Biotransformation and genotoxic biomarkers in mullet species (Liza sp.) from a contaminated coastal lagoon (Ria de Aveiro, Portugal)

The EU Interreg Project "GEREMIA" on waste management for the improvement of port waters: results on monitoring the health status of fish as bioindicator

Highly anthropized areas as ports represent complex scenarios that require accurate monitoring plans aimed to address the environmental status. In this context, the activities of the EU Interreg Project "GEstione dei REflui per il MIglioramento delle Acque portuali (GEREMIA)" were focused on comparing sites differently affected by human presence, as the Port of Genoa and the natural area of the S'Ena Arrubia fishpond: a panel of analyses was carried out on Mugilidae fish sampled in these two areas, aimed to address trace metal accumulation in the liver, gills, and muscle, as well as cytochrome P450 (CYP450) induction in liver and biliary polycyclic aromatic hydrocarbon (PAH) metabolites, and histopathological alterations in the liver and gills. Chemical analyses in the liver, gills, and muscle of specimens collected in the port area showed an overall higher degree of trace metal contamination compared to the natural fishpond, and similar results were obtained in terms of CYP450 induction and biliary PAH metabolites, suggesting a higher exposure to organic compounds. In addition, histopathological analyses revealed a significant alteration and then a loss of functionality of liver and gill tissue in individuals from the port. Overall, this study describes the complex environmental pollution scenario in the Port of Genoa, confirming the importance of using multidisciplinary approaches and different types of analyses to address both the presence and the effects of contaminants in marine environments.

Bioaccumulation of trace metals and genotoxicity responses in Liza aurata as an indicator of industrial pollution

Heavy metal contamination in the coastal and marine ecosystems is becoming a serious risk to aquatic organisms and humans. This study reports the effects, including genetic damage, of accumulations of trace metals on Liza aurata, which is used as a bio-indicator species, in the Payas coast of Iskenderun Bay, north-eastern Mediterranean by COMET Assay. L. aurata were seasonally collected from a sampling site and a reference site for one year. Physicochemical parameters in water and trace metals in the tissues of fish collected from these sites were determined by electrochemical techniques. High DNA damage frequency in L. aurata was observed along the Payas coast of Iskenderun Bay compared to the reference site because of pollutants. The detected high levels of Cd, Pb, Fe and Cu accumulation in L. aurata exceed the maximum levels allowed by the national and international limit values. Significant positive correlations between Cd, Pb, Hg, Cr, Fe, Zn, and Cu accumulations and DNA damage parameters were observed in the present study. Additionally, we first reported the successful use of the electrochemical technique in the determination of trace metal concentrations in mullet. Moreover, L. aurata constitutes a key tool as a sentinel organism for biomonitoring of coastal ecosystems.

Twists and turns of an oyster's life: effects of different depuration periods on physiological biochemical functions of oysters

Aquaculture activities are often established in the vicinity of highly populated, potentially contaminated areas. Animals cultured at such locations, namely bivalves, are frequently used as test organisms in ecotoxicological testing. In this case, a period of depuration is required to allow the normalization of physiological processes, which are likely to be altered after exposure to a multiplicity of waterborne contaminants occurring in the wild. One of the most important species in modern marine aquaculture is the oyster species Crassostrea gigas. The aim of this study was to assess if the current depuration time frame of 24 h (adopted by most aquaculture facilities), is long enough to permit oysters to revert potential toxic effects exerted by environmental contaminants, allowing their use in laboratory-based ecotoxicological studies. The selected approach involved the monitoring of biochemical (antioxidant defence, oxidative damage, phase II metabolism, and neurological homeostasis) and physiological (condition index) parameters, along a period of 42 days. The obtained results showed that a period of 24 h does not revert any of the potential toxic effects caused by environmental contaminants to which animals may have been previously subjected; even a period of 42 days was not long enough for the oysters to completely normalize the levels of their antioxidant defences, namely total GPx activity, which increased over time. Lipid peroxidation was also increased during the depuration period, and the activity of the metabolic isoenzymes GSTs was significantly decreased. Furthermore, AChE activity measured in the adductor muscle of oysters was increased over time. These assumptions suggest that a period of depuration longer than 24 h is mandatory to obtain adequate test organisms of this oyster species, to be used for ecotoxicological testing purposes.

