An in situ bioassay integrating individual and biochemical responses using small fish species

Cholinesterases of marine fish: characterization and sensitivity towards specific chemicals

Inhibition of cholinesterases has been frequently used as a biomarker for contamination of aquatic environments, because these enzymes are frequent targets for toxic effects of contaminants, such as insecticides derived from phosphoric and carbamic acids. However, this enzyme is also responsive to other contaminants, including metals. The use of cholinesterase inhibition as effect criterion in ecotoxicology studies requires the previous characterization of the specific enzymatic forms that can be present in the different tissues and/or organs of species. This work characterized the soluble ChEs present in the brain and dorsal muscle of three marine fish species, namely Scomber scombrus, Sardina pilchardus and Chelidonichthys lucerna. Pesticides (chlorpyrifos) and metals (copper sulphate) in vitro assays were conducted to quantify the effects of these contaminants on cholinesterases activity. The results of this study showed that acetylcholinesterase (AChE) was the predominant form present in the brain tissues of the three species and in the muscle tissue of one species (Sardina pilchardus). For Scomber scombrus and Chelidonichthys lucerna, the cholinesterase form present in the muscle tissue evidenced properties between the classic acetylcholinesterase and those of pseudocholinesterase forms. The results for the metal (copper) and pesticide (chlorpyrifos) showed that this species may be suitable for monitoring contaminations for these types of contaminants.

Long-term adverse effects of microplastics on Daphnia magna reproduction and population growth rate at increased water temperature and light intensity: Combined effects of stressors and interactions

In many ecosystems, the zooplankton community has been pressured simultaneously by microplastic pollution and alterations resulting from global climate changes. The potential influence of light intensity rise (from 10,830 lx to 26,000 lx) and water temperature rise (from 20 °C to 25 °C) on the long term-toxicity of microplastics (MPs) to Daphnia magna were investigated. Three 21-day laboratory bioassays with model MPs (1-5 μm diameter) were carried out at (i) 20 °C/10830 lx, (ii) 20 °C/26000 lx, and (iii) 25 °C/10830 lx. In each bioassay, one control (no MPs) and three MP concentrations (0.04, 0.09, 0.19 mg/L) were tested. In all the bioassays, MPs caused parental and juvenile mortality, and reduced the somatic growth, reproduction and population growth rate. The MP EC₅₀s on living offspring (95% confidence interval within brackets) were 0.146 mg/L (0.142-0.151 mg/L) at 20 °C/10830 lx, 0.102 mg/L (0.099-0.105 mg/L) at 20 °C/26000 lx, and 0.101 mg/L (0.098-0.104 mg/L) at 25 °C/10830 lx. Relatively to the respective control group, 0.19 mg/L of MPs decreased the mean of the population growth rate by 27% at 20 °C/10830 lx, 38% at 20 °C/26000 lx and 59% at 25 °C/10830 lx. Based on the population growth rate and in relation to 20 °C/10830 lx (control, no MPs), the interaction between increased light intensity (26,000 lx) and MPs was synergism (at all the MP concentrations tested). The interaction between water temperature rise (25 °C) and MPs was antagonism at 0.04 mg/L of MPs and synergism at 0.09 and 0.19 mg/L of MPs. In the present scenario of climate changes and global MP pollution such findings raise high concern because zooplankton communities are crucial for aquatic biodiversity conservation, ecosystem functioning and services provided to humans. Further studies on the combined effects of MPs, other common pollutants, and alterations due to climate changes are needed.

In situ exposure of amphibian larvae (Rhinella fernandezae) to assess water quality by means of oxidative stress biomarkers in water bodies with different anthropic influences

In situ bioassays provide valuable information about the environment and offer more realistic results than usual laboratory experiments. The aim of this study was to evaluate the quality of water bodies from the lower Paraná River basin, the second most important in South America, through analysis of physiochemical parameters, metals and pesticides and in situ exposure of Rhinella fernandezae larvae to assess oxidative stress biomarkers. The sites were: S1(Morejón stream, reference); S2, S3(De la Cruz stream upstream and downstream, respectively) and S4(Arrecifes River). In all sites, dissolved oxygen was low, atrazine was detected and Cu was higher than the limit for aquatic life protection. According to the water quality index, S2, S3 and S4 presented bad water quality, while S1 good water quality. Larvae were exposed in situ for 96h in order to analyze: lipid peroxidation(TBARS) as oxidative damage, antioxidant enzymatic (catalase-CAT-, superoxide dismutase-SOD- and glutathione s-transferase-GST-) and non-enzymatic defenses (reduced glutathione-GSH-). Larvae exposed in the most impacted sites (S2, S3 and S4) presented oxidative stress since the levels of TBARS were around 2 times higher than in S1. Also, the other oxidative stress biomarkers were altered in larvae exposed at S2, S3 and S4. These results highlight the importance of analyzing oxidative stress biomarkers during in situ exposures since they are useful tools for documenting the extent of exposure at sublethal levels. The complex pollution of the water bodies affected the exposed larvae, which may jeopardize the native populations.

Comparison of behavioral assays for assessing toxicant-induced alterations in neurological function in larval fathead minnows

Neuroactive compounds are routinely detected in surface waters at concentrations that pose potential threats to wildlife. Exposure to neurotoxicants can adversely affect exposed organism by altering ecologically-important behaviors (e.g., feeding and predator response) that are likely to have important repercussions for populations. These compounds can elicit behavioral effects at concentrations lower than those that induce overt toxicity as indicated by mortality or decreased growth. Though a wide variety of methods have been employed to assess the behavior of early life stage fish, it is unclear which assays are best suited for identifying ecologically-relevant behavioral changes following exposures to neurotoxicants. The goal of the present study was to promote the use of behavioral assays for assessing the behavioral impacts of exposure to neurotoxic compounds by comparing the performance of different behavioral assays in larval fish. To achieve this goal, the sensitivity and practicality of three behavioral assays (i.e., feeding, optomotor response, and C-start assays) were compared in larval fathead minnows exposed to a known neurotoxicant, chlorpyrifos. There were significant alterations in the performance of fathead minnow larvae in all three behavioral assays in response to a 12-d embryo-larval exposure to chlorpyrifos. However, feeding and C-start were the most practical of the selected assays, as they took less time and allowed for larger samples sizes. Further work to standardize behavioral testing methods, and to link alterations to ecologically-relevant behaviors, will help promote the use of these assays when investigating the potential environmental impacts of neurotoxic compounds.

Ecotoxicity of chlorpyrifos to aquatic organisms: A review

Pesticides play an important role in promoting agricultural development, while their unreasonable use has led to environmental problems. Chlorpyrifos (CPF), a typical organophosphate pesticide, is used globally as an insecticide in agriculture. The extensive application of CPF has resulted in water contamination, and CPF has been detected in rivers, lakes, seawater, and even in rain. In the present review, CPF was selected due to its extensive use in agriculture and higher detection rate in surface waters. In this review we summarised the evidence related to CPF pollution and focused on discussing the ecotoxicity of CPF to aquatic systems and revealed the mechanism of action of CPF. The aim of this literature review was to summarise the knowledge of the toxicity to marine and freshwater organisms of CPF as well as try to select a series of sensitive biomarkers, which are suitable for ecotoxicological assessment and environmental monitoring in aquatic systems.

Combined toxic effects of fludioxonil and triadimefon on embryonic development of zebrafish (Danio rerio)

Pesticides scarcely exist as individual compounds in the water ecosystem, but rather as mixtures of multiple chemicals at relatively low concentrations. In this study, we aimed to explore the mixture toxic effects of fludioxonil (FLU) and triadimefon (TRI) on zebrafish (Danio rerio) by employing different toxicological endpoints. Results revealed that the 96-h LC₅₀ values of FLU to D. rerio at multiple developmental stages ranged from 0.055 (0.039-0.086) to 0.61 (0.33-0.83) mg L^-1, which were less than those of TRI ranging from 3.08 (1.84-5.96) to 9.75 (5.99-14.78) mg L^-1. Mixtures of FLU and TRI exerted synergistic effects on embryonic zebrafish. Activities of total superoxide dismutase (T-SOD) and catalase (CAT) were markedly altered in most of the individual and pesticide mixture treatments compared with the control. The expressions of 16 genes involved in oxidative stress, cellular apoptosis, immune system and endocrine system displayed that embryonic zebrafish were affected by the individual pesticides and their mixtures, and greater variations of four genes (ERɑ, Tnf, IL and bax) were found when exposed to pesticide mixtures compared with their individual compounds. Therefore, more studies on mixture toxicities among different pesticides should be taken as a priority when evaluating their ecological risk.

