A morpho-histopathological study in the digestive tract of three fish species influenced with heavy metal pollution

Chronic Cr(VI) exposure-induced biotoxicity involved in liver microbiota-gut axis disruption in Phoxinus lagowskii Dybowski based on multi-omics technologies

Cr(VI) is widely used in industry and has high toxicity, making it one of the most common environmental pollutants. Long-term exposure to Cr(VI) can cause metabolic disorders and tissue damage. However, the effects of Cr(VI) on liver and gut microbes in fish have rarely been reported. In this study, 240 fish were randomly divided into 3 groups: the control group, low-dose Cr(VI) group (0.5 mg/L), and high-dose Cr(VI) group (2 mg/L). The mechanism by which Cr(VI) affects the enterohepatic axis of common carp was elucidated via multiomic analysis, serology, histomorphology, and physiological and biochemical indices. The results revealed that Cr(VI) stress led to hepatocyte damage, nuclear lysis, inflammatory cell infiltration, and vacuolated degeneration. The structure of the intestinal villi was severely damaged, and the length and width of the intestinal villi were significantly reduced. We also found that the accumulation of Cr(VI) in tissues increased in a concentration-dependent manner, and the content of Cr(VI) in each tissue increased in the order of gut > gill > liver > muscle. Multiple omics studies have revealed that chronic Cr(VI) stress leads to disturbances in the intestinal flora, with a significant reduction in the abundance of the beneficial bacterium Akkermansia and a significant increase in the abundance of the harmful bacterium Escherichia/Shigella. Intestinal injury and dysbiosis lead to an increase in blood LPS levels, further inducing metabolic disorders in the liver. The metabolites in the liver, including geniposide, leucine, C17 sphingosine, and 9,10-DiHODE, were significantly increased, whereas the beneficial metabolites, such as carnitine propionate and palmitoyl ethanolamide, were significantly reduced. In conclusion, our results suggest that chronic Cr(VI) stress leads to disturbances in gut microbial homeostasis and disturbed fatty acid and amino acid metabolism in the liver. LPS released into the bloodstream reaches the liver through the portal circulation, further exacerbating Cr(VI) stress-induced hepatotoxicity. This study revealed the mechanism of Cr(VI) toxicity to the liver-microbiota-gut axis of common carp. Our study provides new insights into the effects of Cr(VI) on the liver-microbiota-gut axis.

Histopathological and histochemical analysis of the digestive tract of adult horseshoe crabs under mercury stress

Mercury (Hg) contamination is a major environmental concern that continuously impacts marine organisms, including the mangrove horseshoe crab (Carcinoscorpius rotundicauda). As a vulnerable species, C. rotundicauda holds significant ecological and evolutionary value, making it particularly susceptible to Hg pollution and deserving of focused conservation efforts. This study presents the first comprehensive histopathological and histochemical analysis of mercury toxicity in the digestive tract of adult C. rotundicauda. Through both qualitative and quantitative analyses of histopathological and histochemical alterations, we evaluated the effects of acute Hg exposure (0.5 mg/L and 5 mg/L) on the esophagus, stomach, and intestines over time. The results revealed significant dose- and time-dependent tissue damage, with the stomach exhibiting the most pronounced alterations, including epithelial detachment, vacuolation caused by fibers degradation in the loose connective tissue, and muscle layer disruption, followed by the esophagus and intestines. Additionally, mucous cell density in the hindgut submucosa decreased by 30 % after 96 h of acute Hg exposure (0.5 and 5 mg/L HgCl2), indicating a weakened protective barrier. The tissue damage of the digestive tract may further have a negative impact on the health of the adult horseshoe crab, thus threatening the survival of C. rotundicauda population and reducing the biodiversity of the mangrove ecosystem. These findings underscore the critical threat posed by Hg pollution to the digestive system of C. rotundicauda and offer novel insights into the toxicological impact on marine invertebrates. Considering the tissue-damaging effects of Hg on adult horseshoe crabs, this study underscores the importance of regular monitoring of Hg contamination in natural habitats. The results offer valuable guidance for future habitat restoration and effective management of existing habitats.

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.

Structural alterations in scales of Capoeta capoeta (Güldenstädt, 1773) from heavy metal-contaminated river water

Heavy metal pollution, especially in freshwater, is a serious problem for aquatic organisms and human health. In this study, the scales of Capoeta capoeta living in the Karasu River (Turkey), which is estimated to be contaminated with pollutants, especially heavy metals, were examined for structural anomalies. Two stations on the river were selected for this purpose. Fish and surface water samples were taken at the stations. The heavy metal analyses were carried out in the water and the fish tissue. Heavy metal pollution was detected in the surface water. It was also observed that some heavy metals (As, Cu, Cd, Cr, Mn, Pb, Ni, Zn) accumulate in the fish tissue. Significant structural differences were observed on the dorsal surface of the scales, such as interrupted primary radii, damaged circuli, damaged focus, damaged anterior scale margin, broken focus, deformed scale structure, scattered chromatophores, dilatation of primary radii, loss of focus, damaged annuli, symmetry shift in the lateral line canal, eroded circuli, damaged posterior scale margin, double focus, branching in the primary radii, asymmetric circuli, incomplete annuli and interrupted secondary radii in each of the fish collected from the contaminated site. Heavy metals are suspected to be responsible for the structural anomalies in the scales. Based on these observations, it can be said that fish scales can be used as an effective indicator of water quality.