Cholinesterase characterization and effects of the environmental contaminants chlorpyrifos and carbofuran on two species of marine crabs, Carcinus maenas and Pachygrapsus marmoratus

Among the most frequent targets for toxic effects of modern pesticides, namely organophosphates and carbamates, one may find cholinesterases (ChEs). ChEs exist in a wide variety of animals and have been used actively to discriminate among the environmental effects of different pollutant groups, including the aforementioned pesticides. This study had three purposes, namely (i) identifying the ChE forms present in tissues (eyes and walking legs muscle) of two crab species, Carcinus maenas and Pachygrapsus marmoratus; to (ii) determine the in vitro toxicological effects, and (iii) compare the sensitivity of such enzymatic forms towards commonly used anti-ChE pesticides, namely the organophosphate chlorpyrifos and the carbamate carbofuran. Our results showed that there was not a clear preference for any of the tested substrates in any of the tissues from both species. Furthermore, the ChE activity was almost completely suppressed following incubation with eserine and with the specific inhibitor BW284C51 in all tissues from both species. In vitro exposure to chlorpyrifos promoted a significant decrease in ChE activity in both species. Furthermore, the ChE activity was completely suppressed following incubation with carbofuran and chlorpyrifos. These results suggest that the major ChE forms present in tissues of both crab species show intermediate structural properties and activity patterns, halfway between classic acetylcholinesterase and pseudocholinesterases. However, the sensitivity of the found forms towards ChE inhibitors was established, and the responsiveness of such forms towards common anti-ChE chemicals was established. Both tested species seem to be promising test organisms to be used in marine and coastal scenarios of putative contaminations by anti-ChE chemicals, considering the here reported patterns of response.

Micronuclei in Fish Erythrocytes as Genotoxic Biomarkers of Water Pollution: An Overview

Freshwater and marine water bodies receive chemical contaminants from industrial, agricultural, urban, and domestic wastes. Eco-genotoxicity assays are useful tools to assess the cumulative genotoxicity of these pollutants. Fish are suitable indicators for biomonitoring of mutagenic and carcinogenic pollution.In this review, we present a complete overview of the studies performed so far using the micronucleus test in peripheral erythrocytes of fish exposed to polluted water. We have listed all the species of fish used and the geographical distribution of the investigations. We have analyzed and discussed all technical aspects of using this test in fish, as well as the advantages and disadvantages of the different experimental protocols. We have reported the results of all studies. This assay has become, for years, one of the simplest, fastest, and most cost-effective for assessing genotoxic risk in aquatic environments. However, there are still several factors influencing the variability of the results. Therefore, we have given indications and suggestions to achieve a standardization of experimental procedures and ensure uniformity of future investigations.

Genotoxicity of gold nanoparticles in the gilthead seabream (Sparus aurata) after single exposure and combined with the pharmaceutical gemfibrozil

Due to their diverse applications, gold nanoparticles (AuNPs) are expected to increase of in the environment, although few studies are available on their mode of action in aquatic organisms. The genotoxicity of AuNPs, alone or combined with the human pharmaceutical gemfibrozil (GEM), an environmental contaminant frequently detected in aquatic systems, including in marine ecosystems, was examined using gilthead seabream erythrocytes as a model system. Fish were exposed for 96 h to 4, 80 and 1600 μg L^-1 of 40 nm AuNPs with two coatings - citrate or polyvinylpyrrolidone; GEM (150 μg L^-1); and a combination of AuNPs and GEM (80 μg L^-1 AuNPs + 150 μg L^-1 GEM). AuNPs induced DNA damage and increased nuclear abnormalities levels, with coating showing an important role in the toxicity of AuNPs to fish. The combined exposures of AuNPs and GEM produced an antagonistic response, with observed toxic effects in the mixtures being lower than the predicted. The results raise concern about the safety of AuNPs and demonstrate interactions between them and other contaminants.

