Distribution of metals (Fe, Mn, Zn, Cu) in fish tissues in two lakes of different trophy in Northwestern Poland

Effects of antimony on antioxidant system, damage indexes of blood-brain barrier and ultrastructure of zebrafish (Danio rerio)

Antimony (Sb) and its compounds can be harmful to people and are known to cause cancer, so they are a key pollutant to control. This study investigated the influence of antimony on non-enzymatic antioxidants and the blood-brain barrier (BBB) in zebrafish(Danio rerio), a model organism that shares a high degree of genetic similarity with humans. Zebrafish were exposed to different doses of antimony in water for 7, 18, and 30 days. The results indicated that antimony accumulated most in the liver, followed by the gills, flesh, and brain, with the accumulation increasing as the exposure duration extends. Additionally, under identical antimony concentrations, the buildup in the four tissues was positively correlated with the duration of exposure. After 18 days of exposure, the total antioxidant capacity (T-AOC) and endogenous non-enzymatic antioxidants vitamin C (VC) and vitamin E (VE) decreased as a result of antimony ingestion in zebrafish, although cysteine secretion was increased in the liver, gills, and brain. The structural integrity of the BBB was compromised by the elevation of ApoE4 and MMP-9 levels as a result of antimony exposure, which led to the breakdown of the basal lamina, tight junctions, and nerve fibers in the brain. At this injured region, 5-HT and MBP were also able to easily enter and leave the BBB, albeit at variable rates. Additionally, when the antimony exposure level reached 16.58 mg·L-1, antimony penetrated the BBB and bound to erythrocytes, causing their lysis.

Interrelation between environmental conditions, acanthocephalan infection and metal(loid) accumulation in fish intestine: an in-depth study

Metal(loid) bioaccumulation in acanthocephalans (Dentitruncus truttae) and intestines of fish (Salmo trutta) from the Krka River, influenced by industrial and municipal wastewaters, was investigated in relation to exposure to metal(loid)s from fish gut content (GC), water, and sediment to estimate potentially available metal (loid)s responsible for toxic effects and cellular disturbances in biota. Sampling was performed in two seasons (spring and autumn) at the reference site (river source, KRS), downstream of the wastewater outlets (Town of Knin, KRK), and in the national park (KNP). Metal(loid) concentrations were measured by ICP-MS. The highest accumulation of As, Ba, Ca, Cu, Fe, Pb, Se and Zn was observed mainly in organisms from KRK, of Cd, Cs, Rb and Tl at KRS, and of Hg, Mn, Mo, Sr and V at KNP. Acanthocephalans showed significantly higher bioaccumulation than fish intestine, especially of toxic metals (Pb, Cd and Tl). Metal(loid) bioaccumulation in organisms partially coincided to exposure from water, sediments and food, while in GC almost all elements were elevated at KNP, reflecting the metal(loid) exposure from sediments. Seasonal differences in organisms and GC indicated higher metal (loid) accumulation in spring, which follows enhanced fish feeding rates. Higher number of acanthocephalans in the intestine influenced biodilution process and lower concentrations of metal(loid)s in fish, indicating positive effects of parasites to their host, as supported by high values of bioconcentration factors. Fish intestine and acanthocephalan D. truttae were confirmed as sensitive indicators of available metal fraction in conditions of generally low environmental exposure in karst ecosystem. Since metal(loid) accumulation depended on ecological, chemical and biological conditions, but also on the dietary habits, physiology of organisms and parasite infection, continuous monitoring is recommended to distinguish between the effects of these factors and environmental exposure when assessing dietary associated metal(loid) exposure in aquatic organisms.

An assessment of the potential health hazards associated with metal contamination in a variety of consumable species living along the industrialized coastline of East Java, Indonesia

The massive industrial growth in Gresik, East Java, Indonesia has the potential to result in metal contamination in the nearby coastal waters. The purpose of this study was to analyze the metal concentrations in edible species from the Gresik coastal waters and evaluate the potential health risks linked to this metal contamination. Metal concentrations (Cu, Fe, Pb, Zn, As, Cd, Ni, Hg, and Cr) in fish and shrimp samples mostly met the maximum limits established by national and international regulatory organizations. The concentrations of As in Scatophagus argus exceed both the permissible limit established by Indonesia and the provisional tolerable weekly intake (PTWI). The As concentration in Arius bilineatus is equal to the PTWI. The target cancer risk (TCR) values for both As and Cr in all analyzed species exceed the threshold of 0.0001, suggesting that these two metals possess the potential to provide a cancer risk to humans.

Evaluation of the toxic metals, proximate composition and length-weight relationships of selected fish species from the Gadananathi River, Southern Tamil Nadu

The present study reveals toxic metals, proximate composition, and growth conditions in seven fish species, aiding their nutritional importance and conditions. The samples of seven different small indigenous fish species, including Xenentodon cancila, Glossogobious giuris, Pseudambassis ranga, Puntius dorsolis, Mystus vittatus, Dawkinsia filamentosa, and Dawkinsia tambraparaniei, were collected in river Gadananathi, Tamilnadu, India. A total 14 fish samples were analyzed for lead, cadmium, and copper using atomic absorption spectrometry. The standard procedures were used to determine the length-weight and proximate composition of the seven fishes. The findings revealed that the seven fish species had variable amounts of metal buildup. Cu levels were highest in D. tambraparniei gills and lowest in M. vittatus gills and livers; nonetheless, substantial amounts of Cu were found in P. dorsalis livers. In the length-weight correlations of the regression parameters of coefficient value r2, the "a" and "b" values revealed a positive allometric growth rate in all fish species except G. giuris and M. vittatus. However, X. cancila had the highest composition in the proximate analysis, while D. tambraparniei and D. filamentosa had the highest protein content mean value at a significant level (P ≤ 0.05). Overall, discrepancies in nutritional content might be related to species, environmental circumstances, fish age and size, and food availability.

Tissue Distribution and Metabolization of Ciguatoxins in an Herbivorous Fish following Experimental Dietary Exposure to Gambierdiscus polynesiensis

Ciguatoxins (CTXs), potent neurotoxins produced by dinoflagellates of the genera Gambierdiscus and Fukuyoa, accumulate in commonly consumed fish species, causing human ciguatera poisoning. Field collections of Pacific reef fish reveal that consumed CTXs undergo oxidative biotransformations, resulting in numerous, often toxified analogs. Following our study showing rapid CTX accumulation in flesh of an herbivorous fish, we used the same laboratory model to examine the tissue distribution and metabolization of Pacific CTXs following long-term dietary exposure. Naso brevirostris consumed cells of Gambierdiscus polynesiensis in a gel food matrix over 16 weeks at a constant dose rate of 0.36 ng CTX3C equiv g-1 fish d-1. CTX toxicity determination of fish tissues showed CTX activity in all tissues of exposed fish (eight tissues plus the carcass), with the highest concentrations in the spleen. Muscle tissue retained the largest proportion of CTXs, with 44% of the total tissue burden. Moreover, relative to our previous study, we found that larger fish with slower growth rates assimilated a higher proportion of ingested toxin in their flesh (13% vs. 2%). Analysis of muscle extracts revealed the presence of CTX3C and CTX3B as well as a biotransformed product showing the m/z transitions of 2,3-dihydroxyCTX3C. This is the first experimental evidence of oxidative transformation of an algal CTX in a model consumer and known vector of CTX into the fish food web. These findings that the flesh intended for human consumption carries the majority of the toxin load, and that growth rates can influence the relationship between exposure and accumulation, have significant implications in risk assessment and the development of regulatory measures aimed at ensuring seafood safety.