Tributyltin (TBT) toxicity: Effects on enteric neuronal plasticity and intestinal barrier of rats' duodenum

Tributyltin (TBT) is a biocide used in the formulation of antifouling paints and it is highly harmful. Despite the ban, the compound persists in the environment, contaminating marine foodstuffs and household products. Therefore, considering the route of exposure to the contaminant, the gastrointestinal tract (GIT) acts as an important barrier against harmful substances and is a potential biomarker for understanding the consequences of these agents. This work aimed to evaluate histological and neuronal alterations in the duodenum of male Wistar rats that received 20 ng/g TBT and 600 ng/g via gavage for 30 consecutive days. After the experimental period, the animals were euthanized, and the duodenum was intended for neuronal histochemistry (total and metabolically active populations) and histological routine (morphometry and histopathology). The results showed more severe changes in neuronal density and intestinal morphometry in rats exposed to 20 ng/g, such as total neuronal density decrease and reduction of intestinal layers. In rats exposed to 600 ng/g of TBT, it was possible to observe only an increase in intraepithelial lymphocytes. We conclude that TBT can be more harmful to intestinal homeostasis when consumed in lower concentrations.

Metal bioaccumulation and histological alterations in Oreochromis andersonii at Itezhi-tezhi Dam downstream of a mining area in the Central Province of Zambia

The Itezhi-tezhi Dam on the Kafue River in Zambia is a major capture fishery. However, the upstream reaches of the Kafue River receive effluents from copper mines. It was unclear whether fish health in the dam is adversely affected due to the mining effluents. We investigated the health status of fish in Itezhi-tezh Dam using a histology-based fish health assessment protocol with Oreochromis andersonii as a bioindicator. Fish were sampled in the Itezhi-tezh Dam and at a reference site further upstream on the Kafue River before it enters the mining region. Metal bioaccumulation, biometric indices and histological alterations in the gills, gonads, hearts, kidneys and livers were assessed. The findings revealed significantly higher copper and selenium sediment concentrations (p = 0.02843 and p = 0.02107 respectively), bioaccumulation of copper and selenium, and increased histological alterations in the gills, kidneys and livers of fish in the Itezhi-tezhi Dam.

Pollutant levels in the waters of the industrial area of North Aceh and Lhokseumawe Regency, Indonesia

This research was conducted from June to August 2023. Data and samples were collected using an exploratory survey method in four locations around the industrial area, namely PT. ASEAN Aceh Fertilizer and PT. Kertas Kraft Aceh in North Aceh Regency, while PT. Pupuk Iskandar Muda and PT. Harun NGL in Lhokseumawe Regency, Indonesia. Observations of physico-chemical parameters including measurements of salinity, bicarbonate, calcium, magnesium, nitrate, nitrite, orthophosphate, total alkalinity, and total ammonia were analyzed in the Laboratory of PT Intraco Agroindustri, Langkat Regency, North Sumatra, Indonesia. Microplastic analysis was carried out at the Faculty of Marine and Fisheries, Universitas Syiah Kuala, Banda Aceh, Indonesia. The biological parameters measured in this research include the chlorophyll concentration in the water locations observed. Based on the results of the analysis, it shows that the calcium, magnesium, orthophosphate content at the four research locations has exceeded the quality standards, while the nitrate content is only at PT. ASEAN Aceh Fertilizer and PT. Kertas Kraft Aceh that exceeds the quality standards. The bicarbonate, nitrite, salinity, total alkalinity, and total ammonia content at the four research locations were under normal conditions. The chlorophyll content in the four research locations was categorized as low fertility (oligotrophic). Based on the analysis, it also shows that the four research locations were contaminated with microplastics with a range of 2.78-5.49 particles/l.

