Monitoring pollution in River Mureş, Romania, part II: metal accumulation and histopathology in fish

Acute toxicity of palm oil mill effluent on zebrafish (Danio rerio Hamilton-Buchanan, 1822): Growth performance, behavioral responses and histopathological lesions

Evaluating the toxicity of Palm Oil Mill Effluent (POME) is critical as part of the effort to develop waste management regulations for the palm oil industry. In this study, we investigated the acute toxicity of POME on growth performance, behavioral response, and histopathology of gill and liver tissues of zebrafish (Danio rerio). In total, 550 adult male zebrafish were used for the toxicity experiment including range finding test, acute toxicity test, growth performance and behaviour test. Static non-renewal acute toxicity bioassays were conducted by exposing fish to POME (1.584-9.968 mL/L) for 96 h. Growth performance, behavior response, and histopathological lesions in untreated and POME treated (96-h LC50: 5.156 mL/L) fish were measured at 24, 48, 72 and 96 h. Time-dependent significant decline in body length and body weight of POME-exposed zebrafish was observed. Furthermore, several behavioral changes were recorded, including hyperactivity, loss of balance, excessive mucus secretion, and depigmentation. Decreasing operculum movement and oxygen consumption rate as well as alterations in gill tissues (i.e. hyperplasia, hypertrophy, hemorrhage, and necrosis) of POME-exposed zebrafish were observed, suggesting a dysfunction in respiratory performance. On the other hand, liver tissue alterations (congestion, hemorrhage, hyperplasia, shrinkage of hepatocytes, hydrophilic degeneration, and necrosis) indicated a disruption in detoxification performance. We conclude that exposure to POME at acute concentration caused histopathological lesions both in gill and liver tissue along with changes in fish behaviors which disrupted respiratory and detoxification performance, resulting in mortality and reduced growth of zebrafish. These findings might provide valuable information for guiding POME management and regulation.

Integrated physiological, biochemical, and transcriptomic analysis of thallium toxicity in zebrafish (Danio rerio) larvae

Although several studies have evaluated the effects of Thallium (Tl) in adult species of fish, the developmental toxicity of Tl has not been previously explored. In this study, zebrafish embryos (<4 h post fertilization (hpf)) were exposed to Tl at concentrations from 0.8 to 400 μg L^-1 for 7 d. The results showed that the decreased hatching rate and increased malformation rate were observed in the larvae. The swimming velocity of larvae from 200 and 400 μg L^-1 treatments was respectively reduced by ~26 % and 15 %. Histopathological analysis of liver indicated the number of cells of karyolysis (143 % and 202 %) and pyknosis (170 % and 131 %) were respectively increased in 200 and 400 μg L^-1 Tl treatments. Meanwhile, the Tl body burden and metallothionein (MT) levels in the larvae were increased with elevated Tl concentrations. The level of malondialdehyde (MDA) was increased by ~20 to 51 % in all Tl treatments and total antioxidant capacity (TAC) was decreased by ~12 % at 200 μg L^-1. The activities of Na⁺/K⁺-ATPase and protease were inhibited in 200 and 400 μg L^-1 Tl treatments. Moreover, the transcripts of genes (Nrf2, HO-1, TNF-α, IL-1β, IL-8, IL-10, TGF) were significantly altered. In addition, a total of 930 differentially expressed genes (DEGs) and 1549 DEGs were found in the 200 and 400 μg L^-1 treatments with 458 overlapped DEGs by transcriptomic analysis. The protein digestion and absorption, ECM-receptor interaction, and complement and coagulation cascades pathways were shown to be the most significantly enriched pathways. This study helps better understand the molecular mechanisms of Tl toxicity in fish.

The European Chub (Squalius cephalus) as an indicator of reservoirs pollution and human health risk assessment associated with its consumption

Five reservoirs (Vlasina, Medjuvršje, Zaovine, Perućac, and Garaši) in Serbia were chosen as study sites, which differ by their position, purpose, stages of eutrophication, management policies, and levels of anthropogenic pressure. The objectives of this research were to: determine the concentrations of 26 elements in muscle, gills, and liver of the European chub by inductively-coupled plasma optical emission spectrometry (ICP-OES); determine the concentrations of 17 organochlorine pesticides in fish muscle by gas chromatography with mass spectrometric detection (GC-MS); compare these findings with condition factor (CF) and histopathological (HP) biomarkers; and assess the potential human health risks due to consumption of chub muscle tissue. The highest elemental accumulation was found in the gills. The European chub was not a good indicator of Pb pollution between reservoirs. Concentrations of Hg, As, and Cu were low and did not exceed the proscribed maximum allowed concentrations (MACs). 4,4'-DDE was detected only in individuals from Vlasina, 4,4'-DDD from Perućac and Zaovine, and heptachlor from Zaovine. Low to moderate levels of HP were observed for both gills and liver in all studied reservoirs. HP index for gills was significantly higher for Zaovine compared to Vlasina. Significantly lower HP index for liver and the total HP index value were observed for fish from Vlasina compared to Perućac. No significant human health risks due to the intake of examined pollutants in each reservoir were recorded; women were at higher risk compared to men. A reason for concern is a few muscle samples from Garaši, Vlasina, Perućac, and Medjuvršje in which Cd exceeded the MAC. A reservoir for water supply (Garaši) is generally considered the safest for fish consumption.

Swimming behaviour in two ecologically similar three-spined (Gasterosteus aculeatus L.) and nine-spined sticklebacks (Pungitius pungitius L.): a comparative approach for modelling the toxicity of metal mixtures

Sticklebacks (Gasterosteiformes) are increasingly used in ecological and evolutionary research and have become well established as role model species for biologists. However, ecotoxicology studies concerning behavioural effects in sticklebacks regarding stress responses, mainly induced by chemical mixtures, have hardly been addressed. For this purpose, we investigated the swimming behaviour (including mortality rate based on 96-h LC₅₀ values) of two ecologically similar three-spined (Gasterosteus aculeatus) and nine-spined sticklebacks (Pungitius pungitius) to short-term (up to 24 h) metal mixture (MIX) exposure. We evaluated the relevance and efficacy of behavioural responses of test species in the early toxicity assessment of chemical mixtures. Fish exposed to six (Zn, Pb, Cd, Cu, Ni, and Cr) metals in the mixture were either singled out by the Water Framework Directive as priority or as relevant substances in surface water, which was prepared according to the environmental quality standards (EQSs) of these metals set for inland waters in the European Union (EU) (Directive 2013/39/EU). The performed behavioural analysis showed the main effect on the interaction between time, species, and treatment variables. Although both species exposed to MIX revealed a decreasing tendency in swimming activity, these species' responsiveness to MIX was somewhat different. Substantial changes in the activity of G. aculeatus were established after a 3-h exposure to MIX solutions, which was 1.43-fold lower, while in the case of P. pungitius, 1.96-fold higher than established 96-h LC₅₀ values for each species. This study demonstrated species-specific differences in response sensitivity to metal-based water pollution, indicating behavioural insensitivity of P. pungitius as model species for aquatic biomonitoring and environmental risk assessments.

Effectiveness and Characterization of Novel Mineral Clay in Cd2+ Adsorption Process: Linear and Non-Linear Isotherm Regression Analysis

The excellent adsorption properties of clay minerals make the optimization of heavy metal removal the subject of numerous research projects. In the present study, ASLAVITAL cosmetic clay (ACC) powder was applied for the removal of Cd2+ from water. The main deposit of ACC clay is the Pădurea Craiului Mountains in Romania. A wide range of morpho-structural approaches (SEM, EDX, FTIR, Raman, XRD) were used to characterize the morphology and elemental composition of the adsorbent. As expected for clay minerals, Al (Wt(%) = 11.4 ± 0.9) and Si (Wt(%) = 13.7 ± 1.4) are the main constituents of ACC. After adsorption, Wt(%) = 0.2 ± 0.01 Cd2+ was detected in the sample. As proved before, the initial metal concentration is the primary influencing factor; therefore, batch adsorption of 10–160 mg/L Cd2+ was investigated. After 190 min, an efficiency of 99% was reached, and the quantity in equilibrium increased from 1–8 mg/g. The best fit in linear form was obtained for the Langmuir II. model, where R2 = 0.954 (RL = 0.037–0.027). Based on linear isotherm models, physical bonds formed between ACC and Cd2+ during the favorable adsorption. For the non-linear fits, the Liu model proved to be the best R2 = 0.965, χ2 = 1.101. Pseudo-II-order kinetic model described the experimental data R2 = 0.988–0.999; qexp and qcalc were almost identical (the differences ranged 0.03–0.34).

