Fish bioaccumulation and biomarkers in environmental risk assessment: a review

Hepatoprotective role of ascorbic acid against fenvalerate-induced histopathological, ultrastructural, and antioxidant disruptions in Ctenopharyngodon idella

Ctenopharyngodon idella, a herbivorous fish, is widely used in aquaculture to control aquatic weeds. Owing to its significant role, the present study investigates the protective effects of ascorbic acid (AA) against fenvalerate (FEN) toxicity in the liver of Ctenopharyngodon idella. Dietary AA supplementation (1000 mg/kg diet) was tested against 1.2 and 2 µg/L of FEN and fish were dissected on the 15th, 30th, and 60th day of the experiment. The results revealed a significant (p < 0.05) increase in liver antioxidant enzyme levels (superoxide dismutase, catalase, glutathione peroxidase, glutathione-S-transferase, and reduced glutathione) on the 15th and 30th days of FEN treatment followed by a decrease on the 60th day as compared to control group. While as, the malondialdehyde level was elevated throughout the experiment. Histopathological analysis revealed severe liver damage in FEN-treated fish, with notable infiltration of sinusoids, necrosis, and pycnotic nuclei, resulting in a mean degree of tissue change (DTC) value of 117.12 ± 1.27 at 2 µg/L of FEN on the 60th day of the experiment. Transmission electron microscopy displayed significant anomalies, including glycogen depletion, fragmented rough endoplasmic reticulum, swollen mitochondria, loss of heterochromatin, and necrotic hepatocytes with disrupted cytoplasm. However, dietary AA supplementation significantly minimized antioxidant enzyme activity and reduced liver pathology in FEN-treated fish, demonstrating its hepatoprotective efficacy. The study concludes that AA supplementation is recommended in aquaculture systems to mitigate the adverse effects of FEN.

Toxic and essential elements determination in edible tissues of different elasmobranch species from Southeastern Brazil and potential human health risks

Brazil is the largest consumer of shark meat, which is sold by fishmongers under the umbrella term cação. The population consumes this meat due to its low cost and lack of fish bones. In this work, morphometric measurements and metal/metalloid concentration (75As, 202Hg, and 82Se) were assessed in the muscle tissue of species from Dasyatis spp., as well as Rhizoprionodon porosus and Zapteryx brevirostris, obtained from Farol de São Tomé beach in Southeastern Brazil. A principal component analysis (PCA) was conducted to evaluate the separation of species based on morphometric variables and elemental concentrations. Additionally, human health risk assessment indices-estimated daily intake (EDI), target hazard quotient (THQ), target cancer risk (TCR), and selenium health benefit values (HBVSe)-were calculated to estimate the risks associated with the consumption of elasmobranch meat in the region. The PCA revealed distinct clustering patterns by species. The human health risk assessment indices indicated potential risks associated with the consumption of the analyzed species. For Dasyatis spp., the EDI of As, THQ of inorganic As (iAs), and TCR exceeded their respective thresholds. For R. porosus, the EDI of As, THQ of iAs and Se, and TCR exceeded the established thresholds. For Z. brevirostris, the EDI of As and Hg, THQ of iAs and MeHg, TCR, and HBVSe exceeded the thresholds. These results suggest a potential risk to public health associated with the consumption of elasmobranch meat from the analyzed species, especially Z. brevirostris.

Multidisciplinary approach to determine the influence of human pressure on nearshore Antarctic fish

Concentrations of five metals together with hematological and morphological parameters were measured in three coastal fish species collected in two sites of the Antarctic Peninsula. Furthermore, we assessed isotopic niche widths among fish populations to better understand their trophic ecology. Nothotenia coriiceps from Fildes Bay displayed high concentrations of Fe and Cu, while those from South Bay had higher concentrations of Cd. All fish from South Bay had higher Zn levels than specimens from Fildes Bay. Effects such as biomagnification of Fe, increased fish metal levels and niche width expansion of Nothotenia coriiceps and Harpagifer antarcticus could be attributed to suboptimal environmental conditions in Fildes Bay. Our findings suggest that early warning signals in coastal Antarctic fish may be linked to increased metal bioavailability as a result of climate change and increased human pressure.

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.

Legacy DDT and its metabolites in Brook Trout from lakes within forested watersheds treated with aerial applications of insecticides

To manage defoliation from insect outbreaks, about half of the forested land in New Brunswick, Canada, was treated with dichlorodiphenyltrichloroethane (DDT) between 1952 and 1968. Aerial applications of DDT have thus likely increased the risk of chronic effects in aquatic ecosystems from this legacy insecticide given its high persistence in soil and sediments and its bioaccumulation potential within the food web. We investigated DDT and its metabolites (total ΣDDTs =  ∑ DDT +  ∑ DDD +  ∑ DDE) in Brook Trout (Salvelinus fontinalis) associated with geospatial data of historical applications to lake watersheds and sedimentary measures of DDT and its metabolites from five "impact" and two "reference" study lakes. Total ΣDDTs in recent lake sediments were significantly correlated with cumulative DDT applied aerially to the lake's watershed. Brook Trout muscle tissue showed total ΣDDTs that were significantly higher from impact lakes than reference lakes. On average, total ΣDDTs in Brook Trout from impact lakes exceeded ecological guidelines for consumers of aquatic biota by about ten times. Most legacy DDT in Brook Trout and lake sediments were the metabolites ΣDDE and ΣDDD, which suggests the importance of environmental conditions and transport of weathered sources of this organochlorine insecticide to biota. Stable isotopes from fish and common invertebrate prey also suggested that Brook Trout were at a similar trophic position among all study lakes and thus storage pools of legacy DDT likely explain contamination levels within biota. Our findings clearly demonstrate that chronic effects of historical DDT applications likely persist throughout aquatic environments in north-central New Brunswick.

Co-Exposure to Different Zinc Concentrations and High-Fat Diet Modules Endoplasmic Reticulum Stress and Lipotoxicity through the MTF-1/GPx7 Axis in Yellow Catfish (Pelteobagrus fulvidraco)

As industrialization and societal development accelerate, various organisms, including humans, are exposed to environmental hazards, such as zinc (Zn) and high-fat diet (HFD). These widespread exposures pose significant threats to public health; however, the combined effects and underlying mechanisms of these environmental factors on lipotoxicity remain unclear. In this study, the yellow catfish (Pelteobagrus fulvidraco) was used as a model to investigate the impact of different Zn levels and HFD coexposure on hepatic lipotoxicity. The results indicated that low concentrations of Zn (L-Zn) significantly reduced hepatic lipid accumulation, oxidative stress, and endoplasmic reticulum (ER) stress compared to HFD-only treatment, while high concentrations of Zn (H-Zn) exacerbated these effects. Mechanistically, L-Zn alleviated ER stress by scavenging H2O2 and O2•- within the ER via the MTF-1/GPx7 pathway. Glutathione peroxidase 7 (GPx7), an ER-resident antioxidant enzyme, played a crucial role in mitigating ER stress and lipotoxicity, with metal-responsive transcription factor 1 (MTF-1) identified as its regulator. This study is the first to demonstrate the dual role of Zn in hepatic lipotoxicity, revealing the Zn2+/MTF-1/GPx7 axis as a key modulator of ER stress and lipid metabolism. These findings highlight the importance of considering combined environmental exposures in public health and environmental risk assessments.

Caging Gammarus roeseli to track pesticide contamination: How agricultural practices shape water quality in small waterbodies?

Contaminant monitoring in agroecosystems is increasingly revealing overlooked molecules, particularly within complex pesticide mixtures. This study assessed the effectiveness of chemical and ecotoxicological methods for evaluating contamination and biological responses in Gammarus roeseli exposed to pesticides and transformation products (TPs) in lentic small water bodies (LSWBs) near agricultural zones. We examined 7 LSWBs, finding variable contamination levels shaped by watershed composition differences. Analysis of 136 compounds identified key TPs, including chlorothalonil R471811, metazachlor ESA, and OXA, which collectively represented 86.2 % of the total quantified contaminants. These results underscore the persistence of both current and banned pesticides in the ponds studied. While G. roeseli showed favorable survival rates, significant reductions in locomotion and ventilation were observed at heavily contaminated sites, with biochemical analyses suggesting neurotoxic effects and activation of detoxification mechanisms in response to contaminants. Multivariate analyses revealed site-specific variations, highlighting the complex interactions between contamination levels and environmental conditions. Biomarker responses in gammarids served as sensitive indicators of residual toxicity in LSWBs, with frequent associations with historical contamination or current pesticide applications. This in situ caging approach across a contamination gradient demonstrates strong potential for biomonitoring and ecotoxicological assessments in agroecosystems. Extending exposure durations and including more heavily contaminated ponds could further enhance risk evaluation, thereby improving biomonitoring accuracy in headwater aquatic ecosystems. By integrating site-specific environmental conditions, contamination profiles, and biological responses, this study provides valuable insights into the influence of agricultural practices on LSWBs contamination and underscores the critical need to incorporate TPs into future risk assessment frameworks.

