Accumulation of metals relevant for agricultural contamination in gills of European chub (Squalius cephalus)

Exploring microplastic pollution in a Mediterranean river: The role of introduced species as bioindicators

Studies of plastic contamination in freshwater ecosystems and their biota remain scarce, despite the fact that the vast majority of plastic waste initially passes through lotic ecosystems. Biomonitoring provides valuable information regarding plastic pollution and microplastic threats to biota and human health. The aim of this study was to explore the potential use of a non-indigenous fish species as a bioindicator of microplastic pollution in an Eastern Mediterranean River. Our study area is located in a heavily modified and vastly impacted urban river which flows through the largest part of the Metropolitan area of Athens, Greece. We used an introduced chub species (Squalius vardarensis) to assess microplastic ingestion in the river. The results indicated moderate occurrence and abundance of microplastics in the fish gastrointestinal tracts; one-third of specimens (35%) contained microplastics, although the average number of microplastics per specimen was relatively low (1.7 ± 0.2). Overall, the abundance of microplastics in the water confirmed the moderate level of microplastics contamination in our study area. The major polymer types of microplastics identified by FT-IR analysis were: polyethylene (PE), polyvinyl alcohol (PVA) and polypropylene (PP); reflecting the fragmentation of larger litter from industrial packaging and/or household goods. Surface runoff of the urban environment, via motorways and major road networks, could be the contributing factor to the reported microplastics. Our results suggest that generalist's non-indigenous species such as chubs could be used as bioindicators of microplastics in inland waters. Introduced fishes can be a feasible, nondestructive, and cost-effective option for the assessment of microplastics in freshwater ecosystems, while freshwater chubs' high abundance and omnipresence in European rivers further serve this scope. However, it is worth noting that the suitability of any particular species as a bioindicator of microplastics may depend on a variety of factors, including their feeding behavior, habitat, and exposure to microplastics in their environment.

Metal accumulation in relation to size and body condition in an all-alien species community

Metal pollution is one of the main environmental threats in freshwater ecosystems. Aquatic animals can accumulate these substances and transfer them across the food web, posing risks for both predators and humans. Accumulation patterns strongly vary depending on the location, species, and size (which in fish and crayfish is related to age) of individuals. Moreover, high metal concentrations can negatively affect animals' health. To assess the intraspecific relationship between metal accumulation and size and health (proxied by the body condition) of individuals, the concentration of 14 metals (Al, As, Cd, Co, Cr, Cu, Fe, Hg, Mg, Mn, Ni, Pb, Se, Zn) was analyzed in six alien species from the highly anthropogenically altered Arno River (Central Italy): five fish (Alburnus alburnus, Pseudorasbora parva, Lepomis gibbosus, Ictalurus punctatus, and Silurus glanis) and one crayfish (Procambarus clarkii). We found that in P. clarkii, Cu was negatively related to size, as well as Al in L. gibbosus and Mg for adult I. punctatus. Positive size-dependent relationships were found for Hg in L. gibbosus, Fe in S. glanis, and Cr in juvenile I. punctatus. Only Co and Mg in S. glanis were found to negatively correlate with individual health. Since metal concentrations in animal tissue depend on trade-offs between uptake and excretion, the few significant results suggest different types of trade-offs across different species and age classes. However, only predatory fish species (L. gibbosus, I. punctatus, and S. glanis) presented significant relationships, suggesting that feeding habits are one of the primary drivers of metal accumulation.

Mining waste as a cause of increased bioaccumulation of highly toxic metals in liver and gills of Vardar chub (Squalius vardarensis Karaman, 1928)

Freshwater contamination with mining waste can result with high concentrations of toxic metals in the water and in fish organs. In North-Eastern Macedonia, several rivers (e.g., Zletovska, Kriva) are exposed to acid mine drainage from active Pb/Zn mines. Previous studies confirmed high concentrations of dissolved metals in their water. This study was performed in liver and gills of Vardar chub (Squalius vardarensis Karaman, 1928) from three Macedonian rivers (Bregalnica, Kriva and Zletovska) in spring and autumn 2012. The aim was to establish if increased exposure to certain metals have resulted with their increased bioaccumulation. The concentrations of 19 elements were measured in cytosolic tissue fractions, to obtain information on metabolically available metal species. The following ranges of cytosolic concentrations of highly toxic elements were measured in the Vardar chub liver (in μg/L): Cd, 1.18-184; Cs, 0.25-25.4; Tl, 0.02-5.80; Pb, 0.70-61.1. Their ranges measured in the gills (in μg/L) were the following: Cd, 0.24-59.2; Cs, 0.39-24.4; Tl, 0.01-1.00; Pb, 0.65-87.2. Although the water of the mining impacted Zletovska River was highly contaminated with several essential metals, especially with Mn and Zn, the majority of essential elements (Na, K, Ca, Mg, Co, Cu, Fe, Mn, Mo, and Zn) did not reflect the exposure level. In contrast, seven nonessential elements reflected the level of exposure in the water. Significantly increased hepatic and gill concentrations of Cs, Rb, Sr, and Tl were detected in Vardar chub from the Zletovska River compared to the other two rivers, of Cd and Pb in the Zletovska and Kriva River compared to Bregalnica, and of V in the Bregalnica River compared to Zletovska and Kriva rivers. Observed significant metal bioaccumulation, in particular of highly toxic elements, as a consequence of exposure to water contaminated with mining waste points to necessity of intensified supervision of mining impacted rivers.