Oxidative stress, antioxidant defense responses, and histopathology: Biomarkers for monitoring exposure to pyrogallol in Clarias gariepinus

Pyrogallol promotes free radicals leading to oxidative stress and toxicity. There are however a lack of studies on oxidative stress and the antioxidant system of fish following exposure to pyrogallol. This study measured oxidative stress markers, antioxidant responses, and histological changes in catfish exposed to pyrogallol. Fish were divided into one of four experimental groups: control only, or 1, 5 or 10 mg/L pyrogallol. After 15 days, glutathione-S-transferase in the serum was decreased in fish exposed to either 5 or 10 mg/L pyrogallol relative to controls while superoxide dismutase and total antioxidant capacity were decreased significantly in fish exposed to 1, 5, or 10 mg/L pyrogallol. Conversely, catalase was increased in serum of fish exposed to 1, 5, or 10 mg/L pyrogallol compared to controls. The liver of fish treated with 1, 5, or 10 mg/L pyrogallol had significantly higher levels of oxidative stress markers (malondialdehyde, lipid peroxidation, hydroperoxide content, oxidised protein content, and DNA fragmentation %) that varied with concentration. Catfish exposed to either 1, 5, or 10 mg/L pyrogallol presented with notable histological alterations in the intestine, kidney, and muscles with prominent fibrosis, as intense deposition of collagen fibre was observed by Masson's trichrome staining. Overall, endpoints related to oxidative stress and antioxidant defence enzymes in fish may be early biomarkers of pyrogallol exposure and contamination in aquatic ecosystems. Additional studies should characterize oxidative stress indicators for their utility as biomarkers of effect.

The effects of enrofloxacin exposure on responses to oxidative stress, intestinal structure and intestinal microbiome community of largemouth bass (Micropterus salmoides)

Antibiotic residues in the aquaculture environments may lead to antibiotic resistance, and potentially exert adverse effects on health of the non-target organisms and humans. In order to evaluate the effect of enrofloxacin of environmental concentrations on largemouth bass (Micropterus salmoides). Two hundred and seventy largemouth basses (with an average weight of 7.88 ± 0.60 g) were randomly divided into three groups, and separately exposed to 0, 1, 100 μg/L enrofloxacin (Control, ENR1, ENR100) for 30 days to detect the effect of enrofloxacin on the growth performance, oxidative stress, intestinal microbiota structure, inflammatory response and structure of the intestine. The results showed that ENR significantly reduced the final body weight (FBW) and weight gain rate (WGR), and increased feed conversion ratio (FCR) (P < 0.05). The histopathological analysis revealed that the villus width and muscular thickness of anterior intestine were significantly decreased with the increasing of enrofloxacin concentration. The activity of SOD was significantly increased at enrofloxacin stress, while CAT and POD activity were significantly decreased compared to control group (P < 0.05). The activities of lysozyme (LZM), alkaline phosphatase (AKP) and peroxidase (POD) in ENR1 was higher than that of control and ENR100 groups. Enrofloxacin treatment up-regulated the expression IL-1β and TNF-α, and down-regulated IL-10, and decreasing the expression level ZO-1, claudin-1, and occludin. Furthermore, the enrofloxacin treatment significantly decreased the intestinal bacterial diversity (P < 0.05). Exposure to 100 μg/L enrofloxacin obviously increased the relative abundance of Bacteroidota, Myxococcota, and Zixibacteria of fish gut, and reduced Firmicutes; 1 μg/L enrofloxacin considerably increased Bacteroidota, Myxococcota, and Actinobacteria, and reduced Firmicutes. The relative abundance of DTB120 and Elusimicrobiota was positively correlated with the occludin and claudin-1 gene. Taken together, exposure to enrofloxacin inhibited the growth of largemouth bass, influenced intestinal health, and induced dysbiosis of the intestinal microbiota.

Current Status of Biotechnological Approaches to Enhance the Phytoremediation of Heavy Metals in India-A Review

Rising waste construction, agricultural actions, and manufacturing sewages all contribute to heavy metal accumulation in water resources. Humans consume heavy metals-contaminated substances to make sustenance, which equally ends up in the food circle. Cleaning of these vital properties, along with the prevention of new pollution, has long been required to evade negative strength consequences. Most wastewater treatment techniques are widely acknowledged to be costly and out of the grasp of governments and small pollution mitigation businesses. Utilizing hyper-accumulator plants that are extremely resilient to heavy metals in the environment/soil, phytoremediation is a practical and promising method for eliminating heavy metals from contaminated environments. This method extracts, degrades, or detoxifies harmful metals using green plants. The three phytoremediation techniques of phytostabilization, phytoextraction, and phytovolatilization have been used extensively for soil remediation. Regarding their ability to be used on a wide scale, conventional phytoremediation methods have significant limitations. Hence, biotechnological attempts to change plants for heavy metal phytoremediation methods are extensively investigated in order to increase plant effectiveness and possible use of improved phytoremediation approaches in the country of India. This review focuses on the advances and significance of phytoremediation accompanied by the removal of various harmful heavy metal contaminants. Similarly, sources, heavy metals status in India, impacts on nature and human health, and variables influencing the phytoremediation of heavy metals have all been covered.

