Mercury (Hg) is considered one of the most widespread toxic environmental pollutants, which seems to have multiple effects on organisms even at low concentrations. It has a critical role in many health problems with harmful consequences, with Hg primarily targeting the brain and its components, such as the central nervous system (CNS). Hg exposure was associated with numerous CNS disorders that frequently trigger Alzheimer’s disease (AD). Patients with AD have higher concentrations of Hg in blood and brain tissue. This paper aims to emphasize a correlation between Hg and AD based on the known literature in the occupational field. The outcome shows that all these concerning elements could get attributed to Hg. However, recent studies did not investigate the molecular level of Hg exposure in AD. The present review highlights the interactions between Hg and AD in neuronal degenerations, apoptosis, autophagy, oxidative stress (OS), mitochondrial malfunctions, gastrointestinal (GI) microflora, infertility and altering gene expression.

The trophic level highlights the relation between fish and macroinvertebrates. This was achieved by qualitative and quantitative analysis of the macroinvertebrates found in the stomach contents of chub (Squalius cephalus) and European bitterling (Rhodeus amarus) living in the Dâmbovnic River, a tributary of the Neajlov River. Fish sampling was performed by electro-shocking method in the summer of 2006. Macroinvertebrates in the stomach contents were identified down to the lowest taxon possible. The analysis revealed that nearly all the specimens found in the stomach contents of the fish belong to the class Insecta. The highest values of abundance were recorded from the Order Diptera.

To investigate the feeding habits of fish, a qualitative and quantitative analysis of macroinvertebrates in the stomach contents is necessary. In this study, 6 fish species sympatric in the Oituz river basin were considered. The total number of specimens investigated was 840, as follows: 414 Phoxinus phoxinus (Linnaeus, 1758), 262 Squalius cephalus (Linnaeus, 1758), 75 Gobio obtusirostris (Valenciennes, 1842), 71 Barbatula barbatula (Linnaeus, 1758), 14 Alburnoides bipunctatus (Bloch, 1782) and 4 Salmo trutta (Linnaeus, 1758). They were collected by the electric fishing method from 9 different stations between 2004-2015 and kept in the faculty collection until the moment of analysis. The trophic spectrum analysis was performed in the laboratory using a binocular microscope and subsequently statistically analyzed using biodiversity indices. Ecological information is very important for assessing biodiversity and trophic resources in freshwaters.

Freshwater has been polluted with plastics for decades, but only a few scientific papers have described it until now. This is the first study to investigate the presence of meso- and microplastic particles in the digestive tract of fish from an inland river in Romania. Fish specimens representing the ichthyocenosis of the Oituz River were sampled by electrofishing at different sampling sites (upstream to downstream) in 2004, 2008 and 2015, and the results were compared. Plastic particles were classified and counted according to shape as: fibers, films, and fragments (in decreasing order) and their size measured, and according to color (eight groups were recorded, blue being the most numerous, followed by transparent and red). There was no correlation between length and number of plastic particles. There was a positive correlation between weight and number of plastic particles. All fish species investigated are omnivorous, so no differences in feeding habits were observed. Feeding habitats were compared and demersal species accumulated more plastic particles than the benthopelagic ones. Scanning Electron Microscopy (SEM) was used to observe the surface morphology of the found microplastics. The main polymers were identified by FTIR spectroscopy and most common type of polymer was polyamide. Older samples contained a higher number of micro- and mesoplastics (mainly polyamide and polyethylene terephthalate), with the recent lower amounts likely due to pollution control measures through the recycling of both PET bottles and other plastics that previously reached the riverbed.

This study analyzes, based on stomach content data, the trophic spectra of eight freshwater fish species collected from the Neajlov River Basin. Prey items, primarily macroinvertebrates, were identified to the taxonomic group level. The food composition was assessed using abundance, frequency of occurrence, Shannon diversity (H), and Pielou’s evenness (J). Chironomidae (Diptera) was the most dominant prey taxa across most species, followed by Coleoptera, Diptera (indeterminate) and Baetidae (Ephemeroptera). Pseudorasbora parva, an invasive species in Romania, exhibited a significantly low trophic diversity (H = 0.23; J = 0.118), dominated almost exclusively by Chironomidae. However, this does not necessarily indicate a specialized feeding behavior, but rather reflects limited prey availability at the sampling site. Conversely, species like Squalius cephalus and Alburnus alburnus showed higher dietary diversity and more balanced prey distribution. The results offer insights into feeding strategies, interspecific trophic overlap, and highlight potential ecological impacts of non-native species in freshwater ecosystems.