Long-Term Changes in the Course of Ice Phenomena on the Oder River along the Polish–German Border

Ice phenomena are a major component of the hydrological regime of east-central and northern European rivers. However, their occurrence disturbs inland water transportation, particularly affecting the major rivers of the Central European Plain that are part of Europe’s international waterways. The Oder is one of these rivers, and is located on the boundary between the much warmer and the much colder part of the temperate climatic zone. This makes the course of ice phenomena on the river difficult to predict. The main purpose of this work is to document and analyse the dynamic of changes occurring for over 60 years (1956–2015) in the ice phenomena of a river that demonstrates a transitional ice regime. It was found that the duration of all ice phenomena decreased (by up to 0.58 days·year^?1) and so did the duration of ice cover (by up to 0.46 days·year^?1). The rates and trends of the two parameters were, however, different in different parts of the lower stretch of the river. This fact is especially important in the context of climate changes whose characteristics include an increased incidence of extreme weather situations, both meteorological and hydrological. There was also found to be a strong correlation (R² from 0.69 to 0.81) between the duration of ice phenomena and the mean air temperature in winter (December to February) and a much weaker correlation between the duration of ice phenomena and the NAO index (R² from 0.42 to 0.48). Such a little correlation of ice phenomena with NAO is likely to result from the pollution of the Oder River (in particular in the second half of the twentieth century) and icebreaking operations on the river.

     

Understanding Abiotic and Biotic Conditions in Post-Mining Pit Lakes for Efficient Management: A Case Study (Poland)

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 Bogda?ów 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.