Mitigating marine hazardous contaminants: A sustainable management perspective

Marine hazardous contaminants, such as cadmium (Cd) and lead (Pb), pose significant risks to both human health and aquatic organisms. Traditional methods may not remove contaminants to safe levels, leading to the release of hazardous materials into marine environments. This research proposes polymeric membrane bioreactors as a potential solution to this problem. We determined Cd and Pb levels in three freshwater fish species (Rita, Ompok bimaculatus, and Heteropneustes fossils) from two distinctive regions (Zone 1 and Zone 2). Additionally, Cd and Pb concentrations in feeding materials, water, and sediments were analyzed to estimate daily intake and potential hazardous effects of these contaminants on the fish species. These findings underscore the need for effective regulatory measures and policies to reduce the discharge of hazardous contaminants into freshwater and marine environments, protecting both human health and the environment. Implementing polymeric membrane bioreactors in wastewater treatment and industrial facilities could mitigate the risks associated with consuming contaminated fish species. Significantly, the Cd and Pb levels in all three fish species from both fishponds exceeded the Food and Agriculture Organization's (FAO) maximum permissible limits. These findings carry important implications for policymakers, regulators, and industries, urging them to act appropriately to ensure the safety of the environment and public health. This study suggests that polymeric membrane bioreactors are a promising technological approach to address marine contamination, emphasizing their potential role in safeguarding human health and aquatic ecosystems.

Effects of microplastics and lead exposure on gut oxidative stress and intestinal inflammation in common carp (Cyprinus carpio L.)

Microplastics (MPs) are increasingly being detected in freshwater environments, which have the potential to cause combined toxicity with other contaminants on aquatic organisms. To reveal the ecological risks, the combined effects of lead (Pb) and polyvinyl chloride microplastics (MPs) were explored in the gut of common carp (Cyprinus carpio L.). The results confirmed that exposure of Pb alone accelerated Pb accumulation, increased oxidative stress, and activated the inflammation response of the gut. However, the aforementioned effects all decreased under the co-exposure of Pb and MPs. In addition, MPs altered intestinal microbial community of common carp, especially the abundance of immune system-related species. All measured variables were organized for partial least square path modeling, which revealed the combined effects of Pb and MPs on inflammation response. The results implied that MPs reduced inflammation response in two ways, including the reduction of intestinal Pb accumulation and the alteration of the intestinal microbial community. Overall, this study provides a novel aspect of ecological effects on aquatic animals from Pb and MPs exposure. The interesting results remind us that when exploring the ecological risks of MPs, combined effects from other toxic substances must be considered simultaneously.

Heavy metals (HMs) pollution in the aquatic environment: Role of probiotics and gut microbiota in HMs remediation

The presence of heavy metals (HMs) in aquatic ecosystems is a universal concern due to their tendency to accumulate in aquatic organisms. HMs accumulation has been found to cause toxic effects in aquatic organisms. The common HMs-induced toxicities are growth inhibition, reduced survival, oxidative stress, tissue damage, respiratory problems, and gut microbial dysbiosis. The application of dietary probiotics has been evolving as a potential approach to bind and remove HMs from the gut, which is called "Gut remediation". The toxic effects of HMs in fish, mice, and humans with the potential of probiotics in removing HMs have been discussed previously. However, the toxic effects of HMs and protective strategies of probiotics on the organisms of each trophic level have not been comprehensively reviewed yet. Thus, this review summarizes the toxic effects caused by HMs in the organisms (at each trophic level) of the aquatic food chain, with a special reference to gut microbiota. The potential of bacterial probiotics in toxicity alleviation and their protective strategies to prevent toxicities caused by HMs in them are also explained. The dietary probiotics are capable of removing HMs (50-90%) primarily from the gut of the organisms. Specifically, probiotics have been reported to reduce the absorption of HMs in the intestinal tract via the enhancement of intestinal HM sequestration, detoxification of HMs, changing the expression of metal transporter proteins, and maintaining the gut barrier function. The probiotic is recommended as a novel strategy to minimize aquaculture HMs toxicity and safe human health.

