Biomonitoring of heavy metals in fish from the Danube River

Elevated Heavy Metal(loid) Blood and Feather Concentrations in Wetland Birds from Different Trophic Levels Indicate Exposure to Environmental Pollutants

The research assessed the exposure to total mercury (THg), lead (Pb), and arsenic (As) in Colombian wetland species of different trophic levels Platalea ajaja, Dendrocygna autumnalis and Nannopterum brasilianus. The results show high THg blood levels in P. ajaja (811.00 ± 349.60 µg L-1) and N. brasilianus (209.50 ± 27.92 µg L-1) with P. ajaja possibly exhibiting adverse effects. Blood Pb concentration was high in D. autumnalis (212.00 ± 208.10 µg L-1) and above the threshold for adverse effects, suggesting subclinical poisoning. Levels of blood As were below the assumed threshold for detrimental effect (20 μg L-1). The mean concentration of feather THg was below the assumed natural background levels (5 µg g-1) for all three species. Feather Pb levels exceeded the levels for assumed threshold effects in all sampled N. brasilianus (7.40 ± 0.51 µg g-1). Results for feather As concentration were below the threshold for adverse impacts in all species, although a positive correlation between As and THg concentrations was detected in P. ajaja feathers. The overall results could help understand how metal(loid)s biomagnify through trophic levels and how wetland species may serve as environmental indicators. By exploring the interactions of metal(loid)s within different matrices and body, this study offers insights into the dynamics of contaminant accumulation and distribution in the environment. This concept can be applied to wetlands worldwide, where bird species can serve as indicators of ecosystem health and the presence of contaminants such as heavy metals and metalloids.

The influence of climate changes on heavy metals accumulation in Alosa immaculata from the Danube River Basin

This research report provides a comprehensive overview of the historical trends in heavy metal concentrations in the Pontic shad (Alosa immaculata) populations from both the Danube River and the Black Sea, while also exploring the potential influence of global warming on metal accumulation. Through bibliometric modeling analysis, it reveals significant limitations in existing international research, particularly the lack of comprehensive data on the impact of hydroclimatic changes on heavy metal accumulation in Alosa immaculata. Recognizing the critical importance of studies on heavy metal bioaccumulation in Danube shad, this research underscores their significance in defining tolerance thresholds, quantifying the impact of toxic elements along the aquatic food chain, and enhancing the economic sustainability of ichthyofauna monitoring efforts. Furthermore, these studies contribute invaluable insights into the complex dynamics of aquatic ecosystems, offering essential decision-making support for optimizing commercial fishing management practices on the Danube and ensuring robust support systems for industrial fishing endeavors.

Bio-Monitoring of Metal(loid)s Pollution in Dry Riverbeds Affected by Mining Activity

The aim of this study was to evaluate the most abundant native plants that could be used as a bio-monitor of metal(loid) concentration in dry riverbeds affected by mining activities. Three plants species and their respective rhizospheric soils were sampled from the El Beal (Piptatherum miliaceum, 15 samples), La Carrasquilla (Foeniculum vulgare, 10 samples), and Ponce (Dittrichia viscosa, 12 samples) dry riverbeds from the mining district of Cartegena-La Unión (SE Spain). There is scanty bibliography of the capacity of these species to be used as bio-monitors in the dry riverbeds. Plants categorized as a bio-monitor were established according to the bioaccumulation factor (BF), mobility ratio (MR), and linear correlations between metal(loid) concentrations in plants tissues (root or stem)-rhizospheric soils. The rhizospheric soils were highly contaminated for As, Cd, Pb, and Zn (Cf ≥ 6), and moderately contaminated for Mn (1 ≤ Cf < 3). Piptatherum miliaceum presented on Cd similar mean concentrations on rhizospheric soil and root, BF = 1.07, with a strong correlation soil-root (r = 0.61, p = 0.02). Therefore, of the three species with the capacity to grow in the area, Piptatherum miliaceum showed characteristics to be considered as a bio-monitor for Cd, with a BF > 1, and a positive-significant correlation between the rhizospheric soil and roots.

Effects of white-tailed eagle (Haliaeetus albicilla) nestling diet on mercury exposure dynamics in Kopački rit Nature Park, Croatia

The present study assessed for the first time the magnitude and dietary ecological source of total mercury (THg) exposure in a southern population of white-tailed eagles (Haliaeetus albicilla), an apex predator species shown valuable for environmental biomonitoring. This population depends on the Kopački rit Nature Park - the most important breeding site. We assessed THg exposure, using nestling body feathers collected between 2014-2019 (n = 72), and potential dietary ecological sources, proxied by prey remains and stable isotope analysis. Results show THg concentrations vary significantly over the years, though not showing any time trend. Prey remains analysis shows nests with aquatic prey remains to exhibit higher THg concentrations (median: 7.57 μg g-1 dw; min - max: 6.00-13.16 μg g-1 dw) compared to those with terrestrial remains (median: 3.94 μg g-1 dw; min - max: 0.28-12.04 μg g-1 dw) or evidencing a mixed diet (median: 7.43 μg g-1 dw; min - max: 3.38-12.04 μg g-1 dw). Nests with a predominant aquatic diet show elevated lower δ13C and higher δ15N values, indicating agreement between both dietary approaches. The model selection reveals a combination of year and δ15N best explain the variability in feather THg concentrations. Complementing these predictors with a dietary descriptor based on prey remains results in a poorer model fit and lowered explanatory power, similar to sexing the nestlings. The observed body feather THg concentrations (median: 6.99 μg g-1 dw; min - max: 0.27 - 17.16 μg g-1 dw) exceeded putative biogeochemical background levels (5.00 μg g-1 dw) in 71% of the nestlings, though, did not seem to exceed a threshold at which detrimental physiological effects are expected (40 μg g-1 dw). Continued monitoring is warranted as the studied population is likely exposed to a larger cocktail of contaminants while resident-protected bird areas.