Sex-biased response of pollution biomarkers in fish: Insights from the killifish Poecilia vivipara

Copper ions (Cu) are one of the most frequent trace-contaminants found in Brazilian waters and, although considered as an essential element, in high concentrations can accumulate and induce toxicity. Biomarkers are important tools that can be used to assess these impacts, but to be considered trustworthy, they have to be previously tested in target organisms through laboratory studies under controlled conditions. However, many of these experiments are conducted using only males, as it is believed that the hormonal variation of females can bias the results, increasing data variability. Notwithstanding, few studies have actually tested this hypothesis, highlighting the importance of considering and measuring the role of sex in ecotoxicological studies. The aim this study was to evaluate the influence of sex on biomarkers classically used in environmental monitoring programs using the fish Poecilia vivipara as model. For this, females and males were exposed for 96 h to two Cu concentrations (9 and 20 μg/L) and a control group. In liver and gills, Cu accumulation, total antioxidant capacity (TAC) and lipid peroxidation (LPO) were evaluated. In addition, samples of peripheral blood were used for neutrophil to lymphocyte ratio determination, a measure of the onset of secondary stress. Results show that Cu hepatic accumulation did not differ between females and males, but higher levels of this metal were observed in exposed animals compared to control fish. Additionally, interactive effects were observed for hepatic LPO, as males showed elevated oxidative damage in comparison to females. Moreover, Cu exposure elevated hepatic LPO relative to control only in males, but this increase in oxidative damage was not accompanied by changes in liver TAC. On the other hand, differences in branchial Cu accumulation and LPO were not observed. Conversely, control females showed elevated TAC in comparison to control males, but Cu exposure eliminated this difference. Cu exposure also induced an increase in the N:L ratio, indicating the presence of a secondary stress response unrelated to sex. Ultimately, the findings of this study demonstrate that sex can influence the response of biomarkers that are typically used in ecotoxicological investigations in a multifaceted manner. As a result, using animals from a singular sex in such studies may result in consequential outcomes, potentially leading to underestimation or overestimation of results.

Combined use of biomarkers to assess the impact of untreated wastewater from the Danube River, Serbia

In this study a battery of bioassays, both in vivo (metals and metalloids concentrations, erythrocyte morphometry, comet assay, micronucleus assay, and histopathological analyses) on vimba bream Vimba vimba (L., 1758) and white bream Blicca bjoerkna (L., 1758), and in vitro (treatment of HepG2 cells with native water samples) was applied to assess the harmful potential of untreated wastewater. Faecal indicator bacteria were quantified to assess the microbiological water quality. Vimba bream had significantly higher Fe concentrations in both liver and muscle, while white bream had higher Ca and Cu concentrations in liver. Vimba bream had a significantly higher level of DNA damage in both liver and blood cells, in comparison to white bream. Low levels of micronucleus and nuclear abnormalities were observed in both species. Erythrocytes morphometry did not show significant interspecific differences. Histopathological analyses revealed a similar response of the studied species, with a significantly higher presence of ceroid pigments in the liver of vimba bream. Treatment of HepG2 cells revealed the high genotoxic potential of water downstream of the discharge point. The results of this study clearly demonstrate the importance of effect-based monitoring, in order to enforce more efficient management of natural resources and implementation of wastewater treatment systems.

Snapshot of the pollution-driven metabolic and microbiota changes in Carassius gibelio from Bucharest leisure lakes

In the last decades, increased intakes of contaminants and the habitats' destruction have produced drastic changes in the aquatic ecosystems. The environmental contaminants can accumulate in aquatic organisms, leading to the disturbance of the antioxidant/prooxidant balance in fish. In this context, we evaluated the level of organic, inorganic and microbiological pollutants in four leisure lakes (Chitila, Floreasca, Tei and Vacaresti) from Bucharest, the largest city of Romania, in order to compare their effects on hepatopancreas and gills metabolism and antioxidant defense mechanisms in Carassius gibelio, the most known and widespread freshwater fish in this country. The lowest level of oxidative stress was recorded in the case of fish collected from the Vacaresti lake, a protected wetland area where aquatic organisms live in wild environmental conditions. In contrast, significant oxidative changes were observed in the hepatopancreas and gills of fish from the Chitila, Floreasca and Tei lakes, such as reduced glutathione S-transferase activity and glutathione level, and increased degree of lipid peroxidation, being correlated with elevated levels of pesticides (such as 2,4'-methoxychlor) and Escherichia coli load in these organs. Although different patterns of pollutants' accumulation were observed, no important interindividual variations in cytosine methylation degree were determined. In conclusion, the presence and concentrations of metals, pesticides and antibiotics varied with the analyzed tissue and sampling site, and were correlated with changes in the cellular redox homeostasis, but without significantly affecting the epigenetic mechanisms.

Health risk assessment and differential distribution of Arsenic and metals in organs of Urophycis brasiliensis a commercial fish from Southwestern Atlantic coast

The concentrations of As, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, Sr, and Zn were analyzed in muscle, gills, and liver of Urophycis brasiliensis from two Southwestern Atlantic catch areas (Brazil and Argentina). Additionally, the health risk of general and fishermen populations through fish consumption was estimated. The gills showed the highest concentrations of most of the elements, followed by the liver. With the exception of As, the muscle was the organ with the lowest concentrations of most elements. Levels of arsenic in muscle of U. brasiliensis were exceeded the maximum permissible levels for human consumption recommended by local and international guidelines. The target hazard quotients (THQs) and the carcinogenic risk (CR) showed no risk for individual and all elements. These results highlight the importance of arsenic speciation in U. brasiliensis muscle in order to generate more reliable risk estimates.

Health risk assessment and metal contamination in fish, water and soil sediments in the East Kolkata Wetlands, India, Ramsar site

East Kolkata Wetlands (EKW) is an important site for fish culture in sewage-fed areas, which are major receivers of pollutants and wastages from Kolkata. EKW is internationally important as the Ramsar site was declared on Aug 2002 with an area of 125 km². EKW is a natural water body where wastewater-fed natural aquaculture has been practiced for more than 70 years. It is ecologically vulnerable due to the discharge of toxic waste through sewage canals from cities. Assessing the EKW to understand the inflow and load of the toxic metal (s) in fish, water, and sediments samples is essential. The field (samples collection from 13 sites) and lab (determination of toxic level of metals) based research were carried out to assess metal toxicity and health risk assessment in EKW. The levels of eighteen metals (18), namely Chromium, Vanadium, Cobalt, Manganese, Copper, Nickel, Zinc, Silver, Molybdenum, Arsenic, Selenium, Tin, Gallium, Germanium, Strontium, Cadmium, Mercury, and Lead, were determined using Inductively coupled plasma mass spectrometry (ICP-MS) in five fish tissues viz. muscle, liver, kidney, gill and brain, along with the water samples and soil sediments in 13 sampling sites. The bioaccumulation and concentration of metals in fish tissues, soil sediments, and water samples were well within the safe level concerning the recommendation of different national and international agencies except for a few metals in a few sampling sites like Cd, As, and Pb. The geoaccumulation index (Igeo) was also determined in the soil sediments, indicating moderate arsenic, selenium, and mercury contamination in a few sites. The contamination index in water was also determined in 13 sampling sites. The estimated daily intake (EDI), reference dose (RfD), target hazard quotient (THQ), slope factor and cancer risk of Cr, Mn, Co, Ni, Cu, Zn, As, Se, Cd, Pb and Hg from fish muscle were determined. Based on the results of the present investigation, it is concluded that fish consumption in the East Kolkata Wetland (EKW) is safe. The effects of bioaccumulation of metals in muscle tissue were well within the safe level for consumption as recommended by WHO/FAO.