Searching for antigenotoxic properties of marine macroalgae dietary supplementation against endogenous and exogenous challenges

The functional characterization of marine macroalgae toward their potential to strength genome protection is still scarce. Hence, the aim of this study was to assess the antigenotoxic potential of Ulva rigida, Fucus vesiculosus, and Gracilaria species in Drosophila melanogaster following dietary exposure and adopting the somatic mutation and recombination test (SMART). All macroalgae displayed a genoprotection activity, namely against an exogenous challenge (streptonigrin). The action against subtler endogenous pressures was also noted indicating that supplementation level is a critical factor. Gracilaria species provided ambivalent indications, since 10% of G. vermiculophylla inhibited the egg laying and/or larvae development, while 10% of G. gracilis promoted spontaneous genotoxicity. The effects of U. rigida were modulated (in intensity) by the growing conditions, demonstrating higher genoprotection against streptonigrin-induced damage when grown in an aquaculture-controlled system, while the effectiveness against spontaneous genotoxicity was more apparent in specimens grown under wild conditions. In contrast, F. vesiculosus did not produce significant differences in its potential under varying growing conditions. Overall, these findings shed some light on the macroalgae ability toward genome protection, contributing to the development of algaculture industry, and reinforcing the concept of functional food and its benefits.

Brain morphometric profiles and their seasonal modulation in fish (Liza aurata) inhabiting a mercury contaminated estuary

Mercury (Hg) is a potent neurotoxicant known to induce important adverse effects on fish, but a deeper understanding is lacking regarding how environmental exposure affects the brain morphology and neural plasticity of specific brain regions in wild specimens. In this work, it was evaluated the relative volume and cell density of the lateral pallium, hypothalamus, optic tectum and molecular layer of the cerebellum on wild Liza aurata captured in Hg-contaminated (LAR) and non-contaminated (SJ) sites of a coastal system (Ria de Aveiro, Portugal). Given the season-related variations in the environment that fish are naturally exposed, this assessment was performed in the winter and summer. Hg triggered a deficit in cell density of hypothalamus during the winter that could lead to hormonal dysfunctions, while in the summer Hg promoted larger volumes of the optic tectum and cerebellum, indicating the warm period as the most critical for the manifestation of putative changes in visual acuity and motor-dependent tasks. Moreover, in fish from the SJ site, the lateral pallium relative volume and the cell density of the hypothalamus and optic tectum were higher in the winter than in summer. Thus, season-related stimuli strongly influence the size and/or cell density of specific brain regions in the non-contaminated area, pointing out the ability of fish to adapt to environmental and physiological demands. Conversely, fish from the Hg-contaminated site showed a distinct seasonal profile of brain morphology, presenting a larger optic tectum in the summer, as well as a larger molecular layer of the cerebellum with higher cell density. Moreover, Hg exposure impaired the winter-summer variation of the lateral pallium relative size (as observed at SJ). Altogether, seasonal variations in fish neural morphology and physiology should be considered when performing ecotoxicological studies in order to better discriminate the Hg neurotoxicity.

Addressing the impact of mercury estuarine contamination in the European eel (Anguilla anguilla L., 1758) - An early diagnosis in glass eel stage based on erythrocytic nuclear morphology

The decline of the European eel (Anguilla anguilla L., 1758) population throughout Europe has been partially attributed to pollution. As glass eel estuarine migration may represent a considerable threat, the impact of mercury (Hg) contamination at this stage was evaluated through an in situ experiment (7days). Total Hg (tHg) bioaccumulation was evaluated concomitantly with erythrocytic nuclear morphology alterations: erythrocytic nuclear abnormalities assay (ENA), frequency of immature erythrocytes (IE) and the erythrocytic maturity index (EMI). The ENA results suggested a genotoxic pressure at the most contaminated sites, in line with the tHg increase. The EMI data, together with IE frequency, showed that fish exposed to high levels of Hg exhibited alterations of haematological dynamics, translated into an erythropoiesis increment. Despite the presence of these compensatory mechanisms, the present findings suggest a harmful impact of Hg on genome integrity at this early development stage, potentially affecting eels' condition and ultimately the population sustainability.