Integration of histopathology, transcriptomics and non-targeted metabolomics reveals toxic effects of thiamethoxam under acute stress in mirror carp (Cyprinus carpio var. Longke-11 mirror)

In recent years, the increasing application of thiamethoxam (THM), coupled with its high leaching and solubility in water, has led to growing concerns regarding THM residues in aquatic environments, which may pose toxic effects on aquatic organisms, particularly fish. However, the toxicological mechanisms of THM in freshwater fish remain unclear. In this study, using histopathology, transcriptomics, and non-targeted metabolomics, the toxic effects of different concentrations of THM under acute stress (96 h) were investigated in mirror carp (Cyprinus carpio var. Longke-11 mirror). The results showed that under acute THM stress, liver tissues of the mirror carp exhibited vacuolation, cellular degeneration, and enhanced cytoplasmic eosinophilia, while gill tissues displayed epithelial structure loss, epithelial cell detachment, degeneration, and vacuolation, with the severity of lesions increasing with exposure concentration. Transcriptomic analysis revealed that the number of differentially expressed genes (DEGs) increased with the concentration of THM. Genes related to immune response and antioxidant stress were mostly downregulated, while genes related to inflammation and apoptosis were predominantly upregulated. The downregulation of common DEGs (SLC7A11, ITLN, CDH17) further confirmed these results. Gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis revealed significant enrichment in pathways related to inflammation and oxidative stress, with the NF-kappa B signaling pathway identified as the key pathway affected. Metabolomic analysis showed that differentially expressed metabolites (SCMs) associated with amino acid and lipid metabolism were significantly downregulated. The downregulation of SCM acetylcysteine further affected the antioxidant capacity of mirror carp. Moreover, different concentrations of THM affected phenylalanine metabolism, cysteine and methionine metabolism, and biosynthesis of unsaturated fatty acids in the liver of mirror carp. Integrated analysis of apoptosis-related factors (TP53INP1, PRF1, Sphingosine) upregulation and anti-apoptotic factors (Bcl2l1) downregulation suggested that THM induces apoptosis in mirror carp cells. These results indicate that THM stress affects the immune system, amino acid, and lipid metabolism in mirror carp, leading to inflammation, oxidative stress, and apoptosis. This study provides preliminary insights into the toxic mechanisms of THM in fish and can serve as a scientific basis for THM risk assessment and environmental protection.

A non-lethal technique for sampling liver from live juvenile Siberian sturgeon (Acipenserbaerii)

The liver, as a pivotal organ in the body responsible for a wide range of functions, including metabolism, detoxification, nutrient storage, and overall well-being is commonly sampled for various studies in fish research. Traditional methods for liver sampling require euthanizing the specimens. This study demonstrated a non-lethal or minimally invasive technique for collecting liver tissue from live juvenile Siberian sturgeon (Acipenser baerii) using a needle biopsy. We successfully collected small liver samples (100-250 mg) from each individual without any recorded mortalities. The incision was fully closed after 10 days post sampling. No significant differences in growth performance were observed between the needle-biopsied and control fish after 10 and 30 days. This technique offers a practical and valuable method for liver sampling, suitable for various research studies without sacrificing and harming fish. This is particularly beneficial for endangered and threatened species.

Acute toxicity of mercury in response to metallothionein expression and oxidative and cellular metabolic stress in Barbonymus gonionotus

Mercury (Hg) is one of the most harmful contaminates posing significant health risks to ecosystems worldwide. Fish, recognized for its affordability and accessibility, serves as a vital source of protein for the global population. To understand the impact of Hg exposure, an experiment was conducted using Barbonymus gonionotus (average weight: 9.64 ± 0.76 g) to determine the median lethal concentration (96 h-LC50) and the definitive dose of Hg. This study employed a static, non-renewable bio-assay to assess acute toxicity, using Hg concentrations of 0.3, 0.4, 0.5, 0.6, and 0.7 mg L⁻¹ in the definitive acute toxicity test. These concentrations were further evaluated for their effects on stress and cellular biomarkers, including metallothionein expression, oxidative stress indicators, histopathology, and bioaccumulation. Metallothionein (MT) expression in the liver was evaluated at 48 and 96 h, while oxidative stress markers were assessed in the liver, gill, kidney, and brain tissues. Additionally, glycolytic enzyme activity in the liver, gill, muscle, and kidney, as well as protein metabolic enzymes in the liver, gill, and kidney, were examined over the 96-hour exposure period to understand the effects of Hg at varying concentrations on B. gonionotus. Histopathological changes in the liver and gill and observed, along with the bioaccumulation of Hg in experimental water and different fish tissues. The study concluded that acute Hg exposure caused significant adverse effects on metallothionein expression, stress biomarkers, and the cellular and metabolic activities of B. gonionotus.

Oviposition Deterrence and Larvicidal Activity of Propyl Ether Dillapiole and Piperidyl Dillapiole Against Aedes (Stegomyia) aegypti (Diptera: Culicidae)

The study of substances of botanical origin is fundamental for the development of new effective alternatives for the control of Aedes (Stegomyia) aegypti (Culicidae), a vector of arboviruses in humans. In this study, the potential of two new dillapiole derivatives, propyl ether dillapiole and piperidyl dillapiole, was tested to determine their ability to deter oviposition and their larvicidal and residual effects against Ae. aegypti under simulated field conditions, as alternatives for the control of this mosquito. The ability of these substances to deter oviposition by pregnant Ae. aegypti females was assessed in the laboratory, and then the larvicide and residual effects of different concentrations were tested under simulated field conditions. The determination of the enzymatic activity in exposed larvae was carried out using sublethal concentrations. The LC50 values of propyl ether dillapiole after 24 and 48 h were 24.60 µg/mL and 14.76 µg/mL, and those of piperidyl dillapiole were 31.58 µg/mL and 24.85 µg/mL, respectively. After 48 h of exposure to aged, treated water, the mortality of propyl ether dillapiole (100 µg/mL) and piperidyl dillapiole (200 µg/mL) fell to 81.7% and 75% on the second day, and to 73.3% and 66.7% on the fourth day, respectively. The concentrations of 100 µg/mL of propyl ether dillapiole and 200 µg/mL of piperidyl dillapiole caused oviposition rates of only 3.80% and 4.63% of the eggs of the females, respectively, compared to 22.01% in the negative control (water and DMSO at 2%). In the larvae exposed to propyl ether, piperidyl dillapiole, dillapiole, or the chemical insecticide temephos (positive control), inhibition of acetylcholinesterase (AChE) occurred. Propyl ether dillapiole and piperidyl dillapiole have potential for use as alternative forms of control of Ae. aegypti, with propyl ether dillapiole being the most promising molecule. Further studies are needed to understand the effects of these substances on this mosquito and on non-target organisms.

Recent developments in conductive polysaccharide adsorbent formulations for environmental remediation: A review

Environmental remediation is crucial for human life and ecosystems, involving the cleanup of contaminated water to protect health and restore ecological balance. However, rapid industrialization and population growth have worsened pollution, particularly in water bodies, making effective wastewater treatment a key challenge in ensuring clean drinking water, and the adsorption of toxic gases for air treatment are the main strategies for environmental remediation. Among the various treatment methods, adsorption stands out for its high selectivity, low energy and chemical use, ease of operation, and cost-effectiveness. To date, innovative, highly efficient, non-toxic, engineered adsorbent materials have received potential interest from scientific and governmental communities. Conducting polymer-modified polysaccharide formulations are crucial in wastewater treatment due to their high surface area, adsorption efficiency, excellent stability, and eco-friendly, biodegradable properties. This review offers an extensive overview of recent progress in synthesizing conducting polymer-modified polysaccharide formulations (hydrogels, aerogels, nanofibers, and nanocomposites) for capturing toxic heavy metal ions, organic dyes, pharmaceuticals, phenols as well as adsorbing different toxic gases using various adsorption mechanisms. It also emphasizes the integration of different nanofillers, including carbon-based materials, Mxenes, nanoclay, metal/metal oxides, and hybrid nanomaterials, into conductive polysaccharide chains to improve their physicochemical properties and adsorption efficiency. The reported data showed that these engineered adsorbent materials based on conductive polysaccharide formulations have immense potential for wastewater treatment applications, offering more effective and sustainable solutions.

Contaminant bioaccumulation and biochemical responses of the bivalve Scrobicularia plana and the polychaete Hediste diversicolor to ecosystem restoration measures using Zostera noltei

A Nature-based Solution (NbS) using Zostera noltei transplants was implemented to restore an area historically contaminated with metals and enhance local environmental conditions. However, the benefits of this restoration approach on the health of resident benthic communities remained unclear, considering the time span of one year of implementation. This study evaluated the short-term effects of transplantation by evaluating bioaccumulation and biochemical responses in Scrobicularia plana and Hediste diversicolor. Overall, the transplanted vegetation played a crucial role in controlling contaminant accumulation, with both species exhibiting lower contaminant levels in vegetated sites compared to bare-bottom sites. The study also revealed species-specific responses to oxidative stress, antioxidant defences and energy budgets, with H. diversicolor being more vulnerable to the absence of vegetation than S. plana. These findings highlight the critical role of vegetation in improving environmental quality and promoting the health of benthic communities, validating the positive effect of the applied restoration measures.