Determination of trace element and fatty acid levels in tissues of mirror and scaly carp (Cyprinus carpio L., 1758) living in Keban Dam Reservoir (Elazig)

This study investigated the concentrations of some accumulated trace metals (iron, manganese, zinc and copper) and fatty acids in liver and muscle tissues of mirror and scaly carp varieties (Cyprinus carpio L., 1758) living in Keban Dam Reservoir (Elazig), which is the second-largest artificial lake in Turkey that hosts commercially valuable and preferred fish varieties for human consumption. The inductively coupled plasma mass spectrometry (ICP-MS) method was used to analyse the concentrations of trace elements. Fatty acid levels were measured in a gas chromatography mass spectrometry (GC-MS) device, using a flame ionization detector (FID). Considering the two fish varieties and tissues that were studied, the mean metal concentrations (μg g^-1 ) were found in the following ranges: Fe 12.32-49.97, Mn 0.12-0.62, Zn 10.45-86.59 and Cu 2.74-11.86. Although the lowest levels were detected in the muscle tissue for all the metals examined, the levels in the liver tissue were significantly higher. According to the results of the analyses on fatty acid concentrations, the mean total saturated fatty acid levels in the muscle tissue of the scaly carp and mirror carp varieties were found to be 31.07 and 31.43 (%), respectively, whereas these values for the liver tissue were consecutively 22.36 and 22.08 (%). Successively, the mean total levels of unsaturated fatty acids were determined as 68.93 and 68.40 (%) in the muscle tissue and 77.64 and 77.92 in the liver tissue. This study, with the finding that the trace (metallic) element accumulation rates were below the upper limits of the tolerable range, and the examined fish varieties were rich in fatty acids, shows that mirror carp and scaly carp living in Keban Dam Reservoir are highly nutritious for human diets.

Species, tissue and gender-related metal and element accumulation in fish species in a large reservoir (Turkey) and health risks and nutritional benefits for consumers

Concentrations of 18 metals and elements (MEs) in the gills, skin, muscle and liver of Carasobarbus luteus and Cyprinus carpio from the Atatürk Reservoir in Turkey were investigated. The results revealed that variations in the ME contents between fish species can be attributed to different diets. The highest contents of most MEs were recorded in the gills. Gender had no significant effect on the contents of most MEs in the tissues of fish species investigated. The relations between MEs in tissues and fish size were not clear and consistent. Health risk assessment methods indicated that consumption of the studied fish species is safe. It was estimated that daily consumption of 140 g of C. carpio or 170 g of C. luteus would not be expected to cause any health risks. Furthermore, it was found that fish species would provide significant benefits in terms of intake of essential MEs.

Linking trophic ecology with element concentrations in a coastal fish community of the Bijagós Archipelago, West Africa

We report the concentration of 13 elements in the muscle and liver of 17 coastal fish species of the Bijagós Archipelago, Guinea-Bissau, and link element concentrations to trophic ecology as assessed by carbon (δ¹³C) and nitrogen (δ¹⁵N) stable isotopes. We found higher concentrations of Hg, Fe, Mn, Cu, Zn, Se and As in liver as compared to muscle tissue, and the opposite pattern for Sr and Ca in all fish species. The concentration of Hg and Se in muscle samples increased significantly with δ¹⁵N, suggesting a biomagnification of these elements in this food chain. The concentrations of Ca and Sr, Fe and Cr, Ca and Mn, and Fe and Mn were positively correlated to each other in more than 50% of the studied species. Fish constitute the most important animal protein source for people in Guinea-Bissau, and thus assessing the concentrations of potentially toxic elements is relevant for human health.

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.

Tissue-specific distribution and bioaccumulation pattern of trace metals in fish species from the heavily sediment-laden Yellow River, China

The Yellow River is one of the largest contributors to the global riverine sediment flux from the land to the ocean. Tissue-specific bioaccumulation of trace metals in fish from heavily sediment-laden rivers remains unclear to date. The concentrations and distributions of trace metals in water, suspended matters, sediments, and various fish tissues were investigated in the mainstem of the Yellow River were investigated. The concentrations of most metals in abiotic media were high in the Gan-Ning-Meng of upstream and downstream segments, and were highest in fine-sized suspended matters. The highest concentrations of most metals were in the gill and liver, followed by the gonad, and lowest in the muscle, and there were a significant overall differences among the tissues. The concentrations of metals in some tissues (e.g., muscle and gill) significantly differed among regions and feeding habits. The highest values of the bioaccumulation factor for suspended matters (BF_SPM) were observed in the midstream region (e.g., reaching to 19.0 for Se in the liver). This was determined by metal type and tissue specificity, food composition, and concentration of metals in abiotic media. The results highlight the significance of suspended matters for the distribution of trace metals in abiotic and biotic media.

Metal behaviour in water, sediment and fish from the St Lucia system: implications for public health and ecosystem impact

The purpose of this study is to assess metal concentrations and their bioavailability, and relate them to concentrations in fish tissues (gill, muscle and skin) as part of the ecotoxicological and public health assessment of the St Lucia system. Eight metals from six sites (Co, Cr, Cu, Fe, Mn, Ni, Pb and Zn) and five metals (Cu, Fe, Mn, Pb and Zn) from 60 fish, Oreochromis mossambicus, were analysed. Dissolved metal concentrations were highest in the north lake and lowest at the estuary. Sediment metal concentrations were highest in the north lake and lowest in the south lake. Most sediment metals displayed minimal to no anthropogenic enrichment. Normalisation with Fe showed all linear regressions as significant (p < 0.01) and Cr, Cu, Mn, Ni and Zn had R² values well above 0.9. Only sediment Ni values were above the ERM. Tissue Cu, Fe and Pb concentrations were highest in the gills and Mn and Zn concentrations were highest in the skin. Skin Mn concentrations were highest as compared to the gills and muscle for all sites. The spatial differences in metal concentrations and BCF values for St Lucia suggest distinct populations of fish in the different areas of St Lucia. All concentrations of metals in fish tissues were below the permissible values indicating low human health threat. While higher sediment concentrations justified the economic benefit of mining, evidence of natural enrichment emphasised the need for continual conservation of the greater St Lucia area.

Endocrine disruption caused by the aquatic exposure to aluminum and manganese in Astyanax altiparanae (Teleostei: Characidae) females during the final ovarian maturation

Aluminum (Al) and manganese (Mn) can be toxic to aquatic biota and cause endocrine disruption in fish, affecting reproduction. This study evaluates the physiological responses of the ray-finned teleost fish Astyanax altiparanae vitellogenic females after acute exposure (96 h) to Al and Mn (alone and combined) in acid pH followed by the same period of exposure to metal-free water in neutral pH. The aim of this second period of exposure was to assess the recovery capacity from the toxic effects these metals. Five experimental groups were established: a control in neutral pH (Ctrl), and acidic pH (Ac), aluminum (Al), manganese (Mn), and Al + Mn groups, maintaining the acidic pH in the groups to which metals were added. The following biological parameters were evaluated: metal tissue concentration, relative fecundity (RF: absolute fecundity/body mass). Plasma levels of cortisol (proxy for stress) and 17α hydroxyprogesterone (17α-OHP), and gene expression of pituitary lhβ mRNA (proxies for final maturation) were measured to evaluate endocrine disruption. In the synchronic exposure, the presence of Mn potentiated the accumulation of Al in gills. The females from acidic pH and Al groups showed a reduced RF. Exposure to Al and Mn triggered an endocrine disruption response, evidenced by a decrease in the plasma concentration of 17α-OHP and cortisol. Despite this anti-steroidogenic effect, no changes occurred in the pituitary gene expression of lhβ. The endocrine changes and the metal accumulation were temporary, while the impacts on RF under the experimental conditions suggest permanent impairment in the reproduction of this species.