Assessing metal(loid)s concentrations and biomarkers in tilapia (Oreochromis niloticus) and largemouth bass (Micropterus salmoides) of three ecosystems of the Yaqui River Basin, Mexico

Aquatic ecosystems have been suffering deleterious effects due to the development of different economic activities. Metal(loid)s are one of the most persistent chemicals in environmental reservoirs, and may produce adverse effects on different organisms. Since fishes have been largely used in studies of metal(loid)s exposure, tilapia and largemouth bass were collected in three ecosystems from the Yaqui River Basin to measure the concentrations of metal(loid)s (chromium (Cr), copper (Cu), iron (Fe), manganese (Mn), nickel (Ni), zinc (Zn) arsenic (As), mercury (Hg), and selenium (Se)) and some biomarkers (somatic indices, metallothionein expression and histopathological analysis) in tissues of both species. Metal(loid) concentrations varied seasonally among ecosystems in tissues of both species. The elements varied seasonally and spatially in tissues of both species, with a general distribution of liver > gills > gonads. Also, biomarkers showed variations indicative that the fish species were exposed to different environmental stressor conditions. The highest values of some biomarkers were in largemouth bass, possibly due to differences in their biological characteristics, mainly feeding habits. The multivariate analysis showed positive associations between metal(loid)s and biomarkers, which are usually associated to the use of these elements in metabolic and/or regulatory physiological processes. Both fish species presented histological damage at different levels, from SI types (changes that are reversible for organ structure) to SII types (changes that are more severe but may be repairable). Taken together, the results from this study suggest that the Yaqui River Basin is moderately impacted by metals and metalloids.

Synthesized nanoliposome-encapsulated kaempferol attenuates liver health parameters and gene expression in mice challenged by cadmium-induced toxicity

In the present research, we encapsulated a flavonoid called kaempferol into nanoliposomal structures and the health-promoting effects of synthesized nanoliposome-loaded kaempferol (NLK) were evaluated in mice challenged by cadmium-induced . The NLK characteristics, such as size, zeta potential, and polydispersity index, were 218.4 nm, -28.55 mV, and 0.29, respectively. The in vivo experiment revealed that the mice receiving water containing cadmium (2 mg/kg body weight/day) showed significant (p < 0.05) weight loss, an increase in liver enzyme activities, and hepatic oxidative stress. Dietary supplementation with NLK at concentrations of 2.5 and 5 mg/kg mice body weight notably (p < 0.05) improved the body weight, liver enzyme activities, hepatic oxidative stress, and antioxidant potential of the liver. Our findings elucidated that NLK could alleviate the toxicity of cadmium in mice challenged by cadmium-induced toxicity.

Potentially Harmful Elements Accumulation and Health Risk Assessment of Edible Fish Tissues Caught from the Phander Valley, Northern Pakistan

This study investigated the concentrations of potentially harmful elements (PHE) in edible tissues of trout fish (Salmo trutta) in the Phander Valley, Northern Pakistan. For this purpose, fish were sampled from the Phander Valley (Gilgit River and Phander Lake). PHE concentrations in edible fish tissues (muscle, fins, and skin) were determined using atomic absorption spectrometry (AAS, AAnalyst 700, Perkin Elmer, USA). Among PHE, zinc (Zn) showed the highest concentration of 1097 μg/kg in the skin, followed by manganese (Mn) of 241 μg/kg in the muscle, and the lowest of 3.78 μg/kg for cadmium (Cd) in fins. The concentration of PHE in fish tissues of the study area was observed within the threshold limits set by the food and agriculture organization (FAO). PHE concentration of fish tissues was used for the calculation of chronic risk assessment using the chronic daily intake (CDI) and hazard quotient (HQ) indices. The highest CDI values were observed for Zn through fish tissue consumption in juveniles, followed by Mn, and the lowest for Cd in adults. The HQ values were observed less than 1 for adults through PHE consumption in fish tissue; however, that of juvenile surpassed the threshold limit through Cd consumption in all studied tissues and that of Pb in the muscle and skins only. Higher HQ values than the threshold limit could pose a potential chronic risk to the exposed community. Spearman's non-parametric correlation showed a varying degree of correlation among PHE in fish tissues and canonical discriminant analyses were used to differentiate the tissues based on PHE accumulation tendencies.

Distribution and Bioaccumulation of Essential and Toxic Metals in Tissues of Thaila (Catla catla) from a Natural Lake, Pakistan and Its Possible Health Impact on Consumers