Effects of Difenoconazole on Tubifex tubifex: Antioxidant Activity, Insights from GUTS Predictions, and Multi-Biomarker Analysis

The increasing demand for agricultural products has led to a rise in pesticide use, resulting in the pollution of aquatic habitats and raising significant health concerns for both aquatic life and humans. Difenoconazole, a triazole fungicide, is becoming increasingly popular in agriculture, yet its effects on non-target organisms, such as annelids, are not well understood. This study aimed to investigate the toxicological effects of difenoconazole and assess its potential impact on toxicity biomarkers, using Tubifex tubifex as a model organism, to better understand the ecotoxicity of difenoconazole on freshwater annelids. The 96-h LC50 value of difenoconazole was determined to be 2.68 mg/L. Sublethal concentrations (10% and 20% of the 96-h LC50 value; 0.268 and 0.536 mg/L, respectively) caused significant changes in the activities of oxidative stress enzymes. A concentration- and time-dependent decrease in the activities of superoxide dismutase (SOD), catalase (CAT), and glutathione transferase (GST) was observed compared to control organisms. Additionally, malondialdehyde (MDA) concentrations increased throughout the exposure period. An Integrated Biomarker Response (IBR) assessment was used to characterize and illustrate the impact of difenoconazole on T. tubifex. In conclusion, exposure to this fungicide appears to reduce the survival rate of T. tubifex at acute levels and disrupt its normal behavioral patterns. Moreover, it alters oxidative stress enzyme levels during sublethal exposure. Long-term exposure to the fungicide could potentially have population-level consequences, including a reduction in the number of individuals within a population.

Influences of parasitic stress on the health condition of African Catfish (Clarias gariepinus): Biochemical and histopathological alterations

This study investigates the prevalence, severity, and impacts of parasitic infestations in Clarias gariepinus. Additionally, the study assesses the detrimental impacts of parasite infestation on the health condition of affected catfish, focusing on biochemical and histopathological alterations. A total of 160 fish were sampled from local markets. Parasitological examinations involved the dissection of key organs from each fish. The organs were processed and examined microscopically for parasites identified based on morphometric characteristics. Parasitological indices such as prevalence, mean intensity, and abundance were calculated. Fish blood and liver samples were collected to assess hematological and biochemical parameters. Microscopic and ultrastructural examinations identified the gills and liver as highly infected organs, so they were utilized for transmission electron microscopy (TEM). Analysis of catfish tissues unveiled the existence of Cyathocotylid sp. and Prohemistomum vivax, across all organs with dominance noted in the liver, emphasizing their pathogenic significance and notable ability to invade and establish within multiple organs or the immunocompromised response of the host. Meanwhile, Centrocestus formosanus and Quadriacanthus aegyptiacus were exclusively detected in the gills, with an overall parasitic infection rate of 60 %. The present study is one of the few studies documenting Centrocestus sp. in catfish which reflects its ability to spread in new hosts and environments. A novel morphological dimension was recorded for the recovered metacercariae. The hematological, along with the identified lesions from light histological and TEM examinations in heavily infected catfish, indicate the detrimental impact of parasite infiltration on fish health status. Besides the biochemical biomarkers were significantly (p ≤ 0.05) affected by increasing the degree of infection. This study underscores the profound influence of parasitic infestations on the health of C. gariepinus, emphasizing the urgent need for effective management strategies in aquaculture to mitigate these effects, the spread of new pathogens, and ensure the sustainability and productivity of catfish farming. By integrating parasitological, morphological, histopathological, and biochemical analyses, this research provides valuable insights that contribute to better health management strategies in aquaculture and a deeper understanding of parasite biology.

Revealing hidden risks: in vitro analysis of PFAS hazards in Mytilus galloprovincialis gills and digestive gland

Per- and polyfluoroalkyl substances (PFAS) are synthetic chemicals known for their persistence and bioaccumulation, leading to widespread environmental contamination. Despite their recognised environmental risks, particularly to aquatic wildlife, including marine invertebrates, detailed impact studies are limited. PFAS can be categorised according to the length of the compound chain, with short-chain PFAS announced as a safer alternative to the more commonly used long-chain PFAS. However, recent evidence suggests that also short-chain PFAS pose significant environmental risks. The present study evaluated the adverse effects of six PFAS compounds-two short-chain (PFHxA, 6:2 FTA) and four long-chain (PFUnDA, PFDoA, PFTriDA, PFTeDA)- on the digestive gland and gills of mussels, Mytilus galloprovincialis, using in vitro assays. The results showed organ-specific responses: the digestive gland was more sensitive to PFHxA, with increased catalase activity and decreased total antioxidant capacity, and cellular damage was observed only at higher concentrations of PFTriDA. Gills were more affected by PFDoA and PFTeDA, with inhibited antioxidant enzyme activity and increased oxidative stress. PFHxA and PFTriDA also showed inhibition of acetylcholinesterase activity. 6:2 FTA had the lowest effects for both organs, while PFHxA was the most harmful. These findings underscore the need for thorough risk assessments of PFAS, considering both chain length and organ-specific effects.

Tissue bioaccumulation and distribution of organic contaminants in Brazilian guitarfish Pseudobatos horkelii reveal a concerning impact of contraceptive hormones and fecal sterols

The critically endangered Brazilian guitarfish faces significant threats from environmental contamination. Assessing the impacts of such stressor is paramount from a conservational perspective. This study investigated the concentrations, distribution and accumulation patterns of organic contaminants in pregnant Brazilian guitarfish Pseudobatos horkelii. Blood, gill, gonad, liver, and muscle concentrations of polychlorinated biphenyls (PCBs), organochlorine pesticides (OCPs), polybrominated diphenyl ethers, fecal sterols, and synthetic hormones used as human contraceptives were assessed. Synthetic hormones, especially D-norgestrel, showed the highest concentrations, mainly in the liver. Together with the results of fecal sterols, this finding suggests that guitarfish are exposed to sewage discharge. OCPs, especially hexachlorobenzene, mirex, endosulfans, and drins, showed considerably high concentrations, indicating the relevance of agricultural inputs. PCBs presented significant concentrations in the muscle, indicating long-term exposure, in contrast with other analytes that were primarily concentrated in the liver. These results have conservational implications, since contaminants analyzed herein have endocrine disruptive effects.

Subchronic exposure to nonylphenol ethoxylate (NPE) induces cardiotoxicity and oxidative stress in American bullfrog tadpoles: a mechanistic approach

Tropical regions, particularly those with high levels of endemism such as South America, harbor a diverse array of amphibian species. However, these regions often lack specific regulations governing the release of emerging contaminants, including the surfactant nonylphenol ethoxylate (NPE), into water bodies, which can have devastating consequences for these sensitive ecosystems. This study evaluated the sublethal effects of 16-day subchronic exposure to NPE at an environmentally relevant concentration of 30 µg/L on American bullfrog (Lithobates catesbeianus) tadpoles using multiple endpoints, including biometric parameters, antioxidant responses, oxidative stress biomarkers, heart rate, and myocardial contractility. Our results revealed that exposure to NPE elicited a range of harmful effects on tadpoles, including significant reductions in hepatic and ventricular mass, disruptions in antioxidant defenses leading to oxidative stress-mediated damage in cardiac, hepatic, and muscular tissues, and changes in heart function such as negative inotropism and lusitropism, and tachycardia. These sublethal effects could have significant ecological impacts, affecting not only immediate survival but also compromising overall fitness through the reallocation of energy reserves.

Activity pattern of antioxidant enzymes in relation to the time of exposure of hexavalent chromium to Nile tilapia Oreochromis niloticus

Hexavalent chromium (Cr (VI)), a toxicant of environmental concern, frequently enters into water bodies and produces oxidative stress in fish. The antioxidant enzymes, Superoxide dismutase (SOD), Catalase (CAT), and Glutathion S-transferase (GST) are activated to counteract the oxidative stress in fish. This study explores the pattern of activation of these enzymes in gill, muscle, liver, and kidney tissues of Nile tilapia Oreochromis niloticus exposed to 9.35 mg/L and 18.70 mg/L of Cr (VI) for 96 h. The optimal hour of activity of these enzymes was revealed through extensive regression analysis. The results indicate a bell-shaped time response curve in the activity of the enzymes in both the treatments, except CAT in the gill of fish exposed to 18.70 mg/L Cr (VI) and GST in the gill, liver, and kidney of fish exposed to 18.70 mg/L Cr (VI). The results indicate that the optimal hour of activity of SOD changes in tandem with CAT, SOD responding first followed by CAT, both diminishing within 96 h. However, deviating from the bell-shaped pattern, the activity of CAT in gill and GST in gill, liver, and kidney in fish exposed to 18.70 mg/L Cr (VI) continued to rise even at 96 h, indicating that these antioxidant enzymes could not diminish the oxidative stress produced by the higher dose of Cr (VI). It was concluded that the activity of SOD, CAT, and GST between 30 and 70 h in the gill, liver, and kidney of Nile tilapia could serve as excellent biomarkers of oxidative stress under low doses of Cr (VI).