Potential health risk assessment of some bioaccumulated metals in Nile tilapia (Oreochromis niloticus) cultured in Kafr El-Shaikh farms, Egypt

In Egypt, using agricultural drainage water is a serious challenge for fish farming, due to water scaristy. Metals could be a potential threat to the quality of the cultured fish. Thus, this study aimed to assess the content of the metals in the cultured fish, their effect on the fish tissues, and the possible human health risk upon their consumption. This accomplished firstly, by determining the levels of essential Fe, Mn, Zn, Cu, beside the top three most toxic metals (Cr, Cd, and Pb) in the edible muscles and liver of 200 samples of Oreochromis niloticus cultured at three fish farms, using inductively coupled plasma optical emission spectroscopy (ICP-OES). The results showed the order of abundance: Fe > Zn > Cu ≥ Cr > Mn > Pb > Cd. Levels of Fe, Zn, Mn, and Cu in the fish liver were higher than corresponding values of muscles by 3, 3, 5, 9 order of magnitude, respectively. The histopathological examination showed alternations in muscles and liver tissues of fish farms irrigated with drainage water. However, the risk assessment indicated the safe human consumption of cultured fish produced from these fish farms.

Magnetic properties and its application in the prediction of potentially toxic elements in aquatic products by machine learning

Magnetic measurement was provided to substitute for time-consuming conventional methods for determination of potentially toxic elements. Both the concentrations of 12 elements and 9 magnetic parameters were determined in 700 muscle tissue samples from the snail Bellamya aeruginosa, shrimp species Exopalaemon modestus and Macrobrachium nipponense, and fish species Hemisalanx prognathous Regan, Coilia ectenes taihuensis, and Culer alburnus Basilewsky collected from Chaohu Lake during different hydrological periods. Spherical and irregular iron oxide particles were observed in the muscle tissues of the studied aquatic products. A field survey of the exposure parameters in humans, such as per capita intake dose of local aquatic products, found no evidence that consumption of the tested species poses a potential health risk. Redundancy analysis revealed different degrees of correlation between the magnetic parameters and concentrations of elements in aquatic products. Back-propagation artificial neural network (BP-ANN) and support vector machine (SVM) models were applied to predict elemental concentrations in aquatic products, using magnetic parameters as input. SVM models performed well in predicting the presence of Cr and Ni, with R and index of agreement values of >0.8 in both training and validation stages as well as relatively low errors. The BP-ANN and SVM models both performed relatively poorly in predicting the presence of Cd and Zn in aquatic products, with R values between 0.333 and 0.718 for Cd and between 0.454 and 0.664 for Zn in training and validation stages. For most of the elements, a better R value was obtained with the SVM than with BP-ANN model. The R of Co, Cr, Cu, Ni, and Ti in the training and validation stages of snail in the SVM model were >0.8. This study is a first step in developing a novel approach allowing the rapid monitoring of potentially toxic elements concentrations in aquatic products.

Nannochloropsis oculata feed additive alleviates mercuric chloride-induced toxicity in Nile tilapia (Oreochromis niloticus)

Using microalgae to alleviate the adverse effects of aquaculture pollutants, including metals, has recently gained much attention. In this context, bioaccumulation, hematological indices, oxidative and antioxidant responses, and histopathological alterations were investigated in Nile tilapia (Oreochromis niloticus) fed with either a control diet or diets containing Nannochloropsis oculata (N. oculata) after exposure to mercuric chloride in order to evaluate the role of this microalgae in protecting against mercury-induced toxicity. Fish exposed to HgCl2 at a dose of ¼ LC50 (0.3 mg/L) (Hg group) for 7-21 days exhibited a significant increase in total mercury concentration with a bioaccumulation pattern of liver>gills>muscle, and a significant decrease in all blood indices except mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH), monocyte counts, and neutrophil counts. Malondialdehyde (MDA) levels were significantly increased in the Hg group at all time points relative to the control. Glutathione peroxidase (GPx) activity was significantly increased at days 14 and 21, while catalase (CAT) and GPx activities increased and decreased, respectively, at day 7 compared to the control. Additionally, lysozyme activity and immunoglobulin M (IgM) were significantly decreased in the Hg-exposed group. Severe histopathological alterations were evident in the liver, kidneys, and gills. However, supplementation with N. oculata at a low (5%, 50 g/kg feed) or high (10%, 100 g/kg feed) dose stabilized all parameters and reduced the severity of the histopathological alterations with the high N. oculata diet showing more prominent effects. These results suggest that feeding N. oculata protects Nile tilapia against mercuric chloride-induced toxicity.

Comparative Assessment of Metal Bioaccumulation in Tilapia and Largemouth Bass from Three Dams of the Yaqui River

In the present paper, we investigated the accumulation of six metals in tilapia (Oreochromis nilocticus) and largemouth bass (Micropterus salmoides) as indicators of the environmental pollution present at three constructed dams in the Yaqui River basin in Sonora, Mexico. The La Angostura (ANG), El Cajon de Onapa (ECO), and El Oviachic (OVI) dams are ecosystems under different degrees of anthropogenic stress. The collected fishes were dissected to obtain liver, gonad, stomach, gill, and muscle samples to determine the metal concentrations of Fe, Mn, Ni, Cu, Zn, and Cr. The results of a PERMANOVA showed that the concentrations of Fe, Cu, and Zn were significantly higher in tilapia liver, stomach, and gill tissues compared with those of the largemouth bass. Also, differences were detected between seasons, with the metal concentrations during the dry season being significantly higher than those of the rainy season (p < 0.001). The results of a principal component analysis showed an association between metals, tissues, and dams with significantly higher (p < 0.001) concentrations in tilapia from the ECO dam compared with those from the ANG and OVI dams. The general distribution of metals in the tissues was as follows: liver > stomach-gills > gonads > muscle. Variations in metal concentrations may be indicative of the different sources of anthropogenic stress in each ecosystem.

Tissue and gender-related differences in the elemental composition of juvenile ocean sunfish (Mola spp.)

Trace elements are potentially critical contaminants of aquatic environments and fish, occupying upper trophic levels, are especially vulnerable to bioaccumulation. Due to public health concerns, however, data on the elemental composition of non-commercially important marine species are particularly lacking. Ocean sunfish (Mola spp.) attain a low commercial value worldwide and information on their elemental composition is limited. In this context, we examined the concentration of 11 trace elements (V, Cr, Mn, Co, Ni, Cu, Zn, As, Se, Cd and Pb) in eight tissues [brain, gills, gelatin (subcutaneous white gelatinous layer), gonads, spleen, liver, white muscle and red muscle] of 20 juvenile specimens (37.5-85.5 cm TL). Gender-related differences were solely found in the gonads and chiefly for essential elements possibly as a result of their importance in embryo development. Overall, Zn and As were the elements observed in greatest concentrations in body tissues. The considerably high presence of As should be related to the dietary preferences of juvenile ocean sunfish. Considerable inter-individual variability in the concentration of each element in any given tissue was observed, especially in the liver, likely originating from the inclusion of both benthic and pelagic prey in the diet of analysed fish. Greatest elemental loads were found in the liver and gills whereas lowest loads were observed in white muscle, brain and gelatin. Moreover, a clear distinction in elemental load and elemental composition was observed between white and red muscles, likely deriving from existing divergent metabolism-related physiological adaptations linked to their different roles in locomotion.