Although fish are often recommended as a component of a healthy diet, the environmental accumulation of heavy metals in many fish species has been of considerable concern for those weighing the nutritional health benefits against adverse toxic outcome of excess intake of toxic metals. This study aimed to determine the concentration of essential and toxic metals in the tissues of Catla catla in Mangla Lake and to assess the possible risk to the consumers. Fifty samples of Catla catla were collected from Mangla Lake, Mirpur, Azad Jammu and Kashmir, Pakistan and analyzed for eighteen metals including essential and trace metals. The measured range concentrations (µg/g, wet weight) in muscle tissues, in decreasing order, were: K (955–1632), Ca (550–2081), Na (449–896), Mg (129–312), Zn (61.2–215), Fe (11.6–26.8), Sr (2.60–9.27), Pb (1.72–7.81), Se (1.55–3.55), Co (0.12–4.08), Mn (1.04–4.33), Ni (0.69–3.06), Cu (0.88–2.78), Cr (0.45–1.88), As (0.67–1.58), Cd (0.28–0.56), Hg (0.17–0.57) and Li (0.12–0.38). The metal concentrations found in this study were comparatively higher than those reported in literature. A majority of the metals exhibited higher accumulation in gills compared with those in scales and muscles. Mean levels of Pb, As, Co, Mn, Cd, Cr and Zn in Catla catla muscle were found to be exceeding the international permissible limits for the safe human consumption. The condition factor (K), as an indicator of fish health status, indicated that Catla catla of Mangla Lake are in good health condition. The metal pollution index (MPI) of gills (27.9), scales (12.5) and muscle (7.57) indicated low contamination. Moreover, human health risk was evaluated using estimated weekly intake (EWI) and daily intake (EDI), target hazard quotient (THQ), hazard index (HI) and target cancer risk (TCR). Estimated weekly and daily intake values for As, Cd, Cr, Hg, Ni and Pb were higher than provisional permissible tolerable weekly intake and permissible tolerable daily intake while THQ for As, Cd, Cr, Hg, Pb, Se and Zn was higher than 1. The THQ for As, Hg and Pb was several folds higher than 1, indicative of lifetime non-carcinogenic health risks to the consumers. The hazard index indicated cumulative risk, which greatly increased with increasing fish consumption. Target cancer risk indicated that the people eating the Catla catla from Mangla Lake were exposed to As, Cd, Cr, Ni and Pb with a significant lifetime carcinogenic risk. In summary, consumption of Catla catla from this lake was found to be associated with an increased lifetime risk to the general health of the consumers.

Comparison of cellular mechanisms induced by pharmaceutical exposure to caffeine and its combination with salicylic acid in mussel Mytilus galloprovincialis

Urban and hospital-sourced pharmaceuticals are continuously discharged into aquatic environments, threatening biota. To date, their impact as single compounds has been widely investigated, whereas few information exists on their effects as mixtures. We assessed the time-dependent biological impact induced by environmental concentrations of caffeine alone (CAF; 5 ng/L to 10 µg/L) and its combination with salicylic acid (CAF+SA; 5 ng/L+0.05 µg/L to 10 µg/L+100 µg/L) on gills of mussel Mytilus galloprovincialis during a 12-day exposure. Although no histological alteration was observed in mussel gills, haemocyte infiltration was noticed at T12 following CAF+SA exposure, as confirmed by flow cytometry with increased hyalinocytes. Both the treatments induced lipid peroxidation and cholinergic neurotoxicity, which the antioxidant system was unable to counteract. We have highlighted the biological risks posed by pharmaceuticals on biota under environmental scenarios, contributing to the enhancement of ecopharmacovigilance programmes and amelioration of the efficacy of wastewater treatment plants.

Integrated analysis of fish intestine biomarkers: Complementary tools for pollution assessment

The gastrointestinal tract and its enteric nervous system are the first routes of food and xenobiotics uptake. Considering the importance of this organ, this study evaluated intestinal biomarkers of Sphoeroides testudineus integrating the data to generate tools for pollution assessment. The fish were collected in three sites of São Paulo Coast and their intestines were analyzed for biochemical, histology, and neuronal density and morphometry biomarkers. To evaluate the differences among the data, a PERMANOVA was applied, followed by a FA/PCA. The PERMANOVA indicated differences (P < 0.001) between the regions (RA, A1, and A2). Four factors were extracted from the FA/PCA (62% cumulative), showing that the animals from A2 presented severe alterations, mainly in intestinal morphometry and neuronal density. A1 alterations refer mainly to the increase of neuronal metabolism. Our results also evidence a gradient of environmental quality related to the protection level (AR > A1 > A2).

Water Hardness Can Reduce the Accumulation and Oxidative Stress of Zinc in Goldfish, Carassius auratus

We investigated the changes in toxicity stress in goldfish, Carassius auratus, under exposure to different concentrations of Zn and water hardness for 14 days. We analyzed the changes in water hardness and Zn accumulation after exposure. To investigate the stress levels, the expression of metallothionein, caspase-3 activity, NO activity, and total antioxidant capacity were detected. Terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assays were also performed to measure apoptosis in the liver. The results showed that compared to the control group, a more significant difference in the accumulation of Zn in body stress markers (metallothionein, caspase-3 activity, NO activity, and total antioxidant capacity) were observed with increasing Zn concentration and exposure time. Notably, at the same Zn concentration and exposure time, lower stress levels were discovered in the samples under harder water conditions. Finally, the TUNEL assay showed that Zn accumulation caused apoptosis and high water hardness could reduce the apoptosis. In conclusion, we found that high water hardness can influence the absorption of Zn, and alleviating the hardness levels can reduce the toxicity stress caused by Zn.