Cholinesterase characterization of two autochthonous species of Ria de Aveiro (Diopatra neapolitana and Solen marginatus) and comparison of sensitivities towards a series of common contaminants

Biomonitoring of chemical contamination requires the use of well-established and validated tools, including biochemical markers that can be potentially affected by exposure to important environmental toxicants. Cholinesterases (ChEs) are present in a large number of species and have been successfully used for decades to discriminate the environmental presence of specific groups of pollutants. The success of cholinesterase inhibition has been due to their usefulness as a biomarker to address the presence of organophosphate (OP) and carbamate (CB) pesticides. However, its use in ecotoxicology has not been limited to such chemicals, and several other putative classes of contaminants have been implicated in cholinesterasic impairment. Nevertheless, the use of cholinesterases as a monitoring tool requires its full characterization in species to be used as test organisms. This study analyzed and differentiated the various cholinesterase forms present in two autochthonous organisms from the Ria de Aveiro (Portugal) area, namely the polychaete Diopatra neapolitana and the bivalve Solen marginatus, to be used in subsequent monitoring studies. In addition, this study also validated the putative use of the now characterized cholinesterasic forms by analyzing the in vitro effects of common anthropogenic contaminants, such as detergents, pesticides, and metals. The predominant cholinesterasic form found in tissues of D. neapolitana was acetylcholinesterase, while homogenates of S. marginatus were shown to possess an atypical cholinesterasic form, with a marked preference for propionylthiocholine. Cholinesterases from D. neapolitana were generally non-responsive towards the majority of the selected chemicals. On the contrary, strong inhibitory effects were reported for ChEs of S. marginatus following exposure to the selected pesticides.

Effect of historical contamination in the fish community structure of a recovering temperate coastal lagoon

This study aimed to assess the impact of trace element concentrations in fish assemblages of a recovering coastal lagoon. Fish, water and sediment were sampled in winter and summer in the Ria de Aveiro (Portugal). Multivariate analyses were used to examine the relationship between fish assemblages and environmental variables (physical-chemical parameters, contaminants and sediment grain size). In winter, fish density and biomass were mainly affected by the water turbidity, while Li concentration in the water column was found to be significant for fish biomass. During summer, a significant relationship was found between fish density and temperature, Hg, Li and Zn concentration in the sediment. These contaminants were mainly associated with the historically contaminated area, were Liza spp. and Dicentrarchus labrax appeared as dominant species. Environmental variables were not significant for fish biomass. The historical contamination in the Ria de Aveiro still seems to exert some influence on fish community structure.

Pollution effects on biochemical pathways determined in the polychaete Hediste diversicolor collected in three Portuguese estuaries

Biomonitoring is an important tool for the assessment of the quality and functions of ecosystems, providing information about the pollutants present and the direct effects that they exert on organisms. Biomonitoring relies upon the quantification of variables that can be biochemical, genetic, morphological and physiological changes. Such variables are designated as biomarkers, and multiple biomarkers are usually determined simultaneously in order to have a more integrated analysis and information about sublethal early effects of contaminants. In this work, we quantified biomarkers, associated with oxidative stress (glutathione-S-transferases GSTs, and catalase CAT, activities; levels of peroxidative alterations, by the thiobarbituric acid reactive substances assay, TBARS) and neurotoxicity (acetylcholinesterase activity, AChE) in the polychaete Hediste diversicolor. Organisms were collected at three distinct estuaries, Ria de Aveiro (Laranjo and São Jacinto), Douro River (São Paio, Afurada, and Ribeira da Granja), both impacted by human activities, and Minho River (Seixas), which has been used as a reference site. Obtained data showed the occurrence of anti-oxidant responses, in most samples from contaminated sites, which was not followed however by the occurrence of oxidative damage in organisms from Ria de Aveiro. None of the analyzed organisms had significant impairment of cholinesterasic activity, suggesting the absence of a prior exposure to neurotoxic compounds. In fact, organisms collected at Ria de Aveiro had largely increased AChE activity, suggesting an uncommon paradoxical biological response that is further discussed.

