Effects of chronic exposure of 2,4-dichlorophenol on the antioxidant system in liver of freshwater fish Carassius auratus

There were few reports on the antioxidant response of aquatic organisms exposed to 2,4-dichlorophenol (2,4-DCP). This research explored the hepatic antioxidant responses of fish to long-term exposure of 2,4-DCP for the first time. Freshwater fish Carassius auratus were chosen as experimental animals. The fish were exposed to six different concentrations of 2,4-DCP (0.005-1.0 mg/l) for 40 days and then liver tissues were separated for determination. As shown from the results, 40 days afterwards, the activities of catalase (CAT) and selenium-dependent glutathione peroxidase (Se-GPx) and the content of oxidized glutathione (GSSG) were induced significantly on the whole compared to control group; superoxide dismutase (SOD) responded to 2,4-DCP exposure at only 0.005 mg/l; the content of reduced glutathione (GSH) was suppressed continuously except Group 7; the activity of glutathione reductase was inhibited initially and then restored to control level from Group 4 on; glutathione S-transferase had only slight responses in Groups 3 and 4. Total glutathione (tGSH) and GSH/GSSG ratio were also calculated to analyze the occurrence of oxidative stress. Besides, good dose-effect relations, which cover most of the exposure concentration range, were found between 2,4-DCP level and CAT activity, GSSG content, Se-GPx activity, respectively. In conclusion, SOD and Se-GPx may be potential early biomarkers of 2,4-DCP contamination in aquatic ecosystems, and further studies will be necessary.     

The effects of fenvalerate on different tissues of freshwater fish Cirrhinus mrigala

The histopathological changes of fenvalerate on the gill, kidney, liver and intestine tissues of the Cirrhinus mrigala were determined by light microscopy. The fish were exposed to two sub-lethal concentrations of fenvalerate (1.5-3.0 ppb). The most common gill changes at all concentrations of fenvalerate were epithelial hyperplasia, epithelial necrosis, desquamation and lamellar fusion. Besides, epithelial lifting, oedema, swelling at the tips of secondary lamellae and curling of secondary lamellae were other histopathological changes. Necrosis of tubular epithelium, pycnotic nuclei in the hematopoietic tissue, hypertrophied epithelial cells of renal tubules, narrowing of the tubular lumen, expansion of space inside the Bowman's capsule and contraction of the glomerulus were observed in kidney tissues of fish. Hepatic lesions in the liver tissues of fish exposed to fenvalerate were characterized by congestion, cloudy swelling of hepatocytes and focal necrosis. Atrophy of epithelial cells, necrosis of epithelial cells, desquamation of mucosal epithelium and infiltration of lymphocytes into the lamina propria were detected in intestine tissues of fish after exposure to fenvalerate.     

Assessment of the pollution impact on biomarkers of effect of a freshwater fish

Changes in biomarkers of fish captured from stressed environments may represent a reliable tool in revealing sublethal effects of the pollutants found in aquatic ecosystems. The response patterns of selected biochemical and morphological variables biomarkers of effect were assessed in adult females of an indigenous teleost Cnesterodon decemmaculatus, caught at a polluted site (San Francisco) of the Reconquista river (Buenos Aires, Argentina). Combined field-caging experiments with controlled laboratory exposure to clean media were performed. The biochemical parameters measured were specific activities of gill (Na+ + K+)-ATPase, liver AlaAT and AspAT, and brain AChE; LSI and CF were also calculated. The changes in gill (Na+ + K+)-ATPase and liver AlaAT activities of fish captured in the field in most cases were reversible after transfer to clean media. The results were interpreted in association with the physicochemical profile of the water samples taken simultaneously with the capture of the fish. Results suggested the suitability of the test species used as tools in environmental monitoring programs of risk assessment.     