The legacy of artisanal gold mining and its impact on fish health from Tapajós Amazonian region: A multi-biomarker approach

Tapajós Region, is an area with intense historical artisanal and small-scale gold mining. Therefore, the core objective of this study was to evaluate the environmental status of different rivers located in this region, using biomarker endpoints in Serrasalmus rhombeus as a tool. Fish and sediment were collected from two rivers, Tropas and Crepori, affluent of Tapajós River, located inside a Federal Protection Area and in a Reference site. Mercury concentration in sediment and fish were traced, and biomarkers in gills and liver were analyzed. Results showed a clear difference between these two rivers compared to the Reference site. Fish tissues presented biomarker responses according to the site of collection. Catalase (CAT) activity was statistically higher in fish gills from Crepori, confirming the capacity of mercury interference with redox equilibrium. High levels of lipid peroxidation were also noted to contribute greatly in incidence of morphological changes in the liver and gills, suggesting that mercury bioaccumulation during continuous exposure promote biological responses in a cumulative manner, from molecules to tissues. This study also indicates adaptation in fish defense mechanisms given the conditions in the Tropas River, as well as a variation in biomarker responses to that of the Crepori river. In summary, Tapajós affluents presented high mercury levels in fish tissues leading to biomarker responses, demonstrating a hazardous signal of a long history of mercury pollution.

Chromium Exposure Causes Structural Aberrations of Erythrocytes, Gills, Liver, Kidney, and Genetic Damage in Striped Catfish Pangasianodon hypophthalmus

Heavy metal pollution due to anthropogenic activities poses a great threat to aquatic organisms. The present study was conducted to evaluate the cytotoxic and genotoxic effects of hexavalent chromium (potassium dichromate) on hemato-biochemical, histo-pathological, and genetical changes in striped catfish Pangasianodon hypophthalmus. Three sub-lethal doses (0.8, 1.6, and 3.2 mg/L) of chromium (Cr) were selected and fish were exposed in vivo contrasting with a control (0 mg/L) for 30 days. The study revealed that various hemato-biochemical parameters showed a significant decrease in hemoglobin (Hb), red blood cells (RBCs), and blood glucose content, whereas white blood cells (WBCs) significantly increased in Cr exposed fish. Frequencies of all forms of structural abnormalities of erythrocytes (erythrocytic cellular abnormalities; ECA, erythrocytic nuclear abnormalities; ENA and erythroblasts; Ebs) were significantly increased in higher two test concentrations (1.6 and 3.2 mg/L) when compared to control. Differential leucocyte count exhibited significant increase in neutrophil and decrease in lymphocytes in the highest Cr treated group. The severity of various histo-pathological changes in the gills, liver, and kidney were increased considerably with the increase of Cr concentrations. Similarly, the amount of DNA (ng/μl) decreased significantly in blood and tissues of different vital organs where the liver showed the highest decline compared to control in a concentration-dependent manner. Taken altogether, P. hypophthalmus is susceptible to Cr and can be used as a bio-indicator to assess aquatic metal pollution.

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

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

Bioaccumulation of heavy metals in water, sediment, and tissues of major fisheries from Adyar estuary, southeast coast of India: An ecotoxicological impact of a metropolitan city

Heavy metal content in water, sediment, and tissues of six commonly used edible fishes from Adyar estuary, southeast coast of India, was assessed for metal bioaccumulation. The enrichment of metals in estuarine sediment is due to the discharge of contaminated water from the Chennai Metropolis. The enrichment factor indicated that metals such as Cr (EF=30.9) and Cu (EF=31.9) are highly enriched and fall under the very severe category. Bioaccumulation factor (BAF) revealed that the concentration of heavy metals viz. Ni, Cr, Pb, Cu, Co, Zn, Fe, and Mn in different tissues of fishes was several times higher than their concentrations in water. Moreover, high concentration of heavy metals, especially Cu and Cr was noticed in the muscle and liver tissues of the fishes which are higher than the WHO standards. Among the studied fishes, Arius parkii and Gerres oyena showed higher levels of bioaccumulation in terms of toxic metals.

Histopathological assessment of seven year-classes of Delta Smelt

The Delta Smelt (Hypomesus transpacificus) is an imperiled, annual fish endemic to the Sacramento-San Joaquin Delta and San Francisco Estuary. This study examined the severity and prevalence of liver and gill lesions of juvenile through adult Delta Smelt from 2011 through 2017 collected from five regions throughout its habitat (n = 1,053). The first and last years of the study were wet, but bracketed an extreme drought in CA (2012-2016), during which the Delta Smelt population reached historical lows. Overall, the three most common lesions were gill ionocyte hyperplasia, liver lipidosis, and gill aneurysm. Individuals with higher fork lengths exhibited increased gill and liver lesion score (summations of the severity scores), suggesting that Delta Smelt accumulate lesions through their lives, and that larger individuals were more tolerant of liver and gill lesions. Liver lesion score showed significant regional differences, while salinity was a better predictor of gill lesions than region, with lower gill lesion scores associated with higher salinities. Largely consistent with previously reported histopathology patterns, Delta Smelt collected from the Confluence and Suisun Marsh had the lowest liver lesion score, while Delta Smelt collected from Cache Slough and Suisun Bay had the highest lesion scores, and Suisun Marsh had the lowest glycogen depletion, suggesting heterogeneous levels of exposure to environmental stressors across regions. Gill and liver lesion score also varied significantly with year-class. The highest gill lesion score occurred in the 2015/16 year-class, and the lowest occurred in the 2017/18 year-class, a 2.8-fold difference. Controlling for size and regional effects, individuals with comparatively high liver lesion scores were prevalent in the population until the 2014/15 year-class. In the two subsequent year-classes, Delta Smelt livers were in the best condition, coinciding with peak drought conditions and record low abundances.

Toxicity and bioaccumulation of Cadmium, Copper and Zinc in a direct comparison at equitoxic concentrations in common carp (Cyprinus carpio) juveniles

The individual toxicity and bioaccumulation of cadmium, copper and zinc for common carp juveniles was evaluated in a direct comparison in two experimental setups. First, fish were exposed for 10 days to different metal concentrations in order to link metal bioaccumulation to LC₅₀ values (concentration lethal to 50% of the animals) and incipient lethal levels (ILL, concentration where 50% survives indefinitely). Accumulated metals showed a positive dose dependent uptake for cadmium and copper, but not for zinc. Toxicity was in the order cadmium>copper>zinc with 96h LC₅₀ values for cadmium at 0.20±0.16 μM, for copper at 0.77±0.03 μM, and for zinc at 29.89±9.03 μM respectively. For copper, the 96h exposure was sufficient to calculate the incipient lethal level and therefore 96h LC₅₀ and ILL levels were the same, while for cadmium and zinc 5 to 6 days were needed to reach ILL resulting in slightly lower values at 0.16 μM and 28.33 μM respectively. Subsequently, a subacute exposure experiment was conducted, where carp juveniles were exposed to 2 equitoxic concentrations (10% and 50% of LC₅₀ 96 h) of the three metals for 1, 3 and 7 days. Again a significant dose-dependent increase in gill cadmium and copper, but not in zinc, was observed during the 7-day exposure. Copper clearly affected sodium levels in gill tissue, while zinc and cadmium did not significantly alter any of the gill electrolytes. The overall histopathological effects (e.g. hyperemia and hypertrophy) of the metal exposures were mild for most of the alterations. Our study showed that copper an cadmium (but not zinc) showed dose dependent metal accumulation, however this bioaccumulation was only correlated with mortality for cadmium. Metal specific alterations were reduced gill sodium levels in copper exposed fish and oedema of the primary epithelium which typically occurred in both levels of zinc exposure.

Photocatalytic Degradation of Methyl Orange by Magnetically Retrievable Supported Ionic Liquid Phase Photocatalyst

A magnetically retrievable ferrocene appended supported ionic liquid phase (SILP) photocatalyst containing a molybdate anion has been synthesized and characterized by Fourier transform infrared, X-ray photoelectron spectroscopy, transmission electron microscopy, X-ray diffraction, energy dispersive spectroscopy, and vibrating sample magnetometer analysis. The optical properties of the photocatalyst were probed by photoluminescence and UV-vis diffuse reflectance spectroscopy. The discharge of undesirable dye effluents from textile industrial plants in the environment is the major concern of environmental pollution and toxicity. In this context, we employed the as-prepared SILP photocatalyst for degradation of methyl orange (MO) under UV light (365 nm) irradiation, and subsequently, recycling studies were performed. The histological alteration in gills of the fish is employed as a tool for monitoring toxins in the environment. In view of this, the histo-toxicological assessment on freshwater fish Tilapia mossambica gills asserted the damage of secondary gill lamellae due to MO. Conversely, structural modifications in the gill architecture were not observed by virtue of photodegraded products confirming that the degraded product is nontoxic in nature. Additionally, the normal behavior of fishes on exposure to photodegraded products reveals that research findings are beneficial for the aquatic ecosystem.