Trophic transfer potential of nTiO2, nZnO, and triclosan in an algae-algae eating fish food chain

Little is known about the trophic transfer of nanoparticles and personal care products via dietary exposure in an algae-algae eating fish food chain. The bioaccumulation of nano-TiO₂ (P25 - nTiO₂), nano-ZnO (nZnO), and triclosan (TCS) in eight different combinations were explored in this study through algae, Asterococcus superbus, to fish, Gyrinocheilus aymonieri. Results found the bioaccumulation of TCS changed with algal biomass, while the bioaccumulation of Ti and Zn varied with the amount of lipids and proteins in algal cells. In algae, Ti was in the form of nTiO₂ and Zn in the form of zinc ion. Due to dietary exposure, Ti and Zn quantity in fish was closely related to that in algae. The quantity of Ti and Zn in algae and fish exposed to the interaction of nTiO₂ * nZnO* TCS was higher than that in other treatments. The uptake of Ti and Zn in algae exposed to the interaction of nTiO₂ * nZnO had been inhibited, and the corresponding fish also had less Ti and Zn in their tissues. nTiO₂-containing treatments had higher Ti proportion in muscle than gill in fish. Treatment nZnO had the most Zn in gill, whereas nZnO * TCS-containing treatments had higher Zn proportion in gut than other tissues. No observation of TCS in fish in all treatments suggested the removal and metabolism of TCS might be induced by tissue recovery and acclimation. This is the first report on trophic transfer of mixed nanoparticles and personal care product in an algae-algae eating fish two-stage food chain.

Correlation between Heavy Metal-Induced Histopathological Changes and Trophic Interactions between Different Fish Species

This study assessed the distribution of heavy metals in the gills, kidney, and liver, correlated with the severity of histopathological changes, of three fish species with different feeding habitats (Barbus barbus, Squalius cephalus, and Chondrostoma nasus) from the Crișul Negru river, Romania. The levels of copper (Cu), chromium (Cr), cadmium (Cd), lead (Pb), and zinc (Zn) in fish tissues were measured by atomic absorption spectrophotometry. Histopathology and the expressions of TNF-α and proliferation cell nuclear antigen (PCNA) were investigated by immunohistochemistry and Western blot. Our data suggest a significant correlation between the bioconcentration level of metals and structural changes. The carnivorous species was the most affected compared to the omnivorous and herbivorous ones, and the most affected organ was the kidney. Moreover, the correlation of tissue damage with the PCNA and TNF-α expression levels revealed that the herbivorous species presented less extended lesions, likely due to higher activated repair mechanisms and lower levels of inflammation. In conclusion, our data and the subsequent statistical analysis suggest that feeding behavior could be correlated with the histopathological alterations and might be used for a more profound evaluation of aquatic environment safety and analysis of aquatic ecosystems.

The Impact of Lake Ecosystems on Mineral Concentrations in Tissues of Nile Tilapia (Oreochromis niloticus L.)

This study evaluates the differences in mineral and toxic trace element concentrations of Nile tilapia (Oreochromis niloticus) tissues from three aquatic ecosystems in Ethiopia-Lake Ziway, Lake Langano, and Gilgel Gibe reservoir-with a focus on edible (fillet) and discarded (digestive tract, gills, skin, and liver) parts. A total of sixty (n = 60) Nile tilapia samples were collected, comprising twenty (n = 20) fish from each lake, and analyzed by inductively coupled plasma mass spectrometry. All elements varied markedly among tissues and between the lakes. Some differences in element concentrations were attributed to differences in nutrient load in the ecosystems and the function of the tissues. For instance, the calcium concentrations in skin and gill were distinctly higher in fish from calcium-rich Lake Langano. The d iscarded parts were richer in essential trace elements, showing an opportunity to promote their use in human nutrition to increase the intake of important minerals. However, the accumulation of elements toxic to humans, such as aluminum, should be monitored and, in particular, controlled when rearing these fish in aquaculture.

Possible human health risk of some heavy metals from consumption of tilapia fish from Lake Mariut, Egypt

Lake Mariut Main Basin (MB) is not only one of the three basins composing Lake Mariut (LM) but is also the main source of the popular tilapia fish to Alexandrian people. Unfortunately, this basin was consistently for about 50 successive years receiving a continuous discharge of agricultural, sewage, and industrial effluents. This has led to contamination of the flesh of its tilapia fish living there particularly with some toxic heavy metals like Cd and Pb. Lately, in 2010, a rehabilitation program was adopted and carried out to save this vital MB from such intensive pollution. This had been achieved by diverting all those polluting sources. The present work is made after elapsing about 7 years from the diversion process date, to assess and evaluate the levels of those two metals (in addition to the other four one's Fe, Cu, Cr, and Zn) in the edible flesh part besides the liver and gills of this fish (Nile tilapia spec., Oreochromis niloticus), and in ambient water of this restored basin to measure the efficiency of the rehabilitation program on quality of endogenous fish. A simultaneous parallel sampling program was also commenced for the other two basins of LM. The obtained results revealed that the concentration level of the studied metals in each of the muscles of the fish and the ambient water of the restored MB becomes now not only almost alike the metal levels of the corresponding compartments of the other two basins of LM, but also they became at concentration levels lay below those of their counterpart permissible limits in fish and water recommended by national and international standards. Health risk assessment indices: bioaccumulation factor (BAF), metal pollution index (MPI), estimated daily intake (EDI), hazardous index (HI), and relative risk (RR) for the present case were estimated, assessed, and subsequently evaluated. All are referring to a fact that MB is currently in good environmental condition and producing safe fish for human consumption.

A Machine Learning Approach in Analyzing Bioaccumulation of Heavy Metals in Turbot Tissues

Metals are considered to be one of the most hazardous substances due to their potential for accumulation, magnification, persistence, and wide distribution in water, sediments, and aquatic organisms. Demersal fish species, such as turbot (Psetta maxima maeotica), are accepted by the scientific communities as suitable bioindicators of heavy metal pollution in the aquatic environment. The present study uses a machine learning approach, which is based on multiple linear and non-linear models, in order to effectively estimate the concentrations of heavy metals in both turbot muscle and liver tissues. For multiple linear regression (MLR) models, the stepwise method was used, while non-linear models were developed by applying random forest (RF) algorithm. The models were based on data that were provided from scientific literature, attributed to 11 heavy metals (As, Ca, Cd, Cu, Fe, K, Mg, Mn, Na, Ni, Zn) from both muscle and liver tissues of turbot exemplars. Significant MLR models were recorded for Ca, Fe, Mg, and Na in muscle tissue and K, Cu, Zn, and Na in turbot liver tissue. The non-linear tree-based RF prediction models (over 70% prediction accuracy) were identified for As, Cd, Cu, K, Mg, and Zn in muscle tissue and As, Ca, Cd, Mg, and Fe in turbot liver tissue. Both machine learning MLR and non-linear tree-based RF prediction models were identified to be suitable for predicting the heavy metal concentration from both turbot muscle and liver tissues. The models can be used for improving the knowledge and economic efficiency of linked heavy metals food safety and environment pollution studies.