Bioconcentration of Essential and Nonessential Elements in Black Sea Turbot (Psetta Maxima Maeotica Linnaeus, 1758) in Relation to Fish Gender

This study investigates the influence of gender in the bioconcentration of essential and nonessential elements in different parts of Black Sea turbot (Psetta maxima maeotica) body, from an area considered under high anthropogenic pressure (the Constanta City Black Sea Coastal Area in Romania). A number of 13 elements (Ca, Mg, Na, K, Fe, Zn, Mn, Cu, Ni, Cr, As, Pb and Cd) were measured in various sample types: muscle, stomach, stomach content, intestine, intestine content, gonads, liver, spleen, gills and caudal fin. Turbot adults (4–5 years old) were separated, according to their gender, into two groups (20 males, 20 females, respectively), and a high total number of samples (1200 from both groups) were prepared and analyzed, in triplicate, with Flame Atomic Absorption Spectrometry and High-Resolution Continuum Source Atomic Absorption Spectrometry with Graphite Furnace techniques. The results were statistically analyzed in order to emphasize the bioconcentration of the determined elements in different tissues of wild turbot males vs. females, and also to contribute to an upgraded characterization of the Romanian Black Sea Coast, around Constanta City, in terms of heavy metals pollution. The essential elements Mg and Zn have different roles in the gonads of males and females, as they were the only elements with completely different patterns between the analyzed groups of specimens. The concentrations of studied elements in muscle were not similar with the data provided by literature, suggesting that chemistry of the habitat and food plays a major role in the availability of the metals in the body of analyzed fish species. The gender influenced the bioaccumulation process of all analyzed elements in most tissues since turbot male specimens accumulated higher concentration of metals compared to females. The highest bioaccumulation capacity in terms of Ca, Mg, Na, Ni, As, Zn and Cd was registered in caudal fin, liver and intestine tissues. Also, other elements such as K, Fe, Cu and Mn had the highest bioaccumulation in their muscle, spleen, liver and gills tissues. The concentrations of toxic metals in Black Sea turbot from this study were lower in the muscle samples compared with the studies conducted in Turkey, suggesting that the anthropogenic activity in the studied area did not pose a major impact upon the habitat contamination.

Assessing Genotoxicity and Mutagenicity of Three Common Amphibian Species Inhabiting Agroecosystem Environment

Amphibians are constantly exposed to pollutants and the stress of agricultural activities. We selected three anuran amphibian species Dendropsophus minutus, Boana albopunctata, and Physalaemus cuvieri, totaling 309 individuals. We collected tadpoles in 15 permanent ponds: 5 soybean crops, 3 corn crops, and 7 nonagricultural lands. Our study provides the first comparative data on the genotoxicity and mutagenicity of three common amphibian anurans. Dendropsophus minutus was the most vulnerable species compared with B. albopunctata and P. cuvieri for comet assay and micronuclei test. However, the more significant amount of DNA damage seen in D. minutus does not mean that their populations are threatened once such species adapt well to anthropogenic disturbances. Despite, P. cuvieri was less sensitive than the other two species; the DNA damage was significantly higher in soybean crops. Physalaemus cuvieri is a leptodactylidae species that deposit their eggs in foam nests, which are essential to protect eggs from dehydration. Moreover, the foam reduces the contact of eggs with water; thus, P. cuvieri eggs could be less exposed to contaminants present in pounds, compared with D. minutus and B. albopunctata, which deposit their eggs directly in the water. Therefore, this study was sufficiently sensitive to detect genotoxic and mutagenic effects in tadpoles exposed to agroecosystems. We strongly suggest D. minutus in future biomonitoring studies that involve the comparison of anthropized versus not anthropized environments. Overall, we recommend the comet assay and micronucleus test as effective methods for the detection of genotoxic damage in amphibian anurans to the environmental disturbance, especially in agricultural sites.

Interactive effects of 3,4-DCA and temperature on the annual killifish Nothobranchius furzeri

Although aquatic organisms are increasingly exposed to pollutants and abnormally high temperatures as a consequence of climate change, interactive effects between those stressors remain poorly assessed. Especially in ectotherms, such as fish, increases in ambient temperature are expected to affect fitness-related traits and physiology. We used the turquoise killifish Nothobranchius furzeri to study the effects of a range of 3,4-dichloroaniline concentrations (0, 50, 100 μg/L) in combination with two temperature conditions (control and control +4 °C) during four months of exposure. As part of an integrated multi-level approach, we quantified effects on classic life history traits (size, maturation time, body mass, fecundity), critical thermal maximum and physiology (energy reserves and stress-associated enzymatic activity). While no interactive effects of 3,4-DCA exposure and increased temperature emerged, our results do show a negative effect of 3,4-DCA on thermal tolerance. This finding is of particular relevance in light of increasing temperatures under climate change. Due to increases in pest species and faster degradation of 3,4-DCA under higher temperatures, increased use of the pesticide is expected under climate change which, in turn, could result in a decreased tolerance of aquatic organisms to high temperatures.

Behavioral effects of copper on larval white sturgeon

Early-life stage white sturgeon are sensitive to copper (Cu), with adverse behavioral responses observed during previous studies. The objectives of the present study were to quantify the effects of Cu exposure on white sturgeon swimming and feeding behaviors and determine their time to response. Larval sturgeon (1-2, 28, or 35 d posthatch [dph]) were exposed to Cu (0.5-8 μg/L) for 4 to 14 d. Abnormal behavioral changes were observed within the first few days of exposure including loss of equilibrium and immobilization. Digital video tracking software revealed decreased swimming activity with increasing Cu concentration. Significant changes in behavior and mortality occurred at concentrations of Cu between 1 and 8 μg/L. Juvenile white sturgeon, 58 dph, exposed to 12 μg/L Cu consumed 37 to 60% less food than controls after 3 d of exposure. The present results indicate that behavioral endpoints were more sensitive than some standard toxicity test endpoints and can effectively expand the sensitivity of standard toxicity tests for white sturgeon. Swimming behavior was impaired to the extent that survival in the field would likely be jeopardized. Such data would provide managers a useful metric for characterizing the risks of Cu contamination to white sturgeon. Environ Toxicol Chem 2019;38:132-144. Published 2018 Wiley Periodicals Inc. on behalf of SETAC. This article is a US government work and, as such, is in the public domain in the United States of America.

The Response of Neotropical Fish Species (Brazil) on the Water Pollution: Metal Bioaccumulation and Genotoxicity

The streams and rivers of the Upper Paraná River Basin have been seriously affected by impacts of high population density around the basin area. Fishes are widely used as models to assess the health of aquatic ecosystems, being considered as bioindicators of environmental pollution. In this context, our objective was to assess the potential genotoxic and mutagenic effects of the polluted water in three native fish species (Astyanax lacustris, Hypostomus ancistroides, and Rhamdia quelen) from Tarumã Microbasin, Upper Paraná River, Brazil. We also investigated the concentration of metals in water and in fish muscle to verify bioavailability and bioaccumulation of metals. For both less impacted sites (LI) and impacted sites (IMP) of the microbasin, the concentrations of metals were above the maximum limit allowed by Brazilian legislation (Resolution CONAMA 357/2005), except for Pb, total Cr, and Cu at LI sites and total Cr at IMP sites. A. lacustris showed a higher frequency of micronuclei (MN) at IMP sites compared with LI sites (p < 0.0001). We found no significant differences in MN frequency between site classes for H. ancistroides and R. quelen (p > 0.05). There were no significant differences between site classes regarding to nuclear abnormalities in erythrocytes frequencies (p > 0.05). A. lacustris from IMP sites had higher concentrations of Pb, Cu, Fe, Zn, and Ni in muscle tissue (p < 0.05), whereas H. ancistroides from IMP sites had higher concentration of Cr, Cu, and Ni (p < 0.0001) and R. quelen showed higher concentration of Cd, Fe, and Ni at these sites (p < 0.0001). So, the chosen biomarkers are able to identify the environmental risk of the water pollution.

Evaluation of joint effects of cyprodinil and kresoxim-methyl on zebrafish, Danio rerio

Aquatic organisms are usually exposed to a mixture of pesticides instead of individual chemicals. However, risk assessment of pesticides is traditionally based on toxicity data of individual compounds. In this study, we aimed to examine the joint toxicity of two fungicides cyprodinil (CYP) and kresoxim-methyl (KRM) to zebrafish (Danio rerio) using a systematic experimental approach. Results from 96-h semi-static test indicated that the LC₅₀ values of KRM to D. rerio at multiple life stages (embryonic, larval, juvenile and adult stages) ranged from 0.034 (0.015-0.073) to 0.61 (0.39-0.83) mg a.i. L^-1, which were higher than those of CYP ranging from 1.05 (0.88-1.52) to 4.42 (3.24-6.02) mg a.i. L^-1. Pesticide mixtures of CYP and KRM exhibited synergistic effect on embryonic zebrafish. The activities of carboxylesterase (CarE) and cytochrome P450 (Cyp450) were significantly altered in most of the individual and combined exposures compared with the control group. The expressions of seven genes (Mnsod, cyp17, crhr 2, crh, gnrhr 4, gnrhr 1 and hmgrb) were significantly altered upon exposure to combined pesticides compared with their individual pesticides. Collectively, these findings suggested joint effects should be considered in the risk assessment of pesticides and development of water quality criteria for the protection of aquatic environment.