Characterization and identification of selected metal-binding biomolecules from hepatic and gill cytosols of Vardar chub (Squalius vardarensis Karaman, 1928) using various techniques of liquid chromatography and mass spectrometry

Metals play crucial physiological roles, but they can also cause irreparable toxic effects through binding to important cellular biomolecules in aquatic organisms.

Anthropogenic particles in the stomach contents and liver of the freshwater fish Squalius cephalus

Anthropogenic particles (APs) are a very broad category of particles produced directly or indirectly by human activities. Their ingestion by biota is well studied in the marine environment. In contrast, studies on AP ingestion in wild freshwater organisms are scarce despite high contamination levels in some rivers and lakes. In this study, we aimed to evaluate the ingestion of APs and the possible occurrence of APs in the liver and muscle of a freshwater fish, Squalius cephalus, from the Parisian conurbation. After isolation, the particles were analyzed using Raman spectroscopy. In sixty stomachs, eighteen APs were found, half of which were plastics and the other half were dyed particles. Twenty-five percent of sampled individuals had ingested at least one AP. The mean length of the APs was 2.41 mm. No significant difference was found between the sites upstream and downstream of Paris. Additionally, 5% of sampled livers contained one or more APs, which were characterized as microplastics (MPs). No APs were found in the muscle tissue. The majority of APs isolated from stomach contents were fibers, which is similar to the findings of a previous river contamination study. This highlights that fish could be more exposed to fibers than previously thought and that more studies on the impacts of fiber ingestion are required. Despite their low occurrence, MPs are reported, for the first time, in the liver of a wild freshwater fish species. While the pathways and impacts are still unknown, MPs also occur in liver of marine mollusks and fish. Physiological in vitro studies are needed to better evaluate the impacts of such phenomena.

Accumulation of Heavy Metals in Some Organs in Barbel and Chub from Crn Drim River in the Republic of Macedonia

Heavy metal pollution of aquatic ecosystems is worldwide problem with consequences on the aquatic organisms. The concentrations of selected heavy metals (Fe, Mn, Zn, Cu, Cd and Pb) were determined in liver, kidney, gills, muscle and bone of barbel (Barbus rebeli) and chub (Squalius squalius) from the river Crn Drim in Macedonia. In general, liver and kidney in both fish species contained the highest concentration of the investigated metals, while muscle showed lowest bioaccumulation of heavy metals. Analyses supported significant seasonal differences in some organs for some metals: highest value in spring-summer compared to autumn-winter period. Generally, metal concentration was higher in the barbel than chub. The concentration of metals in muscle are bellow permissible value and do not constitute any threat for human health due to the consumption of metal loaded fish.

Cytosolic distributions of highly toxic metals Cd and Tl and several essential elements in the liver of brown trout (Salmo trutta L.) analyzed by size exclusion chromatography and inductively coupled plasma mass spectrometry

Cytosolic distributions of nonessential metals Cd and Tl and seven essential elements among compounds of different molecular masses were studied in the liver of brown trout (Salmo trutta) from the karstic Krka River in Croatia. Analyses were done by size exclusion high performance liquid chromatography and high resolution inductively coupled plasma mass spectrometry. Common feature of Cd and Tl, as highly toxic elements, was their distribution within only two narrow peaks. The increase of cytosolic Cd concentrations was reflected in marked increase of Cd elution within low molecular mass peak (maximum at ∼15 kDa), presumably containing metallothioneins (MTs), which indicated successful Cd detoxification in brown trout liver under studied exposure conditions. Contrary, the increase of cytosolic Tl concentrations was reflected in marked increase of Tl elution within high molecular mass peak (maximum at 140 kDa), which probably indicated incomplete Tl detoxification. Common feature of the majority of studied essential elements was their distribution within more peaks, often broad and not well resolved, which is consistent with their numerous physiological functions. Among observed associations of essential metals/nonmetal to proteins, the following could be singled out: Cu and Zn association to MTs, Fe association to storage protein ferritin, and Se association to compounds of very low molecular masses (<5 kDa). The obtained results present the first step towards identification of metal-binding compounds in hepatic cytosol of brown trout, and thus a significant contribution to better understanding of metal fate in the liver of that important bioindicator species.