Genotoxicity induced by Roundup® (Glyphosate) in tegu lizard (Salvator merianae) embryos

Environmental contaminants produce multiple adverse consequences at individual, population and ecosystem levels. High volumes of agrochemicals applied to great variety of crops, together with agricultural expansion, generate great concerns due to the impact for the environment and large risk implicated for wildlife. The lack of data on these threats is striking. The tegu lizard (Salvator merianae) is one of the species that live in environments under contaminant effects. Several characteristics allow proposing this species as a potential sentinel organism for the monitoring of pesticides in their habitat. The present study is the first report about genotoxicity in tegu lizard neonates after embryonic exposure to Roundup® (glyphosate 66.2%). The micronucleus test (MN), nuclear abnormalities (NAs) assay and comet assay (CA) were used as biomarkers of genotoxic effects induced in erythrocytes by topical exposure of the eggs to the glyphosate commercial formulation Roundup® (RU), in laboratory controlled conditions. A total of 96 eggs were distributed in six groups exposed to RU (50, 100, 200, 400, 800, 1600μg/egg), one positive control (PC; 200μg cyclophosphamide/egg) and one negative control (NC; distilled water). No teratogenic effects were observed in any of the exposed or control neonates. A significant increase in DNA damage was observed in all concentrations higher than 100μg/egg with respect to NC (p<0.05). However, no statistical differences were found in the frequencies of MN and NAs in any group exposed to RU compared to the NC. No statistically significant differences were found in the size of the lizards at birth or after six months post-exposure (p>0.05). Our results provide new information about the undesirable effects of the glyphosate-based herbicide formulations RU on this lizard species that inhabits areas permanently exposed to several pesticide formulations. We consider of utmost necessity a strict regulation of the agrochemical application conditions in those environments near to places where wild populations of terrestrial and aquatic species live, in order to minimize the adverse effects on ecosystems.

Insights into neurosensory toxicity of mercury in fish eyes stemming from tissue burdens, oxidative stress and synaptic transmission profiles

This study aims to contribute to fill a knowledge gap related with Hg effects in fish eyes. As a pioneering strategy, Hg bioaccumulation in eye wall of the wild grey mullet (Liza aurata) was assessed, together with oxidative stress and synaptic transmission profiles. This approach was complemented by the characterisation of environmental contamination (both in water and sediment). Sampling was conducted in winter and summer in two sites of a Portuguese coastal lagoon (Aveiro lagoon): Largo do Laranjo (LAR) - located in an Hg contaminated/confined area; São Jacinto (SJ) - closer to the lagoon inlet and selected as reference site. Levels of total Hg (tHg), inorganic Hg (iHg) and methylmercury (MeHg) in eye wall were higher at LAR than SJ, both in winter and summer, reflecting the environmental contamination patterns. Moreover, fish caught at LAR in winter showed a significant decrease of catalase and superoxide dismutase activities, in line with the occurrence of peroxidative damage. A different spatial pattern was recorded in summer, being characterised by the increment of glutathione peroxidase and glutathione reductase activities at LAR, as well as total glutathione content, preventing the occurrence of lipid peroxidation. Also in summer, a significant decrease of acetylcholinesterase activity was recorded in fish eyes at LAR, pointed out Hg as an anticholinergic agent. Besides Hg, water salinity had probably an indirect effect on spatial and winter-summer variation patterns of AChE. Current data pointed out that Hg (in iHg and MeHg forms) could exert ocular toxicity both by the promotion of oxidative stress and by the interference with neurotransmission processes.

The sub-cellular fate of mercury in the liver of wild mullets (Liza aurata)--Contribution to the understanding of metal-induced cellular toxicity

Mercury is a recognized harmful pollutant in aquatic systems but still little is known about its sub-cellular partitioning in wild fish. Mercury concentrations in liver homogenate (whole organ load) and in six sub-cellular compartments were determined in wild Liza aurata from two areas - contaminated (LAR) and reference. Water and sediment contamination was also assessed. Fish from LAR displayed higher total mercury (tHg) organ load as well as in sub-cellular compartments than those from the reference area, reflecting environmental differences. However, spatial differences in percentage of tHg were only observed for mitochondria (Mit) and lysosomes plus microsomes (Lys+Mic). At LAR, Lys+Mic exhibited higher levels of tHg than the other fractions. Interestingly, tHg in Mit, granules (Gran) and heat-denaturable proteins was linearly correlated with the whole organ. Low tHg concentrations in heat stable proteins and Gran suggests that accumulated levels might be below the physiological threshold to activate those detoxification fractions.