Trace metal levels in freshwater fish, sediment and water

The trace metal concentrations in water, sediment and aquatic organisms, such as fish, could indicate the level and tendency of the pollution. This is important not only for the protection of the environment, but for evaluation of the quality of fish meat either captured from natural waters or cultured in fishponds. The total trace metal concentrations in samples of fish from different regions of Hungary and from different species have been determined by using an X-ray fluorescence technique (EDXRF). Water, sediment and fish samples from fishpond systems with different feeding and stocking has also been analyzed. In the case of zinc contents, differences have been traced between the cultured and wild common carp. In the case of common carp reared under different feeding conditions, differences were also observed in the zinc concentration. The retention of the trace metals in the fish has been studied by measuring the levels in sediment, water and feed. The different retention can be explained by the different availability of zinc in the applied feeds, which can be related to the presence of different metal species in the feeds.     

Insecticides biomarker responses on a freshwater fish Corydoras paleatus (Pisces: Callichthyidae)

This study was undertaken to investigate the effects of sublethal concentration of three different classes of insecticides (carbamate, organophosphate, and pyrethroid compounds) on the freshwater fish Corydoras paleatus. For this purpose, fish were exposed for 96 hours to commercial pesticides. Different biomarkers were analyzed as levels of lipid peroxidation (LPO), piscine micronucleus test, and enzymatic activities of catalase (CAT), glutathione S-transferase (GST), and acetylcholinesterase (AChE). The brain AChE was inhibited with carbaryl and methyl parathion, but no inhibition was observed with deltamethrin. The insecticides did not cause oxidative stress or genotoxic effects at the tested concentrations. Further studies are needed to elucidate the biotransformation of Corydoras paleatus insecticides and a possible resistance mechanism.     

Half a century of changing mercury levels in Swedish freshwater fish

The variability of mercury (Hg) levels in Swedish freshwater fish during almost 50 years was assessed based on a compilation of 44 927 observations from 2881 waters. To obtain comparable values, individual Hg concentrations of fish from any species and of any size were normalized to correspond to a standard 1-kg pike [median: 0.69 mg kg^?1 wet weight (ww), mean ± SD: 0.84 ± 0.67 mg kg^?1 ww]. The EU Environmental Quality Standard of 0.02 mg kg^?1 was exceeded in all waters, while the guideline set by FAO/WHO for Hg levels in fish used for human consumption (0.5–1.0 mg kg^?1) was exceeded in 52.5 % of Swedish waters after 2000. Different trend analysis approaches indicated an overall long-term decline of at least 20 % during 1965–2012 but trends did not follow any consistent regional pattern. During the latest decade (2003–2012), however, a spatial gradient has emerged with decreasing trends predominating in southwestern Sweden.     

Bioavailability of 2,3,7,8-tetrachlorodibenzo-p-dioxin from municipal incinerator fly ash to freshwater fish

The bioavailability of 2,3,7,8-TCDD from municipal incinerator fly ash to freshwater fish was determined. It was observed that carp exposed to fly ash containing all 22 TCDD isomers, or the solvent extract of the fly ash, retain only 2,3,7,8-TCDD. Exposures with fly ash appears to follow a dose response relationship for bioconcentration, however, the bioavailability of 2,3,7,8-TCDD was not directly related to the level of 2,3,7,8-TCDD in fly ash for two fly ash samples studied.     

Effects of simetryne on growth of various freshwater algal taxa

The sensitivity of 56 algal strains, representing 7 taxonomic groups to the triazine herbicide, simetryne, was examined using EC50 values for growth. There was a wide range of values from 6.5 to 1500 microg litre(-1). The Volvocales (Chlorophyceae, Chlorophyta) and Cyanophyceae (Cyanophyta) as a whole were the most sensitive, whereas the Desmidiales (Charophyceae, Chlorophyta) and Bacillariophyceae (Chromophyta) were the most tolerant, although sensitivity differed among strains of a single species. Sensitive and tolerant species were both isolated from samples collected at the same site. The results suggest that changes in species composition and relative abundance will occur when herbicides are applied in natural habitats.     

