and ship navigation along a river. Addressing these issues will also help research and ice flood management in a Canadian context. A research program would aim to develop a modelling system by addressing fundamental issues that impede the prediction of ice jam events and their consequences in cold regions.

The assessment and mapping of riverine flood hazards and risks is recognized by many countries as an important tool for characterizing floods and developing flood management plans. Often, however, these management plans give attention primarily to open-water floods, with ice-jam floods being mostly an afterthought once these plans have been drafted. In some Nordic regions, ice-jam floods can be more severe than open-water floods, with floodwater levels of ice-jam floods often exceeding levels of open-water floods for the same return periods. Hence, it is imperative that flooding due to river ice processes be considered in flood management plans. This also pertains to European member states who are required to submit renewed flood management plans every six years to the European governance authorities. On 19 and 20 October 2022, a workshop entitled “Assessing and mitigating ice-jam flood hazard and risk” was hosted in Poznań, Poland to explore the necessity of incorporating ice-jam flood hazard and risk assessments in the European Union’s Flood Directive. The presentations given at the workshop provided a good overview of flood risk assessments in Europe and how they may change due to the climate in the future. Perspectives from Norway, Sweden, Finland, Germany, and Poland were presented. Mitigation measures, particularly the artificial breakage of river ice covers and ice-jam flood forecasting, were shared. Advances in ice processes were also presented at the workshop, including state-of-the-art developments in tracking ice-floe velocities using particle tracking velocimetry, characterizing hanging dam ice, designing new ice-control structures, detecting, and monitoring river ice covers using composite imagery from both radar and optical satellite sensors, and calculating ice-jam flood hazards using a stochastic modelling approach.

Soil transformations in catchment of disappearing Sumówko Lake (Brodnickie Lake District, Poland)Lake disappearing is a natural process which contemporarily escalates in consequence of human activity. It is estimated that within the area of Northern Poland from the last glaciation period (ca. 17 000 years ago) a half of lakes totally have disappeared. Areas exposed after water basins desiccation have become native rocks for new soils. Reduced water level results in changes of morphology and properties of the soils situated in direct vicinity of former water basins. The aim of this study was to estimate impact of the catchment groundwater level fall on morphology and properties of direct lake catchment soils, exemplified by the lake Sumowko (Northern Poland) as well as description of new soils formed of lake sediments. The analysis covered 11 soil profiles emerging within former lake basin (newly formed soils) and soils from direct vicinity of former lake (modified through ground water level fall). Obtained results prove that newly formed soils (Limnic Histosol Drainic and Haplic Gleysol) in majority are utilized as grasslands. Soils of the former lake surroundings prove relic features of gleying while they are also subject to mucking process because of dehydration.