Heat-shock protein 70 modulates apoptosis signal-regulating kinase 1 in stressed hepatocytes of Mugil cephalus

Oxidative stress causes damage at the cellular level and activates a number of signaling pathways. Heat-shock proteins (HSPs) play an important role in repair and protective mechanisms under cell response to stress conditions. HSP70 has been shown to act as an inhibitor of apoptosis. Apoptosis signal-regulating kinase-1 (ASK1) activity is regulated at multiple levels, one of which is through inhibition by cytosolic chaperons HSP70. The current study was aimed to investigate the alteration in signaling molecules that allow the fish to survive under stressed natural field conditions. The study also investigates the variation in biomolecular composition of hepatocytes by using Fourier transform infrared spectroscopy. The impact of stress on hepatocytes was assessed by measuring the level of lipid peroxides (LPO), catalase activity (CAT) and assessing the changes in hepatocytes of Mugil cephalus inhabiting Kovalam and Ennore estuaries. The expression of HSP70 and ASK1 were analyzed by immunoblot analysis and ELISA, respectively. The spectral analysis showed variations in biomolecular composition of hepatocytes at a wave number region of 4,000-400 cm(-1). There was significant decrease of CAT activity (p < 0.01) (25 %) with significant increase of LPO (p < 0.001) (35 %) and HSP70 (p < 0.001) and insignificant increase of ASK1 (p < 0.05) (16 %) in fish hepatocytes inhabiting Ennore estuary than Kovalam estuary. In conclusion, the present study suggests that the survival of fish in the Ennore estuary under stressed condition may be due to the upregulation of HSP70 that mediates the altered signal pathway which promotes cellular resistance against apoptosis.

Mercury accumulation and tissue-specific antioxidant efficiency in the wild European sea bass (Dicentrarchus labrax) with emphasis on seasonality

The main goal of this study was to assess both mercury (Hg) accumulation and organs' specific oxidative stress responses of gills, liver and kidney of Dicentrarchus labrax with emphasis on seasonality. Fish were collected in cold and warm periods in three stations: reference, moderated and highly contaminated sites. Our results showed that seasonal factors slightly influenced Hg accumulation between year periods (cold and warm) and strongly affected organs' response basal levels. In contrast, seasonality seemed not to influence oxidative stress responses, since similar response patterns were obtained for both year periods, and moderate degree of antioxidant responses was obtained. Moreover, the oxidative stress profile may be attributed to Hg contamination degree, which showed organ-specific response and accumulation patterns. Hence, gills showed to be able to adapt to Hg contamination, and in opposition, kidney and liver demonstrated some vulnerability to Hg toxicity. The critical Hg concentrations indicated specific threshold limits for each organ. Overall, seasonality should be taken into account in monitoring programmes, helping to characterize the individuals' reference values of response and thus to discriminate between the effects induced by natural causes or by contamination.

Mercury-induced chromosomal damage in wild fish (Dicentrarchus labrax L.) reflecting aquatic contamination in contrasting seasons

Ria de Aveiro (mainly Laranjo basin, Portugal) has been subjected to mercury contamination from a chlor-alkali plant, currently presenting a well-described mercury gradient. This study aimed to assess mercury genotoxicity in this area by measuring the frequency of erythrocytic nuclear abnormalities (ENA) in the European sea bass (Dicentrarchus labrax), addressing the relation with total mercury concentration in the blood and the modulatory role of seasonal variables. Fish were collected, in warm and cold periods, at three locations differing in their distances to the main mercury source: reference (R), moderately (M), and highly (H) contaminated sites. Genotoxicity was detected in both degrees of contamination (M and H) and in both periods of the year (warm and cold), which is in line with the greater levels of mercury measured in fish blood. No significant seasonal variations were observed for mercury bioaccumulation or ENA frequency. The apparent low imperviousness of ENA frequency to seasonal factors reinforced its consistency as a genotoxicity biomarker, thus enabling a clearer identification of cause-and-effect relationships. Overall, the results reflected a serious environmental risk to native ichthyofauna at Laranjo basin due to mercury contamination, showing a potential of mercury to induce genetic damage in fish blood cells through clastogenic and/or aneugenic actions.