Multi-biomarker approach to assess the toxicity of carbamazepine, a neuropharmaceutical, in the female fish Astyanax lacustris (Teleostei: Characidae)

Carbamazepine (CBZ) is a pharmaceutical commonly used in the treatment of epilepsy and bipolar disorder and has been detected in different aquatic ecosystems worldwide. Considering its possible role in altering nervous system and reproduction, this study aimed to evaluate the effects of CBZ on molecular and cellular biomarkers of the teleost Astyanax lacustris. Results demonstrated that CBZ, in environmentally relevant concentrations (500 ng L-1) increases fshβ gene expression levels, decreases muscle protein content and hepatic LPO (500 ng L-1 and 1250 ng L-1 of CBZ). Nonetheless, no effects were observed towards enzymatic activities, steroid plasma levels and/or lipid content. Considering that A. lacustris inhabits clean and polluted environments, it is possible to suggest that animals possess a level of tolerance to stressors, allowing them to maintain reproductive functions regardless of environmental challenges.

From wetlands to landfills: white stork (Ciconia ciconia L., 1758) as a reliable bioindicator of ecosystem health

White storks (Ciconia ciconia L., 1758) and their nestlings have emerged as valuable bioindicators of environmental pollution, particularly in ecosystems affected by human activities. This review explores the role of white storks in biomonitoring, focusing on the use of biomarkers and pollutant analysis to understand the physiological consequences of environmental stressors. Key biomarkers, such as oxidative stress markers, immune responses, and hormonal alterations provide insight into the effects of pollutants like heavy metals, pesticides, and other toxic compounds. The biomarkers are typically measured in matrices such as blood, feathers, eggs, and tissues, each offering unique advantages in assessing pollutant exposure. However, ethical concerns regarding wildlife monitoring and the potential harm caused by invasive sampling techniques call for non-invasive methods. Future research should explore novel non-invasive techniques and employ long-term monitoring programmes to understand the cumulative effects of pollution. Despite challenges such as biological variability and environmental factors, white storks remain reliable indicators of ecological change and pollutant burden, providing critical data that can guide pollution management policies, inform conservation strategies, and protect both wildlife and human health from current environmental threats.

Development of zebrafish (Danio rerio) mesh-type model at multi-life stages and Monte Carlo simulations of dosimetric parameters

As socioeconomic development progresses, nuclear energy and technology advance rapidly. Concurrently, nuclear accidents may result in the release of additional radioactive isotopes into the environment. Groundwater and oceans are key pathways for radioactive nuclides in the environmental cycle, with aquatic organisms being particularly vulnerable to radiation exposure. Aquatic model organisms are essential for studying radiation effects on non-human species in aquatic environments and for extrapolating dose-response relationships to humans. However, current models for calculating radiation doses in the aquatic model organism zebrafish remain underdeveloped. To better elucidate the mechanisms of radiation damage effects, integrating Micro-CT and 3D modeling techniques, a series of zebrafish mesh-type models (including adults and larvae, named zebrafish-mesh family: ZF-mesh family) with multiple internal organs are established in this study. The Monte Carlo software PHITS is used to simulate and calculate the Absorbed Fractions (AFs) and S-values for single-energy electrons ranging from 0.001 to 10 MeV, single-energy photons from 0.001 to 5 MeV, and eight radioactive nuclides commonly found in nuclear power plant liquid effluents: 3H, 14C, 90Sr, 106Ru, 134Cs, 137Cs, 60Co, 131I, across various source-target organ configurations. The results indicate that the mesh-type models of zebrafish at multiple developmental stages can be used for radiation dosimetry calculations. Analysis of the dosimetry parameter database, established through Monte Carlo calculations with this series of mesh-type models, shows that the maximum difference in self-AFs between the geometric and curved models reaches 52.8%. Comparisons between models at different developmental stages show that the impact of radioactive nuclides on internal organs depends on both the decay properties of the nuclides and the organ volumes. For adult fish, the dose contribution from 90Sr is most significant, reaching up to 1.81 ×10-5mGy·MBq-1·s-1 in the heart of male fish. In larvae fish, 14C has the most notable impact, with a dose rate of 4.38 ×10-3mGy·MBq-1·s-1 in the heart at 48 h post-fertilization (hpf). Comparisons of yolk mass changes at various developmental stages in larvae fish reveal that organ location is a key factor influencing self-AFs. This influence is often more significant than the variations caused by changes in organ volume. Due to the small size of zebrafish organs, the increase in energy deposition caused by secondary electrons is not evident in adult fish. In the smallest larvae hearts, no increase in energy deposition is observed. In summary, detailed surface modeling of model organisms across multiple developmental stages and the establishment of a comprehensive dosimetric parameter database are crucial. This approach significantly improves the reliability of radiation impact assessments for non-human species.

Sex-specific reproductive impairment in Pacific oysters (Magallana gigas) exposed to TiO2 NPs: A focus on gonadal status

Environmentally realistic concentrations of titanium dioxide nanoparticles (TiO2 NPs) are considered reprotoxic for marine bivalves. However, further investigation is needed to understand their impact on gonadal health, particularly concerning sex-specific responses. Thus, this study aimed to understand sex-based effects of TiO2 NPs environmentally realistic concentrations in the gonad of Pacific oysters (Magallana gigas). Oysters were exposed to 10 and 100 μg·L-1 of TiO2 NPs for 3 and 7 days. Morphological parameters (condition index, sex and gametogenic stage), energy-related responses (carbohydrates, lipids, proteins, and electron transport system (ETS) activity), digestive function (alpha-amylase activity), and oxidative stress profile (antioxidants and damage) were assessed to address gonadal status. The results revealed sex-specific responses based on duration and concentration. Females reflected a drop in carbohydrate levels after 3 days at 100 μg·L-1, suggesting mobilization of this energy reserve to counteract TiO2 NP effects, followed by recovery after 7 days. Males showed reduced metabolic activity after 3 days at 10 μg·L-1, marked by ETS depletion, independently of oxidative stress demonstrating a compensatory response to TiO2 NP exposure. After 7 days, both concentrations triggered male lipid peroxidation despite carbohydrate mobilization at 10 μg·L-1, indicating oxidative damage in testes. These findings revealed that TiO2 NPs are reprotoxic for male oysters at 10 μg·L-1, through oxidative stress pathways, while females reflected vulnerability to 100 μg·L-1. This study provides valuable insights into understanding TiO2 NP's reprotoxicity at environmental concentrations, highlighting gonads as a target for these NPs, and their potential risks to marine bivalves.

Pesticide and hydrocarbon toxicity in fish: effects on Chelon labrosus (Risso, 1827) along the northeastern Sicilian coast (Italy) evaluated by enzymatic biomarkers

Pesticides intoxication affects aquatic organisms as well as a group of contaminants that are represented by crude oil, petroleum hydrocarbons (PHs), polycyclic aromatic hydrocarbons (PAHs) and their derivatives. Useful tools for ecotoxicological studies of marine ecosystems are based on biomarker application on bioindicator key fish species. The aim of the present study was to highlight the presence of pesticides and hydrocarbons in a coastal marine environment, the harbour of Capo d'Orlando town (northeastern Sicily, Italy), by using the ecotoxicological biomarker Acetylcholinesterase (AChE) and Butyrylcholinesterase (BChE) enzymatic activities in the key fish species Chelon labrosus. A reference site was selected. Chemical analysis of water samples was also carried out to analyze and eventually confirm the presence of pesticides in the study area. Results showed significant inhibition in AChE (80%) and BChE (77%) activities in fish from the harbour of Capo d'Orlando compared to the reference site. The esterase inhibition is primarily due to the presence of organophosphorus insecticides and carbamates, that resulted in higher concentrations of contaminants in the water of the harbour of Capo d'Orlando compared to the reference quality standard decree (Ministerial Decree 260, 2010). This study highlighted the contamination by insecticides and most probably by hydrocarbons in fish from the harbour of Capo d'Orlando, which also represents a threat to the human population consuming affected fish.

In situ synthesis of a UIO-66-NH2@Ti3C2 composite for advanced electrochemical detection of acetaminophen

Acetaminophen (AP) is a widely used analgesic and antipyretic drug, but its excessive use poses health risks and contributes to environmental contamination. In response to the need for rapid, accurate, and cost-effective detection methods, we developed a highly sensitive and selective electrochemical sensor for AP. The sensor was based on a composite of UIO-66-NH2 (UN) and an MXene (Ti3C2). UIO-66-NH2 was in situ synthesized onto the MXene via a one-step hydrothermal process with a varying MXene content, followed by calcination at 300 °C under an argon (Ar) flow. This treatment induced the formation of TiO2 on the MXene surface and increased the interlayer spacing, which enhanced its electrochemical performance. The resulting UN@Ti3C2-C electrode exhibited remarkable electrochemical activity due to the high surface area and excellent conductivity of the MXene. The fabricated sensor demonstrated a simple yet effective approach for the rapid and quantitative detection of AP, with a linear detection range of 0.032-160 μM and a low detection limit of 10 nM. Moreover, the sensor was successfully applied to detect AP in different water samples, validating its potential as a reliable and efficient tool for AP monitoring.