Feeding inhibition in Corbicula fluminea (O.F. Muller, 1774) as an effect criterion to pollutant exposure: Perspectives for ecotoxicity screening and refinement of chemical control

Bivalves are commonly used in biomonitoring programs to track pollutants. Several features, including its filter-feeding abilities, cumulatively argue in favour of the use of the Asian clam (Corbicula fluminea) as a biosentinel and an ecotoxicological model. Filtration in bivalves is very sensitive to external stimuli and its control is dictated by regulation of the opening/closure of the valves, which may be used as an avoidance defence against contaminants. Here, we investigate the filter-feeding behaviour of the Asian clam as an endpoint for assessing exposure to pollutants, driven by two complementary goals: (i) to generate relevant and sensitive toxicological information based on the ability of C. fluminea to clear an algal suspension, using the invasive species as a surrogate for native bivalves; (ii) to gain insight on the potential of exploring this integrative response in the refinement of chemical control methods for this pest. Clearance rates and proportion of algae removed were measured using a simple and reproducible protocol. Despite some variation across individuals and size classes, 50-90% of food particles were generally removed within 60-120 min by clams larger than 20 mm. Removal of algae was sensitive to an array of model contaminants with biocide potential, including fertilizers, pesticides, metals and salts: eight out of nine tested substances were detected at the μg l^-1 or mg l^-1 range and triggered valve closure, decreasing filter-feeding in a concentration-dependent manner. For most toxicants, a good agreement between mortality (96 h - LC₅₀ within the range 0.4-5500 mg l^-1) and feeding (2 h - IC₅₀ within the range 0.005-2317 mg l^-1) was observed, demonstrating that a 120-min assay can be used as a protective surrogate of acute toxicity. However, copper sulphate was very strongly avoided by the clams (IC₅₀ = 5.3 μg l^-1); on the contrary, dichlorvos (an organophosphate insecticide) did not cause feeding depression, either by being undetected by the clams' chemosensors and/or by interfering with the valve closure mechanism. Such an assay has a large potential as a simple screening tool for industry, environmental agencies and managers. The ability of dichlorvos to bypass the Asian clam's avoidance strategy puts it in the spotlight as a potential agent to be used alone or combined with others in eradication programs of this biofouler in closed or semi-closed industrial settings.

Benzoylecgonine exposure induced oxidative stress and altered swimming behavior and reproduction in Daphnia magna

Several monitoring studies have shown that benzoylecgonine (BE) is the main illicit drug residue commonly measured in the aquatic system worldwide. Few studies have investigated the potential toxicity of this molecule towards invertebrate and vertebrate aquatic non-target organisms focusing on effects at low levels of the biological organization, but no one has assessed the consequences at higher ones. Thus, the present study was aimed at investigating the toxicity of a 48-h exposure to two concentrations of BE, similar to those found in aquatic ecosystems (0.5 μg/L and 1.0 μg/L), on the cladoceran Daphnia magna at different levels of the ecological hierarchy. We relied on a multi-level approach focusing on the effects at biochemical/biomolecular (biomarkers), individual (swimming activity) and population (reproduction) levels. We measured the amount of reactive oxygen species and of the activity of antioxidant (SOD, CAT, and GPx) and detoxifying (GST) enzymes to assess if BE exposure can alter the oxidative status of D. magna specimens, while the lipid peroxidation (TBARS) was measured as a marker of oxidative damage. Moreover, we also measured the acetylcholinesterase (AChE) activity because it is strictly related to behavioral changes in aquatic organisms. Changes in swimming behavior were investigated by a video tracking analysis, while the consequences on reproduction were assessed by a chronic toxicity test. Our results showed that BE concentrations similar to those found in aquatic ecosystems induced oxidative stress and inhibited AChE activity, affecting swimming behavior and the reproduction of Daphnia magna individuals.

Gender-specific histopathological response in guppies Poecilia reticulata exposed to glyphosate or its metabolite aminomethylphosphonic acid

Ecotoxicity of glyphosate (GLY) and its metabolite aminomethylphosphonic acid (AMPA) was investigated in guppies, Poecilia reticulata. We tested the effects of these chemicals on the gills and liver of both male and female guppies using qualitative and quantitative histopathological analyses associated with histopathological condition indexes. Both genders showed similar median lethal concentration (LC50 ) at 96 h for GLY (68.78 and 70.87 mg l-1 ) and AMPA (180 and 164.32 mg l-1 ). However, the histopathological assessment of both fish organs exposed to sublethal concentrations of GLY (35 mg l-1 ) and AMPA (82 mg l-1 ) for 96 h showed a tissue- and gender-specific histopathological response. In both exposure assays, fish presented mainly progressive changes, such as proliferation of the interlamellar epithelium, partial and total fusion of secondary lamellae. The liver showed mainly regressive changes, such as steatosis, pyknotic nuclei and high distribution of collagen fibers. Unusually large hepatocytes as degenerated cells were also detected. Histopathological changes in gills were similar for the males and females, but the liver response was different between the genders. The hepatic inflammatory changes were more common in males. The increase in the area of hepatocyte vacuoles is gender dependent with higher values in the male compared to the female guppies exposed to GLY and AMPA. Multiparametric analysis indicated that the male guppies are more sensitive than females, particularly in the presence of AMPA. Our study shows that the histopathological assessment associated with gender-specific response can be successfully used in ecotoxicological assessment of GLY and the metabolite AMPA. Copyright © 2017 John Wiley & Sons, Ltd.

Intoxication and biochemical responses of freshwater snail Bellamya aeruginosa to ethylbenzene

No acute toxic data of ethylbenzene on gastropod is available in literature. In the present study, the acute toxicity of ethylbenzene was assessed on a freshwater snail Bellamya aeruginosa, which was exposed to ethylbenzene concentration from 1 to 100 mg/L for 96 h. No mortality occurred, but a manifestation of intoxication (distress syndrome) was observed in part of exposed snails, and meanwhile, another part was moved normally. The distress syndrome showed clear dose- and time-dependent effects, and the 96-h EC₅₀ value for distress syndrome was 13.3 mg/L in snail. The biochemical responses induced by ethylbenzene to the snail, including acetylcholinesterase (AChE) in the whole body and superoxide dismutase (SOD), catalase (CAT), glutathione S-transferases (GST), and reduced glutathione (GSH) in the hepatopancreas, were evaluated both for distressed snail and moved snail. The AChE activity of distressed snail was all inhibited more than 45 %, and the inhibition of AChE activity in the moved snail was all less than 30 % and more than 20 %, demonstrating that ethylbenzene exerted nervous toxicity to both distressed snail and moved snail. Meanwhile, the difference for AChE activity between the two different response snails was significant. Among the antioxidant biomarkers (SOD, CAT, GST, and GSH), only GST displayed significant difference between the distressed snail and moved snail. However, the activities of enzymes (SOD, CAT, and GST) in the moved snail were greater than those in the distressed snail, no matter significantly or insignificantly, which indicated that the ability of antioxidant defense in the distressed snail was weaker than that in the moved snail. The findings here reported manifest that ethylbenzene exerted nervous toxicity to snail, and the snail with intoxication response (distress syndrome) presented larger inhibition on AChE activity and weaker antioxidant ability in comparison with the moved snail.

Temperature rise and microplastics interact with the toxicity of the antibiotic cefalexin to juveniles of the common goby (Pomatoschistus microps): Post-exposure predatory behaviour, acetylcholinesterase activity and lipid peroxidation

The goal of this study was to investigate the toxicity of cefalexin to Pomatoschistus microps juveniles in relation to the presence of microplastics in the water and temperature rise. After acclimatization, groups of wild juveniles were exposed for 96h to artificial salt water (control), microplastics alone (0.184mg/l), cefalexin alone (1.3-10mg/l) and in mixture with microplastics (cefalexin: 1.3-10mg/l; microplastics: 0.184mg/l) at 20 and 25°C. Effect criteria were mortality, post-exposure predatory performance (PEPP), acetylcholinesterase activity (AChE) and lipid peroxidation levels (LPO). At 20°C, concentrations of cefalexin alone≥5mg/l significantly reduced PEPP (up to 56%; 96h-EC₅₀=8.4mg/l), indicating toxicity of the antibiotic to juveniles after short-term exposure to water concentrations in the low ppm range. At 20°C, fish exposed to microplastics alone did not have significant differences in any of the parameters tested relative to the control group but tended to have an inhibition of the PEPP (23%) and AChE (21%); at 25°C, microplastics alone caused mortality (33%) and PEPP inhibition (28%). Thus, microplastics are toxic to P. microps juveniles. At 20°C, under simultaneous exposure to cefalexin and microplastics, the PEPP was significantly reduced (at cefalexin concentrations≥1.25mg/l). Moreover, at 25°C, the toxicity curves of cefalexin (PEPP based), alone and in mixture with microplastics, were significantly different (p<0.05; 96h-EC₅₀ of 3.8 and 5.2mg/l, respectively), and the integrated data analysis indicated significant interactions between the two substances for all biomarkers. Thus, the presence of microplastics in the water influenced the toxicity of cefalexin. The rise of water temperature (from 20°C to 25°C), increased the microplastics-induced mortality (from 8 to 33%), and the inhibitory effects of cefalexin on the PEPP (up to 70%). Significant differences (p<0.05) between the toxicity curves of cefalexin alone at distinct temperatures were found, with a lower 96h-EC₅₀ at 25°C (3.8mg/l) than at 20°C (8.4mg/l). Moreover, at 25°C, increases of AChE activity (14%) and LPO (72%) in fish exposed to the mixture treatment containing the highest cefalexin concentration were found, and the integrated analysis of data indicated significant interactions between cefalexin and temperature for PEPP, and among all stressors for LPO. Thus, the temperature rise increased the toxicity of microplastics and of cefalexin, alone and in mixture with microplastics, to P. microps juveniles. These findings raise concern on the long-term exposure of wild populations to complex mixtures of pollutants, likely decreasing their fitness, and highlight the need of more research on the combined effects of widely used pharmaceuticals, microplastics and temperature increase on wild species to improve environmental and human risk assessments of chemicals and their safe use under a global warming scenario.

