Effects of heavy metals on fish physiology - A review

Ecotoxicological effects of short-term exposure to elongated tunnel particles from two road construction sites on juvenile Atlantic salmon (Salmo salar)

Tunnelling through rock to facilitate transportation and logistics is common worldwide. However, the negative impacts of discharge emissions from tunnel construction on aquatic environments are not well understood. This study aimed to increase knowledge about the ecotoxicological effects of particle discharge from two tunnel construction sites (Rafoss and Verket) in Norway on juvenile Atlantic salmon (Salmo salar). Fish were exposed to environmentally relevant (100 mg/L) and high concentrations (Rafoss: 2800 mg/L, Verket: 5000 mg/L) for 192 h. Particles from both sites (47-51 % < 10 μm in diameter), primarily granite-gneiss bedrock and slightly more elongated than naturally eroded particles, created distinct water environments due to geological and chemical differences. This is the first peer-reviewed study to utilize μCT for quantification of particle retention in gills and it allowed identifying concentration-dependent retention, with higher retention for Verket particles, likely due to water chemistry differences. Despite high retention, no histological changes were observed. Mortality occurred at ≥3500 mg/L Verket particles after 48 and 24 h, plausibly due to suffocation from gill clogging. The LC50 for Verket particles was 3137 mg/L. Suffocation likely caused a drop in plasma Cl levels due to elevated pCO2. Elements with high particulate fractions accumulated in gills and stomach contents in a concentration-dependent manner for both particle types, and in livers at ≥3500 mg/L. No acute or sublethal effects, including metal toxicity, were observed at concentrations up to 2000 mg/L Verket and 2800 mg/L Rafoss particles for 192 h. These results suggest that common benchmarks of 50-400 mg/L in emission permits do not cause acute or sublethal effects in juvenile Atlantic salmon during short-term exposures.

Effect of legacy and emerging pollutants on genome-wide methylation patterns in black hake (Merluccius polli) natural populations

Exposure to pollutants such as non-essential metals and microplastics can have harmful consequences for marine organisms. Detecting the impact of pollutants in wild populations can be especially challenging. Such environmental disturbances might prompt rapid responses in the affected organisms, generating changes in their gene expression mediated by epigenetic regulation. Here we use an epiRADseq approach to determine the effect of four non-essential metals (As, Cd, Hg, Pb) and microplastics (MP) on the methylation pattern of Benguela hake, Merluccius polli, captured in the FAO fishing area 34, along the coasts of Mauritania and Senegal. We analysed 49 hake specimens and generated 44,201 epigenetic loci. Despite moderate levels of pollution identified from tissue analysis, we found significant differentially methylated loci associated with the level of the five pollutants analysed (119 significant loci for As, 134 for Cd, 92 for Hg, 119 for Pb, and 159 for microplastics). Elevated Pb was significantly associated with a reduction in hake condition factor. Differentially methylated loci were associated with diverse pathways associated to responses for all pollutants (e.g. immune response, gene expression regulation), pointing to signs of stress within the population. It is worth noting that all pollutants were differentially methylated for a locus in NLRC3, previously associated with innate immune response in fishes. Overall, we found evidence of the effects of moderate concentration of pollutants in the methylation pattern in wild populations of M. polli.

The combined effect of cadmium and copper induces bioaccumulation, and toxicity and disrupts the antioxidant enzymatic activities of goldfish (Carassius auratus)

An aquatic environment polluted with cadmium (Cd) and copper (Cu) has threatened fish health and adversely affected the aquaculture industry's sustainable development. The study revealed that exposure to Cd and Cu caused significant bioaccumulation in goldfish tissues, particularly in gills, intestine, and muscles. The bioaccumulation of these heavy metals increased with exposure time, with the highest levels recorded after 96 hours. This prolonged exposure led to a range of adverse effects on the fish's physiological functions. Hematological parameters, including white blood cells, red blood cells, and platelets, decreased significantly, indicating a compromised immune system. Conversely, some hematological parameters, such as hemoglobin and hematocrit, increased with exposure, suggesting a potential compensatory response. Biochemical parameters, including serum glutamic pyruvic transaminase, blood urea, and serum triglycerides, also increased with exposure, indicating liver damage and disrupted metabolic functions. Furthermore, the study found that antioxidant enzymes, including superoxide dismutase, catalase, and ascorbic acid, decreased significantly, while malondialdehyde concentration increased, indicating oxidative stress and lipid peroxidation. These findings collectively suggest that Cd and Cu exposure can cause significant toxicity in goldfish, affecting their hematological, biochemical, and enzymatic functions, and highlighting the need for further research into the effects of these heavy metals on aquatic organisms.

Toxic elements and fatty acid composition in the freshwater fish family Cyprinidae (Rafinesque 1815): balancing nutritional benefits and health risks

The aim of this study was to assess the toxicity of heavy metals/metalloids, including arsenic, cadmium, lead, and mercury accumulated in the muscle of commonly consumed fish from the Cyprinidae. We discussed the importance of fatty acids in the human diet and investigated their profile in the muscle of different fish species. Additionally, our goal was to evaluate the benefits of fish consumption in relation to its risks, not only by considering the advantages of fatty acids and the drawbacks of heavy metal toxicity but also by examining how these pollutants may alter the fatty acid profile in fish muscle, potentially reducing the quality of their nutritional benefits. We categorized these fatty acids based on their proportions in total lipids into muscle tissue of the SFA (saturated fatty acids), MUFA (monounsaturated fatty acids), and PUFA (polyunsaturated fatty acids) groups. Subsequently, we have described the toxic effects of selected elements on human health, reviewing that investigated exposure levels of these toxic elements in fish muscle and the safety of consumption through risk assessment tools such as total hazard quotient (THQ) and carcinogenic risk (CR) calculations. In the final section we focused on lipid metabolism, which is significantly affected by exposure to toxic elements. We searched for a possible relationship between the presence of toxic elements and changes in the fatty acid profile of fish muscle. The knowledge from other studies led us to the possibility of a lower PUFA content due to the damage of double bonds and the subsequent degradation of these fatty acids. Total fatty acid profile is a crucial factor in evaluating health risks and serve as an important indicator of fish meat quality. On the other hand, it can serve as a potential indicator of environmental contamination by these toxicants.

Effects of Hematological Parameters and Plasma Components of Starry Flounder, Platichthys stellatus, by Waterborne Copper Exposure

Starry flounder (Platichthys stellatus) (weight 96.42 ± 19.17 g, length 20.65 ± 1.04 cm) were exposed to waterborne copper at 0, 0.5, 1, 3, 6, 12, 24, and 48 mg Cu2+/L for 96 h. The lethal concentration 50 (LC50) of the P. stellatus exposed to waterborne copper was 15.644 mg Cu2+/L. Hemoglobin, hematocrit, and RBC count were significantly decreased by waterborne copper exposure. MCV (mean corpuscular volume) (µL) and MCHC (mean corpuscular hemoglobin concentration) (%) were also significantly decreased. The inorganic components, plasma calcium, and plasma magnesium were significantly increased. The organic components, such as plasma glucose, were significantly increased. In enzymatic components, the AST and ALT were also significantly increased by copper exposure. The results of this study indicate that exposure to copper may have effects on the survival rates and hematological parameters of the P. stellatus.

Toxicological, Hematological, and Pathological Effects of Acute Copper and Lead Intoxication in Grass Carp (Ctenopharyngodon idella)

Environmental contamination by heavy metals, particularly fish poisoning, is a growing concern due to its impact on aquatic ecosystems. Fish serve as bioindicators and play a crucial role in the food chain. This study evaluated the toxic effects of acute copper and lead exposure in Ctenopharyngodon idella, analyzing hematological, biochemical, and pathological alterations. Fifty-six grass carp were exposed for 96 h to copper and lead (2, 3, and 4 mg/L). Blood samples were analyzed for hematological and oxidative stress parameters, while brain, gills, liver, and kidneys were assessed for enzymatic activity (acetylcholinesterase, catalase, glutathione S-transferase) and histopathology. Data were analyzed using ANOVA and Tukey's test (p < 0.05). Significant increases in gill glutathione S-transferase (GST) activity (Cu2 and Cu3, p < 0.05) and catalase activity (Pb3 e Pb4, p < 0.05) indicated oxidative stress. Lead exposure caused a significant reduction in erythrocyte count (Pb2, p < 0.05). Although not statistically significant, erythrocyte osmotic fragility increased at higher metal concentrations. Histopathology revealed epithelial hyperplasia, inflammatory infiltrates, and edema in gills, hepatocellular degeneration, and subcapsular/interstitial renal hemorrhages in all exposed groups. These renal lesions diverge from typical heavy metal nephrotoxicity, usually characterized by tubular degeneration. These findings highlight the systemic effects of copper and lead, particularly their oxidative impact and unexpected renal damage. These findings underscore the complex toxicopathological effects of copper and lead in fish, particularly their impact on oxidative stress.

First report on Technology-Critical Elements in seahorses from Rio de Janeiro, Southeastern Brazil

Electronic waste poses a growing environmental threat due to the presence of metals essential for electronic devices. Improper disposal can lead to severe ecological consequences. This study assessed Technology-Critical Elements (TCE) in Longsnout seahorses (Hippocampus reidi) along the Rio de Janeiro coast. Dorsal fin samples from 50 individuals across five locations (Guanabara Bay, Armação dos Búzios, Ilha Grande Bay, Araruama Lagoon, and Arraial do Cabo) were analyzed by the ICP-MS technique. Various metals were detected, with titanium present at the highest concentrations (19.8 ± 28.5 mg kg-1 in females and 11.9 ± 16.9 mg kg-1 in males). Significant differences in TCE levels were found across sites, where Guanabara Bay samples contained higher neodymium and erbium, while Armação dos Búzios exhibited the lowest thulium, lutetium, and rubidium concentrations. Arraial do Cabo presented notably lower lutetium levels than Guanabara Bay. Negative correlations were observed between seahorse height and praseodymium, lanthanum, europium, rubidium, and titanium, suggesting potential growth impacts. No significant sex-based differences were detected. These findings highlight the importance of monitoring TCE accumulation in marine species, particularly in vulnerable ecosystems. This study provides baseline data on E-waste contamination impacts on marine biodiversity, emphasizing the need to mitigate anthropogenic pollution to protect aquatic life and maintain ecological balance.