Analysis of the Mercury Content in Fish for Human Consumption in Poland

Mercury (Hg) is a metal with toxic effects on the environment, including living organisms. Organic Hg derivatives readily penetrate biological membranes and pose a particular health risk. Food of aquatic origin is the main source of human exposure to methylmercury (MeHg). In Poland, the consumption of fishery and aquaculture products has been gradually increasing. The aim of this study was to determine the content of Hg in fish intended for human consumption and purchased in Poland. The total Hg content of the edible parts of different species of marine and freshwater fish was analysed. The range of Hg content in all fish was 0.004-0.827 mg/kg, with an arithmetic mean of 0.084 mg/kg. The concentration of Hg in marine fish (0.100 mg/kg) was higher than in freshwater fish (0.063 mg/kg). The highest concentration of Hg was found in tuna. The Estimated Hazard Quotient (EHQ) calculated for the tuna samples analysed was >1. This may represent a potential health risk for consumers. The consumption of the other fish analysed was considered safe on the basis of the EHQ. The Hg content of the analysed fish samples did not exceed the current limits for food.

Heavy metals in fish, rice, and human hair and health risk assessment in Wuhan city, central China

The current study investigated the concentration of heavy metals (HMs) in human hair associated with fish and rice consumption in Wuhan City, central China. The mean values of As in 8/10 fish species exceeded the food safety standard of 0.015 mg/kg. The mean values (mg/kg) of HMs in rice followed a descending order of Zn (13.7)> Cu (1.9)>Cr (0.51)>As (0.11) >Cd (0.08) >Pb (0.04). The ascending order of HMs for male hair was Cd < As < Cr < Pb < Cu < Zn, while As < Cd < Cr < Pb < Cu < Zn for female. 30% of hair Cr and 22% of hair Zn contents exceeded the recommended values. The middle age (19-44) and adult (45-59) groups were the most vulnerable group, as the concentration for most elements was high in these age groups. A significant correlation was found between fish-eating frequency and hair Zn (r = 0.213; p < 0.05), and As (r = 0.204; p < 0.05). High odd ratios were found in a population with high fish-eating frequency, especially for Pb (7.19), As (3.1), Zn (3.83), and Cd (3.7). A significant non-carcinogenic risk was associated with Cr exposure through consuming herbivores, filter feeders, and omnivorous fish. The cancer risk values of Cd exposure (1.54E-04) via rice consumption and As exposure (1.25E-04) via consumption of omnivores fish indicate precautionary measures.

Comparative assessment of human health risk associated with heavy metals bioaccumulation in fish species (Barbus grypus and Tenualosa ilisha) from the Karoon River, Iran: Elucidating the role of habitat and feeding habits

Concentrations of Cd, Ni, and Pb were measured in the liver and muscle tissues of benthic omnivorous (Barbus grypus) and pelagic herbivorous (Tenualosa ilisha) fish collected from two sampling sites along the Karoon River, Khuzestan Province, southwest of Iran. Potential human health risks were evaluated by measuring the estimated daily intake (EDI), target hazard quotient (THQ), hazard index (HI), and target cancer risk (TR). The results highlight the important role of habitat and feeding habits in the uptake of HMs by the two species. The EDI for all HMs exceeded the oral reference doses (RfDo) provided by the USEPA, indicating the two fish species are not entirely safe for human consumption. The THQ values were within the permissible limit (< 1), while HI values (> 1) showed there was non-carcinogenic risk for consumers. The TR values for Pb were within the acceptable range (1.00E-06-1.00E-04) for both species.

Comparative study on metal concentrations in water, sediments, and two fish species (Cyprinus carpio and Pelteobagrus fulvidraco) from the Wujiang River, China

In order to assess the metal pollution in the Wujiang River, concentrations of Cu, Zn, Fe, Mn, Pb, Cd, As, and Hg in the water, sediments, and two fish species Cyprinus carpio and Pelteobagrus fulvidraco from the middle reaches (Tuomugang, TMG) and lower reaches (Wulong, WL) of the Wujiang River were examined. The results indicated that all metal concentrations were lower than the values for grade one water quality according to the Environment Quality Standard for Surface Water of China (GB 3838-2002). The bioavailable fraction concentrations of Zn, Fe, Mn, Pb, and Hg in WL were significantly higher than those in TMG (p < 0.05), indicating that these metals in sediments of WL have higher bioavailability and mobility. The Cu, Zn, Fe, Pb, As, and Hg were mainly related to the residual fraction, while the Mn and Cd were mainly associated with the non-residual fraction. The risk assessment code (RAC) and the secondary phase to the primary phase (RSP) values indicated that Mn and Cd have a high risk of secondary release. The mean metal concentrations in the liver of the two fish species were higher than those in muscle. The higher metal concentrations of fish in WL suggested that bioaccumulation of metals in fish could be influenced by metal bioavailability. No identical relationships between metal concentrations and fish length were manifested in the present study. The values of target hazard quotient (THQ) and hazard index (HI), and carcinogenic risk (CR) of metals for the consumption of C. carpio and P. fulvidraco indicated that the anglers would likely not experience significant non-carcinogenic risk, but the carcinogenic risk of As cannot be ignored. Thanks to prohibited commercial fishing in the Wujiang River, the metal pollution will probably not pose a health risk to the general public for wild fish consumption.

Bioaccumulation of potentially toxic elements in fish species of Serbia: a review

In the first review of potentially toxic elements (PTEs) in fish in water ecosystems in Serbia, 40 studies related to fish contamination with PTEs were identified and evaluated. Studies of concentrations of PTEs in fish tissues covered 28 ecosystems (108 localities). The main studied river ecosystems were the Danube and the Sava, and the Međuvršje reservoir was the most studied standing water ecosystem. Among the most studied fish species were catfish (Silurus glanis), followed by pikeperch (Sander lucioperca), bream (Abramis brama), carp (Cyprinus carpio), and barbel (Barbus barbus). There were 48 "hot spot" sampling sites where concentrations of Hg, Cd, Pb, As, Ni, Fe, and/or Cu exceeded the maximum permitted concentrations (MPCs) prescribed by legislation. Elevated concentrations of these elements were the most detected in fish species sampled in the Danube, Sava, and rivers belonging to the Velika Morava basin. Hg concentrations were the most common above MPC in muscle tissue of species sampled from the Danube and Sava rivers. On the other hand, we can single out the species Vimba bream (Vimba vimba), sampled in Danube River in Zemun near Belgrade, as the safest species for human consumption due to the largest number of elements in fish meat below detection limits. Finally, having in mind all the criteria prescribed by U.S. EPA (2000), we identify and recommend two predatory fish species pikeperch (S. lucioperca) and catfish (S. glanis), and bottom-feeding fish species barbel (B. barbus) as bioindicators of PTEs contamination in Serbian waters.