Molecular Response and Metabolic Reprogramming of the Spleen Coping with Cold Stress in the Chinese Soft-Shelled Turtle (Pelodiscus sinensis)

The Chinese soft-shelled turtle (Pelodiscus sinensis), as a type of warm-water reptile, could be induced to massive death by sharp temperature decline. Hence, the mechanism of spleen tissue responding to cold stress in the P. sinensis was investigated. The present results showed that the superoxide dismutase (SOD) activity declined from 4 to 16 days post-cold-stress (dps), while the catalase (CAT) and glutathione peroxidase (GSH-Px) activities increased, from 4 to 8 dps in the 14 °C (T14) and 7 °C (T7) stress groups. The spleen transcriptome in the T7 group and the control group (CG) at 4 dps obtained 2625 differentially expressed genes (DEGs), including 1462 upregulated and 1663 downregulated genes. The DEGs were enriched mainly in the pathways "intestinal immune network for IgA production" (Pigr, Il15ra, Tnfrsf17, Aicda, and Cd28), "toll-like receptor signaling pathway" (Mapk10, Tlr2, Tlr5, Tlr7, and Tlr8), and "cytokine-cytokine receptor interaction" (Cx3cl1, Cx3cr1, Cxcl14, Cxcr3, and Cxcr4). The metabolomic data showed that esculentic acid, tyrosol, diosgenin, heptadecanoic acid, and 7-ketodeoxycholic acid were obviously increased, while baccatin III, taurohyocholate, parthenolide, enterolactone, and tricin were decreased, in the CG vs. T7 comparison. Integrated analysis of the two omics revealed that "glycine, serine and threonine metabolism", "FoxO signaling pathway", and "neuroactive ligand-receptor interaction" were the main pathways responding to the cold stress. Overall, this work found that low temperature remarkably influenced the antioxidant enzyme activities, gene expression pattern, and metabolite profile in the spleen, indicating that immunity might be weakened by cold stress in P. sinensis.

Characterization of acetylcholinesterase and carboxylesterases in the mangrove oyster Crassostrea gasar as biomarkers of exposure to environmental pollutants

Brazil is one of the world's leading consumers of agricultural pesticides, highlighting the urgent need to identify responsive biomarkers as diagnostic and prognostic tools for monitoring aquatic pollution. Acetylcholinesterase (AChE) and carboxylesterases (CbE) are B-esterases enzymes expressed in several organisms. AChE plays an essential role in neural transmission at cholinergic synapses, while CbE are directly involved in the detoxification of organic pollutants, including organophosphorus pesticides. The activities of AChE and CbE in bivalves have not been extensively investigated, despite their suitability as sentinel organisms for environmental monitoring. In this study, we characterized the activities of AChE and CbE in the mangrove oyster Crassostrea gasar, collected from an estuarine system in southern Brazil. We compared enzymatic activities between the gills and the digestive gland, revealing that CbE activity was significantly higher in the digestive gland, while AChE activity did not differ between the two tissues. These results indicate that the digestive gland functions as the primary metabolic organ in C. gasar. Additionally, we observed notable differences in CbE activity depending on the substrate used: ρ-nitrophenyl acetate (ρNPA), ρ-nitrophenyl butyrate (ρNPB), α-naphtyl acetate (αNA), and α-naphtyl butyrate (αNB). Our findings suggest that more lipophilic substrates are metabolized more rapidly in both the digestive gland and gills. These results enhance our understanding of the biotransformation processes and neurotoxicity potential of pesticides in oysters. However, further in vitro validation is needed to confirm the utility of these biomarkers for monitoring environmental pollution in coastal waters.

Bioaccumulation and genotoxic effect of heavy metal pollution in marine sponges from the Niger Delta

In this study, levels of Al, Cu, Ni, Cd, Cr and Pb were quantified in seawater, sediments, and sea sponges from six sites in the Niger Delta and one relatively clean site outside the Niger Delta area using Inductively Coupled Plasma Optical Emission Spectroscopy and Inductively Coupled Plasma Mass Spectrometry. The metal levels in sponge tissues in μg/mg ranged from 0.22 ± 0.03-0.70 ± 0.10 (Al), 0.002 ± 2.2 × 10-5 - 0.004 ± 5.6 × 10-5 (As), 2 × 10-5 ± 5.3 × 10-6 -1.5 × 10-3 ± 4.6 × 10-6 (Cd), 2.3 × 10-3 ± 1.4 × 10-5 -0.02 ± 2,2 × 10-4 (Cu), 2.5 × 10-4 ± 8.6 × 10-6- 2.0 × 10-3 ± 1.4 × 10-5 (Pb). In Sediment samples in mg/kg, the ranges were (0.883 ± 0.114-73.33 ± 0.10 (Al), 0.0007 ± 0.026-0.304 ± 0.009 (As),0.0086 ± 0.0045-0.198 ± 0.010 (Cr); 0.005 ± 0.001-0.063 ± 0.001 (Cu), 0.039 ± 0.004-0.0783 ± 0.0024(Ni), 0.0017 ± 0.002-0.056 ± 0.0046 (Pb). In the water sample, the metal levels in mg/L 0.06-0.92 (Al), 0.001-0.007 (Cd), 0.001-0.001 (Cr), 0.01-0.02 (Cu), 0.003-0.01 (Ni), 0.001-0.01(Pb). Metal levels in all sampling sites occurred in the order of decreasing concentration as Al > Cu > Ni > Cd > Cr > Pb (in seawater), Al > Cr > Ni > Pb > Cu > Cd (in sediment) and Al > As>Cu > Pb > Cd (in the sponge). The study further assessed DNA strand breaks in sea sponges as a biomarker of genotoxicity using the comet assay. There was a strong correlation between % DNA strand breaks in sponge cells from all sample locations and aluminium levels in sponge tissues from all sample locations. The highest metal levels were recorded in Sea sponges, followed by Sediment and then Sea water, with aluminium significantly higher than other metals in all three matrices studied. We, therefore, conclude that sea sponges are excellent sentinel species for toxic metal bioaccumulation, and DNA strand breaks are an efficient biomarker for aquatic pollutants biomonitoring.

2-Ethylhexyl-4-methoxycinnamate on marine and coastal environments: A comprehensive review of its environmental significance and biological impact

Marine and coastal environments are constantly subjected to increasing pressures associated with population growth, industrialization development, pollution and higher demand feeding society's consumerism. Among these pressures, there has been an increasing concern towards UV filters occurrence in aquatic ecosystems due to a greater use of personal care products (PCPs). 2-ethylhexyl-4-methoxycinnamate (EHMC) is one of the most used UV filters in sunscreen formulations, yet few reports address its effects in biota. This literature review intends to collect the available information concerning the environmental presence of EHMC in marine and coastal ecosystems and their effects in biota. The EHMC effects have been reported for the taxonomic groups: Actinomycetes, Alphaproteobacteria, Bacilli, Cytophagia, Flavobacteriia, Gammaproteobacteria, Actinopterygii, Anthozoa, Bacillariophyceae, Bivalvia, Branchiopoda, Coccolithophyceae, Echinoidea, Gastropoda, Malacostraca, Annelida and Thecostraca. The reported literature evaluated endpoints mainly related to development, viability, mortality, estrogenicity, gene transcription disruptions, biochemical alterations and morphophysiological changes. Based on the available information, there is still a clear need for further investigations related to EHMC and its toxicological effects on marine and coastal organisms.

Histopathology and genotoxicity alterations in high Andean catfishes from the Upper Orinoco River Basin, Colombia

Freshwater ecosystem pollution has motivated an extensive list of studies due to deleterious impacts becoming a threat to aquatic organisms that inhabit these environments. This is the first approach to water pollution impact derived from human activities on native ichthyofauna in the Garagoa river basin in Boyacá (Colombian Andes). Therefore, the aim of the present study was to evaluate the occurrence of mercury and arsenic in catfishes and armored catfishes from the Garagoa River basin and the presence of hepatic alterations and genotoxicity in peripheral blood. Biomarkers of effect were analyzed in fishes caught in eight tributaries from Garagoa river basin. The increased presence of lesions in the hepatic architecture and nuclear abnormalities in peripheral blood erythrocytes in Dolichancistrus fuesslii, Chaetostoma joropo, Astroblepus latidens and Trichomycterus cf. knerii individuals could be associated with exposure of pollutants. The tissue alterations observed compromise the fish health, due to the biotransformation processes of xenobiotics such as mercury and arsenic and probably other contaminants. We need to increase surveillance in the Garagoa River to ensure ecological health, recognize hematological and tissue effects in native fishes, and develop effective monitoring strategies to mitigate sources of pollution.