Multi-strain Native Probiotics from the Asian Stinging Catfish (Heteropneustes fossilis) Enhance Growth, Blood Health, and Organ Morphology in the Host

Probiotics are promising substitute to synthetic agrochemicals for improving fish health in the aquaculture system. The probiotics used in the aquaculture sector of Bangladesh are mostly imported. While these probiotics can offer benefits, probiotic-supplemented diet sometimes shows inconsistent results mainly due to incompatibility between the probiotic strains and local aquatic environment or fish species. Therefore, the development of probiotics from native fish species could be an alternative to mitigate the possible detrimental effects of imported probiotics on aquaculture production in Bangladesh. Thus, this study aimed to isolate and identify potential probiotic bacteria from the gut of Asian stinging catfish and to evaluate their efficiency in improving physiological parameters and organ morphology of the host fish. Following morphological and biochemical screening of the bacterial isolates, five isolates having potential probiotic traits were identified as Bacillus safensis (HF8), Bacillus altitudinis (HF10), Bacillus pacificus (HF19), Bacillus cereus (HF20), and Bacillus cereus (HF21) using 16S rRNA sequencing through the Barcode-Tagged Sequencing™ (BTSeq™) platform. Five probiotic bacteria, either individually or as a consortium, showed varying degrees of susceptibility to the thirteen antibiotics tested. Isolates HF8, HF19, and HF21 and the probiotic consortium demonstrated antagonistic activity against Aeromonas hydrophila, with strain HF8 exhibiting better inhibition efficiency. Application of a consortium of probiotic bacterial strains (1.15 × 109 to 2 × 1.15 × 109 CFU/kg feed) through feed supplementation significantly improved the growth of the Asian stinging catfish compared to the untreated control after 60 days of the feeding trial. Similarly, probiotic-fortified diet significantly enhanced the hepatosomatic index and relative intestine weight in the studied fish. The hematobiochemical parameters showed varying responses to the probiotic-supplemented diets. Moreover, the probiotic consortium had positive effects on the morphological parameters of the intestine and liver compared to the control. Principal component analysis (PCA) and Pearson's correlation of the histomorphology indices demonstrated a positive impact of the laboratory-based probiotic-fortified diet on the intestine of the host fish. The gonadosomatic index and developmental stages of the ovary were also improved in the fish treated with probiotic consortium compared to the group fed with normal feed. Multi-location field-level trials should be done before applying this probiotic-fortified diet at the farmers' level, which could substantially improve the commercial fish production in an ecofriendly manner.

Curcumin's role in reshaping the redox dynamics of fish kidneys: NRF2 activation as a strategy against copper-induced nephropathy

From essential to harmful, excess copper compromises aquatic vitality. Curcumin, a potent antioxidant bioactive, counteracts heavy metal toxicity. This study examines its role in modulating the NRF2-KEAP1 pathway to boost antioxidant defenses and mitigate apoptosis in kidneys of Channa punctatus exposed to environmentally relevant Copper concentrations (ERCC). 180 fully habituated fish were categorized into six groups: Group 1 served as control, Group 2 was treated with 3 mg/L Curcumin, Group 3 was exposed to ERCC (0.85 mg/L Copper), while Group 4, Group 5 and Group 6 received co-exposure to ERCC along with the escalating Curcumin concentrations of 1 mg/L, 2 mg/L, and 3 mg/L, respectively, over periods of 15, 30, 45, 60, and 75 days. Biochemical assays were conducted to evaluate oxidative stress markers (Reactive oxygen species, reduced glutathione, glutathione peroxidase, and lipid peroxidation), kidney damage indicators (creatinine), and genotoxicity (micronuclei). Additionally, transcriptional profiling assessed mRNA levels of apoptosis-related factors (p53, bax, apaf1, cas9, cas3 and bcl2), while histopathological examinations revealed changes in renal architecture. Molecular docking analysis confirmed Curcumin's strong binding affinity to KEAP1, providing insights into its role in activating the NRF2-KEAP1 pathway. The results indicated that Curcumin significantly (p < 0.05) reduced Copper-induced oxidative stress, improved antioxidant defenses, suppressed genotoxicity, modulated apoptosis, and maintained renal tissue integrity. These findings validate curcumin's potential in effectively combating copper toxicity in aquaculture, paving the way for enhanced fish health and improved food safety.

Muscle oxidative stress, neurotoxicity and human health risks from consuming fish exposed to metallic settleable atmospheric particulate matter

The concentration of metals/metalloids in settleable particulate matter (SePM) from industrial area and in the muscles were determined in the estuarine fish, Centropomus parallelus, after 96 h-exposure to different SePM concentrations. Antioxidant defenses, oxidative damage and neurotoxicity were also determined. The risk for human consumption was evaluated by estimating daily intake (EDI), target hazard quotient (THQ), and hazard index (HI) and compared with fish collected close to the industries. Eighteen metals/metalloids were quantified in SePM and the muscles. In red muscle, the antioxidant enzymes were unchanged, and the acetylcholinesterase (AChE) activity and protein carbonyls (PC) increased. In white muscle, the glutathione-S-transferase (GST) activity and glutathione content (GSH) decreased, PC levels and lipid peroxidation (LPO) increased; the AChE was unchanged. Metals/metalloids bioaccumulated in muscles induced oxidative damage which may affect muscle function and consequently, fish performance. After short-term exposure to SePM there was no risk for human consumption. However, the EDI of fish collected in field exceeded the acceptable DI for children concerning to As and Hg. HI were lower than 1 revealing no carcinogenic risk.

Sedimentary heavy metal interactions with phytoplankton and zooplankton across the Bohai Sea

Excessive heavy metals (HMs) pose significant threats to aquatic ecosystems and are known to affect plankton communities. However, relatively little is known about the complex interactions between plankton (i.e., phytoplankton and zooplankton) and ecological risks associated with hazardous HMs in surface sediments, limiting our ability to incorporate these metals into planktonic biogeochemical cycles. Here we explored the behavior of surface sedimentary HMs (Cu, Zn, Pb, Cd, Hg, and As) and their interactions with plankton across the Bohai Sea from 2013 to 2014. During the study period, the average abundances of phytoplankton and zooplankton ranged from 0.31 × 103 to 1.96 × 103 cells L-1 and 0.02 × 103 to 0.28 × 103 ind m-3, respectively. The concentrations of Cu, Zn, Pb, Cd, Hg, and As in surface sediments ranged from 18.10 to 22.32, 39.85-56.15, 13.96-21.31, 0.18-1.84, 0.03-0.31, and 5.84-8.53 mg kg-1, respectively. The sediment quality was found to potentially pose ecological risks from Cd and Hg pollution in some cases. Our analysis of the ecological risks associated with various HMs (EHMs) revealed that phytoplankton and zooplankton abundances responded differently to these risks in the Bohai Sea. Specifically, moderate increases in ecological risks from Cu (ECu<8) and Zn (EZn<0.8) promoted phytoplankton growth, whereas elevated risks from Pb and Hg, even at low levels, inhibited their growth. For zooplankton, the optimal ecological risks from Zn were roughly 0.2, but higher EZn levels inhibited their growth. Zooplankton also preferred low ecological risks from Hg and As, as these metals were toxic to them even at lower concentrations, leading to a reduction in their abundance at higher levels. In contrast, zooplankton showed less sensitivity to Pb and Cd, which suggested possible adaptive responses or a greater ability to limit metal uptake at certain concentrations. These differential responses were attributed to species-specific metal sensitivities or genetic variability in tolerance to metal toxicity within plankton communities. Altogether, surface sedimentary HMs markedly influence plankton dynamics across the Bohai Sea and should be considered in future research.

Aluminum chloride (AlCl3) alters the physiological response of rainbow trout

Fish production in terrestrial recirculating aquaculture systems (RAS) has steadily increased over the past decades. Therefore, several studies, both in freshwater and seawater, have shown that increased water reuse in RAS leads to increased levels of heavy metals in the bodies of fish. The objective of the present study was to evaluate the impact on the physiology, osmoregulatory mechanisms, and antioxidant response in fingerlings of rainbow trout (Oncorhynchus mykiss) exposed to varying doses of AlCl3 within a recirculation system. Changes in gills, N+-K+-ATPase activity and H+-ATPase activity, plasma osmolality, lactate, glucose, chloride levels, and gills and liver oxidative stress responses were used to monitor physiology responses. As a result, AlCl3 exposure modified responses in rainbow trout. Plasma parameters increased during the 6-day exposure, while lactate levels decreased in both doses. The enzymatic activities of antioxidant enzymes and the NKA pump increased when fish were exposed to high and low doses of aluminum chloride. Gene expression of glutathione reductase and peroxidase transcripts increased and decreased respectively in the liver, contrary to that observed in gill tissue. AlCl3 was also observed in liver and gill tissues. This study shows that exposure to AlCl3 affects ion regulation and oxidative stress in rainbow trout fry.

Bioaccumulation and Trophic Transfer of Heavy Metals in Marine Fish: Ecological and Ecosystem-Level Impacts

Heavy metal contamination in marine ecosystems poses a critical environmental challenge, with significant implications for biodiversity, trophic dynamics, and human health. Marine fish are key bioindicators of heavy metal pollution because of their role in food webs and their capacity for bioaccumulation and trophic transfer. This review synthesizes current knowledge on the pathways and mechanisms of heavy metal accumulation in marine fish, focusing on factors that influence the uptake, retention, and tissue distribution. We explore the processes governing trophic transfer and biomagnification, highlighting species-specific accumulation patterns and the risks posed to apex predators, including humans. Additionally, we assess the ecological consequences of heavy metal contamination at population, community, and ecosystem levels, emphasizing its effects on fish reproduction, community structure, and trophic interactions. By integrating recent findings, this review highlights key knowledge gaps and suggests future research directions to improve environmental monitoring and risk assessment. Given the persistence and bioavailability of heavy metals in marine environments, effective pollution control strategies and sustainable fisheries management are imperative to mitigate long-term ecological and public health risks.

Interaction of Heavy Metals (Cadmium and Selenium) in an Experimental Study on Goldfish: Hematobiochemical Changes and Oxidative Stress

BACKGROUND

Heavy metal interactions within aquatic ecosystems significantly affect fish physiology. This study evaluated the protective role of selenium against cadmium-induced hematological, biochemical, and electrophoretic alterations in goldfish.