Evaluation of species-specific dissimilarities in two marine fish species: mercury accumulation as a function of metal levels in consumed prey

The aim of this research was to compare mercury (Hg) accumulation (total and organic) and tissue distribution in two marine fish species with contrasting feeding tactics. Thus, juvenile specimens of European sea bass and Golden grey mullet were surveyed in an estuary historically affected by Hg discharges. Total Hg was preferentially accumulated in intestine, muscle, and liver, whereas gills and brain presented the lowest Hg levels observed in both species. Significant differences between species were only verified for muscle, with D. labrax's levels being greater than L. aurata's. Muscle accounted for >87% of the Hg relative tissue burden, whereas liver did not exceed 11%. Organic Hg accumulation occurred mainly in liver and muscle, with D. labrax evidencing significantly greater loads. Moreover, organic Hg in consumed prey items was also significantly greater in D. labrax. Accumulation of organic Hg in liver, intestine, and muscle seemed to vary as a function of the consumed prey items contamination, suggesting fish feeding strategies as the dominant factor determining metal accumulation. For both fish species, a stable ratio was observed between Hg increments from the reference to the contaminated site, possibly indicating that the organic Hg content of diet may regulate the internal levels of this contaminant. Thus, this ratio might prove to be a useful contamination predictor tool in early life stages of fish.

Oxidative stress, genotoxicity and histopathology biomarker responses in mullet (Mugil cephalus) and sea bass (Dicentrarchus labrax) liver from Bizerte Lagoon (Tunisia)

The aim of the study was to evaluate the impact of environmental contaminants on oxidative stress, genotoxic and histopathologic biomarkers in liver of mullet (Mugil cephalus) and sea bass (Dicentrarchus labrax) collected from a polluted coastal lagoon (Bizerte Lagoon) in comparison to a reference site (the Mediterranean Sea). Antioxidant enzyme activities were lower in fish from the polluted site compared with fish from the reference site, suggesting deficiency of the antioxidant system to compensate for oxidative stress. DNA damage was higher in both fish species from the contaminated site indicating genotoxic effects. The liver histopathological analysis revealed alterations in fish from Bizerte Lagoon. Hepatocytes from both fish species featured extensive lipid-type vacuolation and membrane disruption. Results suggest that the selected biomarkers in both fish species are useful for the assessment of pollution impacts in coastal environments influenced by multiple pollution sources.

Fish consumption and risk of contamination by mercury---considerations on the definition of edible parts based on the case study of European sea bass

In the present study, the risk to humans by consuming European sea bass (Dicentrarchus labrax), captured at three sites along a Hg contamination gradient, was evaluated by comparing muscle and kidney total Hg (T-Hg) levels with the European regulations for marketed fish. Moreover, T-Hg and organic Hg (O-Hg) levels in muscle were compared with the Provisional Tolerable Weekly Intake (PTWI) and the Reference Dose (RfD). Although T-Hg levels in muscle were below the European value allowable for marketed fish, kidney's levels were higher than the set value, stressing the importance of redefining the concept of edible tissue and which tissues should be considered. Mercury weekly ingestion in the contaminated areas was higher than the PTWI, and O-Hg daily ingestion rates were higher than the RfD in all sampling sites. Thus, populations consuming sea bass from the contaminated sites may be at risk, with particular relevance for children and pregnant women.

Mercury accumulation patterns and biochemical endpoints in wild fish (Liza aurata): a multi-organ approach

The integration of bioaccumulation and effect biomarkers in fish has been proposed for risk evaluation of aquatic contaminants. However, this approach is still uncommon, namely in the context of mercury contamination. Furthermore, a multi-organ evaluation allows an overall account of the organisms' condition. Having in mind the organs' role on metal toxicokinetics and toxicodynamics, gills, liver and kidney of golden grey mullet (Liza aurata) were selected and mercury accumulation, antioxidant responses and peroxidative damage were assessed. Two critical locations in terms of mercury occurrence were selected from an impacted area of the Ria de Aveiro, Portugal (L1, L2), and compared with a reference area. Although kidney was the organ with the highest mercury load, only gills and liver were able to distinguish mercury accumulation between reference (R) and contaminated stations. Each organ demonstrated different mercury burdens, whereas antioxidant responses followed similar patterns. Liver and kidney showed an adaptive capacity to the intermediate degree of contamination/accumulation (L1) depicted in a catalase activity increase. In contrast, none of the antioxidants was induced under higher contamination/accumulation (L2) in any organ, with the exception of renal GST. The lack of lipid peroxidation increase observed in the three organs denunciates the existence of an efficient antioxidant system. However, the evidences of limitations on antioxidants performance at L2 cannot be overlooked as an indication of mercury-induced toxicity. Having in mind the responses of the three organs, CAT revealed to be the most suitable parameter for identifying mercury exposure in the field. Overall, organ-specific mercury burdens were unable to distinguish the intermediate degree of contamination, while antioxidant responses revealed limitations on signalizing the worst scenario, reinforcing the need to their combined use.