Multibiomarker toxicity characterization of uranium mine drainages to the fish Carassius auratus

The release of acidic effluents, naturally enriched in metals and radionuclides, is the main legacy of uranium mines. Generally, metals dissolved by these acidic effluents can cause significant alterations in exposed organisms, with distinct toxicological outcomes. In this study, 72 individuals of the freshwater fish species Carassius auratus were exposed in situ for different periods (8, 16, 24, and 48 h) to water from a pond (treatment pond (TP)) with a chemically treated effluent and a reference pond (PRP), in the vicinity of the Cunha Baixa uranium mine (Portugal). Comparing the water of the two ponds, the PRP pond was characterized by higher pH and oxygen values and lower conductivity and hardness values. Regarding total metal concentrations, among others, magnesium (56,000 μg/L), sodium (17,400 μg/L), zinc (86 μg/L), manganese (6340 μg/L), and uranium (1380 μg/L) concentrations in the TP pond were above the values obtained for the PRP pond. The values of manganese and uranium exceeded the values of quality criteria established for surface waters for cyprinids and for irrigation purposes. After exposure to pond water, significant differences were recorded for several biomarkers: (i) between ponds for acetylcholinesterase (AChE) with higher activities for animals from the PRP and glutathione-S-transferase (GST) activities that were particularly enhanced in animals from the TP pond; (ii) between ponds and exposure periods for lactate dehydrogenase (LDH) activity, since organisms from PRP pond presented always higher values than those from the TP pond, and among these, organisms exposed for the longer period presented a further depression in LDH activity; and (iii) between exposure periods for erythrocyte micronucleus. GSTs and LDH were the most sensitive biomarkers within the timeframe of the in situ assay performed. Despite the alleged efficacy of the chemical treatment (evidenced by a significantly lower pH), some metals persisted in the treated effluent (TP pond), potentially contributing to the induction of oxidative stress or increased conjugation metabolic activity in fish.

Suitability of enzymatic markers to assess the environmental condition of natural populations of Gambusia affinis and Daphnia magna--a case study

In recent years, the use of biochemical markers, especially in the assessment of toxic effects and modes of action, under controlled laboratory conditions has increased. However, transposing their use to in situ monitoring or risk assessment evaluations has encountered barriers, mainly related to the difficulty in interpreting the meaning of biochemical variation. In this work, we aimed at understanding if biochemical marker activities (cholinesterase, glutathione S-transferase and lactate dehydrogenase) can be used to monitor the health status of natural populations of fish (Gambusia affinis) and daphnids (Daphnia magna). For that, two ponds with different water properties were chosen as study sites, and organisms collected at four sampling periods along the year. The pattern of biochemical marker responses was not the same in the two species, showing higher integrated biochemical marker response values in the winter for G. affinis and in the autumn for D. magna, suggesting specificities that must be taken into account in biomonitoring programmes by including representative species of several trophic levels. In the case of G. affinis, the differences in key physicochemical parameters between the two ponds (especially dissolved oxygen levels) did not seem to affect biochemical marker levels as if organisms were already perfectly adapted to their environment. In general, seasonal variation of water quality seems to have an important role on biochemical marker responses. Several parameters above Environmental Quality Standards were identified such as dissolved oxygen (DO), ammonia, nitrites, sulphides and metals, but eventual responses to these stressors could not be discriminated from natural variation except for particular cases.

A short-term sublethal toxicity assay with zebra fish based on preying rate and its integration with mortality

Contaminant-induced feeding inhibition has direct and immediate consequences at higher levels of biological organization, by depressing the population consumption and thus hampering ecosystem functioning (e.g. grazing, organic matter decomposition). Thus, similarly to lethality and avoidance, feeding is mechanistically linked to ecosystem processes and is therefore an unequivocal ecologically meaningful response. The objective of the present study was to develop a short-term assay with the small freshwater fish Danio rerio, based on feeding. For this, a methodology to easily and precisely quantify feeding was first optimized: each fish was allowed to prey on ten live Daphnia magna juveniles, for 1h, just before the end of a 48-h exposure test period. Secondly, copper sensitivity of feeding relatively to survival and growth was evaluated. At the growth EC20 (40 μg L(-1)), feeding was inhibited by 53%, and at the feeding EC50 (36 μg L(-1)), mortality was negligible (1.3%). Integrating feeding and survival revealed a 97% depression in the population consumption at the LC50 (61 μg L(-1)). Thirdly, the influence of pH, conductivity and hardness on the feeding background variability was assessed by assaying waters collected at eight reference sites and was found to be negligible, within tested ranges. Fourthly, feeding assays with natural waters contaminated with acid mine drainage confirmed the integration of lethality and feeding to be pertinent at estimating contaminant effects at higher levels of biological organization.

AChE inhibition: one dominant factor for swimming behavior changes of Daphnia magna under DDVP exposure

As a key enzyme that hydrolyzes the neurotransmitter acetylcholine in cholinergic synapses of both vertebrates and invertebrates, acetylcholinesterase (AChE) is strongly inhibited by organophosphates. AChE inhibition may induce the decrease of swimming ability. According to previous research, swimming behavior of different aquatic organisms could be affected by different chemicals, and there is a shortage of research on direct correlation analysis between swimming behavior and biochemical indicators. Therefore, swimming behavior and whole-body AChE activity of Daphnia magna under dichlorvos (DDVP) exposure were identified in order to clarify the relationship between behavioral responses and AChE inhibition in this study. In the beginning, AChE activity was similar in all treatments with the control. During all exposures, the tendency of AChE activity inhibition was the same as the behavioral responses of D. magna. The AChE activity of individuals without movement would decrease to about zero in several minutes. The correlation analysis between swimming behavior of D. magna and AChE activity showed that the stepwise behavioral response was mainly decided by AChE activity. All of these results suggested that the toxicity characteristics of DDVP as an inhibitor of AChE on the swimming behavior of organisms were the same, and the AChE activity inhibition could induce loss of the nerve conduction ability, causing hyperactivity, loss of coordination, convulsions, paralysis and other kinds of behavioral changes, which was illustrated by the stepwise behavioral responses under different environmental stresses.

A short-term laboratory and in situ sediment assay based on the postexposure feeding of the estuarine isopod Cyathura carinata

In situ assays based on feeding depression have been proposed as sublethal assays able to assess immediate contaminant effects on key ecosystem functions, long before effects on life-history traits can be detected. The in situ peculiarities provide more realistic exposure scenarios than laboratory-controlled conditions, which is particularly relevant for estuarine ecosystems where environmental conditions are highly variable. In this context, we developed a short-term cost-effective in situ assay based on the postexposure feeding of the estuarine species, Cyathura carinata, through the following steps: i) develop a methodology to quantify feeding under laboratory conditions; ii) quantify the sensitivity of the postexposure feeding response under laboratory conditions; iii) deploy the in situ assay at various field sites covering different environmental variables in a reference estuary and degrees of contamination in a contaminated estuary to, respectively, derive a model to predict postexposure feeding rates across sites varying in environmental variables and evaluate the potential of this in situ tool to assess sediment contamination in estuaries. A quantity of 100 defrosted nauplii of Artemia franciscana per isopod given during a short period of 30 min in darkness was adequate to allow estimating precise postexposure feeding rates. Laboratory toxicity tests showed the high sensitivity of postexposure feeding to Cd as a sublethal endpoint for C. carinata (7-fold lower than the corresponding 48-h LC50). However, this species appears to be able to face high concentrations of non-essential metals as Cd, with 96-h LC50 values (37 mg Cd/L) higher than values reported for other isopods, and among the highest concentrations reported for saltwater invertebrates. Results of in situ deployments at reference sites indicated that sediment with size fraction between 63-125 µm (very fine sand) influences feeding rates. The in situ assay across contaminated sites was able to discriminate between unpolluted and polluted estuaries, and also to detect degrees of toxicity among sampling sites within an estuary, after statistically adjusting feeding rates on the basis of the proportion of the sediment very fine sand influencing baseline feeding rates. The in situ postexposure feeding assay with C. carinata was found to be, therefore, a potential useful cost-effective tool for estuarine sediment toxicity assessments.