Enzymatic, non enzymatic antioxidants and glucose metabolism enzymes response differently against metal stress in muscles of three fish species depending on different feeding niche

Current study aims to determine difference in metal accumulation pattern in muscle of Liza parsia (pelagic, omnivore), Amblypharyngodon mola (surface feeder, herbivore) and Mystus gulio (benthic, carnivore) depending on their niche and feeding habit and how it affects the endogenous antioxidants and glucose metabolism in fish muscle. Fishes were collected from Malancha, Diamond Harbour and Chandanpiri, West Bengal, India. Concentrations of lead, zinc, cadmium, chromium were measured in water, sediment and fish muscle. Metal pollution index (MPI) and bioconcentration factor (BCF) was calculated to evaluate the ability of fish to accumulate specific metals in muscle tissue from the aquatic environment. Metal concentrations were found significantly higher (P < 0.05) in water, sediment, fish muscles from Malancha than Chandanpiri and Diamond Harbour. L. parsia (MPI: 0.4-1.6) showed highest metal deposition in their muscle followed by A. mola (MPI: 0.37-1.38) and M. gulio (MPI: 0.2-1.2). Malondealdehyde, superoxide dismutase, catalase, glutathione S transferase, glutathione reductase and cortisol levels increased in case of L. parsia from Malancha and Chandanpiri. Succinate dehydrogenase, lactate dehydrogenase, Ca⁺² ATPase and cytochrome C oxidase levels were significantly (P < 0.05) lower at Malancha and Chandanpiri than Diamond Harbour. Heat shock protein (HSP70) expression was significantly (P < 0.05) higher in all fish species at Malancha followed by Chandanpiri and Diamond Harbour. Glucose, glycogen, hexokinase, phosphofructokinase and glycogen phosphorylase levels varied between sites and selected fish species. Serum cortisol level was measured and found to be the highest in L. parsia from Malancha (2.94 ± 0.12 ng/ml) and the lowest in M. gulio from Diamond Harbour (0.7 ± 0.05 ng/ml). The results indicate that metal toxicity alters antioxidant levels, oxidative status and energy production in fish in species specific manner. Our results also indicate that Mystus has the highest degree of adaptability in response to metal toxicity possibly due to its specific food habit and niche position. Therefore, it can be concluded that maintenance of oxidative and metabolic status to combat metal-induced oxidative load will be helpful for the fishes to acquire better resistance under such eco-physiological stress. Alteration of niche and interactive segregation in aquatic organism may be one of the key modulator of resistance against such stress.

Condition and Sperm Characteristics of Perch Perca fluviatilis inhabiting Boreal Lakes Receiving Metal Mining Effluents

One of the world's largest, but low-grade, sulfide nickel deposits in northeastern Finland has been exploited by a bioheapleaching technology since 2008. Bioheapleaching is a relatively new, cost-effective technology, but humid climate, e.g., in boreal temperate environments, causes challenges to the management of the water balance in the ore heaps with wide catchment area, and the mining effluents have caused substantial metal and salting contamination of the receiving waterbodies. In our study, the impacts of metal-extracting bioheapleaching mine effluents on muscle and liver element concentrations, body condition, liver and testes mass, and sperm count and motility of male perch Perca fluviatilis were analysed. Liver, testes, and carcass mass of perch in relation to their length were lower in the mining-impacted lakes than in the reference lake, which may be due to the metal contamination, food availability, and energy demand under multistressor conditions. The sperm counts of the males in the mining-impacted lakes were lower, but the endurance of their sperm motility was longer than the endurance of sperm of the reference males. These findings suggested that the condition and sperm characteristics of perch were altered in lakes receiving metal mining effluents. Measured variables seem to be useful indicators for metal mining impacts on freshwater fish but only if high natural variation in these characteristics can be controlled by multiyear monitoring scheme.

Biometry-dependent metal bioaccumulation in aquaculture shellfishes in southwest Taiwan and consumption risk

Shellfishes can easily accumulate metals via water and sediment and which may pose a human health risk by consumption. This study assessed the distribution of metals, including Cd, Cr, Cu, Pb, Ni, Zn, and Hg, in soft tissues of hard clam (Meretrix lusoria), surrounding water body, and sediment in the southwest coast of Taiwan. Hard clams contained the relatively higher concentration of the essential element, such as Zn, Cu, and Ni, and the metal concentration from high to low was Zn > Cu > Ni > Cd > Cr > Pb > Hg. However, the metal concentrations found in hard clam all were lower than the Sanitation Standard for Aquatic Animal of Taiwan. Results of bioaccumulation factors indicated that hard clam shows the ability of metal accumulation from water was higher than that from sediment. Moreover, the metal concentrations in hard clam were negatively correlated with body size except for Hg, which could be presented by the significant power function. Generally, hard clams from the aquaculture pond located on the southwest coast of Taiwan would not be harmful to adult consumers, except for people that consume shellfish more than 100 g. Besides strengthening the management of seafood safety and aquaculture, adjusting the eating and purchasing habits of the consumer could be a practical and feasible way for decreasing health risks. These results can assist the government in determining seafood safety and its implementation in Taiwan.

Accumulation of trace elements in muscle, gill and liver of fish species (Capoeta umbla and Luciobarbus mystaceus) in the Tigris River (Turkey), and health risk assessment

Two fish species (Capoeta umbla and Luciobarbus mystaceus) were collected from the Tigris River (Turkey), and tissues (gill, muscle and liver) of fish samples were analyzed for Cd, As, Mn, Cr, Cu, Co and Ni using the inductively coupled plasma-tandem mass spectrometry. Significant differences were present between fish species in regard to trace element (TE) concentrations in muscle for Mn, in liver for Cu, Cd and Mn, and in gill for As, Co, Cu and Cd (p < 0.05). Liver had the highest total TE concentration, followed by gill and muscle. Significant negative correlations were recorded between fish size (length and weight) and TE concentrations in the tissues. Both fish species showed no gender differences in TE accumulation in muscle, gill and liver (p > 0.05). The estimated daily intakes for all TEs were much lower than the tolerable daily intakes. The target hazard quotient (THQ) and total THQ values of all TEs did not exceed 1, which means that non-carcinogenic health effects are not expected for the consumers. Arsenic carcinogenic risk values were within acceptable range. Mean Cd concentrations in muscle tissue of both fish species exceeded the maximum permissible limit set by the European Commission Regulation, while mean concentrations of As, Cr and Cu were below the legislated limits.

Metals, arsenic, pesticides, and microcystins in tilapia (Oreochromis niloticus) from aquaculture parks in Brazil

The production of Nile tilapia (Oreochromis niloticus) in Brazil exhibits the highest growth rate in the world and represents approximately 45% of the total fish production. The objective of the present study was to assess the risk for human health due the consumption of tilapia farmed in net cages in eight aquaculture parks in Brazil. The concentrations of pesticides (40 compounds), metals (Mn, Ni, Zn, Cd, Pb, and Sn), arsenic, and cyanotoxins (microcystins) were evaluated in 16 fish from each park. Among analyzed pesticides, pyraclostrobin (0.18-0.32 mg/kg) and fenthion (0.0026-0.0037 mg/kg) exhibited values above the limit of quantification in the tilapia from Aracoiaba, Castanhão, and Ilha Solteira. The highest concentrations of As (0.44 μg/g) in fish tissues were found in Juara, Mn (0.21 μg/g) in Castanhão, and Zi (11.5 μg/g) were found in Três Marias. Furnas and Linhares exhibited the lowest metal concentrations. The estimated daily intake of muscle by the average Brazilian with 70 kg body weight is below the reference dose for all studied metals in all parks. Total free microcystins showed an accumulation pattern (muscle < gill < liver). The highest concentration in muscle was found in Castanhão (1043 μg/kg) samples. The results showed that fish exhibited metal, As, and pesticide tolerable daily intake (TDI) below the limit and pose low risk for human consumption. Otherwise, TDI for microcystins in fish of all studied parks was above the maximum level recommended by the World Health Organization, indicating that there exists a toxicity risk of fish consumption.