METHODS

A total of 120 goldfish individuals were divided into four groups: control, cadmium chloride-treated (2.8 mg/L), sodium selenite-treated (2 mg/L), and a combined cadmium and selenium-treated group. After 14 days, blood samples were collected and analyzed for hematological parameters, biochemical markers, and serum protein electrophoresis.

RESULTS

Cadmium exposure led to significant reductions in red blood cell (RBC) and white blood cell (WBC) counts, hemoglobin (Hb), and hematocrit (HCT) (p < 0.001). Selenium supplementation alleviated these declines and improved overall hematological function. Additionally, cadmium exposure decreased albumin and total protein levels while elevating aspartate aminotransferase (AST) and alanine aminotransferase (ALT) levels, indicating liver damage. Selenium co-treatment reduced cadmium accumulation and mitigated liver toxicity. Elevated urea and creatinine levels in cadmium-exposed fish were also significantly lowered in the combined treatment group (p < 0.0001). Furthermore, selenium supplementation enhanced antioxidant defense mechanisms by increasing catalase (CAT), superoxide dismutase (SOD), and glutathione peroxidase (GPx) activity while reducing malondialdehyde (MDA) levels, effectively counteracting cadmium-induced oxidative stress.

CONCLUSION

Sodium selenite at a dose of 2 mg/L effectively mitigated the toxic effects of cadmium chloride on hematological, biochemical, and oxidative stress markers in goldfish, demonstrating its protective potential against heavy metal toxicity.

The ability of dietary essential oils to mitigate nickel-induced growth retardation, immune-antioxidant suppression, and endoplasmic reticulum stress activation in Nile tilapia

Fish immunity is significantly impacted by waterborne metal intoxication. Nickel is a ubiquitous metal in aquatic bodies which badly impacts fish immune responses and survival. In the current research, we looked into the possible protective effects of essential oils of tea tree (TTO) and basil (BEO) against nickel exposure in Nile tilapia, or Oreochromis niloticus. To achieve this, 240 Nile tilapia (27.92 ± 0.22 g) were categorized into six groups for 45 days; three groups were fed on basal control, TTO, and BEO diets without Ni exposure. The other three groups were subjected to Ni at a level of 3.6 mg/L and fed on basal, TTO, and BEO diets. The outcomes showed a substantial decrease in the growth measures and survival % in the Ni-exposed fish. Oxidative stress (higher splenic malondialdehyde and lower splenic catalase, reduced glutathione, and superoxide dismutase), immune suppression (lower serum lysozyme, myeloperoxidase, and nitric oxide), and elevated serum cortisol levels were observed in the Ni-intoxicated group. The Ni-intoxicated group exhibited various pathological alterations detected in the intestinal tissue mainly inflammatory and necrotic changes, moreover, moderate depletion of lymphoid elements represented by necrotic lymphocytes in the splenic tissue. Ni-exposure induced endoplasmic reticulum stress through up-regulation of the splenic expression of protein kinase R-like endoplasmic reticulum kinase, activating transcription factor 6, CCAAT/enhancer-binding protein homologous protein, X-box binding protein 1, α-subunit of eukaryotic initiation factor 2, inositol-requiring kinase 1a, mitogen-activated protein kinase, c-JunN-terminal kinase, and binding protein for immunoglobulins. Feeding on the TTO and BEO diets improved the growth measures, survival, and antioxidant capacity. Immunomodulation, enhancement of the intestinal and splenic architecture, and relief of the endoplasmic reticulum stress condition were noticed when the Ni-intoxicant groups were fed on TTO and BEO diets. Overall, the effect of the TTO diet was more pronounced than the BEO diet in mitigating the negative consequences of Ni-intoxication in Nile tilapia. Dietary fortification of 0.1% TTO and/or 0.1% BEO is recommended during Ni exposure in aquaculture practices.

Health risks of potentially toxic elements in Cyprinus carpio in the karst plateau lake, China

BACKGROUND

Elevated potentially toxic elements (PTEs) in aquatic products could threaten the health of ordinary consumers. Levels of chromium (Cr), arsenic (As), lead (Pb), and mercury (Hg) in Cyprinus carpio in karst plateau freshwater Lake, Caohai Lake, China were quantified using inductively coupled plasma mass spectrometry (ICP-MS) and evaluated using a risk method with Monte Carlo simulation.

RESULT

Levels of Cr, As, Pb, and Hg in muscle tissue were substantially lower than those in viscera. The maximum concentration of muscle-bound Cr, As, Pb, and Hg were less than the standard references set by Chinese Food Codex (GB 2762-2022). The levels of Cr, As, Pb, and Hg in muscle tissue were independent of fish weight and length. The hazard index of all investigated elements in muscle tissue were less than one for adults and children, whereas the target hazard quotients of muscle-bound PTEs for children were higher than those for adults. Results indicated that exposure duration was the largest contributor to the hazard quotient of Cr, As, and Hg, whereas the concentration of Pb in muscle was the most sensitive factor affecting the variation in hazard quotient of Pb.

CONCLUSION

There is no risk related to the normal intake of muscle-bound Cr, Pb, As and Hg with the consumption of Cyprinus carpio. A better definition of the probability distribution for exposure duration and PTEs concentration could result in a more accurate hazard quotient. © 2024 Society of Chemical Industry.

Lead Nitrate (Pb(NO3)2) Toxicity Effects on DNA Structure and Histopathological Damage in Gills of Common Carp (Cyprinus carpio)

The toxic impact of environmentally relevant nominal sub-lethal concentration of lead nitrate (23 mg/L) on the gills of Cyprinus carpio after 30 days of exposure was assessed. Structural alterations were analyzed through histopathology, and the DNA damage rate in peripheral erythrocytes was evaluated by alkaline comet assay. A significant deviation in the gill histoarchitecture was observed compared to the control group. Significant changes, including the curling of secondary lamellae, loss of filaments, necrosis, hyperplasia, hypertrophy of cells of primary filament, and vacuolization, were found in the fish exposed to nominal sub-lethal concentration of lead nitrate. Moreover, the comet assay showed lead nitrate-induced DNA damage, evidenced by the length of the DNA "tail" in the exposed fish. The findings of this study strongly indicated that lead nitrate, even at sub-lethal levels, could significantly alter the overall physiology of the fish. This situation could lead to severe ecological consequences.

Dynamic responses and adsorption mechanisms of Chlamydomonas reinhardtii extracellular polymeric substances under Cd, Cu, Pb, and Zn exposure

Extracellular polymeric substances (EPS) can effectively attenuate heavy metal mobility in aquatic ecosystems and reduce metal toxicity to cells. However, a systematic study of microalgae EPS responses and their adsorption behaviors, characteristics, and mechanisms under different heavy metal exposures has not been performed. In this study, EPS extracted from Chlamydomonas reinhardtii CC-125 was analyzed for compositional changes (monosaccharides and proteins) under Cd, Cu, Pb, and Zn treatments. The EPS adsorption capacities and mechanisms for the four metal ions were also investigated. Cd (10 mg/L), Cu (5 mg/L), and Zn (5 mg/L) exposure induced changes in the microalgal EPS composition and structure, and a protein/polysaccharide ratio of greater than 1 was found. This result indicated the crucial role of proteins in stress resistance. In contrast, Pb stress resulted in an increase of 532.64% and 117.48% in proteins and polysaccharides, respectively, with galactose and glucose playing key roles in this process. A fluorescence analysis revealed that Cd/Pb exposure reduced the tryptophan and tyrosine levels in the EPS, while Cu/Zn only weakened tryptophan. As a biosorbent, the adsorption capacity of the EPS for the four metals followed the order of Pb > Cd > Cu > Zn. The fluorescence quenching titration results revealed that fluorescent compounds in the EPS had the strongest complexation ability with Pb (logKSV: 8.16 × 103), followed by Cu (logKSV: 1.79 × 103), while their abilities for Cd and Zn were weaker. A spectroscopic analysis indicated that the primary functional groups involved in EPS binding with Pb/Cd and Cd/Zn were protein carboxyl groups (C=O/O-C=O) and glycosidic bonds (C-OH/C-O-C), respectively. This study elucidates the response strategies and adsorption mechanisms of the C. reinhardtii EPS to different metals and provides a basis for environmental heavy metal pollution bioremediation.

Concentrations, characteristics, and human health exposure assessment of microplastics and heavy metals in freshwater fish in a potable water supply reservoire

Microplastic pollution in the environment is a global concern because it exposes the ecosystem and biota to microplastics and other contaminants that adsorp to their surfaces. Fish are regularly consumed by humans, exposing people to microplastics through their consumption. In this study, we investigated microplastics and heavy metals in catfish (Clarias gariepinus) and tilapia (Oreochromis niloticus) in a portable water supply reservoir in Ghana. We quantified microplastics (MPs) and polymer composition in the guts and muscles of the fish using microscopic identification and Fourier Transform Infrared Spectroscopy (FTIR). The Atomic Absorption Spectroscopy (AAS) was used to quantified the levels of zinc (Zn), copper (Cu), and lead (Pb) in the muscles and gills. The results indicated that the mean number of MPs in the guts for tilapia and catfish were 9.17 ± 1.47 MPs/individual and 7.655 ± 0.93 MPs/individual respectively. The mean number of MPs in the muscles for tilapia and catfish were 0.86 ± 0.41MPs/g and 1.21 ± 0.61MPs/g respectively. In terms of abundance, fibers were the most common type of microplastic in both species, accounting for 92% in tilapia and 76.5% in catfish. The identified polymers were polyethylene (PE), polypropylene (PP), polystyrene (PS), polyester (PES), and cellophane (CP). PE was the most abundant polymer found in the fish, while CP was the least abundant, accounting for 40% and 8%, respectively. The exposure assessment suggests that consuming catfish exposes people to more microplastics than consuming tilapia. Heavy metals were found to accumulate more in the gills than in the muscles of the fish. The heavy metal levels in the muscles were higher in tilapia than in the catfish, however, the levels of metals detected in both species were within recommended limits, posing no risk to consumers. For tilapia, the concentrations of Zn, Pb, and Cu in the gills were 24.59 ± 1.88 mg/kg, 1.99 ± 0.28 mg/kg, and 1.51 ± 0.12 mg/kg respectively. The concentrations of Zn, Pb and Cu in the muscles of tilapia were 10.67 ± 2.09 mg/kg, 0.31 ± 0.06 mg/kg and 0.18 ± 0.04 mg/kg respectively. The concentrations of Zn, Cu and Pb in the gills of catfish were 8.08 ± 1.31 mg/kg, 1.38 ± 0.14 mg/kg, and 1.18 ± 0.15 mg/kg respectively. In the muscles of catfish, the concentrations of Pb and Cu were below detection, and the concentration of Zn was 3.51 ± 1.39 mg/kg. The study also showed a moderate positive relationship between lead (Pb) levels in gills and muscles and microplastics in the muscle of tilapia. Overall, the study shows the occurrence of MPs and heavy metals in both species, with higher heavy metal concentrations in the gills than in the muscles. The findings suggest that microplastics could potentially act as vectors for heavy metals in fish.