Toxic effect of synthetic pyrethroid permethrin on the enzyme system of the freshwater fish Channa striatus

Treatment with 40% and 80% of the LC50 (24h) of the pyrethroid permethrin after 24h exposure causes significant reduction in the activity of lactate dehydrogenase and cytochrome oxidase and enhanced the succinate dehydrogenase activity in the tissues of the freshwater fish Channa striatus. The results indicate that permethrin blocks aerobic as well as anaerobic metabolism in the exposed fishes.     

A comparison of microplastic contamination in freshwater fish from natural and farmed sources

Contamination of aquatic systems mainly by urbanization and poor sanitation, deficient or lack of wastewater treatments, dumping of solid residues, and run off has led to the presence of particles, including manmade polymers, in tissues of many marine and freshwater species. In this study, the prevalence of microplastics (MPs) in freshwater fish from farmed and natural sources was investigated. Oreochromis niloticus from aquaculture farms in the Huila region in Colombia, and two local species (Prochilodus magdalenae and Pimelodus grosskopfii), naturally present in surface waters were sampled. Of the particles identified, fragments were the predominant type in the three tissue types (stomach, gill, and flesh) derived from farmed and natural fishes. MicroFT-IR spectroscopy was conducted on 208 randomly selected samples, with 22% of particles identified as MPs based on spectra with a match rate ≥ 70%. A total of 53% of identified particles corresponded to cellophane/cellulose, the most abundant particle found in all fish. Not all fish contained MPs: 44% of Oreochromis farmed fish contained MPs, while 75% of natural source fish contained MPs in any of its tissues. Overall, polyethylene terephthalate (PET), polyester (PES), and polyethylene (PE) were the prevalent MPs found in the freshwater fish. A broader variety of polymer types was observed in farmed fish. The edible flesh part of fish presented the lower prevalence of MPs compared to gill and stomach (gut), with gut displaying a higher frequency and diversity of MPs. This preliminary study suggests that the incidence and type of MPs varies in farmed verses natural fish sources as well as across different tissue types, with significantly less detected within the edible flesh tissues compared with stomach and gill tissues.

     

Assessment of copper and zinc levels in fish from freshwater ecosystems of Moldova

Purpose

The aim of this work was to assess the levels of copper and zinc in fish from the main freshwater ecosystems of Moldova, in relation with species, habitat, age, sex, season, and development stage.

Methods

Fish from Cyprinidae and Percidae families (Cyprinus carpio, Carassius auratus gibelio, Rutilus rutilus heckeli, Abramis brama, Aristichthys nobilis, Hypophtalmichthys molitrix, Sander lucioperca) were collected from Prut and Dniester rivers, Cuciurgan, Dubasari, and Costesti-Stanca reservoirs, and ponds of farms in the Dniester delta. The Cu and Zn content of fish tissues (skeletal muscles, liver, gonads, gills, skin, and scales) was determined by flame atomic absorption spectrophotometer AAS-3, of water by graphite furnace HGA 900 of AAnalist 400.

Results

The level of heavy metals accumulation in muscles of immature fish follows their dynamics in water. The highest concentration of zinc was registered in the gonads of mature fish, and of copper??in the liver. The lowest Cu and Zn contents were recorded in the muscles and are in the United Nations Food and Agriculture Organization safety-permissible levels for human consumption. Cu and Zn contents in muscles of fish depend on specimen age. Their level in fish gonads was sharply increasing during pre-spawning period. During the early developmental stages, the metal concentration in fish eggs and larvae varies within wide limits, but the accumulation pattern is similar in the investigated species.

Conclusions

The fish represent one of the most indicative factors for the estimation of trace metals pollution in freshwater systems and this is important not only for monitoring purposes, but also for the fish culture ones.     