Physiological responses of pacu (Piaractus mesopotamicus) to intermittent cold exposure: A comprehensive analysis of stress, immunity, antioxidant, and metabolic adaptations

This study examined the energy-dependent physiological responses, including stress, innate immune, and antioxidant systems, as well as indicators of energy mobilization, in pacu (Piaractus mesopotamicus) exposed to intermittent cold, aiming to assess the correlations between these responses. The fish were acclimated to 28 °C, divided into two groups, a control group maintained at 28 °C, and another exposed to 16 °C for two 24 h periods with a 5-day interval between them. The fish were sampled at six time points: baseline (after acclimatization to 28 °C), 24 h after the 1st exposure to 16 °C, after 5 days of recovery at 28 °C, 24 h after the 2nd exposure to 16 °C, and after 24 and 48 h of recovery at 28 °C. The reduction in temperature activated the stress response, the innate immune system, and the antioxidative system as well as mobilized lipids from the visceral stores and preserved the circulating levels of triglycerides. Intermittent exposure of fish to cold increased plasma cortisol after both exposures, activated leukocyte respiratory activity after the 2nd exposure, and triggered the compensatory lysozyme response after temperature recovery in both cold exposures in addition to increasing the number of circulating monocytes and granulocytes. The activity of the enzymes catalase (CAT) and superoxide dismutase (SOD) increased after the 1st and 2nd cold exposures, respectively. Glutathione peroxidase (GPx) activity increased after the 2nd exposure compared to the control. The subtropical fish pacu was sensitive to intermittent cold exposure and was able to display protective physiological responses.

Active biomonitoring of river pollution using an ex-situ exposure system with two model species

In the context of increasing pollution pressure on aquatic ecosystems, it is essential to improve our knowledge of habitat quality and its suitability for organisms. It is particularly relevant to better integrate early life stages of fish into pollution biomonitoring programs, as they are reliable indicators of ecosystem integrity and because of their high sensitivity to pollutants. To avoid the influence of environmental parameters on their development, a lab-on-field approach, called the ex-situ exposure method, was developed. Aquatic organisms were exposed to a continuous flux of water under semi-controlled temperature, oxygen, and photoperiod conditions to avoid the influence of these confounding factors when interpreting the results. To investigate the potential role of water contamination, this active biomonitoring method was applied to the Garonne River (Southwest France), where migratory fish populations have declined. Two model species from different taxa were used: embryos of the Japanese medaka (Oryzias latipes) and adults of the crustacean Gammarus fossarum. The results showed a significant impact of water quality on embryo mortality and early hatching in two separate experiments on Japanese medaka. In addition, an induction of feeding rate was observed in exposed gammarids, but no impact on their embryo survival, suggesting differences in sensitivity between the two species selected. Chemical and biological analyses did not identify trace metals, pesticides, or microorganisms as potential sources of toxicity in medaka embryos or G. fossarum. These results raise concerns about the quality of the water in the Garonne River and its toxicity to aquatic organisms.

The influence of ammonia-N and salinity levels on oxidative stress markers, hepatic enzymes, and acid phosphatase activity in Nile tilapia (Oreochromis niloticus)

The point of our study was to examine the interaction of ammonia-N poisoning and salinity on serum enzymes and oxidative stress factors of blood and liver in Nile tilapia (Oreochromis niloticus). The 50% lethal concentration (LC50) in 96 h was 0.86 mg/L of ammonia-N. A random allocation was used to divide the fish into 12 treatments. These treatments encompassed various combinations of acute ammonia-N levels (0 and 50% of LC50-96 h), sub-acute ammonia-N levels (30% of LC50-96 h), and salinity levels (0, 4, 8, and 12 ppt). The experimental design employed a factorial arrangement of 3 × 4.The findings revealed that the amounts of aspartate transferase (AST) and alanine transaminase (ALT) in treatments 3 and 4 increased significantly compared to the treatment 2 (4 ppt) and control. Salinity levels did not affect serum glutathione levels (GSH), nevertheless the reduction of serum GSH and levels of total antioxidant capacity (TAC) and superoxide dismutase (SOD) and catalase activities (CAT) in ammonia poisoning treatments, 5 and 9, compared to the control, states ammonia can stimulate oxidative stress in fish. Similar to the serum measurements, increasing salinity in acute ammonia poisoning treatments (5, 6, 7 and 8) caused an increasing effect on the liver TAC value, which was presumably due to the improving effect of salinity in reducing ambient ammonia. The findings indicate that while elevated salinity levels can be beneficial in mitigating the effects of ammonia toxicity in water, the combined presence of salinity, ammonia, and their interaction had detrimental impacts on the physiological well-being of fish over a 96-hour testing period.

Elevated temperature increases the susceptibility of D. magna to environmental mixtures of carbamazepine, tramadol and citalopram

The joint risks assessment of thermal stress and rising loads of pharmaceuticals (PhACs) in surface waters is a relevant topic in aquatic ecotoxicology. This study investigated the relevance of increased water temperature to alter the acute toxicity of environmentally relevant carbamazepine (CBZ), citalopram (CIT) and tramadol (TRA) concentrations as mixtures (ECs) and delayed outcomes in Daphnia magna. Responses of detoxification and antioxidant pathways in premature daphnids post an acute 24 h (pulsed) exposure to the PhACs mixtures and delayed responses as the reproductive output over 14 days recovery were investigated under 21- and 26 °C incubation. Biphasic modulation in glutathione S-transferase (GST) activity and significant inhibition of superoxide dismutase (SOD) activity were observed in both thermal regimes with significant shift in effective thresholds from 10-fold ECs at 21 °C to ECs at 26 °C incubation. Significant induction in catalase (CAT) activity and oxidative stress development were recorded at elevated temperatures from the 10-fold ECs dose onward. Pulsed exposures at 26 °C also led to significant decrease in the reproduction of daphnids above the 10-fold ECs of PhACs. The Integrated Biomarker Response scoring (IBRv2) approach outlined a 1.8-fold increase in alterations of daphnids exposed to 100-fold ECs of PhACs at 26 °C.

Shark-on-a-dish: Elasmobranch cell cultures as a promising tool for the conservation of threatened species

Anthropogenic activities have increasingly contaminated aquatic ecosystems worldwide, requiring the development of adequate methods to assess the effects of environmental pollution on aquatic biota. Currently, ecotoxicological research on fish is largely based on in vivo studies, many times using post-mortem fish samples bought in fish markets or obtained through capture-and-release programs. However, such samples provide a narrow window to the cellular and molecular processes that occur to fish upon exposure to pollutants and other toxicants or pathogens. In thi sense, in vitro cell culture systems have been increasingly proven a valuable tool in several research fields, from molecular biology studies to conservation efforts. To date, however, cell cultures obtained from bony fish have been the most studied and with the best-described protocols and models. Elasmobranchs, comprising shark and rays, play important trophic and environmental roles, employed as chemical contamination environmental sentinels, suffering the effects of such contamination due to bioaccumulation and biomagnification processes. For these reasons, the development of new experimental tools to study elasmobranch cellular and molecular responses to environmental stimuli in controlled conditions is highly desirable. However, only some research groups have attempted to develop elasmobranch cell culture protocols to be used in an ecotoxicological context. In this sense, this review discusses the current elasmobranch cell culture scenario, its importance and potential applications in ecotoxicology assessments and conservation actions.

Does temperature influence on biomarker responses to copper exposure? The invasive bivalve Limnoperna fortunei (Dunker 1857) as a model

Biomarkers are useful tools for assessing the early warning effects of pollutants. However, their responses can be influenced by confounding factors. In this study, we investigated the influence of temperature on multiple biomarkers in the invasive freshwater bivalve Limnoperna fortunei exposed to copper (Cu). The mussels were exposed to low and high environmental Cu concentrations at two temperatures (15 °C and 25 °C). After 96 h, the oxidative stress, neurotoxicity, and metabolic parameters were assessed. Our results showed that temperature is a key factor influencing biomarker responses in mussels, with higher glutathione S-transferase activity and lower energy reserves at cold temperature. In addition, the effects of Cu were greater at the highest concentration at 15 °C (increased lipid peroxidation and cholinesterase activity). Overall, these findings suggest that cold stress increases the susceptibility of L. fortunei to metal effects and highlight the importance of including temperature in toxicity testing and biomonitoring. In addition, using the invasive bivalve L. fortunei as a model could prove valuable in its role as a sentinel species for other organisms.