Hexavalent chromium (Cr6+) induces oxidative stress, inflammatory response, apoptosis, and DNA damage in the liver of largemouth bass by inhibiting the Nrf2-Keap1 signal pathway

Heavy metal pollution poses a significant threat to the growth and health of fish, causing substantial economic losses in aquaculture. This study investigates the toxic effects of Cr6+ on the liver of Largemouth bass (Micropterus salmoides). Juvenile Largemouth bass were randomly divided into a control group (CON) and a chromium stress group (Cr6+), and subjected to a 96-h exposure test with Cr6+ at 96-h LC50 concentration. The results showed that in the Cr6+ group, liver cell nuclei were condensed, cells exhibited vacuolation, liver sinusoidal spaces were enlarged, and cell contours were unclear. Compared to the CON group, the Cr6+ group had significantly reduced activities of liver superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), and catalase (CAT), with a significant decrease in T-AOC levels and a significant increase in MDA content (p < 0.05). Additionally, the relative mRNA expression levels of CAT, SOD, and GSH-Px were significantly decreased in the Cr6+ group (p < 0.05). The Nrf2-Keap1 Signal Pathway showed a significant increase in the relative mRNA expression of Nrf2 and a significant decrease in the relative mRNA expression of Keap1 in the Cr6+ group (p < 0.05). Furthermore, inflammatory response, apoptosis, and DNA damage were observed in the liver of Largemouth bass: the relative mRNA expression levels of interleukin-1β (IL-1β), interleukin-8 (IL-8), interleukin-15 (IL-15), and tumor necrosis factor-α (TNF-α) were significantly increased in the Cr6 + group (p < 0.05); the relative mRNA expression levels of Caspase-3, Caspase-8, Caspase-9, and Bax were significantly increased, while the Bcl-2 was significantly decreased; Tail length, Tail DNA (%), and Olive tail moment of liver cells were significantly increased (p < 0.05). In summary, Cr6+ induces oxidative stress, inflammatory response, apoptosis, and DNA damage in the liver of Largemouth bass by inhibiting the Nrf2-Keap1 signal pathway, thus affecting the health of the fish.

A Multimode fluorescent sensor for sequential detection of Cu2+ and cysteine as well as pH sensor with real sample Applications: Extensive experimental and DFT studies

Highly responsive and optically selective (E)-1-((4-phenoxyphenyl) diazenyl)naphthalen-2-ol) sensor PDN with aggregation induced emission enhancement (AIEE) properties has been developed for the sequential detection of Cu2+ and L- Cysteine through fluorescence On-Off-On strategy. The selectivity of sensor depends on the presence of a diazo functional group and its appropriate cavity location in sensor molecule. Azo dye-based (E)-1-((4-phenoxyphenyl) diazenyl)naphthalen-2-ol) sensor PDN has been synthesized by utilizing a simple diazotization synthetic methodology that showed extraordinary AIEE behavior with bathochromic shift owing to the formation of J-aggregates. The morphology and size of aggregates were analyzed by SEM and DLS analysis, respectively. The calculated LOD of sensor PDN for Cu2+, and L-cysteine is 0.113 nM, and 84 nM, respectively. Fluorescence, UV-visible, LC-MS, 1H and 13C NMR titration were carried out to understand the interaction of sensor with Cu2+. The sensor was practically utilized in the sequential sensing of Cu2+ and Cys in real samples. Interestingly, sensor PDN was successfully employed for the sensing of a strong acid and base as well as the detection of Cu2+ ions in the solid state. Moreover, these experimental results were supported through DFT calculations.

Growth disorders, respiratory distress and skin discoloration in zebrafish (Danio rerio) after chronic exposure to Palm Oil Mill Effluent

Understanding the environmental and health impacts of Palm Oil Mill Effluent (POME) contamination is essential for driving sustainable practices and innovation within the industry. In this study, we elaborated the chronic toxicity of POME on growth disorder, respiratory distress, and skin discoloration of zebrafish (Danio rerio). Zebrafish were exposed to three concentrations of POME (0 mL/L, 0.5 mL/L and 1.0 mL/L) for 28 days. Results revealed that an increase in POME concentration significantly reduced the weight gain, length gain, specific growth rate, specific length rate and oxygen consumption rate of zebrafish. In contrast, the opercular rate increased significantly. Skin discoloration in zebrafish exposed to POME were characterized by reduced red percentage value on the body and tail, increased green and blue percentages on the tail, and decreased brightness values. This result suggests crucial insights for the management and regulation of POME.

Evaluation of the Impact of Selected Metallic Contaminants on Wild Rutilus rutilus Through Integrated Antioxidant Biomarker Responses

The application of biomarkers is often used to better understand the assessment of the toxicity in aquatic organisms within their natural environment. To this end, we examined the gills and liver of roach (Rutilus rutilus) to measure changes in the activity of the antioxidant enzymes superoxide dismutase, catalase (CAT), glutathione peroxidase, glutathione reductase and the phase II biotransformation enzyme glutathione-S-transferase (GST), as well as changes in the concentration of lipid peroxides (LPOs). Roach were collected at two localities, Veliko Ratno ostrvo and Višnjica (VIS), on the Danube River, where the concentrations of dissolved metals (Cu, Cd, Zn, Fe, Mn, Hg, Ni, As, Pb) in both fish tissues were quantified. This paper describes the integrated reaction of antioxidant enzymes and LPO levels of roach from two sampling localities in the Danube River. Principal component analysis revealed obvious differences of the antioxidant biomarkers investigated between tissues and localities, while integrated biomarker response showed that the liver of the VIS locality had the stronger antioxidant biomarker response. Despite the concordant hypothesized antioxidant induction at the VIS locality in both tissues studied, the effects as a sign of contaminant exposure appear to be mediated in part by suppression of the antioxidant system, with CAT and GST as potential candidate tissue toxicity biomarkers of contaminants.

Microelements, Fatty Acid Profile, and Selected Biomarkers in Grass Carp (Ctenopharyngodon idella) Muscle Tissue: Seasonal Variations and Health Risk Assessment

The study assesses associations between microelement levels, fatty acid composition, and oxidative stress markers in grass carp muscle in the summer and autumn seasons. Additionally, various factors were considered, including the estimated daily intake (EDI), target hazard quotient (THQ), total THQ (TTHQ), and metal pollution index (MPI), to evaluate potential health risks for consumers. The microelements (Al, As, Ba, Cd, Co, Cr, Cu, Fe, Hg, Li, Mn, Ni, Pb, Se, Sr, and Zn) were determined using inductively coupled plasma optical emission spectrometry (ICP-OES), and total mercury was determined using cold-vapor atomic absorption spectroscopy (CV-AAS). Fatty acid profiling was realized using gas chromatography (GC) detection with a flame ionization detector (FID). The overall tendency of microelement levels was as follows: Fe > Zn > Al > Sr > Ba > Ni > Se > Cr> Cu > Mn > Pb > As > Li > Hg; Collapse

Key Words

• Biomarker
• Biomonitoring
• Dorsal muscle
• FAs
• Freshwater fish
• Risk assessment
• Trace elements

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MESH Headings

• Animals
• Fatty Acids/metabolism
• Fatty Acids/analysis
• Carps/metabolism
• Seasons
• Biomarkers/metabolism
• Biomarkers/analysis
• Muscles/metabolism
• Muscles/chemistry
• Trace Elements/analysis
• Trace Elements/metabolism
• Risk Assessment
• Oxidative Stress

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Grants

• Slovak University of Agriculture in Nitra

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Affiliation(s)

Anton Kovacik Institute of Applied Biology, Faculty of Biotechnology and Food Sciences, Slovak University of Agriculture in Nitra, Tr. A. Hlinku 2, 949 76, Nitra, Slovak Republic
Marek Helczman Institute of Applied Biology, Faculty of Biotechnology and Food Sciences, Slovak University of Agriculture in Nitra, Tr. A. Hlinku 2, 949 76, Nitra, Slovak Republic
Julius Arvay Institute of Food Sciences, Faculty of Biotechnology and Food Sciences, Slovak University of Agriculture in Nitra, Tr. A. Hlinku 2, 949 76, Nitra, Slovak Republic
Marian Tomka Institute of Biotechnology, Faculty of Biotechnology and Food Sciences, Slovak University of Agriculture in Nitra, Tr. A. Hlinku 2, 949 76, Nitra, Slovak Republic.
Marek Snirc Institute of Food Sciences, Faculty of Biotechnology and Food Sciences, Slovak University of Agriculture in Nitra, Tr. A. Hlinku 2, 949 76, Nitra, Slovak Republic
Ivona Janco AgroBioTech Research Centre, Slovak University of Agriculture in Nitra, Tr. A. Hlinku 2, 949 76, Nitra, Slovak Republic
Martin Fik Institute of Animal Husbandry, Faculty of Agrobiology and Food Resources, Slovak University of Agriculture in Nitra, Tr. A. Hlinku 2, 949 76, Nitra, Slovak Republic
Nikola Stefunkova Institute of Applied Biology, Faculty of Biotechnology and Food Sciences, Slovak University of Agriculture in Nitra, Tr. A. Hlinku 2, 949 76, Nitra, Slovak Republic
Rudolf Dupak Institute of Applied Biology, Faculty of Biotechnology and Food Sciences, Slovak University of Agriculture in Nitra, Tr. A. Hlinku 2, 949 76, Nitra, Slovak Republic Reprofit International s.r.o., Hlinky 48/122, Pisarky, 603 00, Brno, Czech Republic
Lubos Harangozo Institute of Food Sciences, Faculty of Biotechnology and Food Sciences, Slovak University of Agriculture in Nitra, Tr. A. Hlinku 2, 949 76, Nitra, Slovak Republic
Katarina Tokarova Institute of Applied Biology, Faculty of Biotechnology and Food Sciences, Slovak University of Agriculture in Nitra, Tr. A. Hlinku 2, 949 76, Nitra, Slovak Republic
Eva Kovacikova AgroBioTech Research Centre, Slovak University of Agriculture in Nitra, Tr. A. Hlinku 2, 949 76, Nitra, Slovak Republic
Tomas Jambor Institute of Applied Biology, Faculty of Biotechnology and Food Sciences, Slovak University of Agriculture in Nitra, Tr. A. Hlinku 2, 949 76, Nitra, Slovak Republic
Jaroslav Andreji Institute of Animal Husbandry, Faculty of Agrobiology and Food Resources, Slovak University of Agriculture in Nitra, Tr. A. Hlinku 2, 949 76, Nitra, Slovak Republic
Peter Massanyi Institute of Applied Biology, Faculty of Biotechnology and Food Sciences, Slovak University of Agriculture in Nitra, Tr. A. Hlinku 2, 949 76, Nitra, Slovak Republic