Multi-metric Ecosystem Health Assessment of Three Inland Water Bodies in South-west, Nigeria, with Varying Levels of Sand Mining Activities and Heavy Metal Pollution

This study was conducted to determine the health status of three water bodies (Badagry Creek, Ologe Lagoon and River Owo) exposed to varying degrees of sand mining activities and industrial pollution. Water, sediment and fish samples were collected monthly from the three water bodies between April 2019 and March 2020. Standard methods were used for the analysis of physico-chemical parameters, fish diversity indices, length-weight relationship, condition factor, sediment pollution indices, ecotoxicology of heavy metals in sediment, potential ecological risks and health risk assessment of heavy metals. Positive matrix factorization (PMF) was used to identify and quantify metal source. Shannon's diversity index (H') and condition factor varied between 2.03-2.37 and 0.84-4.86 respectively. Enrichment factor had a range of 4.05×10^-4-8.65×10^-1, while geoaccumulation index varied from -12.14 to -0.38. The mean quotients using the probable effect level (m-PEL-Q) are 3.91×10^-4, 4.77×10^-4 and 7.87×10^-4 for Ologe Lagoon, Badagry Creek and River Owo respectively. The trend was the same with mean quotients using effect range-median (m-ERM-Q). The estimated dietary intake ranged from 0.00 mg/kg/day in Pb from River Owo to 1.15 × 10^-3 mg/kg/day in Fe still from River Owo. The range of values of the target hazard quotient of the metals in Badagry Creek, River Owo and Ologe Lagoon are 1.23×10^-4-1.65×10^-2, 0.00-1.64×10^-2 and 5.76×10^-5-1.65×10^-2 respectively. PMF identified three sources of metal into the aquatic ecosystems: agricultural, industrial and geological inputs. The study showed that the three aquatic ecosystems are healthy but require regular monitoring to promptly detect sudden changes in their health status.

Potentially toxic elements in invasive fish species Prussian carp (Carassius gibelio) from different freshwater ecosystems and human exposure assessment

Concentrations of Al, As, Cd, Co, Cr, Cu, Fe, Hg, Mn, Ni, Pb, Se, Sn, and Zn were detected in the muscle and gills of Prussian carp from three different freshwater ecosystems: isolated ponds and the South Morava River in Serbia, and Kopačko Lake in complex wetland ecosystem of the Kopački Rit Nature Reserve in Croatia. The main goals of the present research were to assess the concentrations of potentially toxic elements (PTEs) in the muscle and gills of Prussian carp (Carassius gibelio), to examine whether abiotic factors from three different freshwater ecosystems affect the accumulation of PTEs in fish tissues, and to estimate the human health risk resulting from fish consumption. There were only six concentrations of PTEs in the gill tissue (Cr, Hg, Mn, Pb, Sn, and Zn) that were not significantly different among the different freshwater ecosystems. In the muscles, the differences were much less visible. Kopačko Lake distinguished with the highest values of metal pollution index (MPI) for muscles (0.24) and isolated ponds with the highest values of MPI for gills (0.8). The redundancy analysis (RDA) showed that concentrations of Al, Mn, Zn, Cu, and Fe in the gill tissue were significantly correlated with the environmental variables. In contrast, the RDA based on element concentrations in the fish muscles indicated no significant relationship with the environment. Isolated ponds, with no inflow of freshwater, stand out as the most polluted, followed by Kopačko Lake with occasional floods. Flowing freshwater ecosystem South Morava River can be single out as at least polluted with PTEs. The target hazard quotients (THQ) and hazard index (HI) suggested there were no significant noncarcinogenic health risks. The target carcinogenic risk factor (TR) for As and Pb confirmed there were no cancer risks related to human fish consumption. Since the elevated concentrations of toxic Cd and As in Prussian carp were estimated, an early warning should be assumed, especially for fishing activities in these areas.

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.

Transfer of Heavy Metals Through Three Components: Sediments, Plants and Fish in the Area with Previous Mining Activity

This study aims to evaluate the ecological risk and distribution of heavy metals in sediment, plants and fish in a seriously polluted water reservoir in Krompachy, Slovakia. Special attention was given to the different food web positions of individual fish species (predators, omnivores) and their size. The degree of heavy metal contamination in sediments decreased in the order Cu > Pb > Cr > Hg > Cd, and their mutual proportion was largely consistent with concentrations found in aquatic plants, i.e. water sedges (Carex acutiformis). Of the seven fish species investigated, piscivorous perch (Perca fluviatilis) accumulated higher quantities of metal than fish situated at lower trophic levels. Interestingly, co-equal levels of heavy metals to those found in perch (P. fluviatilis) also occurred in rudd (Scardinius erythrophthalmus). The Hg values in some fish muscles exceeded the maximum permissible limits suggesting a persistent problem of old environmental burden from former mining activities.

Preliminary investigation of lower Danube pollution caused by potentially toxic metals

The current study aims to assess the pollution status of the European river-sea system lower Danube River-Danube Delta-North West Black Sea, through an integrated analysis of metal concentrations in water, sediments and fish community. The Danube flows through numerous industrial cities and receives a significant amount of pollutants due to the reception of urban and industrial emissaries, as well as agricultural land runoff. Samples of water, sediments and fish (10 species) were collected from 7 representative sites along Danube River, Danube Delta and Black Sea shore. For the analysed fish species, potentially toxic and essential elements (Pb, Cd, As, Cu, Fe, Zn, Mg, Ca, Na, K) from muscle and liver samples were measured and discussed. Measurement of elements and other environmental quality parameters were determined for water and sediments. The Black Sea area, represented by S6 and S7, received sediments from Danube with the lowest concentrations of Cd (0.05 ± 0.01 μg g^-1, respectively 0.01 ± 0.001 μg g^-1), Pb (3 ± 0.03 μg g^-1, respectively 2 ± 0.03 μg g^-1), As (2 ± 0.02 μg g^-1, respectively 1.4 ± 0.3 μg g^-1), Ni (8.9 ± 0.1 μg g^-1, respectively 5.2 ± 0.2 μg g^-1), Cr (8 ± 0.7 μg g^-1, respectively 5 ± 0.2 μg g^-1), Cu (3 ± 0.1 μg g^-1, respectively 2 ± 0.04 μg g^-1), Fe(6 ± 0.3 μg g^-1, respectively 3 ± 0.1 μg g^-1) and Zn (0.03 ± 0.003 μg g^-1, respectively 0.017 ± 0.001 μg g^-1). These results suggest that the Danube Delta system plays an important role in filtering the pollutants. Based on the biota and water analysis, there was no correlation observed between Cd, respectively Pb concentration in the environment and fish body (Person Coef. = -0.02 in muscle tissue and -0.01 in liver tissue, respectively Pearson Coeff. = -0.06 in muscle tissue and 0.1 in liver tissue). Cadmium remained an active element in the pollution of the Danube area (S1 and S2), with high concentration in the water matrix (0.14 ± 0.02 μg L^-1, respectively 0.05 ± 0.01 μg L^-1) and fish muscle (0.15 ± 0.03 μg g^-1f.w. in C. carpio - S2). This fact was confirmed by several other studies.