Rare earth element bioaccumulation in the yellow and silver European eel (Anguilla anguilla): A case study in the Loire estuary (France)

In the present work, rare earth elements (REEs) were measured in European eel muscles (Anguilla anguilla) from the Loire estuary in France. This study site is characterized by a large anthropogenic pressure with potential activities releasing REEs such as oil refineries, aeronautic and naval industries, wind turbine industries, hospitals with magnetic resonance imaging and coal-fired power plants. These activities may lead to increased REE concentrations in sediments the primary habitat of European eels. In the present work, REE bioaccumulation was evaluated by determining the concentrations in yellow and silver eel muscles sampled at three different locations in the Loire estuary and at two periods (2011/2012 and 2018/2019). The aims of this study were the understanding of the spatio-temporal influences (sampling site and sampling period) and intraspecific variations (age, sex, sexual maturation, length, weight, and parasitism) on the whole REE bioaccumulation. The mean value of the sum of REE concentrations (∑REEs) was 2.91, 6.48 and 12.60 µg/kg of muscle from respectively yellow eels, female silver eels and male silver eels fished in 2018/2019. The results showed that silver males accumulated more REEs than silver females and silver eels accumulate more REEs than yellow ones. Regarding the determination of spatio-temporal variations, an increase of REE concentrations for silver eel muscles between the two periods was observed, certainly related to the increase of REE uses. Finally, a trend of higher contamination of eels sampled in the downstream of Nantes was noticed for yellow eels.

Seasonal and Spatial Variability of Trace Elements in Livers and Muscles of Three Fish Species from the Eastern Mediterranean

Levels of 20 trace elements (Al, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Se, Ag, Cd, Sn, Sb, Ba, Hg, Pb, and U) were assessed in livers and muscles of two demersal fish species (Siganus rivulatus and Lithognathus mormyrus) and one pelagic species (Etrumeus teres) from the Lebanese coast located in the Eastern Mediterranean. The samples were collected from three sites along the Lebanese coast during the wet and dry seasons in 2017. The trace elements were more concentrated in livers than in muscles and interspecific differences were also found. The herbivorous species S. rivulatus showed the highest levels for most trace elements, while the carnivorous species L. mormyrus showed the least contamination. Elemental seasonal differences were species dependent and were observed for Ti, Cr, Mn, Fe, Ni, As, and Hg, with higher values during the wet season. Multivariate analysis showed spatial differences mainly during the wet season, while being closely related to species that reflected different accumulation patterns in each site. Levels of most trace metals in livers were higher than those reported in other Mediterranean regions (up to 2 to 3 folds). Nevertheless, the levels of Cd, Pb, and Hg in fish muscle were below the maximum levels set by the European Commission indicating that the consumption of these fish species is not likely to have adverse effect on human health. However, exposure depends on dietary habits of the population and a continuous exposure to these elements may result in adverse effects.

Effect of Dietary Probiotic Lactobacillus helveticus on Growth Performance, Antioxidant Levels, and Absorption of Essential Trace Elements in Goldfish (Carassius auratus)

In this study, we have investigated the effect of probiotic Lactobacillus helveticus CD6 supplemented into simple laboratory fish feed (LFF) and complex, multi-ingredient market fish feed (MFF) on growth performance, antioxidant levels, and essential trace element absorption in goldfish (Carassius auratus). Twenty-four healthy goldfish (average weight 3-4 g) were acclimatized and divided into four experimental diets supplemented with 3 × 10⁷ CFU/g of probiotic (LFF + Pro, MFF + Pro) and without probiotic (LFF, MFF) for 14 weeks. Fish fed with probiotic were healthy, active, and intense orange-gold as compared to control (without probiotic). At 14 weeks, fish fed with MFF + Pro/LFF + Pro showed 91/47% weight gain as compared to 34/- 12% weight observed with MFF/LFF. The average weight gain differences recorded between probiotic and control diets were not significant. No mortality to report when fish fed with probiotic. In contrast, fish fed without probiotic showed mortalities (LFF, two fish; MFF, one fish) during the trial. DPPH activity revealed high levels of antioxidants into the intestine of probiotic-fed fish. Trace element analysis showed that probiotic colonization enhanced diet-dependent absorption of Fe and Zn. The in vitro antimicrobial activity was exhibited by probiotic L. helveticus CD6 against infected fish isolate Aeromonas spp. JA showed an ability to protect fish from infections. Moreover, complex, multi-ingredient feed had a highest impact on viability of probiotic during storage. In conclusion, L. helveticus CD6 did not significantly enhance growth performance; however, it improved health and reduced mortalities in goldfish (C. auratus) regardless of the composition of the diet.

Risk assessment of using fish from different types of reservoirs as human food - A study on European perch (Perca fluviatilis)

Concentrations of As, Cd, Cr, Cu, Hg, Pb, and Zn in sediment samples and muscle tissue of the European perch were analyzed using inductively-coupled plasma optical emission spectrometry (ICP-OES), with the aim to assess the potential ecological (RI) and human health risk, and the degree of contamination (C_d) of three types of reservoirs in Serbia, based on their purpose: electricity generation (Vlasina, Perućac, Zaovine, and Međuvršje), drinking water supply (Garaši), and recreation (Lake Sava). The concentrations of the studied elements were higher in sediments than in fish. However, the levels of Cd in fish caught in Vlasina, Zaovine, and Međuvršje, Hg in Perućac and Garaši, and Pb in Lake Sava exceeded the maximum allowed concentrations. The pollution load index (PLI) indicated that sediments in all six reservoirs were contaminated, but C_d was low; a moderate contamination with Cd was observed in Vlasina, Perućac, and Zaovine, Cr in Zaovine and Međuvršje, and Cu in Međuvršje. A low RI was recorded for all studied reservoirs. Cd was found to be the primary contamination and ecological risk factor. Total target hazard quotient (THQ) and target carcinogenic risk factor (TR) were higher for fishers operating in these reservoirs than for the general population. Higher values of PLI, C_d, RI, and TR were observed in electricity generation reservoirs. Results indicated that this type of reservoirs suffer from higher anthropogenic pressure and/or have a worse pollution management policy compared with other types of reservoirs included in this study, especially the drinking water supply reservoir.

Can human nutrition be improved through better fish feeding practices? a review paper

Achieving Sustainable Development Goal 2 of zero hunger and malnutrition by 2030 will require dietary shifts that include increasing the consumption of nutrient dense foods by populations in low- and middle-income countries. Animal source foods are known to be rich in a number of highly bioavailable nutrients that otherwise are not often consumed in the staple-food based diets of poorer populations throughout the world. Fish is the dominant animal source food in many low- and middle-income countries in the global south and is available from both fisheries and aquaculture. Consumers often perceive that wild caught fish have higher nutritional value than fish produced through aquaculture, and this may be true for some nutrients, for example omega-3 fatty acid content. However, there is potential to modify the nutritional value of farmed fish through feeds and through production systems, illustrated by the common practice of supplementing omega-3 fatty acids in fish diets to optimize their fatty acid profile. This manuscript reviews the evidence related to fish feeds and the nutritional composition of fish with respect to a number of nutrients of interest to human health, including iron, zinc, vitamins A and D, selenium, calcium, and omega-3 fatty acids, with low- and middle-income country populations in mind. In general, we find that the research on fortification of fish diet particularly with vitamins and minerals has not been directed toward human health but rather toward improvement of fish growth and health performance. We were unable to identify any studies directly exploring the impact of fish feed modification on the health of human consumers of fish, but as nutrition and health rises in the development agenda and consumer attention, the topic requires more urgent attention in future feed formulations.