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Collaborators Collapse

Temporal variations of metals and trace elements in tuna spines from the canary islands from 1990s to 2000s

Tuna, due to their position in the food web, serve as excellent biomonitors for assessing the health of marine ecosystems. Analyzing their organs and tissues provides valuable insight into element concentrations, as tuna possess the capacity to bioaccumulate pollutants. In the present study, 12 trace elements and metals (Al, B, Cd, Co, Cr, Cu, Fe, Li, Mo, Ni, Pb, Zn) were analyzed in dorsal fin spines samples of four tuna species: Katsuwonus pelamis, Thunnus albacares, Thunnus obesus and Thunnus thynnus from individuals captured in the surrounding waters of the Canary Islands, between 1990 and 2007. To analyze the data, descriptive statistics and one-way and two-way PERMANOVAs were carried out, with species factor and decade-species as factors, respectively. The highest concentrations were recorded for the elements: Al, Fe, B and Zn, with greater significant differences between species in the concentrations of Cu, and in both decades, in Fe, Pb and Zn. The comparison of the concentrations of elements between decades showed a decrease in them, from the 90s to the 2000s. There is no similar information on the metal content in spines for these species, providing relevant information, which may be of interest to future studies.

Metal concentrations, oxidative status and histopathological evaluation of fish species from Doce River, Brazil, after the Fundao dam collapse

Eight years after the tailings dam collapse in Mariana, MG, Brazil, several aspects of this massive disaster are yet to be elucidated. Our goal was to investigate the impact of the mud flow on 16 fish species collected across 15 points from the Doce River, addressing 12 metal concentrations, tissue oxidative status (antioxidant enzymes and stress biomarkers), and histopathological analyses. The species Trachelyopterus striatulus, Prochilodus vimboides, Loricariichthys castaneus, Lophiosilurus alexandri, Hypostomus affinis, Hoplias intermedius were shown to be the most affected regarding the gills tissue integrity; Hypostomus affinis, Oligosarcus acutirostris, Lophiosilurus alexandri, Pygocentrus nattereri, Hoplosternum littorale, and Loricariichthys castaneus showed the highest levels of liver health. Overall, H. affinis was the most affected species, showing high levels of oxidative and histopathological damage, associated with high arsenic (As) and mercury (Hg) concentrations. In fish sampled from impacted regions, As and Hg exhibited higher concentrations compared to fish from unaffected sites, surpassing all the other analyzed metals. These high metal concentrations might be associated to the tailings dam failure, and As and Hg concentrations were positively correlated with alterations in oxidative stress biomarkers and histopathologies. Our results may be used as baseline for monitoring the environmental challenges that the Doce River fish species are facing at the moment.

The content and associated health risk assessment of toxic elements, micro-, and macrominerals in common carp, Wels catfish, and silver carp from the Danube River in Serbia

Three fish species (common carp, Wels catfish, and silver carp) were collected from three locations along the Danube River in Serbia, and fish meat was analyzed for the content of toxic elements, micro- and macrominerals. Silver carp had the highest lead (Pb), arsenic (As), and cadmium (Cd) content, while Wels catfish had the highest level of mercury (Hg). Moreover, metal pollution index (MPI) ranged from 0.1096 to 0.275 and among the fish, the silver carp had the highest MPI (from 0.21 to 0.28), indicating that it could be reliable bioindicator of river pollution. Maximum determined levels of As (0.1968 mg/kg of w.w.), Hg (0.175 mg/kg of w.w.), and Pb (0.0315 mg/kg of w.w.) did not exceed values prescribed by the European Commission Regulation, Codex Alimentarius Commission, Food and Agriculture Organization (FAO), and national regulations, but Cd in silver carp was at levels higher than prescribed (0.0808 mg/kg of w.w.). Furthermore, our study's results showed that the target hazard quotient (THQ) of each analyzed element and hazard index (HI) were < 1, indicating that consumers would not be exposed to adverse health effects after consuming these fish species from the Danube River. Regarding target cancer risk (TR), for Pb this was below 10-6, which was regarded as negligible, while TRs for As and Cr were between 10-4 and 10-6, which was regarded as acceptable. Moreover, since the studied fish had low values of health risk indexes, it could be concluded that fish meat did not pose a significant risk to human health.

Zeolite with Remarkable Pb2+ and Cd2+ Removal Capability Cost-Effectively Synthesized from Postprocessed Natural Stellerite

MER zeolite, a low-silica zeolite with an 8-membered ring aluminosilicate framework, has been recognized as a promising material in sorption, separation, and ion-exchange applications. Herein, we developed a cost-effective and rapid method to convert parent zeolite H-STI, which was derived from natural stellerite, into MER zeolite through interzeolite conversion with a crystallization time of 8 h. This MER zeolite exhibits high efficiency in removing Pb2+ and Cd2+ from simulated heavy metal wastewater over a pH range of 3-8. It also shows excellent selectivity in the presence of competitive cations, including Na+, K+, Ca2+, Mg2+, Zn2+, Cu2+, and Co2+. At 25 °C, with a MER-S dosage of 1/3000 g·mL-1 for Pb2+ and 1/500 g·mL-1 for Cd2+, the removal efficiencies were 99.7 and 99.9%, respectively. The distribution coefficients were 1097 L·g-1 for Pb2+ and 550 L·g-1 for Cd2+, and the sorption capacities reached 513 mg·g-1 for Pb2+ and 171 mg·g-1 for Cd2+, indicating that the product MER zeolite is one of the highest sorbents for Pb2+ and Cd2+ reported for zeolitic materials. The sorption for Pb2+ and Cd2+ both follows the chemisorption-dominated mechanism, driven by the ion-exchange process between the K+ in the channels MER-S and the Pb2+ or Cd2+ in solution. This work highlights the potential of rapidly synthesized MER zeolite for the effective removal of heavy metal cations, emphasizing its performance and practical applicability.

Cleaner cuts: Farmed fish and skin-off fillets are lower in per- and polyfluoroalkyl substances (PFAS)

The ubiquitous occurrence and persistence of per- and polyfluoroalkyl substances (PFAS) in all environmental matrices and biota poses significant health risks to humans. Fish consumption is one of the main pathways humans are exposed to PFAS, yet general patterns in factors influencing PFAS content in fish fillets remain unknown. We assembled information on PFAS content (total quantified PFAS, PFOS, PFOA, and others) in fish fillets to assess the effect of fish origin (marine, freshwater, wild, or farmed), fillet type (skin-on or skin-off), and lipid content on PFAS variation across environments at a global scale. We found that these factors influenced PFAS contents in fish fillets, with concentrations reaching up to 2149 ng•g wet mass-1 (WM). Specifically, PFOS and PFOA in skin-off fillets were consistently lower in farmed than wild fish across freshwater and marine environments. In freshwater wild fish, PFOS was lower in skin-off fillets than skin-on fillets at group and species levels, and multiple PFAS showed an inverse relationship with the lipid content of skin-off fillets, though the slopes showed varying steepness depending on the carbon chain length and functional group of the PFAS. However, the high variability of PFAS content across sites in aquatic environments and the complexity of PFAS bioaccumulation mechanisms in fish tissues may lead to variable results at a fine scale (i.e., species level); this highlights general patterns of factors influencing PFAS bioaccumulation that may inform the management of human exposure to PFAS through dietary consumption.

Emodin Improves Juvenile Largemouth Bass (Micropterus salmoides) Liver Health Through Nrf2/NF-κB Pathway and Fat Metabolism: Growth Performance, Immune Response and Resistance Against Aeromonas veronii Infection

The experiment was aimed at examining the influence of adding emodin to feeds on the growth performance, liver immunity, and resistance against Aeromonas veronii infection among juvenile largemouth basses and other potential mechanisms. A total of 540 fish (45 ± 0.3 g) were randomly divided into 6 diets, including EM-0, EM-250, EM-500, EM-1000, EM-2000, and EM-4000 diets, in which 0, 250, 500, 1000, 2000, and 4000 mg kg-1 emodin was added. Following a 60-day feeding test, it demonstrated that the feed conversion ratio (FCR) of juveniles within the EM-500 and EM-1000 groups remarkably exceeded that of the EM-0 group. Subsequently, unlike those in EM-0 group, the fish in the EM-1000 group showed heightened hepatocyte count, induced hepatic lipolysis-associated expression of peroxisome proliferators-activated receptor α (PPARα) and acyl-coenzyme an oxidase (ACO), and reduced the hepatic triglyceride (TG) levels. Additionally, EM-1000 could up-regulate the expressions of nuclear factor erythroid 2-associated factor 2 (Nrf2) and heme oxygenase-1 (HO-1) in livers compared with controls and boost antioxidant enzymes activities of superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), and catalase (CAT), along with a lower content of reactive oxygen species (ROS) and malondialdehyde (MDA). Meanwhile, the EM-1000 group increased anti-inflammatory cytokines of interleukin-10 (IL-10) while suppressing the interleukin-8 (IL-8) expression of pro-inflammatory cytokines in livers by contrast to controls. In the end, juvenile largemouth bass in the EM-1000 group showed a comparatively highest survival rate, whereas fish in the EM-2000 and EM-4000 groups exhibited a little higher mortality than that of the EM-0 group. To sum up, our study exposed that supplementing emodin with 1000 mg kg-1 in diet could enhance the hepatic antioxidant status and unspecific immunity to reinforce the protective effect on disease resistance, resulting in improving the growth performance in juvenile largemouth bass.