Preliminary study on the distribution of metals and persistent organic pollutants (POPs), including perfluoroalkylated acids (PFAS), in the aquatic environment near Morogoro, Tanzania, and the potential health risks for humans

Metals and persistent organic pollutants (POPs), including perfluoroalkylated acids (PFAS), are chemicals with a bioaccumulative potential that are detected in wildlife around the world. Although multiple studies reported the pollution of the aquatic environment with these chemicals, only limited data is present on the environmental pollution of Tanzania's aquatic environment and the possible risks for human health through consumption of contaminated fish or invertebrates. In the present study, we examined the distribution of metals and POPs in fish, invertebrates, sediment and water, collected at two different years at multiple important water reservoirs for domestic and industrial purposes, in the aquatic environment near Morogoro, Tanzania. Furthermore, we assessed the possible risks for human health through consumption of contaminated fish and shrimp. Metal concentrations in the water, sediment, invertebrates and fish appeared to increase in sites downstream from Morogoro city, likely caused by the presence of the city as pollution source. Significant differences in accumulated concentrations of metals and POPs were observed between species, which was hypothesized to be caused by dietary differences. Concentrations of multiple metals exceeded water and sediment quality guidelines values. Only Cu (2.8-17 μg/L) and Zn (<LOQ - 151 μg/L) in water exceeded chronic and acute effect values. Furthermore, PFOS, PBDE and HCB concentrations exceeded biota quality standard values, suggesting an ecological risk caused by these metals and POPs in the aquatic environment around Morogoro. Our results suggest that potential health effects through consumption of contaminated shrimp, and to minor extent fish, are expected. The daily consumption of these proteins (0.016-0.027 kg/capita/day) in Tanzania is similar or higher than the tolerable maximum consumption of shrimp for Cu (<0.02 kg/capita/day), Co (<0.02 kg/capita/day) and PFOS (<0.01 kg/capita/day). The outcome of this study could be used in future studies on metals and POPs in African aquatic ecosystems.

Chromium, Cadmium, Lead, and Arsenic Concentrations in Water, Vegetables, and Seafood Consumed in a Coastal Area in Northern Vietnam

BACKGROUND

Heavy metal contamination and related risks for the environment and human health are matters of increasing concern.

METHODS

The levels of 4 heavy metals (Cr, Cd, Pb, and As) were evaluated in 2 water types (surface and well), 4 types of seafood (tiger shrimp, stuffed snail, snake-head fish, and catfish), and 27 types of vegetables (12 leafy vegetables, 4 pea plants, 4 tuber vegetables, and 7 herbs) that are commonly consumed in northern coastal communes located in Vietnam. Atomic absorption spectrometry was employed for quantification.

RESULTS

The mean concentrations of heavy metals detected in water, seafood, and vegetable samples exceeded the national permitted standards and World Health Organization (WHO) recommendation values by at least 2-fold, 2.5-fold, and 5-fold for surface water, vegetables, and well water, respectively. The concentrations of all 4 heavy metals detected in seafood samples were higher than the standards. The levels of heavy metals decreased with increasing distance between the sample collection point and the pollution source.

CONCLUSIONS

This is the first report of heavy metal contamination of common sources of food and water in the northern coastal area of Vietnam. Significantly, the concentrations of heavy metals detected in study samples exceeded the regulatory limits. These results underscore the importance of continued monitoring and the development of intervention measures to ensure that the quality of food and water meets established standards and protects the health of the local population.

Metal Accumulation in Muscle and Liver of the Common Nase (Chondrostoma nasus) and Vimba Bream (Vimbavimba) from the Danube River, Serbia: Bioindicative Aspects

Accumulation of 17 elements in muscle and liver of common nase and vimba bream, caught between February and May 2016 in the Danube River (1173 river kilometer), were assessed by ICP-OES. The principal component analysis grouped muscle and liver samples based on element concentrations (muscle grouped by higher Ba and Sr values, and liver grouped by higher Al, B, Cd, Cr, Cu, Fe, Mn, and Zn values), but no grouping between the two species was observed. Concentrations of Ba, Cu, Fe, and Zn were significantly higher in muscle, and concentrations of Ba, Cd, Cu, and Mn in liver of common nase, while vimba bream had significantly higher concentrations of Cr and Fe in liver. Common nase has a higher affinity for bioaccumulation of Cu, Fe, and Zn in muscle, while vimba bream has a higher affinity for Al, Cd, and Cr in muscle.

Multielemental analysis in Nerium Oleander L. leaves as a way of assessing the levels of urban air pollution by heavy metals

In this study, Nerium oleander L. leaves were used as biomonitors to evaluate environmental pollutants levels in a sub-region in the Metropolitan Area of Rio de Janeiro City (Brazil) through X-ray Fluorescence (XRF). Control samples were collected in a rural zone next to the Parque Estadual da Pedra Branca/RJ. The samples were collected during all seasons of 2015 (summer, fall, winter and spring). The concentration of 13 elements (S, Cl, K, Ca, Mn, Fe, Cu, Zn, Br, Rb, Sr, Ba and Pb) was determined. Most of the elements showed, during all seasons, median concentrations of sampling sites higher than the results obtained from the control sites. The principal component analysis (PCA) showed the grouping of the elements in two main factors that can be associated to emission sources of these elements. The elements Cl, K, Ca, Cu, Rb and Sr can be associated as a possible influence from the soil (root uptake and/or resuspension). On the other hand, the elements Fe, Cu, Zn, and Pb can be associated to vehicle and industry emission sources. The study showed that the XRF technique applied to Nerium oleander L. leaves is efficient to environmental pollution analysis in Metropolitan Regions since it is precise, fast and low-cost, besides allowing the monitoring of pollution levels over time.