Does Bti (Bacillus thuringiensis var. israelensis) affect Rana temporaria tadpoles?

Biocides based on toxins of Bacillus thuringiensis var. israelensis (Bti) are established as alternatives to conventional chemical insecticides for mosquito control all across the globe since they are regarded ecologically compatible and harmless to non-target species. Since recent studies on amphibian larvae have called this opinion into question, we exposed Rana temporaria tadpoles to single (1 mg/L), tenfold (10 mg/L) and hundredfold (100 mg/L) field concentrations of VectoBac^® WG (a water dispersible granule Bti formulation) in the laboratory for eleven days to investigate whether larvae were adversely affected by Bti and its endotoxin proteins. In addition to a negative (water) control, a positive control based on organic rice protein (50 mg/L) was run to check for the nutritional relevance of Bti proteins. There was no Bti-related mortality and a histopathological analysis of tadpole intestines revealed no adverse effects. Analyses of biomarkers for proteotoxicity (stress protein family, Hsp70) and neurotoxicity or metabolic action (b-esterases acetylcholine esterase (AChE) and carboxylesterases) revealed no significant differences between Bti treatments and the negative control. The responses of tadpoles in the protein-supplemented positive control differed from those of the negative control and the Bti treatments. Tadpoles in the positive control had reduced body mass and elevated AChE activity.

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

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

Effects of guanylurea, the transformation product of the antidiabetic drug metformin, on the health of brown trout (Salmo trutta f. fario)

Background

Guanylurea is the main transformation product of the antidiabetic drug metformin, which is one of the most prescribed pharmaceuticals worldwide. Due to the high rate of microbial degradation of metformin in sewage treatment plants, guanylurea occurs in higher concentrations in surface waters than its parent compound and could therefore affect aquatic wildlife. In this context, data for fish are scarce up to now which made us investigate the health of brown trout (Salmo trutta f. fario) in response to guanylurea.

Methods

In two experiments, eggs plus developing larvae and juvenile brown trout were exposed to three different concentrations of guanylurea (10, 100 and 1,000 µg/L) and, as a negative control, filtered tap water without this compound. Low internal concentrations were determined. The investigated parameters were mortality, length, weight, condition factor, tissue integrity of the liver and kidney, levels of stress proteins and lipid peroxides, as well as behavioural and developmental endpoints. It was found that guanylurea did not significantly change any of these parameters in the tested concentration range.

Results

In conclusion, these results do not give rise to concern that guanylurea could negatively affect the health or the development of brown trout under field conditions. Nevertheless, more studies focusing on further parameters and other species are highly needed for a more profound environmental risk assessment of guanylurea.

Assessment of adverse outcome of Excel Mera 71 in Anabas testudineus by histological and ultrastructural alterations

Present study was designed to evaluate the adverse effect of glyphosate-based herbicide, Excel Mera 71 in Anabas testudineus on comparative basis under field and laboratory conditions. Field (750 g/acre) and laboratory (17.2 mg/L) experiments were performed for a period of 30 days. For field experiment special type of cages were prepared. Fish gill, liver, and kidney were analyzed for histology and ultrastructural responses. A significant increment in morphometric indices (DTC) was observed in gill, liver and kidney of A. testudineus under laboratory condition (p <  0.05) and responses showed the degree of pathogenicity in the order of liver > kidney > gills. However, under field study significant increase in DTC value was observed in gill and liver (p <  0.05). Among the scanning electron microscopic (SEM) observations necrosis and loss of microridges, and damage in stratified epithelial cells were prominent in gill, although higher prevalence of alterations was observed under laboratory study than field study. Additionally, transmission electron microscopic (TEM) observations also depicted higher prevalence of pathological lesions under laboratory study compared with field observation. Among the TEM observations damage in chloride and pavement cells, degenerative mitochondria and nucleus (in gill); severe vacuolation, necrosed nucleus and vesiculated network in case of liver and degenerated epithelial cells, cytoplasmic vacuolation, and damage in proximal convoluted tubules (PCT) in case of kidney were prominent. Therefore, these findings demonstrated that Excel Mera 71 induces significant damage in tissues of A. testudineus and these responses might be considered as biomarkers for monitoring herbicidal toxicity on fish in aquatic body.

Mutagenic and histopathological effects of hexavalent chromium in tadpoles of Lithobates catesbeianus (Shaw, 1802) (Anura, Ranidae)

The potential mutagenic and histopathological effects of the hexavalent chromium were investigated in Lithobates catesbeianus tadpoles. These larvae (GS 25-31) were exposed to three nominal concentrations of potassium dichromate (4, 12, and 36 mg L^-1) and 5 mg L^-1 of Cyclophosphamide as a positive control (PC), for 24 h. A negative control (NC) was also added to the experiment. Our results showed that, in general, the micronuclei (MN) were less frequent than the erythrocyte nuclear abnormalities (ENA); there was a significant difference in the frequency of MN between the NC and all treated groups (p < 0.05) in a concentration-dependent curve, in addition the PC did not differ from the chromium treatments. Also, only PC and the group treated with potassium dichromate at 36 mg L^-1 showed significantly higher frequencies of ENA than NC (p < 0.05). Chromium treatments promoted cell retention in the Sub-G1 phase and a decrease of cells in the S and G2/M phases indicating inhibition of the cell cycle. All treatments with chromium led to liver and kidney histopathological lesions, especially with 36 mg L^-1 (greater number of lesions). In conclusion, hexavalent chromium was mutagenic to L. catesbeianus tadpoles and its toxic effects also resulted in anti-mitotic activity, besides inducing histopathological alterations in liver and kidney. Amphibians have been proven to be useful bioindicators, and we suggest that tadpoles of different species can be used to represent the environmental impacts in aquatic ecosystems.

Effects of mine tailing and mixed contamination on metals, trace elements accumulation and histopathology of the chub (Squalius cephalus) tissues: Evidence from three differently contaminated sites in Serbia

Chub (Squalius cephalus) specimens were collected in Korenita River seven months after spillover from the waste water of antimony mine tailing pond and compared with chub living in Kruščica reservoir (intended for water supply) and Međuvršje reservoir (influenced by intense emission of industrial, urban and rural wastewater). Concentrations of 15 elements (Al, As, B, Ba, Cd, Cr, Cu, Fe, Hg, Mn, Ni, Pb, Si, Sr, Zn) were determined in muscle, liver and gills of chub by inductively coupled plasma optical spectrometry (ICP-OES) and histopathological alterations in liver and gills were assessed. Chub specimens from Korenita River had higher concentrations of As, Ba and Pb in all three investigated tissues as well as higher total histopathological index values than chub from reservoirs. Specimens from Međuvršje reservoir were characterized by higher values for concentrations of Cu and Si in muscle tissue and higher values for regressive histopathological alterations in gills. Individuals of chub from Kruščica reservoir had the highest concentrations of Fe in liver, Hg in muscle and Sr and Zn in muscle while gills had the lowest value of total histopathological index. The results from the present study showed higher level of histopathological alterations as a result of mine tailing accident. As a result of mixed contamination on the Međuvršje site, histopathological index values of gills were in line with the index value from Korenita River. Increased values for Fe and Sr in chub tissue from Kruščica reservoir could be explained by geological structure of the site which is characterized by magmatic rock rich in Cu, Fe and Ni as well as dominant carbonate sediment complex of marine origin with increased level of Sr.

Evaluation of Fish Health Status and Histopathology in Gills and Liver Due to Metal Contaminated Sediments Exposure

Health status of freshwater fish, Cirrhina mrigala was studied by qualitative and quantitative histopathological analysis, alterations in frequency/prevalence percentages (%) and histological alteration indices (HAI) in response to metal contaminated sediments of the River Ravi aquatic ecosystem. Histo-structures of gill and liver samples of fish were analyzed and comparison between the degree of damage of the alterations in fish organs was performed after exposure to metal contaminated sediments for 7, 14 and 28 days under semi-static water renewal bioassays. Histopathological studies revealed marked histological alterations in the gills and liver of exposed fish as compared to normal tissue structure observed in control fish. The frequency and prevalence percentages observed in 28-day exposed fish were significantly higher as compared to 7- and 14-day exposed fish. The order of frequency and prevalence percentage for gills and liver of exposed fish was as: 28-day > 14-day > 7-day. The highest prevalence percentages recorded were 83 and 80% as focal area of necrosis in gill and liver, respectively, after 28-day exposure. The lowest prevalence percentage observed in 7-day exposed Cirrhina mrigala was dilation of sinusoids (17%).