Toxicity effects of hexavalent chromium on hematological, biochemical and digestive enzyme profiles of Labeo rohita (Hamilton, 1822)

The study provides a descriptive understanding of the toxic effect of heavy metal chromium on the hematological, biochemical, and digestive enzyme profiles in the fingerlings of Labeo rohita. The 96-h LC50 of hexavalent chromium was found to be 15.76 mg/L. Further, the toxicity study was conducted with four different sub-lethal concentrations of 96-h LC50 viz. 1/40th, 1/20th, 1/10th, and 1/5th respectively. The blood samples from the control and treated groups exposed to different concentrations were examined for various physiological parameters. The obtained data showed that, with the increase in sub-lethal concentration, a significant decrease (p < 0.05) in red blood cell (RBCs), hemoglobin (Hb), and hematocrit (Hct) was observed, while total white blood cell (WBCs), mean corpuscular volume (MCV), and mean corpuscular hemoglobin (MCH) increased significantly (p < 0.05) in all the treatments. Fishes exposed to chromium for 30 days responded by becoming hyperglycemic, hyperproteineric, and hypoalbuminemia with a gradual rise in concentrations. Alteration in the intestinal digestive enzyme profiles was also observed after 30 days of study. The activity of protease (89.76%), and amylase (41.88%) decreased in the intestine with the highest concentration compared to the control. Conversely, compared to the control, the highest concentration resulted in an increase (146%) in lipase activity. Overall, this study has greatly enhanced our comprehension of the impact of chromium toxicity on various hematological, biochemical, and digestive enzyme parameters in Labeo rohita.

Use of biomarkers in bullfrog tadpoles Aquarana catesbeiana (Shaw 1802) for ecotoxicological evaluation of Pirajibú River (São Paulo, Brazil)

This study focused on investigating the water quality in the Pirajibú River, a relevant water body that flows through the industrial zone of Sorocaba (São Paulo/Brazil). Due to the limitations of assessing water quality based solely on standard physicochemical tests, an ecotoxicological approach was used to assess biomarker changes in the liver of bullfrog tadpoles (Aquarana catesbeiana). The animals were divided into groups and exposed to water samples collected upstream and downstream of the industrial zone. After 96 h, the upstream group presented a decrease in the enzymatic activity of glutathione peroxidase (GPx) and superoxide dismutase (SOD) and an increase in the activity of catalase (CAT). For the downstream group, while a decreased activity was observed for SOD, an increase in CAT and glutathione S-transferase (GST) activities was noted. A decrease in lipid peroxidation (LPO) levels was observed in the downstream group, and increased carbonyl protein (PCO) levels in the upstream and downstream groups. Integrated Biomarker Response (IBR) revealed GSH and PCO as the most responsive biomarkers, despite the lack of differences noted between the groups. Regardless of whether the water quality standards of Pirajibú River were following Brazilian environmental legislation, the tadpoles presented high sensitivity when exposed to the water, even for a short period.

Toxicity assessment of effluent from a potato-processing industry in Cyprinus carpio

Potato (Solanum tuberosum) cultivation faces the challenge of excessive pesticide use. During processing, the disposal of large volumes of contaminated water into water bodies can result in severe environmental damage, such as fish deaths. This study aimed to evaluate the toxicological effects of chemical compounds present in the effluent from a potato-processing industry using the test organism Cyprinus carpio. The liver, gills, muscles, and brain were analyzed for biochemical parameters such as catalase (CAT), superoxide dismutase (SOD), acetylcholinesterase (AChE), and lipid peroxidation (TBARS). The highest quantities of pesticides found in the effluent were atrazine, azoxystrobin, fipronil, flutolanil, imidacloprid, tebuconazole, and thiamethoxam. Fish were exposed to the effluent for 7, 14, and 28 days in the laboratory. The CAT enzyme increased activity in the gills at 7 (p-value=0.000) and 14 days (p-value=0.003). Lipid peroxidation showed an increase in the gills at seven days (p-value=0.0281) and in the liver at 7 (p-value=0.000) and 14 days (p-value=0.000). There was also a significant increase (p-value=0.000) in AChE activity in the muscle at all periods. This result highlights the environmental risk and toxicity of potato effluent containing pesticide residues, which can cause biochemical damage to C. carpio and other living organisms.

Commentary: Environmental RNA and the assessment of organismal function in the field

Environmental RNA (eRNA) is an emerging technique with significant potential for the assessment of organismal function in field settings. It has the advantage of being non-invasive, facilitating insight into the physiological status of an organism without complications associated with processes such as capture, handling, and transportation from the field to the laboratory. It is hypothesised that eRNA approaches will be especially valuable for assessing sublethal stress of species living in environmental settings undergoing change and could therefore be integral for examining population health and for testing hypotheses regarding organismal physiology developed from laboratory studies. However, the successful application of eRNA approaches requires further data regarding the stability and persistence of eRNA in natural substrates; established and validated relationships between molecular biomarkers and the physiological processes they participate in; and an understanding of the contributions of different epithelia in direct contact with the environment (skin, gill, gut) to the eRNA transcriptome. The utility of microRNA as a component of the eRNA pool should be an area of specific future research focus. Ultimately, eRNA has the potential to provide fundamental physiological information regarding the responses of organisms in their natural settings and could increase the sensitivity and acuity of biomonitoring efforts.

Proximate composition, microbial quality and heavy metal concentration of fresh Nile tilapia fillet in Lake Tana, Ethiopia

Nowadays, consumption of fish is becoming a public health concern due to quality and safety issues. This study was designed to assess the proximate composition, microbial quality, and heavy metal accumulation in the Nile tilapia fillet at three selected landing sites in Lake Tana. Fifteen samples were collected and analyzed. The mean moisture, ash, fat, protein, salt, and water activity were 81.76%, 0.98%, 1.88%, 14.04%, 0.14%, and 0.9869, respectively. The proximate contents varied slightly among sites but were not significantly different (p > 0.05). The mean aerobic mesophilic bacteria, Staphylococcus aureus, total coliform, and fecal coliform counts were 6.30 log CFU/g, 2.91 log CFU/g, 1.51 log MPN/g, and 0.89 log MPN/g, respectively. Such high microbial loads and the high counts of fecal coliforms are indicative of poor handling practices and unsanitary processing that might lead to foodborne illnesses and economic losses. In addition, the mean concentration of heavy metals in the tissue samples decreased in the order of chromium (0.165 mg/kg) > arsenic (0.085 mg/kg) > lead (0.054 mg/kg) > cadmium (0.010 mg/kg). Except for chromium, the concentrations of the assessed metals were below the maximum permissible limits. Long-term chromium exposure, especially in its hexavalent form, can pose significant health risks like respiratory issues, gastrointestinal distress, and even cancer. Therefore, identifying contamination sources, employing proper waste management strategies, continuous monitoring of heavy metal levels, and proper fish handling practices are highly recommended to address the health implications of microbial contamination and elevated chromium concentrations.

From cells to recapture rates: responses and recovery of a wild fish after an experimental exposure to a widely used herbicide

Freshwater environments are biodiversity hotspots under multiple pressures, including pesticide exposure. S-metolachlor, a widely used herbicide, can induce genotoxic, cytotoxic and physiological effects in captive fish, but we have a limited understanding of the effects of exposure to S-metolachlor in free-living vertebrates. We carried out an original field experiment using integrative approaches across biological levels and temporal scales. The implantation of slow-release implants, an approach to mimic increasing exposure to S-metolachlor of wildlife in realistic multistress conditions, was coupled to a capture-mark-recapture monitoring of bullheads (Cottus perifretum) living in an agriculturally impacted stream. Thanks to our long-term monitoring programme, we evidenced high levels of metolachlor and its metabolites (metolachlor ESA and metolachlor OXA) in water bodies with strong monthly variations. S-metolachlor levels did not differ between treated and control fish and were moderate in bullhead tissues, likely because of xenobiotic metabolism and excretion. S-metolachlor exposure increased erythrocyte abnormalities and the neutrophil/lymphocyte (N/L) ratios. These cellular and physiological damages were observed at 2 weeks, but not at 3 months after the manipulation. This suggests a recovery, likely owing to cell turnover. We also found an increase of body mass of treated fish compared to control fish, and this mass gain persisted at 3 months, suggesting obesogenic effects of S-metolachlor. Antioxidant levels, telomere length and recapture rate were not affected by the experimental treatment. In conclusion, we provide evidence for transient and specific cellular alterations induced by low concentrations of S-metolachlor and long-term mass gain in a wild vertebrate. This study paves the way for integrative field experiments to better understand the impacts of pollutants on fish populations.

Toxic Effects of Lead Exposure on Freshwater Climbing Perch, Anabas testudineus, and Bioremediation Using Ocimum sanctum Leaf Powder

The acute and chronic toxicity of lead to Anabas testudineus was determined in this study using static replacement bioassay testing. During the chronic toxicity studies, an experiment on the bioremediation of lead toxicity using Ocimum sanctum leaf powder was conducted. The 96 h LC50 values of lead for Anabas testudineus was 1.08 mg/L. Different biomarkers, such as the hepatosomatic index, gonadosomatic index, and fecundity, were significantly lower in fish subjected to 10% and 20% of the 96 h LC50 values of lead, compared to controls. The 45-day chronic exposure of fish to lead concentrations of 0.2 mg/L and above significantly lowered the number of total RBC, hemoglobin content, HCT (%), plasma protein, and cholesterol while decreasing the level of total WBC, plasma glucose, creatinine, serum AST and serum ALT. The leaf powder of Ocimum sanctum plays a significant role in ameliorating lead toxicity.