Effects of filtration and pH perturbation on freshwater organic matter fluorescence

Fluorescence of organic matter from six contrasting freshwaters was analysed after filtration (1.2 microm and 0.2 microm filter sizes) and pH perturbation (+/-2 pH units from ambient conditions). Two fluorophores were compared in detail: tryptophan-like fluorescence, whose filtration and pH characteristics are relatively poorly understood, and humic-like fluorescence, which is better characterised. Although there was some variability in both fluorophores, the tryptophan-like fluorescence showed the most significant decrease in fluorescence intensity between raw and 1.2 microm filter samples, and a much smaller decrease between 1.2 and 0.2 microm, demonstrating a significant source associated with particulate material as well as a significant <0.2 microm fraction. In contrast, humic-like fluorescence shows little change with filtration, suggesting that the majority of this fluorescence is associated with truly dissolved material. The pH perturbation experiments demonstrate that tryptophan-like fluorescence is less impacted by pH than with filter fraction. For humic-like fluorescence, pH effects are weak and are not as consistent as those reported in the literature for extracted humic substances. pH perturbation of the freshwaters shows a wide range of sample specific pH responses, significantly more variable than that observed in experiments using extracted humic substances and tryptophan standards, demonstrating the natural variability of freshwater dissolved organic matter.     

Effects of ultraviolet radiation and contaminant-related stressors on arctic freshwater ecosystems

Climate change is likely to act as a multiple stressor, leading to cumulative and/or synergistic impacts on aquatic systems. Projected increases in temperature and corresponding alterations in precipitation regimes will enhance contaminant influxes to aquatic systems, and independently increase the susceptibility of aquatic organisms to contaminant exposure and effects. The consequences for the biota will in most cases be additive (cumulative) and multiplicative (synergistic). The overall result will be higher contaminant loads and biomagnification in aquatic ecosystems. Changes in stratospheric ozone and corresponding ultraviolet radiation regimes are also expected to produce cumulative and/or synergistic effects on aquatic ecosystem structure and function. Reduced ice cover is likely to have a much greater effect on underwater UV radiation exposure than the projected levels of stratospheric ozone depletion. A major increase in UV radiation levels will cause enhanced damage to organisms (biomolecular, cellular, and physiological damage, and alterations in species composition). Allocations of energy and resources by aquatic biota to UV radiation protection will increase, probably decreasing trophic-level productivity. Elemental fluxes will increase via photochemical pathways.     

A survey of mercury,lead and cadmium in muscle of British freshwater fish

Analyses of mercury, lead and cadmium in muscle of 221 fish, mainly eel and roach, from 67 sites in Great Britain are presented. Concentrations of metals in a significant number of fish were above recommended standards for human consumption.     

Effects of sodium pentachlorophenate on the ecology of a freshwater model ecosystem

An outdoor model ecosystem was designed for the ecotoxicological evaluation of xenobiotics. Two years were necessary before the artificial pond reached a steady state. During this time the composition of the community and its functions were investigated. We recorded the amount of nutrients and the O(2)/CO(2)-metabolism in the water, the density and diversity of the phytoplankton, the aquatic macrophytes and the fauna, the microbial activity in the sediment, and the environmental impacts on the ecosystem. A short time before the application of sodium pentachlorophenate (Na-PCP) the ecosystem was divided into three identical subunits. One of these was used as an internal control, the others were contaminated with two different concentrations of Na-PCP (0.1 and 0.3 mg litre(-1)). These concentrations were maintained over a period of eight weeks. Ecological changes in the contaminated compartments were investigated during a period of one year. The results were compared with those of single-species tests. Significant variations were observed only in the unit receiving 0.3 mg Na-PCP litre(-1). A short time after starting the experiment, the number of rotifers and cyclopids decreased. Primary producers were not affected. An increase of the chloride levels in the water indicated degradation processes. One year after application of the chemical, the remineralisation of nutrients was disturbed. This resulted in a diminution of the phytoplankton and the aquatic fauna.