Potentially toxic elements in muscle tissue of different fish species from the Sava River and risk assessment for consumers

Fish from the Sava River are consumed daily by the local people: therefore, concern has been raised about the health implications of eating contaminated fish. In the present study, potentially toxic elements (PTE), such as Zn, Cu, Cr, Ni, Cd, Pb, As, Hg, and methylmercury (MeHg), were determined in ichthyofauna that are commonly consumed. PTE were determined in the fish muscle tissue. Fish were sampled at 12 locations from the source of the Sava River to its confluence with the Danube River during two sampling campaigns, namely; in 2014 under high water conditions and in 2015 under normal water conditions. Due to the different water regimes, different fish species were collected for chemical analysis. We observed that the concentrations of elements analysed in the fish muscle tissue were generally very low, except for those of Hg. Moreover, more than 90% of Hg present in the fish was in its most toxic form, namely MeHg. Especially in fish from the 2015 sampling campaign, Hg and MeHg concentrations increased with fish size, trophic level, and in the downstream direction. In addition, for Pb and As, and to some extent for Cd and Cr, spatial differences were detected in both years. The highest concentrations of PTE were detected in fish from sites with intensive industrial and agricultural activities. The consumption of fish in general does not pose a health risk for the PTE studied, except for Hg/MeHg at selected contaminated sites.

Mercury, Fatty Acids Content and Lipid Quality Indexes in Muscles of Freshwater and Marine Fish on the Polish Market. Risk Assessment of Fish Consumption

Mercury content and fatty acids in muscles of Perca fluviatilis L. (European perch), Leuciscus idus L. (ide), Cyprinus carpio L. (European or common carp), Oncorhynchus mykiss Walb. (rainbow trout), Platichthys flesus L. (European flounder). and Clupea harengus L. (bream) from the Polish market were investigated. The total mercury was processed with AAS. The fatty acids were analyzed by gas chromatography. The concentration of mercury in muscles varied from 0.006 to 0.138 mg/kg and decreased as follows: perch ≈ ide > flounder > herring ≈ bream ≈ rainbow trout > carp (p ≤ 0.05). There were only significant positive correlations between body weight and mercury content in muscle tissue of carp (r = 0.878), flounder (r = 0.925) and herring (r = 0.982) (p ≤ 0.05). The atherogenic index (AI), thrombogenicity index (TI) and flesh-lipid quality index (FLQ) were calculated as follows 0.33-0.70 (IA), 0.16-0.31 (IT) and 13.01-33.22 (FLQ). Hypocholesterolemic (OFA) and hypercholesterolemic fatty acids (DFA) in muscles of fish ranged from 18.26 to 23.01 and from 73.91 to 78.46, respectively. In most cases, there were not significant correlations between size (body weight and total length) and fatty acids in the muscles of the examined fish (p > 0.05). The Target Hazard Quotient (THQ) values were below 1, which shows that there is no non-carcinogenic health risk to the consumer by consuming the examined fish.

Heavy metal accumulation in organs of Oreochromis niloticus (Linnaeus, 1758) from industrial effluent-polluted aquatic ecosystem in Lagos, Nigeria

The concentrations of four heavy metals (Zn, Fe, Cu, and Pb) in water, sediment, and tissues (gill, muscle, brain, and intestine) of Oreochromis niloticus from a segment of the Lagos Lagoon complex were monitored for 10 months (July 2012-April 2013) spanning wet and dry seasons. Three sampling stations were selected: Ologe Lagoon, the nearest to the point where effluent is discharged from Agbara Industrial Estate, the Owo River is upstream before the point of discharge of industrial effluent, and Etegbin is downstream. In most cases, the highest concentrations of heavy metal in fish tissues were recorded in samples obtained from Ologe Lagoon. The ranges of concentrations of heavy metals in the tissues of the fish were 4.06 ± 2.45-49.94 ± 13.11, 81.27 ± 28.52-2044.64 ± 554.77, 10.90 ± 7.69-41.10 ± 11.24, and 0.12 ± 0.07-1.81 ± 3.12 mg/kg for Zn, Fe, Cu, and Pb, respectively. There were significant negative correlations (lowest; r = -0.24, p < 0.01, n = 30; highest; r = -0.58, p < 0.01, n = 30) between fish tissue metal concentrations and size of fish from Ologe Lagoon. Also, significant positive correlations (lowest; r = 0.48, p < 0.05, n = 30; highest; r = 0.93, p < 0.01, n = 30) between concentrations of Cu in sediment and tissues of O. niloticus were observed. The concentrations of the metals in the tissues of O. niloticus have exceeded the limits recommended by WHO. The maximum safe daily consumption (MSDC) value of Fe in Ologe Lagoon was lower than the recommended average daily intake of fish for humans. This indicated that O. niloticus from Ologe Lagoon may not be safe for human consumption. Therefore, there is a need for regular monitoring of heavy metal in these water bodies and enforcement of existing laws on the treatment of effluent before they are discharged into aquatic ecosystems.

Concentrations of Arsenic and Boron in Water, Sediment and the Tissues of Fish in Emet Stream (Turkey)

In this study, the concentrations of arsenic and boron were determined in the water and the sediment, as well as in the muscle tissues of Squalius cephalus, Alburnoides bipunctatus, Barbus plebejus and Capoeta tinca from Emet Stream. The fish samples were caught in May 2011 and September 2012. The metal concentrations in the water samples were as follows: arsenic was 137.1-1002 µg L^-1, and boron was 2421-14490 µg L^-1. The metal concentrations in the sediment samples were as follows: arsenic was 14.51-3317.1 mg kg^-1, and boron was 14.22-1014.01 mg kg^-1. The mean tissue concentration of arsenic was lower than the TFC and WHO limits. Boron has been identified in fish tissues at concentrations between 0.26 and 2.96 mg kg^-1. The bioaccumulation in the muscle tissues of all fish species caught from Emet Stream did not exceed the limit values.