Monitoring metal levels in water and multiple biomarkers in the grouper ( Epinephelus tauvina) to assess environmental stressors on the Arabian Gulf coast of Saudi Arabia

In this field study, the levels of heavy metals (Pb, Fe, Co, Cu, and Zn) in water and a suite of biochemical and histological biomarkers in the grouper ( Epinephelus tauvina) were assessed at four sites in the Arabian Gulf. Samples were taken from a relatively non-urban reference site, called Salwa (S1), and three effluent-dominated sites, namely Al-aziziyah in southern Dammam city (S2), the Al-Jubail coast (S3), and Manifa (S4). Toxic metals, namely Pb and Co (at all sites) and Fe (at S3), were elevated in water samples relative to the internationally permissible limits. In fish, induced levels of heat shock protein 70 (HSP70) in the liver at S3 and S4 were higher than those of the reference fish at S1. Additionally, the level of the lipid peroxidation (LPO) product (malondialdehyde (MDA)) was significantly increased in gills (at S3) and liver (at S2 and S3). There was an inhibition of catalase activities in the gills of fish from S2 to S4 and significantly higher activity levels of superoxide dismutase in the gills of fish from S4. Histopathological features such as aneurysms in gill vessels, deformed gill lamellae, increases in liver melano-macrophage centers, and hepatocellular necrosis were most abundant at sites where significant pollution problems exist (i.e. S2-S4). The results reveal that the eastern coast of Saudi Arabia, in the Arabian Gulf, is still contaminated, as indicated by elevated HSP70, LPO content and numbers of histological lesions, and that monitoring of contaminants and their effects should be continued in this region.

Ecological risk assessment of a contaminated stream using multi-level integrated biomarker response in Carassius auratus

The goal of this study was to evaluate the adverse effects of wastewater effluents on freshwater crucian carp, Carassius auratus, inhabiting Sincheon stream using the integrated biomarker response (IBR) at the genotoxic (micronucleus [MN] test), oxidative stress (activity of catalase [CAT] and glutathione S-transferase [GST], and level of lipid peroxidation [LPO]), histopathological (degree of tissue changes [DTC]), and physiological (condition factor [CF] and liver somatic index [LSI]) levels. The CF and LSI were significantly (p < 0.05) enhanced in fish from downstream sites (DS1 and DS2) as compared to that of upstream (US) fish samples. Moreover, a significant increase in morphometric indices (DTC) was observed in C. auratus collected from downstream sites (p < 0.05) and histopathological responses showed the degree of pathogenicity in the order of liver > kidney > gills. The activities of CAT, GST, and LPO in fish from the DS1 and DS2 sites were notably increased in gills, liver, and kidney compared to that of fish from the US site. Additionally, the MN test level in C. auratus from the DS1 and DS2 were significantly increased (p < 0.05) when compared with that of the US site. Considering the higher bioaccumulation of Cd, Co, Cr, Mn, Ni, and Pb in gills, liver, and kidney of C. auratus collected from downstream sites compared to that of the upstream site (p < 0.05), the observed toxicity was likely attributable to metal accumulation. The multi-level IBR index was higher at the DS1 site (15.08) than at the DS2 (1.02) and the reference US (0.00) sites. Therefore, these findings demonstrated that wastewater effluent discharge induces significant DNA damage, oxidative stress, and tissue injuries in C. auratus and suggested that the multi-level IBR approach should be used to quantify these effects on fish in streams and rivers.

Does the antidiabetic drug metformin affect embryo development and the health of brown trout (Salmo trutta f. fario)?

BACKGROUND

Due to the rising number of type 2 diabetes patients, the antidiabetic drug, metformin is currently among those pharmaceuticals with the highest consumption rates worldwide. Via sewage-treatment plants, metformin enters surface waters where it is frequently detected in low concentrations (µg/L). Since possible adverse effects of this substance in aquatic organisms have been insufficiently explored to date, the aim of this study was to investigate the impact of metformin on health and development in brown trout (Salmo trutta f. fario) and its microbiome.

RESULTS

Brown trout embryos were exposed to 0, 1, 10, 100 and 1000 µg/L metformin over a period from 48 days post fertilisation (dpf) until 8 weeks post-yolk sac consumption at 7 °C (156 dpf) and 11 °C (143 dpf). Chemical analyses in tissues of exposed fish showed the concentration-dependent presence of metformin in the larvae. Mortality, embryonic development, body length, liver tissue integrity, stress protein levels and swimming behaviour were not influenced. However, compared to the controls, the amount of hepatic glycogen was higher in larvae exposed to metformin, especially in fish exposed to the lowest metformin concentration of 1 µg/L, which is environmentally relevant. At higher metformin concentrations, the glycogen content in the liver showed a high variability, especially for larvae exposed to 1000 µg/L metformin. Furthermore, the body weight of fish exposed to 10 and 100 µg/L metformin at 7 °C and to 1 µg/L metformin at 11 °C was decreased compared with the respective controls. The results of the microbiome analyses indicated a shift in the bacteria distribution in fish exposed to 1 and 10 µg/L metformin at 7 °C and to 100 µg/L metformin at 11 °C, leading to an increase of Proteobacteria and a reduction of Firmicutes and Actinobacteria.

CONCLUSIONS

Overall, weight reduction and the increased glycogen content belong to the described pharmaceutical effects of the drug in humans, but this study showed that they also occur in brown trout larvae. The impact of a shift in the intestinal microbiome caused by metformin on the immune system and vitality of the host organism should be the subject of further research before assessing the environmental relevance of the pharmaceutical.

Multivariate and integrative approach to analyze multiple biomarkers in ecotoxicology: A field study in Neotropical region

Aquatic pollution has dramatically worsened in developing countries, due to the discharge of a mixture of pollutants into water bodies, to the lack of stringent laws, and the inadequate treatment of effluents. In this study, the Neotropical fish Astyanax aff. paranae was sampled from three sites with different pollution levels: 1) a Biological Reserve (Rebio), protected by the Brazilian government; 2) an agricultural area in one of the most productive regions of Brazil, upstream of an urban zone; and 3) a site downstream from urban zone, characterized by the influx of different effluents, including wastes from industry, a sewer treatment plant, and agricultural areas. We assess biomarkers at multiple levels, such as the comet assay, hepatic histopathological analysis, brain and muscle acetylcholinesterase (AChE) and the hepatic enzymes glutathione-S-transferase (GST), catalase (CAT), and lipoperoxidation (LPO), during winter and summer. The interpretation of field results is always a very complex operation, since many factors can influence the variables analyzed in uncontrollable conditions. For this reason, we apply an integrative multivariate analysis. The results showed that the environmental risk of the three sites was significantly different. We can see a gradient in data distribution in discriminant analysis: separating, from one side, the fish of Rebio; in the middle are the fish from agricultural area and, in the other side are the animals from downstream site. Overall, the biomarkers responses were more greatly altered in the downstream site, whereas fish from the agricultural area showed an intermediate level of damage. The greatest changes were likely caused by agriculture, industrial chemical effluents and ineffective sewage treatments, in a synergic interaction in downstream site. In conclusion, the use of multiple biomarkers at different response levels to assess the toxic effects of mixed pollutants in a natural aquatic environment is an important tool for monitoring polluted regions.