The combined metabolism and transcriptome of tail muscles reveal the effects of antimony pulse exposure on swimming behavior of Pelophylax nigromaculatus tadpoles

Due to the periodic emission of pollutants, the exposure mode of contaminants in water bodies is mostly pulse exposure, and the toxic effects of fluctuating exposure on aquatic animals are not consistent with traditional toxicological experiments of constant exposure. The toxic effects of heavy metal antimony (Sb) on the swimming behavior of Pelophylax nigromaculatus tadpoles after pulse exposure (PESb) and continuous exposure (CESb) for 28 days were explored. The mechanisms were analyzed from the perspectives of tail muscle metabolism and transcriptomics. Compared to the control group, PESb and CESb decreased the average speed of P. nigromaculatus tadpoles by 25.72 % and 18.08 %, respectively. PESb and CESb led to changes in 70 and 24 metabolites of tail muscle, respectively. PESb led to alterations in metabolic pathways related to pyrimidine metabolism, arginine biosynthesis, and glycerophospholipid metabolism. In contrast, CESb altered metabolic pathways such as alanine, aspartate, and glutamate metabolism. Compared to the control, 1225 and 1139 DEGs were identified for PESb and CESb, respectively. These DEGs were mainly associated with functions such as immune response, DNA replication, protein digestion, and absorption. It can be seen that PESb and CESb can alter the metabolism and transcriptome of the tail muscle of P. nigromaculatus tadpoles, leading to differential expression of individual movements.

Sublethal Concentrations of Cadmium and Lead: Effects on Hemato-Biochemical Parameters and Tissue Accumulation in Wallagu attu

The exposure of fish to heavy metals can significantly impact physiological processes and potentially lead to adverse health effects. This study assesses the effects of exposure to Cd and Pb sublethal concentrations in water on Wallagu attu. A total of 48 fish with an average body weight of 145.5 ± 26 g were distributed among three groups (control, Cd-treated, and Pb-treated) within 60 L fiberglass tanks. They were exposed to 30% sublethal concentrations of Cd and Pb for durations of 1, 15, and 30 days. Following this exposure, an assessment was conducted on metal bioaccumulation and hemato-biochemical responses. Results revealed a significantly (P < 0.05) higher concentration of heavy metals in the fish tissues of metals exposed groups than in the control. The concentration of Cd and Pb increases in fish tissues (kidney > gills > intestine) with exposure time. In most cases, the Pb-exposed group exhibited significantly (P < 0.05) higher concentrations of Pb in different tissues than the Cd-treated group. With extended exposure time, the activities of CAT and SOD show a significant decrease in both Cd and Pb-treated groups. However, the reduction in activities was more pronounced in the Cd-exposed group. On 15 and 30 days, the levels of red blood cells (RBC), hemoglobin (HB), hematocrit (HCT), and total protein (TP) decrease in groups exposed to Cd and Pb. The cortisol and glucose levels exhibit a more noticeable (P < 0.05) increase with prolonged exposure to Cd and Pb than the control group. On day 30, the survival rate decreased more in the Pb-exposed group. The findings of this study indicate that exposure to sublethal doses of Cd and Pb induces stress in Wallagu attu, resulting in rapid changes in specific hemato-biochemical parameters.

Influence of water chemistry and contaminant occurrence on the oxidative stress ecology of Cottus gobio in a high-mountain lake (Carnic Alps)

Understanding oxidative stress in high-mountain lake fish offers crucial insights into their health, resilience, and adaptation to extreme environmental changes. This study investigates the oxidative stress response of Cottus gobio in a high-mountain lake (Dimon Lake) located in the northeast Italy during the ice-free season, focusing on the relationship between oxidative stress biomarkers and physicochemical water parameters, as well as persistent and emerging contaminants. Significant seasonal variations were observed in water parameters, with lower oxygen, pH, conductivity, and phosphate levels in summer compared to autumn, while temperature, ammonium, and nitrate were higher in summer. Metal concentrations in C. gobio muscle were higher in autumn, with Zn showing the most significant increase. PAHs, NDL-PCBs, and pesticides were all below the limit of quantification in the fish muscle samples. No microplastics items were found in the gastrointestinal tracts of fish. Oxidative stress biomarkers revealed organ-specific and seasonal variations. The liver exhibited the highest activities of catalase (CAT), glutathione peroxidase (GPx), glutathione S-tranferase (GST), and glutathione reductase (GR), highlighting its central role in detoxification and metabolic processes. Superoxide dismutase (SOD) activity was notably higher in muscle tissue during summer, suggesting increased metabolic activity. A strong correlation was found between pH and the activities of SOD, CAT, GPx, GR, and metallothioneins (MTs), emphasizing the importance of water chemistry in influencing oxidative stress responses. This approach not only aids in understanding the local adaptations of these fish but also highlights the impacts of environmental stressors on high-mountain ecosystems. Continuous monitoring of water chemistry, particularly pH, is crucial for understanding and managing oxidative stress in aquatic organisms, especially in the context of global environmental changes.

The Genomic Signature and Transcriptional Response of Metal Tolerance in Brown Trout Inhabiting Metal-Polluted Rivers

Industrial pollution is a major driver of ecosystem degradation, but it can also act as a driver of contemporary evolution. As a result of intense mining activity during the Industrial Revolution, several rivers across the southwest of England are polluted with high concentrations of metals. Despite the documented negative impacts of ongoing metal pollution, brown trout (Salmo trutta L.) survive and thrive in many of these metal-impacted rivers. We used population genomics, transcriptomics, and metal burdens to investigate the genomic and transcriptomic signatures of potential metal tolerance. RADseq analysis of six populations (originating from three metal-impacted and three control rivers) revealed strong genetic substructuring between impacted and control populations. We identified selection signatures at 122 loci, including genes related to metal homeostasis and oxidative stress. Trout sampled from metal-impacted rivers exhibited significantly higher tissue concentrations of cadmium, copper, nickel and zinc, which remained elevated after 11 days in metal-free water. After depuration, we used RNAseq to quantify gene expression differences between metal-impacted and control trout, identifying 2042 differentially expressed genes (DEGs) in the gill, and 311 DEGs in the liver. Transcriptomic signatures in the gill were enriched for genes involved in ion transport processes, metal homeostasis, oxidative stress, hypoxia, and response to xenobiotics. Our findings reveal shared genomic and transcriptomic pathways involved in detoxification, oxidative stress responses and ion regulation. Overall, our results demonstrate the diverse effects of metal pollution in shaping both neutral and adaptive genetic variation, whilst also highlighting the potential role of constitutive gene expression in promoting metal tolerance.

Selected micro- and macro-element associations with oxidative status markers in common carp (Cyprinus carpio) blood serum and ejaculate: a correlation study

The aim of this study was to (1) determine complex interactions between macro- and micro-elements present in blood serum and ejaculate of common carp (Cyprinus carpio), and (2) examine the association between alterations in these macro- and micro-elements with markers of oxidative stress. Blood and ejaculate from 10 male carp were collected in the summer period on the experimental pond in Kolíňany (West Slovak Lowland). Reactive oxygen species (ROS), total antioxidant capacity (TAC), protein carbonyls (PC), and malondialdehyde (MDA) levels were measured in blood serum and ejaculate using spectrophotometric methods. The amounts of elements (Ag, Al, Ba, Co, Li, Mo, Ca, K, Na, and Mg) in all samples were quantified using inductively coupled plasma optical emission spectrophotometry. Data demonstrated significant differences in elemental concentrations between blood and ejaculate, specifically significantly higher ejaculate levels were detected for Ag, Al, Ba, Co, Li, Mo, K, and Mg. Potassium was the most abundant macro-element in the ejaculate, while sodium was the most abundant in blood serum. Among the micro-elements, Al was predominant in both types of samples. It is noteworthy that oxidative status markers including ROS, TAC, and MDA were significantly higher in ejaculate indicating the presence of oxidative stress in C. carpio reproductive tissue. The positive correlations between Mg and Ca in blood serum and ejaculate suggest these elements play a functional role in metabolic and physiological processes. In contrast, the positive correlations of Ba and Al with markers of oxidative stress indicated the association of these metals with induction of oxidative stress. Our findings provide insights into the association of metals with biomarkers of physiological function as well as adverse effects in C. carpio.

Impacts of anthropogenic pollutants on social group cohesion and individual sociability in fish: A systematic review and meta-analysis

Anthropogenic pollutants are near-ubiquitous in aquatic systems. Aquatic animals such as fishes are subject to physiological stress induced by pollution present in aquatic systems, which can translate to changes in behaviour. Key adaptive behaviours such as shoaling and schooling may be subject to change as a result of physiological or metabolic stress or neurosensory impacts of pollution. This can result in fitness and ecological impacts such as increased predation risk and reduced foraging success. Here, we conducted a systematic metanalysis of the existing literature, comprising 165 studies, on the effects of anthropogenic pollution on sociability and group cohesion in fish species. Both organic (number of studies = 92, posterior mean (PM) = -0.483, p < 0.01) and inorganic (n = 24, PM = -1.453, p < 0.001) chemical pollutants, as well as light exposure (n = 21, PM = -3.038, p < 0.01) were found to reduce sociability. These pollutants did not reduce group cohesion, indicating that effects may be masked in group settings, though fewer studies were carried out on group cohesion and this is a key area for future research. Mixtures of chemical pollutants (n = 16) were found to reduce cohesion (PM = -43.71, p < 0.01), but increase sociability (PM = 44.27, p < 0.01). Evidence was found that fish may behaviourally acclimate to two forms of pollutant, namely mixed chemical pollutants (PM = -0.668, p < 0.01) and noise exposure (n = 22, PM = -4.043, p < 0.01). While aquatic systems are often subject to pollution from multiple sources and of multiple types, very few studies investigated the effects of multiple stressors concurrently. This review identifies trends in the existing literature, and highlights areas where further research is required in order to understand the behavioural and ecological impacts of anthropogenic pollutants in aquatic systems.