Determination of heavy metals in muscle tissue of six fish species with different feeding habits from the Danube River, Belgrade-public health and environmental risk assessment

The aim of this study was to investigate the presence of heavy metals/metalloids (Pb, Cd, Hg, Cu, Fe, Zn, As) in the muscle tissue of fish from the Danube River (two locations: Zemun and Grocka). For the purpose of heavy metal determination in fish muscle, 120 samples of six different fish species, Prussian carp, barbel, bream, carp, pike perch, and catfish were collected. For determining heavy metals, we used microwave oven digestion and atomic absorption spectrometer methods. The highest average content of Pb (0.084 ± 0.004 mg kg^-1), Cd (0.082 ± 0.003 mg kg^-1), Hg (0.466 ± 0.006 mg kg^-1), and As (0.333 ± 0.007 mg kg^-1) was found in the muscle of carp (an omnivorous fish) from Grocka, while the highest average level of Fe (13.60 ± 0.03 mg kg^-1) was deposited in bream (also omnivorous) from Zemun. Also, the average Cu level (1.62 ± 0.13 mg kg^-1) was the highest in catfish muscle (a carnivorous fish) from Grocka, while the highest Zn content (11.16 ± 0.17 mg kg^-1) was determined in muscle of Prussian carp (an omnivorous fish) from Zemun. The highest content of heavy metals (Cu, Fe, and Zn, respectively) in muscle of the six different types of fish from both locations was symmetrically arranged by species (catfish, barbel, and Prussian carp, respectively). Concentrations of Pb, Hg, and As in the Danube River fish muscle were under the maximum residual levels prescribed by the European Union (EU) and the maximum allowed concentrations (MAC) for Serbia. On the other hand, in all fish muscle from both locations (Zemun and Grocka), higher concentrations of Cd than prescribed (MAC) were found, with the exception of bream and pike perch.

Evaluation of trace metal levels in surface water and sediments of the Hungarian upper section of the Danube River and its tributaries

The objective of this study was to assess the concentration levels of trace metals (Zn, Hg, Cd, Cr, Ni, Pb and Cu) in surface water and bottom sediments of the Hungarian upper section of the Danube River and its main tributaries. A total of 935 samples (water and sediments) were collected from 10 different sampling sites in the period of 2001-2012 and analyzed for the trace metals. Moreover, the dissolved arsenic content was determined in a number of 467 water samples in the period of 2004-2012. The highest dissolved trace element concentrations were observed at the site of Kenyérmezei-patak Creek located near a hazardous waste incinerator. However, the comparison of the dissolved trace metal(loid) concentrations determined with other sections of the Danube River and the European Union environmental quality standards revealed that the dissolved trace metal(loid) concentrations were relatively low in the Hungarian upper section during the 12-year study period (excluding some samples for Hg, Cd and Cr). The concentrations of trace metals in sediments were higher than those found in water samples and varied very much in all sampling sites during the study period. The sediment samples were mainly classified as low or moderate polluted for trace metals. However, some sediment samples collected especially from the Moson Danube branch indicated a considerable (for Zn, Hg, Cd, Ni and Cu) or a very high (for Zn and Hg) contamination.

Heavy Metal Levels in Fish from Heilongjiang River and Potential Health Risk Assessment

Concentrations of Cu, Zn, Cr, As, Cd, Pb and Hg were determined in 153 samples covering 18 fish species collected from Heilongjiang River, China, and the potential health risks to local residents through fish consumption were estimated. Results revealed that all metals were detected with Cd and Pb having considerably lower detection rate. There were 28.6 % of Lethenteron camtschaticum samples exceeding the limit of inorganic As content established by Chinese legislation. Metal bioaccumulation in fish were poorly correlated with fish sizes, and generally tended to increase with trophic levels. The hazard quotient values of all fish species were far below 1 for general population and fishermen. The carcinogenic risk of As in L. camtschaticum for the local fishermen exceeded the acceptable level of 10(-4) rise in cancer rates, but was considered safe given the migratory habits of the fish.

Metal concentrations in water, sediment and three fish species from the Danube River, Serbia: a cause for environmental concern

The aim of this study was to investigate the presence of metal contamination in water, sediments and three different fish species. All samples were taken from the Danube River in Belgrade Region, a location upstream from Grocka. Concentrations of Cd, Hg and Pb in water samples were not detected, while concentrations of Zn, Fe, Cu and As were in the range of 0.004-0.41 mg L(-1). Iron was the most deposited metal in sediment samples (17,530.00 mg kg(-1)). For the purpose of heavy metal determination in fish tissue, silver carp, common carp and wels catfish were collected. Concentrations of Pb, Cd and As were determined in muscle, digestive tract and liver by inductively coupled plasma-optical emission spectrophotometry (IPC-OES). The highest concentration of Pb was in the digestive tract of all three fish species, while Cd was mostly deposited in the liver. The highest concentration of Hg was in the muscle tissue of wels catfish, and these values are above the maximum residual levels prescribed by the European Union and the maximum allowed concentrations (MACs) for Serbia. Concentration of As was mostly deposited in the liver, but under the MAC.

Spatial monitoring of heavy metals in the inland waters of Serbia: a multispecies approach based on commercial fish

The study monitored the contamination of fish muscle tissue by elements Al, As, Cd, Co, Cr, Cu, Fe, Hg, Mn, Ni, Pb, and Zn at 17 sampling sites, in order to assess the pollution status of the main rivers in Serbia. Of the six commercially important fish species included in the study (pikeperch Sander lucioperca, catfish Silurus glanis, bream Abramis brama, barbel Barbus barbus, chub Squalius cephalus, nase Chondrostoma nasus), the bioconcentration factor (BCF) indicated that benthivore bream and barbel and predatory catfish have the highest tendency toward the accumulation of elements. This study achieved its primary objective and produced a contamination map of Serbia as a basis for further research. The estimated metal pollution index (MPI) showed the Tisa River to be unaffected by direct pollution (with an MPI value of 0.31) and the West Morava and Pek rivers to be affected (with MPI values of 1.92 and 0.73 for the WM1 and WM2 sampling sites and 0.65 for the Pek sampling site). Over the past two decades, Serbia has not expanded its industrial activity, which has resulted in the barely noticeable anthropogenic input of heavy metals in the rivers close to industry, and the main rivers are mostly unaffected and slightly affected. We assumed that pollution by heavy metals in the 1990s was trapped in the sediment, thus showing an increased concentration of elements in the species that live and feed on the bottom. Hg concentrations exceeded the maximum permitted concentrations (MPCs) only in catfish samples (0.62 mg kg(-1)) from the Danube (D3 sampling site) and barbel (0.78 mg kg(-1)) from the West Morava (WM1 sampling site), while Cd concentrations exceeded the MPC in catfish samples (0.09 mg kg(-1)) from the Danube (D1 sampling site) and chub samples (0.1 mg kg(-1)) from the South Morava (SM2 sampling site). The average concentrations of Pb exceeded the MPC in chub and barbel samples (0.32 and 0.82 mg kg(-1), respectively) from the West Morava (WM1 sampling site); chub, barbel, and nase samples (0.35, 0.32, 0.31 mg kg(-1), respectively) from the West Morava (WM2 sampling site); chub and barbel samples (0.35 and 0.3 mg kg(-1), respectively) from the Ibar; chub samples (0.39 mg kg(-1)) from the Drina; chub and barbel samples (0.59 and 0.4 mg kg(-1), respectively) from the Great Timok; and nase samples (0.33 mg kg(-1)) from the Pek. These results demonstrate that there is a need for future studies that would involve similar analyses and focus especially on smaller rivers that have been neglected so far.