Longitudinal study on the effects of a synbiotic supplement to Atlantic salmon diets on performance, gut microbiota and immune responses during antibiotic treatment and subsequent recovery

BACKGROUND

Antibiotic use has undesirable side-effects on the host, including perturbations of gut microbiota, immunity, and health. Mammalian studies have demonstrated that concomitant/post antibiotic use of pro-, pre-, and synbiotics could re-establish gut microbiota and prevent detrimental host effects. However, studies evaluating similar effects in fish are scanty. This study evaluated the effects of dietary supplementation with a synbiotic mixture on the post-smolt Atlantic salmon gut microbiota, growth performance, and health during antibiotic treatment and subsequent recovery. Fish in five tanks each were fed either a commercial control diet or a synbiotic diet containing Pediococcus acidilactici and fructo-oligosaccharides, for 6 weeks (S1). Then, fish in three tanks per treatment were fed with medicated diets, containing 3500 ppm florfenicol coated onto the control or synbiotic diets, for 2 weeks (S2) and refed with the respective nonmedicated diets for another 3 (S3) and 5 (S4) weeks of recovery period. The fish not subjected to medication were fed the control or synbiotic diets throughout the experimental period. Samples were collected at S1-S4 from both the nonmedicated and medicated fish.

RESULTS

Florfenicol decreased the feed intake in control group. It reduced the growth rate in both control and synbiotic groups with lesser reduction in synbiotic group. Florfenicol did not significantly affect observed taxa and Shannon indexes. Bacterial composition before and after medication clustered distinctly in control and clustered together in synbiotic groups. Lactobacillus dominated in control while Lactobacillus and Pediococcus dominated in synbiotic group during medication and recovery. Florfenicol did not significantly influence the immune or stress response marker gene expressions, though the expression patterns differed between diet groups. Florfenicol did not cause inflammation in the distal intestine or change hepatosomatic index.

CONCLUSIONS

This study highlighted the negative impact of a two-week florfenicol treatment on feed intake and growth performance in Atlantic salmon, with moderate effects on gut microbiota and gene expression. Concomitant use of a synbiotic diet helped to maintain the gut microbial composition and influenced the performance positively and immune gene expressions differently during medication. This study indicates the importance of nutritional interventions through synbiotic supplementation as a possible strategy for managing Atlantic salmon during antibiotic treatment.

Toxic effects of chronic exposure to BPAF and perturbation of gut microbiota homeostasis in marine medaka (Oryzias melastigma)

Bisphenol AF (BPAF), a substitute for bisphenol A (BPA), exhibits potent endocrine-disrupting properties that pose a serious health hazard to organisms. This study employed marine medaka as a model, subjecting them to different concentrations of BPAF (0.61, 6.65, and 91.88 μg/L) from the embryonic stage for a period of 160 days. Findings showed that 91.88 μg/L BPAF reduced survival rates and altered sex ratios. Furthermore, exposure to BPAF at all concentrations led to a significant increase in body length and weight. Behavioral analysis revealed that BPAF exposure impaired the swimming ability of the medaka. Histological changes included disrupted ovarian development, reduced sperm count, liver inflammation, and intestinal damage. Gene expression analysis revealed impacts on nervous system (e.g., gap43, itr, elavl3), HPG axis (e.g., gthα, erα, 3βhsd), and liver genes (e.g., chgl, vtg2). Additionally, BPAF altered the diversity and richness of gut microbes in marine medaka, leading to significant changes in specific bacterial species and intestinal functions. In conclusion, long-term BPAF exposure induced neurotoxicity, reproductive toxicity, and impaired digestive and immune systems in marine medaka, with sex-specific effects. These results provide further evidence of the potential hazards of BPAF as an environmental pollutant.

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.

Biomonitoring Metal Pollution in a Reservoir and River in Brazil Using Bullfrog Tadpoles' Tissues and Biomarkers

Bullfrog tadpoles were exposed (96 h) to water from two sites (the Ibiúna and the Itupararanga reservoir) on the Sorocaba River (São Paulo, Brazil). Metal concentrations (Ba, Cu, Mn, Sr and Zn) and metallothioneins (MTs) levels were determined in the gills (n = 27) and caudal muscle (n = 18). Metals increased in the gills of the animals exposed to the waters of the Sorocaba River in relation to the control and in relation to the animals exposed to the waters of the Ibiúna point. The levels of MT in gills were higher in animals exposed to the Itupararanga reservoir compared to the control. There was a strong correlation between metals and the presence of MT in gills, indicating that this organ can be used in environmental biomonitoring. The results demonstrate the need to protect the waters of the Sorocaba River, and especially the Itupararanga reservoir, through quality monitoring and reduction of anthropogenic pressure.

Sustainable environmental management impact on tourist areas Anza and Cap Ghir in Agadir (Center of Morocco) between 2010 and 2022: Integrated Biomarker response

This research investigates the effects of environmental interventions on pollution levels along the Anza coast of Morocco from 2010 to 2022 through the analysis of biomarkers in Perna perna. Historically, the Anza area has been highly polluted compared to the nearby Cap Ghir coast. Following the relocation of a cement factory and the establishment of wastewater treatment facilities, notable environmental improvements were noted in Anza. Pollution biomarkers such as acetylcholinesterase (AChE), catalase, glutathione S-transferases (GSTs), and malondialdehyde (MDA) were analyzed to assess these changes. The findings indicated an increase in catalase and AChE levels at Anza, suggesting reduced contamination, while GST activity declined, indicating lower exposure to pollutants. In contrast, Cap Ghir showed an increase in oxidative stress biomarkers, suggesting worsening environmental conditions. The Integrated Biomarker Response (IBR) index demonstrated a significant reduction in pollution levels in Anza, with a corresponding increase at Cap Ghir. Principal Component Analysis (PCA) supported these outcomes, revealing a positive correlation between catalase activity and reduced oxidative stress at Anza, whereas Cap Ghir showed elevated oxidative stress markers linked to variations in temperature and salinity. These results underscore the effectiveness of the interventions in enhancing marine health at Anza and highlight the necessity for protective actions at Cap Ghir. This study emphasizes the importance of biomonitoring in shaping environmental policies for coastal areas of Agadir city.

Biomarker responses in fish caged in a rice field during a bifenthrin application

The use of pesticides in integrated rice-fish farming could have an impact on fish health. The present study aimed to evaluate, for the first time, the biological effects of the insecticide bifenthrin on fish (Piaractus mesopotamicus and Hoplosternum littorale) using a caging experiment. Fish were divided into two sites: control (C) and bifenthrin exposure (BF). Two cages (n = 8 fish/cage) per species were placed separately at each site. The BF application (Seizer ®) was carried out with a coastal sprayer according to the BF recommended dose for rice cultivation (0.1 L/ha). After 72 h, fish were collected, and gills, liver, brain, and muscle were dissected for the analysis of biomarkers of accumulation, oxidative stress, and neurotoxicity. In P. mesopotamicus, the main changes were observed in the muscle, where BF accumulated and induced neurotoxicity (inhibition of cholinesterase activity) and oxidative stress (activation of antioxidant enzymes, decreased glutathione levels, increased lipid peroxidation). The gills and liver also showed changes in some markers of the antioxidant system. In H. littorale, BF exposure induced changes in oxidative stress biomarkers in liver (activation of antioxidant enzymes and lipid peroxidation) and gill tissues (alteration in antioxidant markers). These results show that the use of bifenthrin in rice fields poses a risk to fish farming under current pesticide management practices. Furthermore, its use could affect other species in these agroecosystems, highlighting the need for further studies to assess the ecological and productive consequences in a context of increasing pyrethroid use worldwide.

The trophodynamics of polycyclic aromatic hydrocarbons in marine food webs: The importance of trophic level span from insights into Liaodong Bay (China)

The occurrence and trophic transfer of polycyclic aromatic hydrocarbons (PAHs) in aquatic ecosystems is vital to assess ecological risks. PAHs concentrations were analyzed in seawater, sediment, plankton, and marine species (15 fish species, 8 invertebrate species, 3 marine mammals), collected from Liaodong Bay (China). Bioaccumulation and biomagnification were calculated to demonstrate the biotransfer pattern of PAHs from the environmental matrix to high-level predators through the food web. Total PAHs concentrations ranged from 81.2 to 197.6 ng/L in seawater, 51.4-304.8 ng/g (dw) in sediment, and 65.3 to 28,885 ng/g (lw) in all biota samples. Three- and four-ring PAHs constituted major components (>81% in each case) of PAH congener profiles. Lower biota-sediment accumulation factors (BSAFs) and bioaccumulation factors (BAFs) values indicated limited bioaccumulation of PAHs within marine organisms. Also, 77% of biomagnification factors (BMFTL) values of PAHs in spotted seal and finless porpoise were >1, whereas opposite transfer patterns of PAHs were observed in food webs with trophic values of 1.5-3.5 and 3.0-4.0; that is, trophic dilution (trophic magnification factor (TMF) < 1) and trophic magnification (TMF >1), respectively. This study provides novel insights into the importance of TL span for trophodynamics of PAHs within food webs.