Impact of the NSAID diclofenac on survival, development, behaviour and health of embryonic and juvenile stages of brown trout, Salmo trutta f. fario

The NSAID diclofenac is controversially discussed with respect to its environmental relevance. Since further information is need to assess whether diclofenac should be included as substance of priority in the EU water framework directive, we investigated the impact of this analgesic on the embryonic development of brown trout (Salmo trutta f. fario) from fertilized egg until the end of sac-fry stage and studied effects in juvenile fish six months post hatch. Embryos were exposed to five test concentrations (0.1, 0.5, 1, 10, 100μg/L) over 127days at 7°C. None of the treatments affected mortality, hatching, development or heart rate. Six months old juveniles exposed to five concentrations (0.1, 1, 10, 100, 200μg/L) over 25days at 7°C, however, showed increased mortality, reaching significance at 100μg/L. Furthermore, a significantly higher proportion of juvenile animals bore injuries at concentrations higher 10μg/L. Neither the levels of the stress protein Hsp70, nor the amount of lipid peroxides was affected by any of the treatments. Histological analyses of gill, liver and kidney revealed visible tissue reactions in fish from all experimental groups. Histological responses in livers of diclofenac-exposed fish outstripped the status of laboratory control fish, particularly when exposed to the two highest concentrations. Chemical analyses of fish muscle tissue revealed concentration-dependent uptake of DCF into the animal, but no relevant bioconcentration. Our study supports earlier findings indicating a lower sensitivity of trout early life stages compared to older individuals, suggesting that studies for risk assessment of diclofenac should predominantly focus on later life stages. Furthermore, fish mortality was found to increase with rising diclofenac concentrations, and the lowest observed effect concentration of 10μg/L on the organismic level emphasises the classification of diclofenac as a micropollutant that requires close attention.

Biochemical, Histopathological and Molecular Responses in Gills of Leuciscus cephalus Exposed to Metals

Gills are major targets for acute metal toxicity in fish, due to their permanent contact with aquatic pollutants. To assess the effects of metals on gills of the Leuciscus cephalus (chub), fish individuals were collected from two sites in the Tur River, Romania, in upstream (site 1) and downstream (site 2) of a metal pollution source. Quantitative and hyperspectral analyses showed that Zn, Sr, and Fe concentrations were significantly higher in gills from site 2 compared with site 1. Malondialdehyde and advanced oxidation protein products levels increased 17 and 28%, respectively, whereas reduced glutathione level diminished significantly in the gills of fish collected from site 2 compared to site 1. The activities of superoxide dismutase, catalase, and glutathione-S-transferase increased significantly at 41, 21, and 28%, respectively. Proliferating cell nuclear antigen (PCNA) protein levels, as well as the amount of DNA damage, were significantly increased for site 2 compared with site 1. The induced oxidative stress generated hyperplasia, hypertrophy, and inflammation in the epithelial cells and apoptosis. Hence, this could suggest that gill cells have tried to counteract the oxidative stress-induced DNA fragmentation by PCNA up-regulation, but the PCNA expression decreased on longer time due to the low level of GSH, resulting in apoptosis.

Does wastewater treatment plant upgrading with activated carbon result in an improvement of fish health?

In the present study, the efficiency of a wastewater treatment plant (WWTP) upgraded with a powdered activated carbon unit for the reduction of micropollutants and the related advantages for fish health have been analyzed by means of different biomarkers, i.e. histopathological investigations, analyses of glycogen content and stress proteins, as well as by chemical analyses in different matrices. Comparative analyses were conducted prior and subsequent to the installation of the additional purification unit. Chemical analyses revealed a significant reduction of several pharmaceuticals, including diclofenac, carbamazepine and metoprolol, in samples of effluent and surface water downstream of the WWTP after its upgrade. In addition, diminished concentrations of diclofenac and PFOS were detected in tissues of analyzed fish. Histopathological investigations of fish liver, gills, and kidney revealed improved tissue integrity in fish after improved wastewater treatment. In parallel, biochemical measurements of glycogen revealed increased energy resources in fish liver and, furthermore, hsp70 levels in livers of exposed rainbow trout and in kidneys of exposed brown trout were lower after than before the WWTP upgrade. In summary, additional treatment with powdered activated carbon led to a reduction of potentially hazardous chemicals in the effluent and the adjacent river and, consequently, to an improvement of fish health in the receiving water course.

Water quality assessment in the "German River of the years 2014/2015": how a case study on the impact of a storm water sedimentation basin displayed impairment of fish health in the Argen River (Southern Germany)

BACKGROUND

The present work investigates the impact of discharges from a storm water sedimentation basin (SSB) receiving runoff from a connected motorway in southern Germany. The study lasted for almost two years and was aimed at assessing the impact of the SSB on the fauna of the Argen River, which is a tributary of Lake Constance. Two sampling sites were examined up- and downstream of the SSB effluent. A combination of different diagnostic methods (fish embryo test with the zebrafish, histopathology, micronucleus test) was applied to investigate health impairment and genotoxic effects in indigenous fish as well as embryotoxic potentials in surface water and sediment samples of the Argen River, respectively, in samples of the SSB effluent. In addition, sediment samples from the Argen River and tissues of indigenous fish were used for chemical analyses of 33 frequently occurring pollutants by means of gas chromatography. Furthermore, the integrity of the macrozoobenthos community and the fish population were examined at both investigated sampling sites.

RESULTS

The chemical analyses revealed a toxic burden with trace substances (originating from traffic and waste water) in fish and sediments from both sampling sites. Fish embryo tests with native sediment and surface water samples resulted in various embryotoxic effects in exposed zebrafish embryos (Fig. 1). In addition, the health condition of the investigated fish species (e.g., severe alterations in the liver and kidney) provided clear evidence of water contamination at both Argen River sites (Fig. 2). At distinct points in time, some parameters (fish development, kidney and liver histopathology) indicated stronger effects at the sampling site downstream of the SSB effluent than at the upstream site.

CONCLUSIONS

Our results clearly showed that the SSB cannot be assigned as the main source of pollutants that are released into the investigated Argen River section. Moreover, we showed that there is moderate background pollution with substances originating from waste waters and traffic which still should be taken seriously, particularly with regard to the impairment of fish health at both investigated field sites. Since the Argen is a tributary of Lake Constance, our results call for a management plan to ensure and improve the river's ecological stability.

Alterations in histology and antioxidant defense system in the testes of the lake Van fish (Alburnus tarichi Güldenstädt, 1814)

Recent reports have demonstrated gonadal abnormalities in the Lake Van fish (Alburnus tarichi) from Lake Van caused by increasing pollution. In the present study, the fish was collected from an area of Lake Van receiving mainly sewage treatment plant effluent at prespawning period (April) and from a river (Karasu) which is close to the polluted area of the lake and where the fish migrates at spawning period (May). Collected specimens were examined for testicular alterations, gonadosomatic index (GSI), condition factor (CF), and antioxidant defense system biomarkers based on comparison with a reference lake (Erçek) and a reference freshwater inlet (Memedik River). Histological examinations of the testes of fish from the polluted area and the connected river showed various alterations consisting of macrophage aggregates, vacuolation, pyknosis, germ cell degeneration, seminiferous tubule dilation, disorganization of tubules, reduced spermatozoa, and fibrosis. A lower GSI and CF were also observed. Moreover, alterations in the antioxidant system biomarkers were determined in the testis tissues of fish from the Lake Van and Karasu River, indicating oxidative stress. These results suggest that the abnormalities in the testes are causally related to the increased oxidative stress, and pollution in Lake Van may have adversely affected the reproductive health of the lake Van fish.

Histopathology investigation on the Vardar chub (Squalius vardarensis) populations captured from the rivers impacted by mining activities

Many natural freshwater ecosystems, especially in the north eastern Macedonia, are polluted with heavy metals, which are released by active mines. Long-term exposure to high levels of dissolved metals might result in increased metal bioaccumulation in organs of aquatic organisms, and consequently might cause various sub-toxic and toxic effects. The aim of this study was to assess the health of Vardar chub (Squalius vardarensis) inhabiting mining impacted rivers Zletovska and Kriva, in comparison with chub from the reference Bregalnica River. It was done by use of indicators of tissue damage (histopathology of liver and gonads) and general indicators of exposure to environmental stressors (condition factor, organo-somatic indices and external/internal macroscopic lesions). Histological assessment of gonads revealed good reproductive health in all three rivers, indicating high tolerance of gonads to contaminant exposure. Contrary, several external/internal lesions were more pronounced in chub from severely metal contaminated Zletovska River. Prevalence of hepatic lesions was also higher in mining impacted rivers (in Kriva, 70%; in Zletovska, 59%) compared to Bregalnica River (38%). The spectrum of histological lesions observed in chub liver varied from non-specific minor degenerative conditions, such as lymphocyte infiltration, fibrosis, parasites, granulomas and lipidosis, to extensive and/or more severe changes such as bile duct proliferation, necrosis, megalocytosis, light-dark hepatocytes and hepatocytes regeneration. The results of histopathological investigation for all three rivers showed clear signs of water contamination, especially prominent in mining influenced rivers. More research efforts should be devoted to study of environmental conditions and metal contamination in the mining impacted rivers worldwide, especially of their effects on health of local ichthyofauna.