The Lower Danube River-Danube Delta-North West Black Sea: A pivotal area of major interest for the past, present and future of its fish fauna--A short review

The complex Danube-Black Sea geoecosystem, created by a unique combination of integrated biotopes and biocoenoses related forces and counter-forces in time and space, forms a rich "ichthyosystem". The equilibrium among the fish species captured in the Danube Delta reveals its structural and functional roles in the connectivity of the Danube and Black Sea. The key role of the delta is evidenced by the fact that 57.26% of the Lower Danube-Danube Delta-North West Black Sea fish species use two or three of the subsystems in terms of habitats. Therefore, this convergence area can be considered to be a dynamic and rich "ichthyosystem", with three subsystems. All three evolved interdependently, which permits their flexibility and adaptation in an interdependent way. The habitat heterogeneity, native economic and conservation priority fish species of the Lower Danube-Danube Delta-North Western Black Sea have decreased significantly, and there are no indications that this trend will be halted soon. The Danube "sub-ichtyosystem" seems to be more directly affected than the others. The Lower Danube-Danube Delta-North Western Black Sea "ichthyosystem" exhibits a significant level of flexibility, resilience and adaptation over geological time, but has become much more sensitive to environmental perturbations due to the last century of human impact. This "ichthyosystem" is affected by non-native fish species. The study area represents an interdependent ecological net, without which the specific "ichthyosystem" formed over geological time will disappear. The studied ecological net fish fauna is an accurate indicator of various human pressures. The Lower Danube-Danube Delta-North West Black Sea geoecosystem, in which the Danube Delta provides the pivotal habitat element, is the matrix for a unique "ichthyosystem." However, human impacts decrease its resilience and can induce its extinction.

Cloning metallothionein gene in Zacco platypus and its potential as an exposure biomarker against cadmium

Zacco platypus, pale chub, is an indigenous freshwater fish of East Asia including Korea and has many useful characteristics as indicator species for water pollution. While utility of Z. platypus as an experimental species has been recognized, genetic-level information is very limited and warrants extensive research. Metallothionein (MT) is widely used and well-known biomarker for heavy metal exposure in many experimental species. In the present study, we cloned MT in Z. platypus and evaluated its utility as a biomarker for metal exposure. For this purpose, we sequenced complete complementary DNA (cDNA) of MT in Z. platypus and carried out phylogenetic analysis with its sequences. The transcription-level responses of MT gene following the exposure to CdCl2 were also assessed to validate the utility of this gene as an exposure biomarker. Analysis of cDNA sequence of MT gene demonstrated high conformity with those of other fish. MT messenger RNA (mRNA) expression and enzymatic MT content significantly increased following CdCl2 exposure in a concentration-dependent manner. The level of CdCl2 that resulted in significant MT changes in Z. platypus was within the range that was reported from other fish. The MT gene of Z. platypus sequenced in the present study can be used as a useful biomarker for heavy metal exposure in the aquatic environment of Korea and other countries where this freshwater fish species represents the ecosystem.

Comparison of metal concentrations in the organs of two fish species from the Zabol Chahnimeh reservoirs, Iran

This study was conducted to measure the Cd, Pb, Cu, Zn, Cr, Co, Ni, and Fe concentrations in organs of Cyprinus carpio and Hypophthalmichthys molitrix, in Zabol Chahnimeh reservoirs, Iran. The highest Pb, Cu, Co, Ni, and Fe concentrations in both fish species were observed in the gill of C. carpio at 0.70, 3.7, 0.7, 0.8 and 31.2 µg/g, respectively; while the highest concentrations of Cd, Zn, and Cr were found in the gill of H. molitrix at 0.13, 22.5, and 0.5 µg/g, respectively. The maximum allowable fish consumption rate for an adult person (71.5 kg body weight) were 10.64, 0.677, 0.558, 1.17, and 0.92 kg/day based on Cd, Cu, Cr, Zn, and Fe levels respectively. Results showed that the Cd, Cu, Zn, and Pb (except of Pb in H. molitrix) concentrations in the muscle of both fish species are below levels of concern for human consumption.

Bioaccumulation of heavy metals in blood and tissue of striped mullet in two Italian lakes

Water and sediment from Faro and Ganzirri lakes were tested for cadmium, mercury, and lead. These heavy metals have been assessed in serum and muscles of Striped Mullet Mugil cephalus. A haemogram was performed to find effects of heavy metals on haematological variables. Student's t-test showed higher Pb levels in sediments of Ganzirri Lake than Faro Lake. Two-way analysis of variance showed higher Cd and Pb concentration in muscles samples of Striped Mullet from Ganzirri Lake than from Faro Lake. Significant differences were found among haematological parameters as well. Mullet from Ganzirri Lake had lower white and red blood cell and trombocyte counts and higher mean corpuscular haemoglobin and mean corpuscular haemoglobin concentration than those from Faro Lake. Our results indicate a significant presence of lead in the environmental produces an accumulation of this metal in fish muscles.