Acute toxicity and sublethal effects of fipronil on detoxification enzymes in juvenile zebrafish (Danio rerio)

The acute toxicity of fipronil and its sublethal effects on detoxification enzymes (carboxylesterases (CarEs), glutathione S-transferases (GSTs), and 7-ethoxycoumarin O-deethylase (ECOD)) in zebrafish (Danio rerio) were investigated. The results indicated that the 24-h LC50 of fipronil for zebrafish was 220.4 μg/L (95% CI: 173.7-272.4 μg/L). Sublethal concentrations of fipronil did not cause significant changes in CarEs activities. In the liver and muscle tissues, GST activities at the tested concentrations did not significantly differ from those in the control. In the brain and gill tissues, GST activities at a concentration of 4 μg/L were significantly lower than those at a concentration of 2 μg/L. The results suggest that CarEs and GSTs were not suitable biomarkers for fipronil effects in D. rerio. A significant induction in the ECOD activities in the brain, gill, liver, and muscle tissues was observed compared with the control. Moreover, the dose-dependent responses of the ECOD activity were observed after treatment with sublethal concentrations of fipronil in the range of 2-20 μg/L. The results suggested that ECOD could be a suitable biomarker of fipronil effects in D. rerio.

A subchronic in situ exposure method for evaluating effects in small-bodied fish at contaminated sites

In situ fish-caging studies at contaminated sites can provide information that is more realistic compared to traditional laboratory-based studies. However, few methods have been developed for exposing sentinel fish species for subchronic durations, and fewer still are optimized for exposing small-bodied fish while maintaining fish health and growth throughout the caging trial. Those methods typically lack a feeding regimen during the fish caging trial. While that may be acceptable or even appropriate for typical short-term toxicity testing, it does limit the duration of the exposure, and may not be suitable when post-caging trials or observations are necessary. Returning healthy fish to the lab following the in situ exposure would be important, for example, in studies designed to examine long-term or multigenerational effects following an in situ exposure. In this article we describe a subchronic method for caging small fish at contaminated sites while maintaining growth and reproductive development. Fathead minnow (Pimephales promelas) were caged in situ for 6 weeks, after which time they were returned to the lab where they were evaluated for health and reproductive performance. Growth and reproductive endpoints revealed no adverse effect on fish due to fish caging and related handling, demonstrating the suitability of our caging and feeding method for long-term caging studies.

Biomarker responses and morphological effects in juvenile tilapia Oreochromis mossambicus following sequential exposure to the organophosphate azinphos-methyl

Pesticides are contaminants of aquatic environments. Such ecosystems in the Western Cape, South Africa are at risk as most organophosphates are highly toxic to fish and other aquatic organisms. The objective of this experimental study was firstly to determine the acute toxicity of azinphos-methyl (AZP) to juvenile fish (Oreochromis mossambicus) and, secondly, to investigate the effects of repeated exposure of fish to an array of sublethal concentrations on morphological parameters such as growth, condition factor and organ-somatic indices. Food consumption and feeding response time were investigated as ecologically relevant behavioral endpoints which could affect growth, reproduction and survival and subsequently causes impacts at the population and/or community level. Finally, acetylcholinesterase (AChE) was used as biomarker to investigate effects at sub-organismal level following sequential exposure to AZP. The aim was to determine how sequential spraying procedures, using different exposure concentrations and intervals, affected fish as reflected by their responses at different organizational levels. A dose-dependent effect on feeding impairment was observed in the feeding response experiment. The correlation found between growth impairment, feeding activity and AChE inhibition therefore indicates that frequency of exposure can play an important role regarding the severity of impacts to non-target organisms. This study provides evidence that AZP has harmful effects on non-target aquatic organisms, such as fish which can be manifested in the early developmental stages. Sequential exposures showed that dosage and frequency of spraying and spraying interval could exacerbate harmful effects. AChE inhibition and organosomatic indices can be used effectively to measure effects.

A laboratory and in situ postexposure feeding assay with a freshwater snail

Contaminant-driven feeding inhibition has direct and immediate consequences at higher levels of biological organization, by depressing the population consumption and thus hampering ecosystem functioning (e.g., grazing, organic matter decomposition). The present study aimed at developing a short-term laboratory and in situ assay based on the postexposure feeding of the freshwater snail Theodoxus fluviatilis. A method to precisely quantify feeding rates was first developed, consisting of a 3-h feeding period, in darkness, on 150 defrosted nauplii of the brine shrimp Artemia franciscana. Postexposure feeding after a 48-h exposure to cadmium was approximately as sensitive as survival, with the median effective concentration (EC50) and median lethal concentration (LC50) being 85 µg/L and 102 µg/L, respectively, and the 20% effective concentration (EC20) and 20% lethal concentration (LC20) being 41 µg/L and 77 µg/L, respectively. Together, both effects at the LC20 reduced population consumption by 56%. In situ experiments at reference sites covering broad ranges of current velocity, hardness, conductivity, sediment organic matter content, and sediment particle size distribution revealed the influence of these abiotic conditions on postexposure feeding, in the absence of contamination, to be negligible. The effectiveness of the in situ assay was evaluated at 5 sites contaminated with acid mine drainage. Surviving organisms at the single partially lethal site (37% mortality) presented a 54% feeding inhibition relative to the reference, whereas the population consumption would be inhibited by 71%, confirming the integration of survival and feeding to be pertinent for estimating contaminant effects at higher levels of biological organization.

Biomarkers responses in muscle of Senegal sole (Solea senegalensis) from a heavy metals and PAHs polluted estuary

The biochemical responses in muscle, such as the enzymatic activities of acetylcholinesterase, lactate dehydrogenase and isocitrate dehydrogenase, were studied in sole (Solea senegalensis) collected in Huelva estuary (SW Spain), in the vicinity of a petrochemical and mining industry. The sampling sites showed different type and degree of pollution. The results demonstrated significant differences in muscle activities of AChE and IDH in Odiel and Tinto Rivers compared to control fish. LDH activity did not show any difference between sampling sites. Significant correlations were established between some biomarkers and heavy metals: AChE was correlated with Pb, Cd and Cu concentrations in water; IDH activity was correlated with Cd and Cu concentrations in water and As, Pb and Cd concentrations in sediments; LDH activity was correlated with As and Zn concentration in water and Cd concentration in sediment. Only one correlation was established between the biomarkers analysed and the concentrations of PAHs: benzo(b)fluoranthene concentration in sediment and IDH.

Effects of anticholinesterase drugs on biomarkers and behavior of pumpkinseed, Lepomis gibbosus (Linnaeus, 1758)

The presence of pharmaceutical residues in the aquatic environment has recently received great attention, as potential adverse effects may arise from their presence. Inhibition of cholinesterases (ChE) has been widely used as an environmental biomarker of exposure to organophosphates (OP) and carbamate (CB) pesticides. However, other widespread anthropogenic contaminants - including pharmaceutical drugs - can exert toxic effects through ChE inhibition. Studies with aquatic species have shown that inhibition of ChE is associated with behavioral changes. Bearing this in mind, this work aimed to study the effects on individual behavior and acetylcholinesterase (AChE) activity of selected tissues of Lepomis gibbosus, after exposure to the anticholinesterasic drugs neostigmine and pyridostigmine. Results revealed that neostigmine significantly decreased the activity of AChE in the head (LOEC = 100 mg L(-1)), but not in dorsal muscle. On the other hand, pyridostigmine significantly decreased the activity of AChE in both the head (LOEC = 0.001 mg L(-1)) and dorsal muscle homogenates (LOEC = 100 mg L(-1)). The impairment of this enzymatic form was attained at ecologically relevant concentrations (in the case of pyridostigmine, for head AChE), which is an interesting finding, specially considering that these toxic effects occurred for a pharmaceutical compound. Contrarily, there were no significant differences in the behavior of L. gibbosus in any parameter, for neither drug. These results suggest that the behavioral parameters analyzed (scototaxis and lethargy) in L. gibbosus could not be regarded as suitable markers to assess the effects of drugs such as neostigmine and pyridostigmine. In contrast, the pattern of response elicited by cholinesterasic inhibition showed the usefulness of this toxicological parameter for the assessment of pharmaceuticals in the environment, namely anticholinesterasics.

Responses of juvenile sea bass, Dicentrarchus labrax, exposed to acute concentrations of crude oil, as assessed by molecular and physiological biomarkers

In the present study, juvenile sea bass were exposed for 48 and 96 h to an Arabian light crude oil and their responses were assessed at the molecular and physiological levels. The aim of the study was therefore to assess (i) the short term effects of crude oil exposure by the measurement of several molecular biomarkers, (ii) the consequences of this short term exposure on fish health by using growth and condition indices measured after a decontamination period of 28 and 26 d in seawater. Hydrocarbon petroleum concentrations was monitored during the 96 h experiments and an increase of PAH concentrations were found in fish following both exposure times. An 7-ethoxyresorufin-O-deethylase (EROD) induction was observed after 48 h of exposure, while a significant decrease in the sea bass specific growth rate in length and for the RNA:DNA ratio was observed 28 d after that exposure ceased. The EROD induction doubled after the 96 h exposure, and a significant increase in GST activities was observed. A significant decrease in the specific growth rates, the otolith recent growth, the RNA:DNA ratio and the Fulton's K condition index were then observed in sea bass 26 d after the 96 h exposure to mechanically dispersed crude oil compared to the control. The present study shows that growth and condition indices can prove useful in assessing fish health status following an oil spill. Their complementary analysis with sensitive molecular biomarkers as EROD could improve the determination of oil spill impact on fish populations.