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

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

Environmental safety level of lead (Pb) pertaining to toxic effects on grey mullet (Mugil cephalus) and tiger perch (Terapon jarbua)

Acute and chronic bioassay toxicity test of Lead (Pb) in Grey Mullet (Mugil cephalus), and Tiger perch (Terapon jarbua) was conducted. LC50 values (Lethal Concentration) from acute tests and chronic values were calculated by the geometric mean of the No-Observed-Effect Concentration (NOEC) and the Lowest-Observed-Effect Concentration (LOEC) in a study period of 30 days. This research was conducted to evaluate the quantitative relationship between toxicity test statistics and correlation between toxicant and the organisms exposed. Three test average LC50 was analyzed for 24, 48, 72, and 96 h and the 96 h average LC50 of M. cephalus and T. jarbua is 2.57 ± 0.47 and 2.99 ± 0.23 mg/L of Pb, respectively. Significant correlation is observed with the increased time duration and exposure concentration. The NOEC and LOEC values were calculated based on survival of test organisms for M. cephalus and T. jarbua and the values are 0.014 and 0.029 and 0.011 and 0.022 mg/L, respectively. The chronic value is found to be 0.011 mg/L for M. cephalus and 0.021 mg/L for T. jarbua. The intensity of biochemical and histological alterations increased gradually with increased Pb concentration and the exposure time. Toxicity testing is the primary step to determine the water quality safe limit on marine organisms. The outcome of the study indicates that the sensitivity of juvenile organisms to Pb, persistence of toxic effects and biomarkers as a tool capable of revealing the toxic effects of heavy metals on the environment and aquatic biota.

Histopatological alterations and oxidative stress in liver and kidney of Leuciscus cephalus following exposure to heavy metals in the Tur River, North Western Romania

Pollution of the aquatic environment by heavy metals is a great concern worldwide. Freshwater fish ingests various metals through gills, skin or diet. Our aim was to investigate the oxidative stress and histopathological injuries induced by Fe, Cu, Zn, Pb, Cd in the liver and kidney of Leuciscus cephalus. Fish samples were collected from two sites in the Tur River, NW Romania, in upstream and downstream of a pollution source. Metals were differently distributed in the liver and kidney of fish. The highest concentrations of Fe, Cu and Pb were found in liver, whereas Zn and Cd concentrations were the highest in kidney in specimens collected from the downstream site. The histopathological changes were associated with metal bioaccumulation, being more severe in kidney than liver. Malondialdehyde (MDA) and advanced oxidation protein products (AOPP) increased significantly in the liver and kidney of fish from downstream site compared to upstream one, whereas reduced glutathione (GSH) decreased. The activities of superoxide dismutase (SOD), catalase (CAT) and glutathione-S-transferase (GST) increased significantly in livers, whereas SOD increased in kidney. Our study revealed that liver has a higher capacity and adaptability to counteract ROS compared to kidney. The more pronounced increase of hepatic SOD, CAT and GST activities is related milder structural changes observed in liver compared to kidney, where lesions were not reduced by antioxidant defense system.

A multibiomarker evaluation of urban, industrial, and agricultural exposure of small characins in a large freshwater basin in southern Brazil

Iguaçu River is the second most polluted river of Brazil. It receives agrochemicals and contaminants of urban and industrial sources along its course. A multibiomarker approach was employed here to evaluate the health of a small characin (Astyanax spp.) at two sites along the river, sampled during a dry (autumn) and a rainy (spring) season. Biomarkers were condition factor and somatic indices (gonads and liver); genetic damage (comet assay and micronucleus test); enzyme activities such as hepatic catalase (CAT) and glutathione S-transferase (GST), lipoperoxidation (LPO), branchial and renal carbonic anhydrase (CA), acetylcholinesterase (AChE) in the muscle and the brain, histopathology of the liver and gills, and concentrations of polycyclic aromatic hydrocarbons (PAHs) in bile. There were no consistent differences in biomarker responses between the two study sites. Some biomarkers revealed greater potential impact in the rainy season, when increased amounts of contaminants are washed into the river (combined CAT inhibition and LPO increase, CA upregulation). Other biomarkers, however, revealed potential greater impact in the dry season, when contaminants potentially concentrate (GST induction, AChE inhibition, and liver histopathological alterations). Although of a complex nature, field experiments such as this provide rich data for monitoring protocols and assessment of general risk of exposure to pollutants of river systems.

Ultrastructural effects on gill tissues induced in red tilapia Oreochromis sp. by a waterborne lead exposure

Experiments on hybrid red tilapia Oreochromis sp. were conducted to assess histopathological effects induced in gill tissues of 96 h exposure to waterborne lead (5.5 mg/L). These tissues were investigated by light and scanning electron microscopy. Results showed that structural design of gill tissues was noticeably disrupted. Major symptoms were changes of epithelial cells, fusion in adjacent secondary lamellae, hypertrophy and hyperplasia of chloride cells and coagulate necrosis in pavement cells with disappearance of its microridges. Electron microscopic X-ray microanalysis of fish gills exposed to sublethal lead revealed that lead accumulated on the surface of the gill lamella. This study confirmed that lead exposure incited a difference of histological impairment in fish, supporting environmental watch over aquatic systems when polluted by lead.

Evaluation of histopathological alterations in the gills of Vardar chub (Squalius vardarensis Karaman) as an indicator of river pollution

Quantification of histopathological alterations in the gills of Vardar chub (Squalius vardarensis Karaman) was performed in 2012 in rivers of north-eastern Macedonia, with the aim to examine the effects of water quality in the rivers (Zletovska and Kriva River-impacted by active Pb/Zn mines; Bregalnica River-contaminated by agricultural waste). The biological alterations in chub were classified as: circulatory disturbances, regressive and progressive changes, but their severity differed. Altogether the mildest changes were observed in the gills of chub from the Bregalnica River, a less polluted river, whereas mining impacted rivers were characterized by more severe alterations. In the gills of chub from the Zletovska River, which is highly contaminated with numerous metals, sulphates and chlorides, the highest lesion indices were found for the regressive changes of both epithelium and supporting tissue, with typical lesions referring to atrophy, thinning and lifting of epithelial cells, necrosis of epithelium and chloride cells, as well as deformations of lamellar cartilaginous base. Gill damages of chub from the Kriva River were overall milder compared to the Zletovska River, in accordance with pollution status. In the gills of chub from that river, progressive changes were more pronounced, specifically severe hyperplasia of mucous cells and epithelium in the interlammellar space, leading to fusion of lamellae, as well as hypertrophy of chloride cells. The comparison between seasons indicated higher intensity of progressive changes in all three rivers in autumn, when water level was very low, and consequently, water contamination was more pronounced due to concentration effect. The pattern and severity of histopathological alterations in the chub gills reflected differences in contamination levels and type of contaminants in different rivers and sampling periods, and thus have been proven as a valuable indicator of water quality.

Impact of wastewater on fish health: a case study at the Neckar River (Southern Germany) using biomarkers in caged brown trout as assessment tools

The present work describes a field survey aiming at assessing the impact of a sewage treatment plant (STP) effluent on fish health by means of biomarkers. Indigenous fish were absent downstream of the STP. To elucidate the reason behind this, brown trout (Salmo trutta f. fario) were exposed in floating steel cages up- and downstream of a STP located at the Neckar River near Tübingen (Southern Germany), for 10 and 30 days. A combination of biomarker methods (histopathological investigations, analysis of the stress protein Hsp70, micronucleus test, B-esterase assays) offered the possibility to investigate endocrine, geno-, proteo- and neurotoxic effects in fish organs. Biological results were complemented with chemical analyses on 20 accumulative substances in fish tissue. Even after short-term exposure, biomarkers revealed clear evidence of water contamination at both Neckar River sites; however, physiological responses of caged brown trout were more severe downstream of the STP. According to this, similar bioaccumulation levels (low μg/kg range) of DDE and 12 polycyclic aromatic hydrocarbons (PAHs) were detected at both sampling sites, while up to fourfold higher concentrations of four PAHs, methyl-triclosan and two synthetic musks occurred in the tissues of downstream-exposed fish. The results obtained in this study suggest a constitutive background pollution at both sites investigated at the Neckar River and provided evidence for the additional negative impact of the STP Tübingen on water quality and the health condition of fish.