Spatial and temporal trends of metals and arsenic in German freshwater compartments

Cadmium, lead, mercury, copper, nickel, zinc, and arsenic were analyzed in suspended particulate matter (SPM), zebra mussels, and bream sampled yearly under the program of the German Environmental Specimen Bank (ESB) in the rivers Rhine, Elbe, Danube, Saar, Mulde, and Saale and in Lake Belau. Temporal and spatial trends were analyzed, correlations between metal levels in different specimen types assessed, and sampling sites ranked according to their metal levels by calculating a Multi-Metal Index (MMI) for every specimen type and site. SPM: Highest metal loads were detected in Mulde, Saale, and Elbe right downstream of the Saale confluence. In the Elbe, metal loads in SPM were mostly highest in the upper and middle section of the river while in Rhine and Saar concentrations increased downstream. Temporal trends since 2005 were detected only at three sites. Zebra mussel: MMIs were highest in the tidal section of the Elbe and the lower Rhine and lowest in Lake Belau and the upper Danube. Different temporal trends were detected since the early 1990s depending on site and metal. Bream: As, Pb, Cu, and Hg were analyzed in muscle tissue and Pb, Cd, Cu, and Zn in liver. For both tissues, MMIs were highest in Mulde and Saale and the lower and middle Elbe. Since the early 1990s, Hg, Pb, and Cu decreased in bream muscle at many sites while As increased at 6 of the 17 sites. The findings indicate that Hg, Pb, and Cu have obviously decreased in many freshwater ecosystems in recent years, whereas As and Ni levels have increased at several sites. Metal levels and temporal trends mostly differed between the specimen types under investigation and only few correlations between specimen types were detected. This underlines the importance of including different components of an ecosystem when assessing its environmental quality.

Bioaccumulation of zinc, lead, copper, and cadmium from contaminated sediments by native plant species and Acrida cinerea in South China

This research was conducted to search and identify spontaneously growing heavy metal-tolerant plant species that are potentially useful for phytoremediation in contaminated sediment. Five sites were selected for collection of plants growing on polluted shore (river bank) sediment of the Xiang River, China. The concentrations of Zn, Pb, Cu and Cd in plants, sediments, and grasshoppers were determined using flame atomic absorption spectrophotometer (AAS700, Perkin-Elmer, USA). Considering translocation factor and bioaccumulation factor, Rumex crispus (Polygonaceae), Rumex dentatus (Polygonaceae), and Lagopsis supina (Labiatae) could be potentially useful for phytostabilization of metals. R. crispus can be considered potentially useful for phytoextraction of Cd. In light of the biomagnification factors, grasshoppers are deconcentrators for Pb and Cd, microconcentrators for Zn and macroconcentrators for Cu to the plants, respectively. To the best of our knowledge, the present study is the first report on Zn, Pb, Cu and Cd accumulation in R. crispus and L. supina, providing a pioneer contribution to the very small volume of data available on the potential use of native plant species from contaminated sediments in phytostabilization and phytoremediation technologies.

Heavy metal and trace element bioaccumulation in target tissues of four edible fish species from the Danube River (Serbia)

Pikeperch (Sander lucioperca), European catfish (Silurus glanis), burbot (Lota lota), and common carp (Cyprinus carpio) were collected from the Danube River (Belgrade section, Serbia), and samples of liver, muscle, and gills were analyzed for Al, As, B, Ba, Cd, Co, Cr, Cu, Fe, Hg, Li, Mn, Mo, Ni, Pb, Se, Sr, and Zn using inductively coupled plasma optical emission spectrometry (ICP-OES) to highlight the importance of species and tissue selection in monitoring research, contaminant studies, and human health research. The Kruskal-Wallis test revealed significant differences between fish species in regard to metal levels in liver, muscle, and gills. The principal component analysis (PCA) indicated that the studied fish species could be grouped on the basis of the level of analyzed elements in liver and gills. The Mann-Whitney test showed two subsets (one comprising two piscivorous species, pikeperch and catfish, and the other, two polyphagous species, burbot and carp) in regard to Cr and Hg levels in liver (higher levels in piscivorous species), as well as B, Fe, and Hg in gills (B and Fe with higher levels in polyphagous and Hg in piscivorous species), and As in muscle (higher levels in polyphagous species). Carp had distinctly higher levels of Cd, Cu, and Zn in liver in comparison to other three species. None of the elements exceeded the maximum acceptable concentrations (MAC). However, since Hg levels are close to the prescribed MAC levels, the consumption of these fishes can be potentially hazardous for humans.

Assessment of human health risk for heavy metals in fish and shrimp collected from Subarnarekha river, India

Five fish species and one shrimp species from the Subarnarekha river were analyzed for heavy metals using inductively coupled plasma-mass spectrometry. The geometric mean concentration of As, Cd, Cu, Fe, Pb, Ni, Zn, Cr, Co, and Sr for all the samples was found to be 0.248, 0.031, 5.16, 104.9, 0.121, 4.68, 52.2, 0.784, 0.207, and 42.86 mg kg(-1)fresh, respectively. The concentrations of metals in the fish and shrimp exceed the limits of Indian and FAO standards for food for As, Cu, Ni, Cd, and Zn in many samples. The mean target hazard quotient (THQ) values for the 10 metals were below one for all the samples; however, the maximum THQ was more than one for shrimp in case of As, Cu, and Cr. The results indicate that the concentration of metals in some species, especially shrimp, at some locations is alarming and do present an appreciable hazard risk on human health.

Distribution and accumulation of elements (As, Cu, Fe, Hg, Mn, and Zn) in tissues of fish species from different trophic levels in the Danube River at the confluence with the Sava River (Serbia)

Pikeperch (Sander lucioperca), European catfish (Silurus glanis), common carp (Cyprinus carpio), and gobies (Neogobius gymnotrachelus, Neogobius melanostomus) were collected from the Danube River (Belgrade section), and samples of liver, muscle, or whole-body composites (in the case of gobies) were analyzed for As, Cu, Fe, Hg, Mn, and Zn with inductively coupled plasma optical spectrometry to find out if there was a correlation between accumulation of these elements in predatory and prey species, as well as in pairs of species with overlapping diets. Concentrations of all analyzed elements were either higher (Cu, Fe, Mn, Zn) in liver than in muscle, or equal (As, Hg), except for Hg in carp, which was higher in muscle. Mercury concentration in liver and muscle of predators (catfish, pikeperch) was significantly (<10(-4)) higher than in prey fishes (carp and gobies). The results indicate that Hg concentration was biomagnified through the food chain. Concentrations of As, Fe, and Hg in carp liver and gobies whole-body composite were similar, but carp had significantly (<10(-4)) higher values of Zn and Cu in liver. The regression analysis and trendline equations indicate that the concentrations of all tested elements, except for As in liver, and Mn and Fe in muscle, were similar in predatory fish (pikeperch and catfish), on one hand, and in prey fish (carp and gobies), on the other hand. Distinctly high Zn concentration in carp is very common in this species due to its physiology. Concentrations of Hg and Zn were higher than the maximum acceptable concentration due to the high pollution level in this section of the Danube River, accordingly posing a risk for the human consumption of these fish species.