A freshwater amphipod toxicity test based on postexposure feeding and the population consumption inhibitory concentration

Consumption inhibition in natural populations, namely due to contaminants, may have direct and immediate effects on ecosystems, by hampering ecosystem key functions (e.g., organic matter decomposition, grazing), long before effects at the individual level (e.g., reproduction, growth, emergence) have time-delayed consequences at successively higher levels of biological organization. The present study aimed at developing a cost-effective (short and easy) toxicity test based on the postexposure feeding of a freshwater amphipod present in the Iberian Peninsula and at evaluating the immediate impact of contamination on the population-level consumption rate. First, methodologies to quantify postexposure feeding were developed and optimized, the most important criterion being a feeding period as short as possible to minimize physiological recovery from the contaminant exposure. Second, the sensitivities of 48-h postexposure feeding and 48-h lethality tests were compared, using a reference chemical - copper. Third, the latter responses were integrated in a single parameter, the median population consumption inhibitory concentration. When Echinogammarus meridionalis males were fed on 100 defrosted Artemia franciscana nauplii during 30 min in darkness at 19-21°C, the eaten proportion was approximately 80%, without truncated data distributions. The 48-h median effective copper concentration for postexposure feeding was approximately two times lower than the 48-h LC50 - 91 versus 198 μg L(-1), respectively. Two techniques were used to quantify the median population consumption inhibitory copper concentration, both leading to similar values (75 and 68 μg L(-1)). In conclusion, when contaminant concentrations elicit both lethality and feeding depression, the integration of both responses can provide an ecologically relevant evaluation on the potency of a contaminant to immediately disrupt ecosystem functioning.

Evaluation of the sensitivity of genotoxicity and cytotoxicity endpoints in earthworms exposed in situ to uranium mining wastes

Earthworms were exposed for 56 days to a contaminated soil from an abandoned uranium mine and to the natural reference soil LUFA 2.2. The exposure occurred in situ: the containers with contaminated soil were placed near the mine pit; the containers with reference soil were placed in a reference site. For the assessment of metals bioaccumulation, DNA damages, cell-to-cell variation in DNA content, Median Fluorescence Intensity (MFI), coelomocytes frequency and proliferation, organisms were sampled after 0, 1, 2, 7, 14 and 56 days of exposure. For the assessment of radionuclides bioaccumulation, animals were sampled after 0, 14 and 56 days of exposure. As for growth, organisms were sampled after 0, 14, 28 and 56 days of exposure. The reproduction assay was performed according to the OECD (2004) guideline. DNA damages were assessed by comet assay and flow cytometry was used to determine cell-to-cell variation in DNA content, Median Fluorescence Intensity (MFI), coelomocytes frequency and proliferation. Results have shown a myriad of effects in the organisms exposed to the contaminated soil, namely: the inhibition of reproduction, growth reduction, DNA damages, cytotoxicity, changes in eleocytes fluorescence intensity, coelomocytes proliferation and bioaccumulation of metals and radionuclides. Our results showed that the evaluation of genotoxicity and cytotoxicity endpoints, along with other parameters at an individual level in standard reproduction assays conducted in situ, are important to improve the risk assessment process of areas contaminated with uranium and other radioactive mining wastes.

Effects of carbofuran on the sea bass (Dicentrarchus labrax L.): study of biomarkers and behaviour alterations

The objective of this study was to investigate the acute effects of the pesticide carbofuran on the sea bass (Dicentrarchus labrax) using parameters at different levels of biological organisation (swimming behaviour and several biomarkers) and possible relationships between alterations found in different effect criteria. In a bioassay, sea bass juveniles were individually exposed to different doses of carbofuran (31, 63, 125 and 250 μg/L) for 96 h. At the end of the bioassay, the swimming performance and 11 biomarkers were determined. Biomarkers were: hepatosomatic index (HSI), lipid peroxidation (LPO), reduced glutathione and the activities of the enzymes ethoxyresorufin O-deethylase (EROD), glutathione S-transferases, superoxide dismutase, catalase, glutathione peroxidase, glutathione reductase, brain acetylcholinesterase (AChE) and muscle cholinesterases (ChE). After 96 h of exposure, carbofuran induced a decrease of the swimming velocity and inhibition of EROD activity at all concentrations tested, and inhibition of muscle ChE and brain AChE activities at 250 μg/L. No relevant alterations in any of the other tested parameters were found. These results show that carbofuran induced adverse effects on fish by interfering with neurofunction, capability of detoxication and swimming velocity. In addition, positive and significant correlations between the swimming velocity and (i) brain AChE activity, (ii) muscle ChE activity and (iii) EROD activity suggest that the inhibition of these enzymes may somehow be related to the behavioural changes observed. Since these functions are determinant for the survival and performance of the fish in the wild, the findings of the present study suggest that adverse effects may occur in populations exposed to carbofuran if a sufficient number of animals is affected.

Are biochemical biomarker responses related to physiological performance of juvenile sea bass (Dicentrarchus labrax) and turbot (Scophthalmus maximus) caged in a polluted harbour?

Biomarker responses to toxic exposure have been used for decades to indicate stress in aquatic organisms, or the magnitude of environmental pollution. However, little has been done to compare the simultaneous responses of both biochemical and physiological biomarkers. The purpose of this study was twofold. Firstly to analyse the responses of several biochemical biomarkers measured on juvenile sea bass and turbot caged in a northern France harbour at a reference and contaminated stations. Several biotransformation parameters (Ethoxyresorufin-O-deethylase - EROD - and Glutathione S-transferase -GST) and an antioxidant enzyme (Catalase -CAT) were analysed. Secondly, to compare their responses to several growth and condition indices, measured on the same fish. In the contaminated station, EROD and GST activities were found to be significantly higher, and a decrease of CAT activity was observed for both species. For individual sea bass, biochemical biomarkers showed numerous significant correlations with growth and condition indices, such as the Fulton's K condition index, the RNA:DNA ratio and the lipid storage index. On the contrary, there were only a few significant correlations for turbot, suggesting a species-specific response. Our study indicates that the analysis of the simultaneous responses of both biochemical and physiological biomarkers can be useful for monitoring complex exposure and to assess habitat quality.

In situ aquatic bioassessment of pesticides applied on rice fields using a microalga and daphnids

This study assessed the effects of episodic contamination on a drainage canal adjacent to an area of intensive rice production (Coimbra, Portugal). Four monitoring periods were considered [i) before herbicide application (day-14), ii) at the first application day (day 0), iii) 3 or 5 and iv) 6days after]. Each one consisted in three complementary evaluation lines: a) physico-chemical analyses, b) whole effluent toxicity (WET) assays with Pseudokirchneriella subcapitata, c) in situ bioassays to assess microalgae (P. subcapitata) growth, and the feeding rate and survival of Daphnia longispina and Daphnia magna. Study sites were located upstream, in a protected wetland (L1), and downstream, in the vicinity of rice fields (L2). Along with the application of agrochemicals, there was a general decrease of the water quality, especially in L2, due to nutrient and herbicide inputs. Herbicide peaks (on days 0, 5 and 6) in L2 water samples were recorded concomitantly or immediately after their application. Regarding the in situ bioassessment, the algae growth decrease from day 0 onwards in L1, whilst in L2 its inhibition was generally coherent with the decline of the water quality. Apparently, WET tests indicated that the limitation of nutrients could be affecting algae growth in L1, however, conclusions should be cautious. The feeding depression of daphnids occurred on days 0 and 5 for D. longispina and only on day 0 for D. magna, while significant reductions on survival were restricted to day 0 for both species. The impairments occurring on day 0 were linked to a potential increased toxicity driven by the ingestion of particle-bound herbicides and suspended particles. The feeding rate of daphnids provided an earlier indication of toxic impairments, though it is prompted the use of complementary endpoints and trophic levels in order to understand the cumulative effects due to various herbicide pulses.

An estuarine mudsnail in situ toxicity assay based on postexposure feeding

In situ assays provide more realistic exposure scenarios than laboratory assays, which is particularly pertinent for estuaries because exposure conditions are difficult to simulate. Traditionally, sublethal toxicity testing endpoints, such as growth, emergence, and reproduction, imply time-delayed extrapolations from individuals to populations, communities, and ecosystems. Sublethal responses mechanistically linked to ecosystem functions have been largely neglected. Feeding is an unequivocal ecologically meaningful response because its impairment has direct and immediate effects on ecosystems, by hampering key functions such as organic matter decomposition, long before its effects at the individual level have consequences at successively higher levels of biological organization. The ultimate goal of the present study was to widen the range of ecosystem functions for estuarine quality assessments. Specifically, a short-term in situ assay based on the postexposure feeding of the mudsnail Hydrobia ulvae is presented. Methodologies to quantify precisely postexposure egestion as a surrogate of feeding were achieved. A multiple regression model from laboratory experiments was successfully applied to an in situ assay at reference (Mira River) and contaminated Portuguese estuaries (Sado River) for predicting reference results and allowing unraveling confounding factors during exposure (temperature, salinity, sediment grain size). Sensitivity comparisons of postexposure feeding with survival and growth, after Cu exposure, were carried out and used for a first preliminary appraisal of the relative consequences of ecosystem-level immediate effects.