Histopathological indices in sole (Solea solea) and hake (Merluccius merluccius) for implementation of the European Marine Strategy Framework Directive along the Basque continental shelf (SE Bay of Biscay)

Sole and hake, together with sediments, were collected during two campaigns along the Basque continental shelf to study the utility of two existing histopathological indices for assessing the biological effects of contaminants to implement the European Marine Strategy Framework Directive. Hepatic and gonadal histopathology were measured, and metal and/or organic contaminants were determined in both liver and sediments. Sediments from the Basque continental shelf were found to be moderately impacted by metals but non-impacted by organic compounds. Metal bioaccumulation and histopathological lesions in liver were higher in sole than in hake, although non-specific and early non-neoplastic toxicopathic lesions were observed in both species. No gross alterations were recorded in gonad. The two histopathological indices applied were highly correlated in both organs but the lack of correlation between sediment contamination levels, bioaccumulation and histopathological indices suggests that other factors, rather than pollution alone, are responsible for the biological effects observed.

Biological plausibility as a tool to associate analytical data for micropollutants and effect potentials in wastewater, surface water, and sediments with effects in fishes

Discharge of substances like pesticides, pharmaceuticals, flame retardants, and chelating agents in surface waters has increased over the last decades due to the rising numbers of chemicals used by humans and because many WWTPs do not eliminate these substances entirely. The study, results of which are presented here, focused on associations of (1) concentrations of micropollutants in wastewater treatment plant (WWTP) effluents, surface waters, sediments, and tissues of fishes; (2) results of laboratory biotests indicating potentials for effects in these samples and (3) effects either in feral chub (Leuciscus cephalus) from two German rivers (Schussen, Argen) or in brown trout (Salmo trutta f. fario) and rainbow trout (Oncorhynchus mykiss) exposed in bypass systems to streamwater of these rivers or in cages directly in the rivers. The Schussen and Argen Rivers flow into Lake Constance. The Schussen River is polluted by a great number of chemicals, while the Argen River is less influenced by micropollutants. Pesticides, chelating agents, flame retardants, pharmaceuticals, heavy metals, polychlorinated biphenyls (PCBs), and polybrominated diphenyl ethers (PBDEs) were detected in effluents of a WWTP discharging to the Schussen as well as in surface water, and/or fishes from downstream of the WWTP. Results obtained by biotests conducted in the laboratory (genotoxicity, dioxin-like toxicity, and embryotoxicity) were linked to effects in feral fish collected in the vicinity of the WWTP or in fishes exposed in cages or at the bypass systems downstream of the WWTP. Dioxin-like effect potentials detected by reporter gene assays were associated with activation of CYP1A1 enzymes in fishes which are inducible by dioxin-like chemicals. Abundances of several PCBs in tissues of fishes from cages and bypass systems were not associated with these effects but other factors can influence EROD activity. Genotoxic potentials obtained by in vitro tests were associated with the presence of micronuclei in erythrocytes of chub from the river. Chemicals potentially responsible for effects on DNA were identified. Embryotoxic effects on zebrafish (Danio rerio), investigated in the laboratory, were associated with embryotoxic effects in trout exposed in streamwater bypass systems at the two rivers. In general, responses at all levels of organization were more pronounced in samples from the Schussen than in those from the Argen. These results are consistent with the magnitudes of chemical pollution in these two streams. Plausibility chains to establish causality between exposures and effects and to predict effects in biota in the river from studies in the laboratory are discussed.

Heavy metals bioaccumulation and histopathological changes in Auchenoglanis occidentalis fish from Tiga dam, Nigeria

The assessment of heavy metals concentration in Tiga dam, Nigeria vis-à-vis their bioaccumulation and histopathological alterations in Auchenoglanis occidentalis from it were carried out. The water of the dam and the liver of the fish were analyzed for zinc (Zn), cadmium (Cd), lead (Pb) and iron (Fe) concentrations and their bioaccumulation factors. At the same time, the gills, liver and kidney of the exposed fish were also examined for histopathological alterations. The results revealed that concentrations of the metals differs significantly (p < 0.05) between the dam's water and the liver of the sampled fish. Liver bioaccumulations of the metals were in the order of Zn > Fe > Cd > Pb. However, the degree of tissue alterations in the gills showed their normal functioning despite the observed alterations while liver and kidney were mildly and moderately damaged, respectively. This indicated that Zn, Cd, Pb and Fe polluted the dam.

A histopathological and biometric comparison between catfish (Pisces, Ariidae) from a harbor and a protected area, Brazil

BACKGROUND

Histopathological lesions and biometric variations in catfish species are statistically associated with chemical contaminant exposure. A histopathological and biometric database for the catfish Sciades herzbergii and Bagre bagre from São Luís Island (Port Area) and Caranguejos Island (Reference Area) is presented. Branchial and hepatic lesions were classified into three reaction patterns: 1) circulatory or inflammatory disturbances; 2) regressive changes; 3) progressive changes. This paper summarizes research efforts aimed at characterizing the biomonitoring potential of catfish from two islands in Brazil, which exhibit great habitat diversity and different levels of human intervention.

RESULTS

The weights and lengths of the catfish caught at the Port Area were smaller than those from the Reference Area. No histopathological lesions were observed in S. herzbergii examined at the reference site (Caranguejos Island). In contrast, 90% of S. herzbergii from sites located in the Port Area (São Luís Island) had one or more types of branchial and hepatic lesions. One or more of the five lesions were observed on 16 B. bagre from São Luís Island and Caranguejos Island.

CONCLUSION

The utility of histopathological lesions and biometric data as sensitive indicators of the health of wild catfish populations has been demonstrated. Sciades herzbergii proved to be a better species for biomonitoring because it was more sensitive to the impacted site (Port Area) compared with the region relatively free of contaminants (Reference Area).

The impact of organochlorines and metals on wild fish living in a tropical hydroelectric reservoir: bioaccumulation and histopathological biomarkers

This study evaluates the contaminants in water and their bioaccumulation in the gills and liver of two ecologically distinct fish species, Astyanax fasciatus and Pimelodus maculatus, living in the reservoir of the Furnas hydroelectric power station located in Minas Gerais in the southeastern Brazil. The histological alterations in these organs are also examined. Water and fish were collected in June and December from five sites (site 1: FU10, site 2: FU20, site 3: FU30, site 4: FU40 and site 5: FU50) in the reservoir, and agrochemicals and metals selected based on their use in the field crops surrounding the reservoir were analyzed in the water and in the fish gills and livers. The concentrations of the organochlorines aldrin/dieldrin, endosulfan and heptachlor/heptachlor epoxide as well as the metals copper, chromium, iron and zinc in the gills and livers of both fish species were higher in June than in December; the liver accumulated higher concentrations of contaminants than the gills. The organochlorine metolachlor was detected only in the liver. The histological pattern of changes was similar in both species with regard to contaminant accumulation in the gills and liver. Fish from FU10, the least contaminated site, exhibited normal gill structure and moderate to heavy liver damage. Fish collected at FU20 to FU50, which were contaminated with organochlorines and metals, showed slight to moderate gill damage in June and irreparable liver damage in the livers in June and December. The histological changes in the gills and liver were suitable to distinguishing contaminated field sites and are therefore useful biomarkers for environmental contamination representing a biological end-point of exposure.

Ichthyofauna as bioindicator of environmental quality in an industrial district in the amazon estuary, Brazil

The objective of the present study was to describe the ecological status of ichthyofauna in an industrial district (Pará river, Amazon estuary), through the use of different environmental descriptors. To evaluate the impacts of the industrial area and cargo terminal, three areas were considered: Zone 1 (maximum impact), Zone 2 (median impact) and Zone 3 (low impact). A total of 77 species were captured. Differences in the composition of the ichthyofauna were recorded between Zones and environments (main channel and tidal channel). The ecological indices revealed clear evidence of the impact of the industrial hub and cargo terminal on the fish communities. In Zone 1, there was a reduction in the number of feeding groups (in the main channel) and larger fish and the Shannon diversity index and Margalef's richness were also significantly lower. The multivariate analysis separated the different Zones clearly into three groups, indicating marked differences in the levels of contamination in the different parts of the study area.