The Bioaccumulation, Fractionation and Health Risk of Rare Earth Elements in Wild Fish of Guangzhou City, China

In this study, the total content of REEs ranged from 1.32 to 67.74 μg/kg, with a predominant presence of light REEs. The ΔEu and ΔCe values, which exceeded and approached 1, respectively, indicated positive Eu anomalies and low Ce anomalies. Wild fish were categorized into high-, medium-, and low-REEs-bioaccumulation groups using cluster analysis. Higher LRs/HRs and ΔEu values, coupled with lower ΔCe values, in fish from the high-bioaccumulation group suggested that increased bioaccumulation mitigated fractionation. Omnivorous fish with higher REEs levels and lower LRs/HRs indicated broader feeding sources may enhance REE bioaccumulation and diminish fractionation. Elevated REEs concentrations and LRs/HRs in demersal fish highlighted a preferential accumulation of light REEs in the benthic environment. Smaller fish with higher REEs levels but lower LRs/HRs were likely associated with complex feeding sources. Regression analysis revealed that fish with lengths and weights of less than 18 cm and 130 g, respectively, were more susceptible to REEs bioaccumulation. Despite higher ADI values indicating a greater risk for children and Pelteobagrus fulvidraco, all ADI values within 70 μg/(kg·d) suggested that fish consumption poses no risk. This study confirmed that the fractionation of REEs in fish can be used to trace their bioconversion.

Heavy Metal Distribution in Aquatic Products from Eastern Guangdong and Associated Health Risk Assessment

With the rapid industrialization and urbanization of coastal areas, marine pollution (such as heavy metals) is increasingly contaminating the environment, posing significant public health risks. Eastern Guangdong, a key aquaculture and fisheries hub in China, has a growing market for aquatic products. Heavy metals persist in the environment and are difficult to degrade and bioaccumulate in marine organisms through the food web, presenting carcinogenic and mutagenic risks to humans, as top predators. This study analyzed 10 key species commonly consumed by residents of eastern Guangdong (bivalves, crustaceans, and fish), measuring the concentrations of six heavy metals (As, Cd, Cr, Cu, Ni, Pb) using inductively coupled plasma mass spectrometry (ICP-MS). Pollution levels were assessed using the pollution index (Pi), and dietary exposure risks were evaluated via the target hazard quotient (THQ) for different age groups. Results showed that Pi values for all metals were within normal background levels, but bivalves had a high capacity for Cd accumulation, with pollution severity ranking as bivalves > crustaceans > fish. The THQ values for both adults and teenagers were <1 across all samples, indicating no risk to the health of residents. However, the TTHQ for Sanguinolaria sp. exceeded 1, indicating potential health risks. This study highlights the health risks of consuming heavy metal-contaminated aquatic products, particularly bivalves. Reducing the consumption of these high-metal species could help lower dietary exposure and associated risks. Our findings provide essential data for the quality assessment of aquatic products and offer dietary recommendations for residents in eastern Guangdong.

Appraisal of a synthetic preservative, Quaternium - 15, effect on three model organisms: new insight on environmental risks

After the COVID-19 pandemic, the use of quaternary ammonium compounds increased exponentially due to their efficacy as antimicrobials, stabilizers and disinfectants. Among these, Quaternium-15 is a preservative used in the formulation of a variety of personal care products. The increased use of this substance and the resulting persistence in wastewater treatment systems, which are unable to completely remove the Quaternium-15 from the water, is of increasing environmental concern. Using embryotoxicity analyses, this study aimed to investigate the effects of exposure to Quaternium-15 on non-target species and the resulting risks to the environment. Embryotoxicity endpoints such as mortality, hatching, presence of malformations, altered heartbeat and animal length were used to assess the effects on three model organisms (Cyprinus carpio, Danio rerio, Xenopus laevis) were evaluated during a 96-hour exposure to six different concentrations of Quaternium-15 (1, 5, 10, 15, 20 and 25 mg/L). The results obtained from the analyses highlighted: significant mortality for all three model organisms in the highest concentrations tested in which all the embryos died after 96 hpf, a delay in hatching of C. carpio and D. rerio compared to the control group, the insurgence of malformations in all the model organisms chosen and a significant decrease in heartbeat rate for the fish models. Each of these observations underlies the negative interaction between the Quaternium-15 and aquatic organisms making necessary further investigation to prevent damage to ecosystems and non-target species.

Assessing Metal Toxicity on Crustaceans in Aquatic Ecosystems: A Comprehensive Review

Residual concentrations of some trace elements and lightweight metals, including cadmium, copper, lead, mercury, silver, zinc, nickel, chromium, arsenic, gallium, indium, gold, cobalt, polonium, and thallium, are widely detected in aquatic ecosystems globally. Although their origin may be natural, human activities significantly elevate their environmental concentrations. Metals, renowned pollutants, threaten various organisms, particularly crustaceans. Due to their feeding habits and habitat, crustaceans are highly exposed to contaminants and are considered a crucial link in xenobiotic transfer through the food chain. Moreover, crustaceans absorb metals via their gills, crucial pathways for metal uptake in water. This review summarises the adverse effects of well-studied metals (Cd, Cu, Pb, Hg, Zn, Ni, Cr, As, Co) and synthesizes knowledge on the toxicity of less-studied metals (Ag, Ga, In, Au, Pl, Tl), their presence in waters, and impact on crustaceans. Bibliometric analysis underscores the significance of this topic. In general, the toxic effects of the examined metals can decrease survival rates by inducing oxidative stress, disrupting biochemical balance, causing histological damage, interfering with endocrine gland function, and inducing cytotoxicity. Metal exposure can also result in genotoxicity, reduced reproduction, and mortality. Despite current toxicity knowledge, there remains a research gap in this field, particularly concerning the toxicity of rare earth metals, presenting a potential future challenge.

Distribution, trophic magnification and risk of trace metals and perfluoroalkyl acids in marine organisms from Haizhou Bay

Haizhou Bay, a semi-enclosed key aquaculture area in East China, has had relatively limited research focused on trace metals and perfluoroalkyl acids (PFAAs) in its biota. This study characterized the distribution, biomagnification and health risks of selected trace metals and PFAAs in various marine organisms from Haizhou Bay. Among the species examined, zinc (Zn) was the most prevalent metal, followed by copper (Cu) and chromium (Cr), whereas cadmium (Cd), total mercury (THg), and methylmercury (MeHg) contents were relatively low. Perfluorooctane sulfonate (PFOS) was the most abundant PFAA, followed by perfluorooctanoic acid (PFOA). The calculated trophic magnification factors (TMFs) were above one for Cr, THg, MeHg, and all PFAAs except perfluorobutanoic acid (PFBA) and perfluorotetradecanoic acid (PFTeDA). Across animal groups, gastropods exhibited relatively low levels of THg, MeHg, and perfluorosulfonic acids (∑PFSAs). By comparison, fish generally had lower levels of Cd and Cu compared to other animal groups, and demersal fish had significantly higher MeHg compared to gastropods. Certain organisms, such as cephalopods and shrimps, were found to pose potential health risks due to elevated levels of Cd, while levels of other studied metals, PFOS and PFOA generally appeared to be within safe limits for human consumption. Further research is needed to assess the sources and impacts of these and other contaminants.

The evaluations of oxidative stress and neurotoxicity in threatened endemic fish Barbus meridionalis from Osor River (Spain)

Mediterranean barbel (Barbus meridionalis) an endemic species is currently facing habitat destruction and pollution in Osor River (Spain) due to mining runoff that has severely deteriorated the water quality by metals, primarily zinc (Zn). In order to assess the potential risk of metal contamination and hydrological changes in the Osor River by using oxidative stress and neurotoxicity biomarkers via IBR analyses in the barbel, five different stations were chosen: upstream (S1: reference site and S2: hydrologically changed), mine (S3), and downstream (S4 and S5). The highest tissue metal levels were measured particularly at S3 and following downstream sites. SOD activity and the GSH system parameters (GPX, GST, and GSH) were the most sensitive oxidative stress indicators among the antioxidant system parameters. The organs with the greatest changes in antioxidant biomarkers were the liver and gill. As a sign of neurotoxicity, AChE activities significantly raised in the brain and muscle but drastically lowered in the kidney, liver, and gill particularly in the area of mine and downstream compared to reference site. Integrated biomarker response index (IBR) method was applied to visualize the affect of metal and hydrological alterations with biomarker response according to sites in the Osor River. IBR analyzes together with correlations between metal levels and oxidative stress biomarkers, emphasized that S2 and S3 have the greatest impact on the biomarker levels due to mine activity and hydrological changes highlighting the vulnerability to extinction of native fish B. meridionalis. It is also critical to assess the current data based on the multi-biomarker approach for a range of detrimental effects on fish fitness at the individual level as well as population persistence from an ecological standpoint.

Toxic effects of microplastic and nanoplastic on the reproduction of teleost fish in aquatic environments

Microplastics and nanoplastics are widely present in aquatic environments and attract significant scholarly attention due to their toxicity, persistence, and ability to cross biological barriers, which pose substantial risks to various fish species. Microplastics and nanoplastics can enter fish through their digestive tract, gills and skin, causing oxidative damage to the body and adversely affecting their reproductive system. Given that fish constitute a crucial source of high-quality protein for humans, it is necessary to study the impact of microplastics on fish reproduction in order to assess the impact of pollutants on ecology, biodiversity conservation, environmental sustainability, and endocrine disruption. This review explores the reproductive consequences of microplastics and nanoplastics in fish, examining aspects such as fecundity, abnormal offspring, circadian rhythm, gonad index, spermatocyte development, oocyte development, sperm quality, ovarian development, and changes at the molecular and cellular level. These investigations hold significant importance in environmental toxicology.

Non-phytoremediation and phytoremediation technologies of integrated remediation for water and soil heavy metal pollution: A comprehensive review

Since the 1980s, there has been increasing concern over heavy metal pollution remediation. However, most research focused on the individual remediation technologies for heavy metal pollutants in either soil or water. Considering the potential migration of these pollutants, it is necessary to explore effective integrated remediation technologies for soil and water heavy metals. This review thoroughly examines non-phytoremediation technologies likes physical, chemical, and microbial remediation, as well as green remediation approaches involving terrestrial and aquatic phytoremediation. Non-phytoremediation technologies suffer from disadvantages like high costs, secondary pollution risks, and susceptibility to environmental factors. Conversely, phytoremediation technologies have gained significant attention due to their sustainable and environmentally friendly nature. Enhancements through chelating agents, biochar, microorganisms, and genetic engineering have demonstrated improved phytoremediation remediation efficiency. However, it is essential to address the environmental and ecological risks that may arise from the prolonged utilization of these materials and technologies. Lastly, this paper presents an overview of integrated remediation approaches for addressing heavy metal contamination in groundwater-soil-surface water systems and discusses the reasons for the research gaps and future directions. This paper offers valuable insights for comprehensive solutions to heavy metal pollution in water and soil, promoting integrated remediation and sustainable development.