Effect of Feed Supplementation with Bacillus coagulans on Nrf Gene Family Expression in Common Carp (Cyprinus carpio) under Long-Term Exposure to Cd2+

Nuclear factor-E2-related factor (Nrf) belongs to the Cap ‘n’ collar basic leucine zipper (CNC-bZIP) family, which plays an important role in the resistance to oxidative stress in the body. In this study, 12 Nrf genes were identified in the common carp genome database. Comparative genomic analysis showed that the Nrf genes of common carp had significant amplification, confirming that the common carp had experienced four genome-wide replication events. Phylogenetic analysis showed that all common carp Nrf clustered with scleractinian fish Nrf, indicating that they were highly conserved during evolution. In addition, tissue distribution results showed that most Nrf genes had a broad tissue distribution but exhibited tissue-specific expression patterns, demonstrating functional differences after WGD events. At 30 and 60 days of Cd2+ stress, most of the Nrf genes showed an increase in expression compared with the control group, indicating that they played a key role in the organism’s response to oxidative stress. To find a suitable concentration of Bacillus coagulans to activate the Nrf genes, we added three different concentrations (2.0 × 107 CFU/g, 2.0 × 108 CFU/g, and 2.0 × 109 CFU/g) of B. coagulans into the feed and defined them as L1, L2, and L3 groups, respectively. We investigated the effect of different concentrations of B. coagulans in the feed on the expression level of Nrf genes in the intestine of common carp under Cd2+ stress at 30 and 60 days. The results showed that, compared with the control/stress group, the expression of different Nrf genes was improved to varying degrees at three concentrations, and the effect of the L2 group (2.0 × 108 CFU/g) was the best. This suggests that the L2 group is the optimum concentration for activating Nrf gene expression when subjected to heavy metal Cd2+ stress and may act as an activation switch with a prominent role in the body’s resistance to oxidative stress and immune response.

Changes in the contour of karyology and histoarchitecture of the primary respiratory organ in the fish Oreochromis mossambicus (Peters, 1852) inhabiting the polluted estuarine ecosystem

The wetland ecosystem (WE) is subject to pollution by many anthropogenic activities, including domestic and industrial effluents. These effluents may contain toxic heavy metals that can interact within the aquatic ecosystem and have a capacity to disturb the metabolic activities, histological profile, and genetic structure and functions in aquatic species inhabiting the environment. The present study observed the karyological and histological alterations in gills of the freshwater fish, Mozambique tilapia, Oreochromis mossambicus in two different sublethal concentrations (1% and 3%) of heavy metals in 7, 15, and 30 days of experimental periods. The heavy metals induced various structural damages such as ring chromosome, sister chromatid exchange, acrocentric association region, condensed chromosomal morphology, heterochromatin region, and nucleolar organizer region in the chromosomes of O. mossambicus treated with 1% and 3% sublethal concentrations of water sample collected from Pallikaranai wetland ecosystem. Gills exposed to 1% and 3% effluent exhibited several variations in the respiratory surfaces of gill arches or lamellae in the light and scanning microscopical study. The gills exposed to 1% concentration for 30 days showed marked necrosis, and the secondary lamellae showed the lamellar membrane's dissolution. Exposure of gills to raw effluent in the field condition was observed in the presence of Cd, Pb, Cr, Cu, and Zn. Thus, this present study shows the environmental deterioration by heavy metal pollution on the structure of the gills in tilapia.

Physiological and histopathological alterations in Capoeta baliki and Squalius pursakensis after caused by some environmental pollutants

The present study was aimed to apply physiological and histological biomarkers of pelagic and benthic fish species as biomonitoring of environmental pollutants. Capoeta baliki and Squalius pursakensis were caught from 5 stations in Kirmir Stream (Turkey). After measuring the total length and weight for condition factor analysis, liver, gill, brain, and kidney tissues of fish were taken for histopathological analysis. Dorsal muscles of fish tissues were analyzed for polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), organochlorine pesticides (OCPs), and polybrominated diphenyl ethers (PBDEs). The mean condition factor of C. baliki and S. pursakensis were 1.14 and 0.97, respectively. It was indicated that the first one was in good condition than the latter one. According to histopathological observations, the alterations in the tissues may be associated with the environmental pollutants' exposure. The total concentration of PAHs of dorsal muscle of C. baliki and S. pursakensis found ranged from 0.915 to 108.421 µg/kg and 0.601 to 675.248 µg/kg, respectively. The highest total concentrations of OCPs were found as 44.16 µg/kg for C. baliki and as 562.12 µg/kg for S. pursakensis. The PCB 28 (10.83 µg/kg), PCB 52 (10.92 µg/kg), PCB 138 (226.24 µg/kg), and the total concentrations of PBDEs were found as 151.74 µg/kg in only S. pursakensis. The result of the concentrations of the investigated pollutants was generally found higher in S. pursakensis which is a higher trophic level than C. baliki. Histopathological alterations were detected as hyperemia in liver, gill, and brain; as hydrophobic degeneration in liver; hyperplasia in gill; and tubular degeneration in kidney tissues of both species. The obtained result of the study shows that the environmental pollutants may affect the physiological and histological status of fish.