Invertebrates as indicators for chemical stress in sewage-influenced stream systems: toxic and endocrine effects in gammarids and reactions at the community level in two tributaries of Lake Constance, Schussen and Argen

The present study investigates the impact of releases from waste water treatment plants and storm water overflow basins on gammarids and other macrozoobenthos. The study relates to a recent upgrading of a waste water treatment plant (Langwiese) at the Schussen river, an important tributary to Lake Constance. Samples were taken at different sites at the Schussen river upstream and downstream of a storm water overflow basin and the waste water treatment plant Langwiese and, in parallel, at the Argen river, a less polluted reference stream. We assessed the influence of water quality on the distribution of macrozoobenthos and on the health of gammarid populations by a variety of ecotoxicological methods including biomarkers prior to the expansion of the waste water treatment plant. Through histopathological studies, the impact of parasites on host tissue health was evaluated. Analyses of heat shock protein (hsp70) levels allowed us to draw conclusions about the proteotoxicity-related stress status of the organisms. Furthermore, gammarid populations from all sites were investigated in respect to sex ratio, parasitism rate, and fecundity. Macrozoobenthos community integrity was determined by means of the saprobic index and the abundance as well as by the number of taxa. In gammarids, the sex ratio was significantly shifted towards females, fecundity was significantly decreased, and the hsp70 level was significantly increased downstream of the waste water treatment plant Langwiese, compared to the upstream sampling site. Similarly, these effects could be detected downstream of three small storm water overflow basins. In the macrozoobenthos communities, the abundance of taxa, the number of taxa, the number of ephemeroptera, plecoptera, and trichoptera taxa (EPT-taxa), and the number of sensitive taxa decreased downstream of the storm water overflow basin Mariatal as well as downstream of the waste water treatment plant Langwiese. Our study showed, that waste water treatment plants and storm water overflow basins affected macroinvertebrate communities and the health of gammarids.

Biochemical and histopathological changes in liver of the Nile tilapia from Egyptian polluted lakes

The aim of the present study was to analyze the impact of environmental contamination on oxidative stress and histopathologic biomarkers in liver of the Nile tilapia, Oreochromis niloticus, collected from four sites that differ in their extent of pollution load, including heavy metals: the southeast basin (SEB), main basin (MB), and northwest basin (NWB) of Lake Mariut as well as Boughaz El-Maadiya, a channel in Lake Edku. The SEB was the less-impacted site, and thus considered as a reference. High concentrations of heavy metals (cadmium, copper, iron, lead, zinc, and manganese) were detected in fish liver at sites with anthropogenic pressure. All biomarkers, lipid peroxidation (in the MB, NWB, and Lake Edku), superoxide dismutase (in the MB and NWB), and glutathione peroxidase, and reduced glutathione (in the NWB) were found to be significantly higher compared to the reference values. Catalase, glutathione reductase, and glucose-6-phosphate dehydrogenase showed a varied response and displayed significantly lower activities in the polluted sites. Certain hepatic lesions, detected microscopically, were stimulated in fish from the MB and NWB, reflecting the high contamination of these areas. These included foci of necrosis, melanomacrophage infiltration, congestion, nuclear pyknosis, and extensive vacuolation corresponding to relatively higher lipid content. Overall, our results suggest that the selected biomarkers are useful for the assessment of pollution impacts in natural aquatic environments influenced by multiple pollution sources. The existence of chronic background pollution of the test sites implies that the observed biomarker responses cannot be solely attributed to heavy metals.

Histopathological changes in tissues of Bithynia siamensis goniomphalos incubated in crude extracts of camellia seed and mangosteen pericarp

The present study was performed to observe histopathological changes in tissues of Bithynia siamensis goniomphalos (Gastropoda, Bithyniidae) incubated in crude extract solutions of camellia (Camellia oleifera) seed and mangosteen (Garcinia mangostana) pericarp, and furthermore to estimate the molluscicidal effects of 2 plant substances. Substantial numbers of bithyniid snails were incubated in various concentrations of 2 plant solution for 24 hr. As the positive control, snails incubated in various concentrations of niclosamide, a chemical molluscicide, were used. The histopathological findings were observed in sectioned snail specimens of each experimental and control groups. The results showed that both camellia and mangosteen extracts had molluscicidal effects at 24 hr with 50% lethal concentration (LC50) at concentrations of 0.003 and 0.002 g/ml, respectively, while niclosamide had LC50 at concentrations 0.599 ppm. B. siamensis goniomphalos snail tissues (foot, gill, and digestive system) showed disruption of columnar muscle fibers of the foot, reduction of the length and number of gill cilia, numerous mucous vacuoles, and irregularly shaped of epithelial cells. Irregular apical and calciferous cells, dilatation of the digestive gland tubule, and large hemolymphatic spaces, and irregular apical surfaces, detachment of cilia, and enlargement of lysosomal vacuoles of epidermis were also shown in all groups. By the present study, it is confirmed that 2 plants, camellia and mangosteen, are keeping some substance having molluscicidal effects, and histopathological findings obtained in this study will provide some clues in further studies on their action mechanisms to use them as natural molluscicides.

Matching metal pollution with bioavailability, bioaccumulation and biomarkers response in fish (Centropomus parallelus) resident in neotropical estuaries

Two neotropical estuaries affected by different anthropogenic factors were studied. We report levels of metals and metalloids in water and sediment as well as their influence on genetic, biochemical and morphological biomarkers in the native fish Centropomus parallelus. Biomarkers reflected the fish health status. Multivariate statistics indicated both spatial and temporal changes in both water and sediment, which are linked to the elemental composition and health status of inhabitant fish, showing the biggest influence of surface water, followed by sediments and interstitial water. Bioaccumulation in fish muscle was useful to identify elements that were below detection limits in water, pointing out the risk of consuming fish exceeding allowance limits for some elements (As and Hg in this case). Multivariate statistics, including physical, chemical and biological issues, presents a suitable tool, integrating data from different origin allocated in the same estuary, which could be useful for future studies on estuarine systems.

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

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

Histopathological biomarkers in gills and liver of Oreochromis niloticus from polluted wetland environments, Saudi Arabia

Fish live in direct contact with their immediate external environment and, therefore, are highly vulnerable to aquatic pollutants. In this study, Oreochromis niloticus were caught at three different sites in Al-Hassa irrigation channels, namely Al-Jawhariya, Um-Sabah and Al-Khadoud. The histological changes in gills and liver were detected microscopically and evaluated with semi-quantitative analyses. Also, heavy metals have been determined in the water samples in these sites. Results showed that all sites were polluted by different kinds of heavy metals. Cd and Pb were mostly detected at concentrations above the WHO reference values. Meanwhile, various histopathological abnormalities were observed in gills and liver of fish specimens. In the gill filaments, cell proliferation, lamellar cell hyperplasia, lamellar fusion, lifting of the respiratory epithelium, and the presence of aneurysmal areas were observed. In the liver, there was vacuolization of the hepatocytes, sinusoidal congestion, necrosis of the parenchyma tissue, nuclear pyknosis, eosinophilic hepatocellular degeneration, pigment accumulation, an increase in the number and size of melanomacrophage centers. Liver tumors with severe chronic inflammation were occasionally found in fish at Al-Khadoud area (first-time report). The histological lesions were comparatively most severe in the liver. Despite heavy metals assessment did not show marked differences among sites, histopathological biomarkers indicated that the surveyed fish are living under stressful environmental conditions. So, we suggest use those biomarkers in future monitoring of aquatic systems.

Assessment of the state of the gibel carp Carassius auratus gibelio in the Amur River Basin: heavy-metal and arsenic concentrations and histopathology of internal organs

This study describes the concentrations of heavy metals and arsenic (As) and the basic histopathological changes in the internal organs of gibel carp Carassius auratus gibelio from five sites of the Amur River basin. Gibel carp from Sindinskaya Passage had the highest liver concentrations of zinc (Zn) (31.95 ± 13.443), copper (Cu) (12.52 ± 5.746), manganese (9.22 ± 8.121), and cadmium (0.37 ± 0.660 mg/kg wet weight [ww]) compared with fish captured from the Bol'shoi Ussuriiskii Island area and Kadi Lake; however, concentrations of nickel (0.22 ± 0.156 mg/kg ww) were not significantly different, and concentrations of lead (0.19 ± 0.121 mg/kg ww) were higher than those in fish from Kadi Lake. Mean concentrations of metals and As in muscles were lower than Russia's recommended limits for food products; however, concentrations of Cu, Zn, and Hg in individual fish were greater than the limit. Kidney disease was detected in 100% of sampled carp. Kidney disease was characterized by the formation of numerous granulomas in kidney tissues between the renal tubules. The degree of granulomatosis varied among sites. Granulomatous kidney disease in gibel carp is widespread in many reservoirs of the lower Amur River basin. The following histopathological changes were detected in liver: vacuolization of hepatocytes, hypertrophy of multiple hepatocytes, binuclearity, presence of numerous irregularly shaped nuclei in hepatocytes, karyopyknosis, diffuse necrosis of hepatocytes (in some cases focal), and edema. Necrotic changes in hepatocytes, which are important indices of the toxic effect of pollutants, were found in the majority of investigated carp from the lower Amur River basin. Some fish had simultaneous pathological alterations in multiple organs.