Transformation of the river catchment and the river bed cause significant changes in the functioning of river ecosystems. The main effects of anthropogenic transformations are hydrological changes, such as lower current velocity or an increase of nutrient content, and higher temperature. Zooplankton reacts rapidly to the new environmental conditions in rivers, increasing its richness and abundance. We tried to answer two questions: what type of catchment use has a greater influence on the zooplankton communities in a river and how do dam impoundments influence the zooplankton communities downstream? The study was conducted in the Corgo river (drainage of the Douro river, Northern Portugal) at 17 sampling sites in the lotic, free-flowing sections. Crustaceans present in the Corgo can attain relatively high densities in the rural section, which offers them better trophic conditions. The urban catchment use and the presence of dams have a greater impact on the rotifer density and the increase of zooplankton density downstream. The results of this study confirm that zooplankton properties allow for the evaluation of the degree of river-bed transformation.

The study was carried out on sediments collected from three rivers: Nysa Szalona, Strzegomka and Bystrzyca flowing in southwestern Poland. The content of Al in sediments and in bottom water was determined in relation to chemical conditions. The study was carried out in a four-year cycle, during spring and autumn. The aim of the study was to determine the level and accumulation of aluminum in sediments of rivers supplying dam reservoirs storing water for consumption. The sediments studied were mineral in nature, with neutral pH and moderate sulfate content. The level of Al and heavy metals in the sediments was the highest in the Nysa Szalona River and the lowest in the Strzegomka River, which was also evident in the concentration factor (CF). In terms of season, higher Al contents were recorded in sediments in autumn than in spring, which was also reflected in the concentration factor (CF). Along the course of the river, a gradual decrease in Al levels was observed in successive tributaries in the Nysa Szalona and Strzegomka Rivers, while there was no apparent regularity for the Bystrzyca. Against this background, a comparison of extreme sites below the springs and at the reservoir outlet shows that values were higher in the Nysa Szalona below the springs, and lower in the Strzegomka and Bystrzyca below the reservoir outlet. The general picture of Al and heavy metal loading of the studied sediments shows the lowest loading for the Strzegomka, only the enrichment factor (EF) was the lowest for the Nysa Szalona: metal pollution index (MPI)—S < B < NS, contamination factor (C_f)—S < B < NS, degree of contamination (DC)—S < NS < B, EF—NS < B < S, geoaccumulation index (I_geo)—S < B < NS, CF—S < NS < B. There was no effect of catchment size and river length on Al levels in sediments.

The muscles of lake trout (Salvelinus namaycush Walbaum, 1792), crucian carp (Carassius carassius Linnaeus, 1758), flounder (Platichthys flesus Linnaeus, 1758), gilthead seabream (Sparus aurata Linnaeus, 1758), mackerel (Scomber scombrus Linnaeus, 1758) and tench (Tinca tinca Linnaeus, 1758) were examined. The total mercury (THg) was processed using the Milestone DMA-80 and the fatty acids were analyzed using the 7890A Agilent Technologies chromatograph. The THg content in analyzed fish ranged from 0.024 (lake trout) to 0.092 mg/kg wet weight (gilthead seabream). The muscles of fish examined had lower amounts of SFAs, and n-3 and n-6 PUFAs than MUFAs. The ratio of n-3/n-6 was higher in muscles of mackerel than other fish (p < 0.05). Due to the fact that both the THQ and HI are below 1, the tested fish are safe for the consumer from a nutritional point of view. Similarly, fatty acid indices indicate the safe consumption of selected fish species, and the daily consumption of the recommended dose of EPA + DHA (250 mg/day) and the concentration of mercury in fish calculations showed a hazard quotient for the benefit–risk ratio HQ_EFA below 1, suggesting that the intake of EPA + DHA poses no evident risk to human health. The ratio was calculated for a person weighing 60 kg. Therefore, it is important to monitor the fish, not only bought in the store, but also caught in various aquatic environments.

Applications of nanotechnologies in different sectors and everyday items are very promising and their popularity continues to grow. The number of products containing nanoparticles makes environmental exposure to nanoparticles inevitable. The current understanding of the relationships between nanoparticles and the environment is inadequate despite the fast growth of nanotechnologies. The aim of the study was to investigate the influence of copper and gold nanoparticles on Daphnia pulex survival. Our study included 48-h acute toxicity tests and determination of median lethal concentration values (LC₅₀s) for Cu-NPs and Au-NPs. For nano-copper, 24 h LC₅₀ was assumed > 1 mg/L, and 48 h LC₅₀ = 0.5117 mg/L. For nano-gold the LC₅₀ value after 24 h was 0.4027 mg/L, and after 48 h 0.1007 mg/L. The toxicity of nano -gold solutions was thus found to be higher than that of nano-copper. The addition of Cu-NPs at 0.0625 mg/L and 0.125 mg/L caused an increased multiplication of daphnia, while Au-NPs at 1 mg/L was an inhibitor of reproduction.

Nanotechnology is a rapidly growing field of science, and an increasing number of nanoproducts, including nanometals, can be found on the market. Various nanometals and the products that are manufactured based on them can help to fight bacteria and fungi, but they can also penetrate organisms and accumulate in them. This study aimed to compare the effects of two metals, silver (Ag) and copper (Cu), with known antibacterial and fungicidal properties in their ionic (AgNO₃, CuSO₄·5H₂O) and nanoparticle (AgNPs, CuNPs) forms on rainbow trout eggs and fry. Concentrations of metals ranging from 0 to 16 mg/L were used during egg swelling for 2 h. The swelling of eggs in Cu solutions resulted in an increase in Cu content in the eggs (just like in the case of Ag); however, the changes in fry were not significant in the case of both Ag and Cu. The concentrations of these metals in eggs was greatly affected by the applied form of Ag and Cu. Because CuNPs penetrated the embryo in fish eggs at lower concentrations compared to AgNPs, it would be worth considering them for antibacterial applications during egg incubation.