Physiological assessment of fish health in mineral-rich areas of Ganjam, Odisha, India, and chronic toxicity of zirconium oxychloride on the fishes of Channa punctata

The high concentration of metal toxicants in aquatic ecosystems has a detrimental impact on fish health that ultimately jeopardizes human health. Such threats mostly arise in mineral-rich areas where an increase in metal concentrations occurs in aquatic bodies due to anthropogenic activities like mining. The present study assessed the health of food fish Channa punctata from the mineral-rich areas of Ganjam, Odisha, India, mined for heavy and transition metal ores like ilmenite, zircon, monazite. The fishes collected from these areas showed histopathological anomalies in vital organs like the liver, kidney, gills, stomach and intestine while cytological analysis revealed vacuolated cytoplasm and micronuclei. Biochemical analysis showed a significantly lower lipid concentration in muscle (i.e., 0.177 ± 0.177 mg/gm) and liver (i.e., 0.169 ± 0.002 mg/gm) as compared to non-exposed fishes from adjoining non-mineral rich areas having a mean protein concentration of 87.48 ± 8.16 and 77.75 ± 0.892 mg/gm tissue in the muscle and liver, respectively, and a mean lipid concentration of 0.29 ± 0.009 mg/gm muscle and 0.34 ± 0.009 mg/gm liver. Chronic exposure to sublethal concentrations of zirconium oxychloride, a salt of zirconium, resulted in a significant decline in the concentration of protein, ranging from 57.5 ± 0.929 - 63.88 ± 1.95 mg/gm in muscle and 45.35 ± 2.332 - 51.98 ± 1.036 mg/gm in the liver. The lipid concentrations in muscle (0.03 ± 0.009 - 0.17 ± 0.009 mg/gm) and liver (0.06 ± 0.012 - 0.19 ± 0.007 mg/gm) were also significantly lower than the non-exposed fishes. Marked degenerative changes were identified in the histological sections of the gill, intestine, stomach, liver and kidney of zirconium oxychloride-treated fishes along with various nuclear deformities and micronucleus.

An integrated approach for spatial distribution of potentially toxic elements (Cu, Pb and Zn) in topsoil

In this study, statistical analysis and spatial distribution were performed to compare raw data and centred log-ratio (clr) transformed data of three copper (Cu), lead (Pb), and zinc (Zn) potentially toxic elements (PTEs) concentration for 550 surface soil samples in Khuzestan plain. The results of both approaches showed that classical univariate analysis and compositional data analysis are essential to find the real structure of data and clarify its different aspects. Results also indicated that spatial distributions of raw data and clr-transformed data were completely different in three studied metals. Raw data necessarily shows the effects of anthropogenic activities and needs an additional evaluation of human health risk assessment for these three studied elements. Data obtained from clr-coefficient maps also demonstrated the role of geological processes in the distribution pattern of potentially toxic elements (PTEs). To improve the understanding of the implications for PTE pollution and consequences for human health, a RGB colour composite map was produce to identify the potential origin of PTEs from areas with higher than typical baseline concentrations.

Long-term exposure of high concentration heavy metals induced toxicity, fatality, and gut microbial dysbiosis in common carp, Cyprinus carpio

Heavy metals (HMs) in an aquatic environment mainly affects fish, and thus, fish are convenient pollution bio-indicators. In this study, the toxic effects of HM mixture (chromium (Cr), cadmium (Cd), copper (Cu)) in 0 mg/L to 3.2 mg/L concentration range was investigated in Cyprinus carpio (28 days). HM accumulation, histopathology, oxidative stress, and gut microbial changes were evaluated. HMs accumulated in the order of Cr > Cu > Cd, primarily in the kidneys and finally scales. Reactive oxygen species generation increased in all exposure groups up to day 14, with maximum generation at 3.2 mg/L mixture, which later decreased on day 28 in all. Malondialdehydeand and superoxide dismutase levels increased from day 7 to 28 with increased HM concentrations, while total protein showed an inverse trend. Gill histopathology showed major changes such as uplifted and disintegrated primary lamella, and secondary lamella shortening. The kidneys were characterized by glomerular necrosis, Bowman's capsule expansion, and tubular space dilatation. Proteobacteria and Firmicutes abundance increased up to 59.4% and 99.16% in 0.8 mg/L and 3.2 mg/L treatment groups, respectively. This study provided a better understanding on the physiology and gut microbiota alteration in C. carpio under multiple HM stress.