Effects of pulp and paper mill effluent extracts on liver anaerobic and aerobic metabolic enzymes in rainbow trout

This study investigates whether pulse exposure to Chilean pulp and paper mill effluent solid phase extracted (SPE) extracts via intraperitoneal injection (IP), would result in changes in the activities of the respiratory metabolic enzymes citrate synthase (CS) and lactate dehydrogenase (LDH) in rainbow trout livers. It also investigated if an alteration in liver metabolic capacity influenced the liver detoxification processes and estrogenic effects previously reported. Besides, a comparison of those enzymatic activities with fish IP injected with SPE extracts of two model effluents coming from industries that process 100% different type of feedstock (softwood, SW and hardwood, HW) was also evaluated. An initial induction of the anaerobic metabolism (increase in LDH enzymatic activity) was detected in all Chilean pulp mill effluent extracts evaluated, contrary to the initial unaltered aerobic metabolism (CS enzymatic activity) observed. A compensatory relationship in energy metabolism (Pasteur effect) was observed when comparing both enzymatic activities of fish exposed to those effluent extracts. LDH and CS activities observed in fish injected with Chilean extracts seem to be related to the effects observed in fish injected with SW extracts. This study showed that intraperitoneal injection of pulp and paper mill effluent extracts affected the anaerobic and aerobic metabolic capacities in rainbow trout livers, but this metabolic alteration did not affect detoxification capability or estrogenic effect previously reported.

A postexposure feeding assay using the marine polychaete Neanthes arenaceodentata suitable for laboratory and in situ exposures

This study examined the suitability for the use of the polychaetous annelid Neanthes arenaceodentata in a short-term sublethal bioassay based on postexposure feeding rate. Quantification of feeding rate was determined by an approximately 1-h feeding period to Artemia franciscana nauplii after a 48-h aqueous exposure. Both lethality and feeding rate were assessed after exposure to Cu and phenanthrene, with the Cu results being compared with those available from similar studies that used the polychaete Hediste diversicolor. Laboratory assessment on the effect of manipulating two common variables in estuarine environments (temperature and salinity) on postexposure feeding to both clean and Cu-spiked seawater samples was also conducted. The 48- and 96-h median lethal concentrations (LC50s) for Cu were 156 and 80 µg/L, respectively, whereas the 48-h median effective concentration (EC50) determined by feeding rate was 57 µg/L. The 48-h LC50 for phenanthrene was 2,224 µg/L, whereas the 48-h feeding rate EC50 was 345 µg/L (more sensitive by a factor of >6). The sensitivity of the postexposure feeding rate endpoint to two representative chemicals that are frequently elevated in contaminated sediments, in addition to rapid exposure time, ecological relevance, and relatively simple approach, suggest that this assay with N. arenaceodentata has potential for use as a tool for sublethal effects assessment, with particular promise for in situ applications. The utility of this assay in actual marine and estuarine sediments is being assessed in situ at several North American sediment sites, and will be reported in future publications.

Suitability of five cladoceran species from Mexico for in situ experimentation

Although they are highly suited for site-specific risk assessment, little attention has been given to in situ ecotoxicological experimentation in tropical regions. This study intended to assess the suitability of five freshwater cladocerans from Mexico for in situ experiments. Juveniles of Ceriodaphnia cornuta, Macrothrix triserialis group, Simocephalus vetulus, Diaphanosoma birgei, and Pseudosida cf. ramosa, from two populations, were used to perform seven day laboratory and in situ experiments. Pseudosida cf. ramosa was very sensitive to handling and was discarded from further evaluations. Ceriodaphnia cornuta reproduced significantly more neonates, with smaller coefficients of variation, than M. triserialis and S. vetulus. Also due to its worldwide distribution in the tropics, C. cornuta is suggested to be highly suitable for in situ experiments.

Linking behavioural alterations with biomarkers responses in the European seabass Dicentrarchus labrax L. exposed to the organophosphate pesticide fenitrothion

The acute effects of the organophosphate insecticide fenitrothion on Dicentrarchus labrax juveniles were investigated through a bioassay using biomarkers and swimming behaviour as effect criteria. After 96 h of exposure to sub-lethal concentrations of fenitrothion, the swimming velocity and several biomarkers were individually determined, namely: brain acetylcholinesterase (AChE) activity; muscle cholinesterases (ChE), lactate dehydrogenase and isocitrate dehydrogenase activities; liver ethoxyresorufin-O-deethylase (EROD), glutathione S-transferases, glutathione peroxidase, glutathione reductase, catalase and superoxide dismutase (SOD) activities and lipid peroxidation levels (LPO). A significant decrease of the swimming velocity (LOEC = 2 mg l(-1)), an inhibition of both AChE (LOEC = 0.06 mg l(-1)) and ChE activities (LOEC = 0.03 mg l(-1)), and a positive and significant correlation between the swimming velocity and AChE were found in exposed fish, suggesting an influence of the inhibition of these enzymes in the swimming velocity decrease. An increase of EROD activity (LOEC = 1 mg l(-1)), indicating the involvement of this enzyme in fenitrothion biotransformation, and a negative and significant correlation between EROD activity and swimming velocity were also found, suggesting that the two findings may somehow be related. Furthermore, results show a significant induction of SOD (LOEC = 0.13 mg l(-1)) without LPO increase, suggesting that the enzyme is preventing oxidative stress damage. No significant alterations were found in any of the other parameters tested. Thus, exposure of seabass to fenitrothion in the wild at concentrations similar to those tested here may have adverse consequences at population level as neurotransmission and swimming ability are essential for fish performance and survival.

Ecotoxicological tools for the tropics: Sublethal assays with fish to evaluate edge-of-field pesticide runoff toxicity

This study proposes short-term sublethal assays for the tropics using the fish Poecilia reticulata. Assays were evaluated under realistic exposure scenarios by simulating a runoff over an agricultural area sprayed with deltamethrin (Decis). In situ assays were performed inside microcosms set up to simulate runoff water entrance in lentic systems. Laboratory assays were conducted with water samples from the microcosms. In both assays the biochemical parameters were similarly responsive to Decis, with a significant inhibition of acetylcholinesterase (30-46%) and induction of lactate dehydrogenase (33-67%) and glutathione S-transferases (48-176%) activities, observed as of the lowest Decis dose. Postexposure feeding was more sensitive in the laboratory assay than in situ. Among the additional potential stressors, only acetylcholinesterase was significantly influenced by the runoff per se. The proposed methodologies were well adapted for assays with P. reticulata, as organisms were easily deployed and retrieved and enzymatic activities and postexposure feeding were sensitive endpoints.

Genetic, biochemical, and individual responses of the teleost fish Carassius auratus to uranium

Carassius auratus were exposed for 96 h to different concentrations of uranyl nitrate (corresponding to 0, 100, 450, and 2,025 microg U L(-1)) and killed after different postexposure periods (0, 48, and 96 h) to assess uranium bioaccumulation, peroxisome proliferation (catalase [CAT]), lipid peroxidation (thiobarbituric acid reactive substances [TBARS]), and DNA integrity in erythrocytes (comet assay). In addition, feeding behaviour was recorded as a general response to toxicant exposure. Results provided evidence of uranium bioaccumulation in muscle of C. auratus after exposure to the highest concentrations (450 and 2,025 microg U L(-1)). This tissue was able to depurate uranium to control levels 96 h after exposure ceased. However, no perturbations in feeding behaviour or cell damage were observed in the tested organisms, except for the apparent irreversible inhibition of CAT activity immediately after exposure in the highest concentration tested. Data on DNA integrity (comets) showed that waterborne uranium exposure was able to induce genotoxicity in C. auratus erythrocytes because fish exposed to all concentrations exhibited higher DNA damage than controls 96 h after exposure. No DNA damage repair was apparent throughout the postexposure period, which was contrary to a recovery scenario. This experiment provides evidence of uranium's ability to induce physiologic impairment and genotoxicity in freshwater fish at environmentally relevant concentrations.

European bee-eater (Merops apiaster) populations under arsenic and metal stress: evaluation of exposure at a mining site

Two populations of the European bee-eater were studied, one living at a reference site and the other at a metal mining site. The concentration of arsenic and 11 metals (Al, Cd, Co, Cr, Cu, Fe, Hg, Mn, Ni, Pb, and Zn) was measured in feathers and regurgitated pellets collected at both sites. Cadmium, chromium, mercury, nickel, and lead were at least twofold higher in feathers of birds from the contaminated site than in the reference site, suggesting that this population was exposed to higher metal levels. Similarly, levels of aluminum, arsenic, cadmium, cobalt, chromium, iron, and lead were also at least twofold higher in pellets from the contaminated area. The obtained results suggested that the impacted population of Merops apiaster is at risk due to the exposure to some metals.