Effects of urban streams on muscle non-protein thiols, gill and liver histopathology in zebrafish (Danio rerio) assessed by active biomonitoring

Aquatic biota are exposed to toxic substances resulting from human activities, reducing environmental quality and can compromise the health of the organisms. This study aimed to employ Danio rerio as an environmental bioindicator, analyzing the effects of water from distinct urban aquatic environments. An active biomonitoring system was set up to compare the temporal dynamics of histological biomarkers for gill and liver and the patterns of non-protein thiols (NPSH) in muscle in specimens exposed for 3, 6, and 12 days. Three large urban basins in the city of Campo Grande (Midwest of Brazil) were selected. Two sites are in a very populous area (i.e Lagoa and Bandeira) and another on in an area with agricultural activities (i.e Anhanduí). All the streams displayed distinct qualitative characteristics. The presence of metals, including Mn, Zn, Fe, and Al, as well as pH, temperature, and dissolved oxygen, accounted for 38% of the variability (PC1), while total solids, conductivity, ammonia, nitrite, and explained 24 % (PC2). Degree tissue changes index (DTC) in gill and the concentration of NPSH increased in all streams during 3, 6 and 12 days of exposure. DTC in liver increases in all exposure times in most populous stream (i.e Lagoa and Bandeira). Histopathological evidence in the gill, including proliferation, desquamation, and necrosis of the primary lamellar epithelium; fusion and aneurysms in the secondary lamellar epithelium were observed after three days of exposure. Degenerative nuclear figures were noted in the liver after three days of exposure, followed by hepatocellular hypertrophy, lipidosis, and necrosis at twelve days. Our findings showing time-dependent effects of urban aquatic environments in histopathological (i.e DTC) and biochemical biomarkers in zebrafish. The biomonitoring model enabled a comparison of the temporal dynamics of various health markers, using zebrafish as bioindicator. Future studies might use this experimental model and biomarkers for environmental biomonitoring program.

Bioaccumulation, contamination and health risks of trace elements in wild fish in Chongqing City, China: a consumer guidance regarding fish size

Trace elements generally contaminate wild fish, particularly in megacities, necessitating guided consumption practices. This study investigated the bioaccumulation of trace elements in wild fish from Chongqing City in June 2021. We evaluated their contamination and associated health risks to establish consumption guidance based on fish size. Our results indicate that the concentrations of Zn, Pb, Cr, and As were relatively high, with some fish exceeding the maximum residue limits. Herbivorous and pelagic fish generally exhibited lower bioaccumulation of most trace elements, except for Cr and As, which were higher in pelagic species. The contamination indices (Pi) for Cr, Pb and As were consistently above 0.2, indicating widespread contamination. The most contaminated fish typically measured around 19 cm in length and weighed approximately 90 g. Only the maximum target hazard quotients (THQ) for As, Cr, and Hg exceeded 1, with a notably high ratio of THQ(As) > 1, highlighting concerns over arsenic contamination. The THQ(As) remained below 1 for adults across all fish species, whereas for children, species such as Onychostoma sima, Pseudohemiculter dispar, and Parabramis pekinensis exceeded this threshold. Fish safe for adult consumption generally measured 13 cm in length and weighed 20 g, and for children, 16 cm and 25 g. Consequently, selecting larger fish is likely to reduce the consumption of contaminated fish, thereby decreasing health risks to the public. The centralization of contaminated fish with high risk in specific size range confirmed fish size could be used to gauge the contamination and health risk of fish.

Analysis of Differential Gene Expression under Acute Lead or Mercury Exposure in Larval Zebrafish Using RNA-Seq

This study was first conducted to investigate the effects of acute lead exposure on developing zebrafish embryos or larvae from 24 to 120 h post-fertilization (hpf). Our data showed that treatment with 50-200 μM lead significantly affected larval survivability and morphology compared to the respective control. Second, we chose 120 hpf larvae treated with 12.5 μM lead for RNA sequencing due to its exposure level being sufficient to produce toxic effects with minimum death and lead bioaccumulation in developing zebrafish. A total of 137.45 million raw reads were obtained, and more than 86% of clean data were mapped to the zebrafish reference genome. Differential expression profiles generated 116 up- and 34 down-regulated genes upon lead exposure. The most enriched GO terms for representative DEGs were ion transport and lipid metabolism. Third, a comparison with the dataset of mercury-regulated gene expression identified 94 genes (64 up-regulated and 30 down-regulated) for exposure specific to lead, as well as 422 genes (338 up-regulated and 84 down-regulated) for exposure specific to mercury. In addition, 56 genes were co-regulated by micromolar mercury and lead treatment, and the expression of thirteen genes, including mt2, ctssb.1, prdx1, txn, sqrdl, tmprss13a, socs3a, trpv6, abcb6a, gsr, hbz, fads2, and zgc:92590 were validated by qRT-PCR. These genes were mainly associated with metal ion binding, proteolysis, antioxidant activity, signal transduction, calcium ion or oxygen transport, the fatty acid biosynthetic process, and protein metabolism. Taken together, these findings help better understand the genome-wide responses of developing zebrafish to lead or mercury and provide potential biomarkers for acute exposure to toxic metals.

Plantago asiatica seed as a protective agent for mitigating metals toxicity on Penaeusvannamei

Plantago asiatica seeds (PS) are commonly used as a medicinal plant. This study investigates the efficacy of PS against heavy metal toxicity in white shrimp (Penaeus vannamei). After feeding PS diet (5 g/kg) or basal diet (control group) for 7 days, shrimps were exposed to sublethal concentrations of heavy metals in seawater (As: 12 mg/L, Pb: 250 mg/L, Hg: 0.4 mg/L). The 7-day survival observation showed that the survival in groups fed with PS were significantly higher than that in the control group, revealing that dietary PS had the efficacy to mitigate heavy metal toxicity in white shrimp. Under the same feeding condition, white shrimps were exposed to safety dose of heavy metals (1/10 of sublethal concentrations) to understand the mechanism of mitigation. The metal accumulations in haemolymph, gills, hepatopancreas, and muscle tissues as well as the immune, anti-oxidative, stress related gene expressions in haemocytes, gills and hepatopancreas were measured for 14 days. The As accumulation in gills and hepatopancreas of groups fed with PS were significantly lower than those of control group on day 7 and 14, respectively; The Pb concentration in haemolymph of group fed with PS was significantly lower than that of control group on day 7 and 14; The Hg concentration in hepatopancreas of the group fed with PS was significantly lower than that of control group on day 7. Dietary PS could mitigate heavy metal-induced immune suppression, oxidative stress, and stress response by positively regulating immune (proPO I, Toll, IMD), antioxidant (SOD, GST, Trx), and negatively regulating stress response genes (HSP70, MT). The present study demonstrated that dietary PS could protect white shrimp against metal toxicity by reducing metal accumulations and regulating the immune, antioxidant, and stress response gene expressions in specific tissue. Therefore, PS may serve as a beneficial feed additive in the aquaculture.

Heavy Metals Assessment and Health Risk to Consumers of Two Commercial Fish Species from Polyculture Fishponds in El-Sharkia and Kafr El-Sheikh, Egypt: Physiological and Biochemical Study

Metal pollution is a major environmental concern worldwide, especially in Egypt. The aquaculture industry uses widespread artificial feeds to stimulate fish production, leading to metal accumulation in the aquatic environment. Heavy metal concentrations (HMCs) in sediments, water, and tissues were studied to study the effect of pollution levels on heamatological, and biochemical, immunological aspects of farmed fish as well as on human health. Results declared that the HMC levels in the water and sediment were significantly different between El-Sharkia and Kafr El-Sheikh fishponds (T-test, p < 0.05). This was supported by the metal pollution index in the water and sediment, indicating that El-Sharkia fishponds (ES fishponds) were more contaminated than Kafr El-Sheikh fishponds (KES fishponds). Also, HMCs in fish tissues were significantly increased in fish cultivated in ES fishponds than in KES fishponds. Haematological, immunological, and biochemical alterations of Bolti (Oreochromis niloticus) and Topara (Chelon ramada) fish were significantly different within the different fish species as well as the different fishponds. From the human health perspective, the THQ-HMC and HI-HMC associated with the consumption of muscle suggest a safe non-carcinogenic risk to human health. In contrast, cadmium poses a cancer risk to children who consume the muscular tissue of Bolti fish from ES fishponds, which should be regarded as a warning sign based on data indices and a human health perspective. In order to minimise HMC pollution in the aquaculture sector, it is advisable to take possible assessments and carry out continuous monitoring considering international WHO/FAO assessments.

Effects of mining activities and municipal wastewaters on element accumulation and integrated biomarker responses of the European chub (Squalius cephalus)

This study aimed to determine concentrations of 29 elements in the gills and liver as well as biomarker response in gills, liver, and blood of European chub from Pek River (exposed to long-term mining activities), and to compare these findings with individuals from Ibar River (influenced by emission of treated municipal wastewater) and Kruščica reservoir (source of drinking water) using inductively-coupled plasma optical emission spectrometry (ICP-OES). The metal pollution index (MPI) was also calculated. Supporting analyses for the detection of the municipal wastewater presence at investigated localities included analyses of microbiological indicators (total coliforms and Escherichia coli) of faecal pollution. We have assessed biomarker responses from molecular to organism level using the condition index, comet assay, micronucleus test, oxidative stress parameters, histopathological alterations, and fluorescence spectroscopy parameters. Multibiomarker analysis was summarized by Integrated Biomarker Response v2 (IBRv2). Among these locations, Kruščica exhibited the lowest, whereas the Pek River displayed the highest values for both categories of indicator bacteria. Due to the porphyry copper ores mining, individuals from Pek River had several times higher Cu concentrations in both gills and liver compared to the other localities which was confirmed by biomarker responses and IBRv2 value. On the contrary, fish from Kruščica reservoir were the least affected by elemental pollution which is also confirmed by low MPI and IBRv2 values. Responses of biomarkers correspond to the elemental accumulation in the liver and gills of the Ibar River are positioned between the Pek River and Kruščica reservoir. Of all the biomarkers analyzed in this study, the condition index was the least sensitive. The results of this study showed that fluorescence spectroscopy may be a method for fast screening of structural changes in gills caused by the pollution burden.