Evaluation of multi-biomarker response in fish intestine as an initial indication of anthropogenic impact in the aquatic karst environment

In order to assess the extent of existing anthropogenic influence on biota of the vulnerable karst ecosystem of the Krka River, multi-biomarker approach was applied in the intestinal tissue of brown trout Salmo trutta Linnaeus, 1758. Biomarkers of the general stress (total cytosolic proteins), oxidative stress (malondialdehyde), antioxidant capacity (catalase activity, total glutathione) and of an exposure and effect of contaminants, especially metals (metallothionein) and organophosphorous pesticides and metals (acetylcholine esterase activity) were compared in the intestine of fish from the reference site (river source) and downstream of the technological and municipal wastewater impacted site (town of Knin) in two seasons, October 2015 and May 2016. Biological response was additionally evaluated by metal/metalloid concentrations in intestinal cytosol. Site-specific differences were observed as significantly higher As, Ca, Co, Cu, Se and Sr concentrations in intestinal cytosol of fish from the contaminated compared to the reference site. Significant seasonal differences existed for Ni, Cd, Mo, Cs and Na, with higher levels in autumn, following the trend of most of the dissolved metal levels in the river water. Impact of improperly treated wastewaters was also confirmed by significantly increased levels of glutathione, total proteins and Foulton condition indices, with 1.5, 1.13 and 1.12 times higher average values in fish from that site compared to the river source, respectively. The other biomarkers showed similar trend and pointed to specific biological changes regarding oxidative stress or metal exposure in fish from the anthropogenically impacted site, especially in autumn, but without significant differences. Thus, the anthropogenic impact still seems to be only moderate, although cytosolic metals and most of the biomarkers in fish intestine were confirmed as initial indicators of pollution impact, which pointed to the need of continuous monitoring of the Krka River in order to protect this natural karst world phenomenon.

Mercury, silver, selenium and other trace elements in three cyprinid fish species from the Vaal Dam, South Africa, including implications for fish consumers

The levels of Cr, Cu, Zn, Se, Ag, Cd, Hg, and Pb were determined in muscle and liver samples from 30 specimens of fish belonging to the species Labeobarbus aeneus, Labeobarbus kimberleyensis, and Labeo umbratus from the Vaal Dam. Health risks for human fish consumers were estimated using the target hazard quotient (THQ), the Se:Hg-ratio, and Se health benefit value (Se HBV). This is the first comprehensive report on Hg levels in fish from this lake. Mean concentrations ranging from 0.247-0.481 mg/kg dw in muscle and from 0.170-0.363 mg/kg dw in liver clearly show a contamination with this element. Although levels in muscle did not exceed maximum allowances for human consumption, a calculated THQ of 0.12 and 0.14 for the two Labeobarbus species, respectively, showed a potential risk due to additive effects. All Se:Hg-ratios as well as Se HBVs clearly suggested positive effects for fish consumers. Levels of Cu were remarkably high in the liver of L. umbratus, calling for further investigation on this species. Cadmium levels were above the maximum allowances for fish consumption in the liver of all three species (means between 0.190 and 0.460 mg/kg dw), but below the LOD in all muscle and intestine samples. This is also the first report of Ag in fish from South Africa. Levels were below the LOD in muscle, but well detectable in liver; they varied significantly between the two Labeobarbus species (0.054 ± 0.030 and 0.037 ± 0.016 mg/kg dw) compared to L. umbratus (1.92 ± 0.83 mg/kg dw) and showed a positive correlation with Cu levels (63.7 ± 17.0; 70.3 ± 9.0 and 1300 ± 823 mg/kg dw), possibly due to similar chemical affinities to metallothioneins. The detected Ag levels can serve as a basis to monitor the development of this new pollutant in aquatic environments in South Africa and worldwide.

Seasonal variation in metal concentration in various tissues of the European chub (Squalius cephalus L.)

Due to the increasing industrialization, metals are discharged into all spheres of the environment, in particular, in river courses, which leads to the need for constant monitoring. Metals do not degrade into harmless end products; they are very persistent and have high potential for accumulation in biota. Metals in the fish body are accumulated in different amounts in the tissue specific matter. In relation to the biotic conditions and fish metabolism, the load of food, or the stage of the reproductive cycle, the seasonal variation of metal levels can be expected. Because of that, the objective of our present study was to analyze 15 metals and metalloids in liver, gills, muscle, and gonads of European chub (Squalius cephalus) throughout the 4 seasons, autumn, winter, spring, and summer. The specimens were collected from two rivers, Pestan and Beljanica at the Kolubara basin, and their concentrations were determined with inductively coupled plasma optical emission spectrometry (ICP-OES). Specimens from both rivers have shown similarities in metal accumulation like the highest accumulation of majority of elements in gills, lowest accumulation of majority of elements in muscle (except for Hg), and higher accumulation of some elements in summer (Cu, Fe, Zn). In addition, Cu and Fe showed affinity for liver, while Ba, Cr, Sr, and Zn were specific for gills. Also, Al, B, Fe, Ni, and Pb did not show significant differences in concentrations among different seasons in all investigated tissues.

Potentially toxic elements in freshwater (Alburnus spp.) and marine (Sardina pilchardus) sardines from the Western Balkan Peninsula: An assessment of human health risk and management

The concentrations of 14 potentially toxic elements in freshwater and marine sardines from the Western Balkan Peninsula were determined. In Prespa Lake, a natural lake, the concentrations of toxic Pb and Cd were above the maximum permissible concentrations in freshwater sardines. The As concentrations were elevated in sardines from Boka Kotorska Bay. The Target Hazard Quotient (THQ) and Hazard index (HI) were above their defined limits in Boka Kotorska Bay and Skadar Lake, indicating a health risk for Montenegrin consumers. The results of this study set apart Zavoj, Vlasina and Međuvršje artificial reservoirs as potential ecosystems for developing commercial fishing and for the safe use of freshwater sardines for human consumption. Constant monitoring of Ohrid, Prespa and Dojran natural lakes, as well as Boka Kotorska Bay, may be implemented in the interest of public health.

Metals in a northern Nile Delta lake: water, suspended particulates, sediments, and biota

Lake Edku is one of the important fishing areas in the Nile Delta. It is exposed to different quantities of serious pollutants in particular metals. To overall appraise the risk and status of metals in the lake, a comprehensive study of total concentrations of cadmium (Cd), chromium (Cr), copper (Cu), iron (Fe), manganese (Mn), nickel (Ni), and zinc (Zn) in sediments and spatial-temporal variations of these metals in the dissolved and suspended particulates, and some tissues of Tilapias niloticus, was conducted from ten sampling sites during 2016. Results showed that none of the investigated metals exceeded the limits considered as hazardous for aquatic life in water. The highest concentrations of Cd, Cu, Ni, and Zn were observed in suspended particulate matter, which may precipitate on the surface of the sediments. Potential ecological risk analysis of the majority of the investigated metals in the sediment indicated that Lake Edku posed a low ecological risk. The estimated values of all metals in tissues of Tilapia niloticus were below the international permissible limits. Moreover, the potential risk of metals to human via the consumption of Tilapia niloticus was estimated using the weekly intake levels, which was lower than the WHO's safe provisional tolerant weekly intake levels. These results prove the importance of performing measurements of contaminants in various compartments of Lake Ecosystem including sediment, biota, and suspended particulate matter for proper management.