Biomarker responses in flounder Platichthys flesus from the Polish coastal area of the Baltic Sea and applications in biomonitoring

The objective of this study was to investigate the pattern of enzymatic activities, environmental genotoxicity and cytotoxicity in flounder, Platichthys flesus, from the Polish coastal area of the Baltic Sea. Fish were sampled in different contaminated sites in the Gulf of Gdansk and in a reference area outside the gulf. The activities of acetylcholinesterase (AChE), glutathione S: -transferase (GST), catalase (CAT), alanine aminotransferase (ALT), aspartate aminotransferase (AST), creatine kinase (CK), lactate dehydrogenase (LDH), were studied, as well as the frequency of micronuclei, nuclear buds and fragmented-apoptotic cells. A higher mean activity level of muscular AChE and a lower activity level of hepatic GST were evident in samples taken from the reference site, relative to those found in the gulf. Modeled CAT activity (in both liver and gill tissue), blood plasma LDH and CK activities were all significantly higher in flounder collected at locations within the Gulf of Gdansk than at the reference site. No statistically significant alterations were observed in the activities of ALT and AST in the blood plasma of flounder in this study. Fish collected from a location at the mouth of the Vistula River showed the highest hepatic GST and CAT, the highest gill CAT activity, and the highest frequency of blood micronuclei, nuclear buds and fragmented-apoptotic cell inductions, as well as the lowest level of blood plasma CK. The present study confirms that compared to fish from the reference area, flounder from the Gulf of Gdansk clearly demonstrate a different enzyme activity, genotoxicity and cytotoxicity biomarker response pattern.

Acetylcholinesterase activity in Gammarus fossarum (Crustacea Amphipoda): linking AChE inhibition and behavioural alteration

Relations between whole-body acetylcholinesterase (AChE) inhibition and changes in feeding and locomotor behaviours were investigated in adult male Gammarus fossarum during short-term exposure (96h) to the organophosphorous pesticide chlorpyrifos (CPE) and the carbamate pesticide methomyl (MT). AChE activity was measured after 24, 48 and 96h of exposure. The feeding rate was assessed after 48 and 96h of exposure and locomotor activity was measured at the end of the experiment. A concentration-dependent decrease of AChE activity and behavioural parameters was observed for both CPE and MT. However, these two compounds presented dissimilar modes of action since MT-induced effects appeared rapidly during the first 48h of the experiment and remained constant until the end of experiment, contrary to CPE-induced effects, which occurred gradually during the last 48h. For CPE, significant mortality was observed from 50% AChE inhibition, contrary to MT for which no mortality was observed despite 66% inhibition. These results suggest that, for CPE, the observed mortality was not directly related to AChE inhibition but that an additional toxic mode of action occurred. On the contrary, the feeding rate and locomotion impairment were directly correlated to levels of AChE inhibition for both chemicals, except for the lowest concentrations of MT for which an induction of the behavioural parameters was observed. Although CPE and MT have different modes of action (acting as indirect and direct inhibitors), the relations between AChE activity and inhibition of behavioural parameters were relatively close for these two compounds. This study provides a basis to interpret the biomarker AChE at the upper biological organisation level, on both the feeding rate and locomotor behaviour, which are known to be relevant ecological responses.

Yellow eel (Anguilla anguilla) development in NW Portuguese estuaries with different contamination levels

The aims of the present study were to compare the health status of yellow eels (Anguilla anguilla) developing in three estuaries of the NW Portuguese coast with different levels of pollution and their physiological responses to combined effects of environmental variation and pollution. For this, a field study was performed using a multi-parameter approach, including eels condition indexes and biomarkers, water quality variables and other environmental factors. Sixteen biological parameters were assessed, namely: hepatosomatic index (LSI), Fulton's condition index (K), lipid peroxidation (LPO), total glutathione (TG), reduced glutathione (GSH), oxidised glutathione (GSSG), GSH/GSSG, and the activity of the enzymes acetylcholinesterase (AChE), lactate dehydrogenase (LDH), sodium-potassium ATPase (Na(+)/K(+)-ATPase), ethoxyresorufin O-deethylase (EROD), glutathione S-transferases (GST), catalase (CAT), superoxide dismutase (SOD), glutathione peroxidase (GPx) and glutathione reductase (GR). Ten environmental factors were also measured in water: temperature, salinity, pH, phosphates, nitrates, nitrites, ammonium, silica, phenol and hardness. Globally, the biomarkers indicate exposure and toxic effects of pollutants on eels living in contaminated estuaries. The relationships between biological and environmental variables were assessed through redundancy analysis. K and LSI indexes, AChE and Na(+)/K(+)-ATPase, total glutathione levels and the antioxidant enzymes CAT, GR, and SOD where the factors most discriminating reference (Minho River estuary) from contaminated estuaries (Lima and Douro Rivers estuaries). Moreover, the most striking outcomes of pollutants exposure on biological responses were observed during winter, probably due to a joint effect of cold weather and pollution stress. Altogether, the results indicate that the development of eels in the polluted estuaries of Lima and Douro rivers is interfering with physiological functions determinant for their survival and performance. This may increase the mortality rates during the continental life-phase of the species and decrease the percentage of animals able to successfully complete their oceanic migration and, thus, reduce the contribution of each generation to the next one.

Effects of natural and chemical stressors on Enchytraeus albidus: can oxidative stress parameters be used as fast screening tools for the assessment of different stress impacts in soils?

Enchytraeids are important organisms of the soil biocenosis. They improve the soil pore structure and the degradation of organic matter. These organisms are used in standardized testing, using survival and reproduction (6 weeks) as endpoints. The use of biomarkers, linked to ecologically relevant alterations at higher levels of biological organization, is a promising tool for Environmental Risk Assessment. Here, enchytraeids were exposed for different time periods (two days and three weeks) to different soils (OECD artificial soil, different compositions in its organic matter, clay or pH value, and LUFA 2.2 natural soil) and different chemicals (Phenmedipham and copper). The main question addressed in the present study was if the effects of chemicals and different soil properties are preceded by alterations at the sub-cellular level, and if these endpoints may be used reliantly as faster screening tools for the assessment of different stress conditions in soils. The parameters measured in E. albidus whole body were: lipid peroxidation (LPO), total glutathione (TG), as well as the enzymatic activities of superoxide dismutase (SOD), catalase (CAT), glutathione reductase (GR), glutathione peroxidase (GPx) and glutathione S-transferase (GST). The results showed that biomarker responses in E. albidus were significantly affected by the soil type (GST, CAT, GPx, GR and LPO) and the duration of exposure in OECD artificial soil (GST, GPx, GR, CAT and LPO) but not in LUFA 2.2 natural soil. For the abiotic factors studied, after 2 days, low pH decreased significantly the TG levels and the activities of CAT and GR,and low OM also significantly decreased CAT and GR activities. After 3 weeks, differences in soil properties caused a decrease in GR and GPx activities, whereas increased GST activity was observed due to low organic matter and pH. Copper significantly increased the activities of CAT, GPx and GR, and decreased the activity of GST after 2 days as well as inscreasing LPO levels after 3 weeks. Phenmedipham increased LPO levels, associated with increased levels of TG as well as increased activities of CAT and GPx and decreased GST activity after 3 weeks exposure. This study shows that both abiotic and chemical stresses could be followed through biomarker analysis and that some of these determinations are potential endpoints in a quick soil contamination assessment procedure.

Effects of nonylphenol on cholinesterase and carboxylesterase activities in male guppies (Poecilia reticulata)

Compared to the estrogenic effects of 4-nonylphenol (NP), there is little data available on other potential toxic effects of NP in aquatic animals. The effects of NP on cholinesterase (ChE) and carboxylesterase (CbE) activities of male guppies exposed to 10, 60, 150, or 300 μg L(-1) NP were examined after 1, 2, 4, and 7 days of treatment. A significant muscle ChE inhibition, that used acetylthiocholine iodide as a substrate, was noted in male guppies in all NP treatment groups after a 4-day exposure, and 60 and 150 μg L(-1) of NP treatment groups after a 7-day exposure. All guppies exposed to 300 μg L(-1) NP died during the 7-day treatment. However, there was no significant inhibition of muscle ChE that used butyrylthiocholine iodide as a substrate in male guppies for any NP treatments in different exposure times. There were no CbE activity differences in livers of male guppies among NP treatment groups after different exposure times. This is the first report showing the ChE activity inhibition by NP in fish. Further mechanistic studies are needed to define how NP directly or indirectly alters ChE activities at molecular level. The implication of ChE inhibition of NP on potential impacts of aquatic animals also warrants further research.

In situ bioassay with Eisenia andrei to assess soil toxicity in an abandoned uranium mine

The goal of this study was to develop an in situ bioassay with Eisenia andrei, deploying it in several locations of an abandoned mining area. Our objectives were two-fold: (i) we intended to validate the in situ soil bioassay procedures, while (ii) providing ecologically relevant data to complement the ongoing risk evaluation based on laboratorial assays. To promote cost- and time-effectiveness, the in situ exposure was short (48 h) and the endpoints analysed included oxidative stress biomarkers and metal content in soil and organisms. The bioassay was carried out under different experimental conditions, simulating local (natural soil) vs. control conditions (LUFA soil), and irrigation with artificial rainwater vs. irrigation with diluted acidic effluent. Variation in the data was mostly due to soil type, rather than irrigation water, and substantial spatial heterogeneity was observed. Oxidative stress biomarkers did not fully work as sensitive parameters to environmental contamination. Earthworm metal burdens suggested a potential concern in terms of bioaccumulation of some metallic elements.