Metallothioneins failed to reflect mercury external levels of exposure and bioaccumulation in marine fish--considerations on tissue and species specific responses

The suitability of metallothioneins (MT) in fish as biomarker of exposure to mercury has been questioned. Therefore, this study aimed at investigating the relationship between external levels of exposure, mercury accumulation and MT content, assessing species and tissue specificities. Two ecologically different fish species--Dicentrarchus labrax and Liza aurata--were surveyed in an estuary historically affected by mercury discharges. Total mercury (T-Hg) and MT content were determined in gills, blood, liver, kidney, muscle and brain. All tissues reflected differences in T-Hg accumulation in both species, although D. labrax accumulated higher levels. Regarding MT, D. labrax revealed a depletion in brain MT content and an incapacity to induce MT synthesis in all the other tissues, whereas L. aurata showed the ability to increase MT in liver and muscle. Tissue-specificities were exhibited in the MT inducing potential and in the susceptibility to MT decrease. L. aurata results presented muscle as the most responsive tissue. None of the investigated tissues displayed significant correlations between T-Hg and MT levels. Overall, the applicability of MT content in fish tissues as biomarker of exposure to mercury was uncertain, reporting limitations in reflecting the metal exposure levels and the subsequent accumulation extent.

Fish thyroidal and stress responses in contamination monitoring--an integrated biomarker approach

Xenobiotics may affect fish endocrine system, making endocrine responses relevant in pollution monitoring. Five critical sites in Ria de Aveiro (Portugal), having different contamination profiles, were assessed in comparison to a reference site (Torreira), focusing on Liza aurata stress (plasma cortisol, glucose and lactate) and thyroidal (plasma thyroid stimulating hormone-TSH, thyroxine-T4 and triiodothyronine-T3) responses. L. aurata at Vagos (PAHs contaminated) and Laranjo (mercury contaminated), respectively, displayed, low cortisol and high glucose as well as lactate levels. Considering thyroidal responses, high TSH levels were found at Laranjo; low T4 levels were found at Barra (subject to naval traffic) and low T3 levels were found at Rio Novo do Principe (near a former bleached kraft pulp mill effluent), Laranjo and Vagos. The integrated biomarker index ranked impacted sites as: Laranjo>Vagos>Gafanha>Rio Novo do Principe>Barra>Torreira. Endocrine responses reflected xenobiotics exposure suggesting environmental risk to fish at Ria de Aveiro. However no clear relation was found between stress and thyroidal responses.

Mercury organotropism in feral European sea bass (Dicentrarchus labrax)

The knowledge of mercury (Hg) burdens in a wide set of tissues and organs of exposed fish is crucial to understand the internal distribution dynamics and thus predict Hg bioavailability and implications for ecosystem and human health. Total Hg was measured in six tissues of Dicentrarchus labrax captured along an estuarine contamination gradient, revealing the following pattern: liver > kidney > muscle > brain ≈ gills > blood. All of the tissues displayed intersite differences, although brain and muscle seemed to better reflect the extent of contamination. Hg speciation showed that liver presented higher concentrations than muscle for both organic and inorganic forms. Furthermore, liver seemed to exert a protective action in relation to Hg accumulation in the other tissues and organs. This protection seems to be particularly marked in relation to the brain, whereas liver is assisted in that action by kidney and muscle.

Multi-biomarker responses to estuarine habitat contamination in three fish species: Dicentrarchus labrax, Solea senegalensis and Pomatoschistus microps

Several biomarker responses were determined in three fish species, Dicentrarchus labrax, Solea senegalensis and Pomatoschistus microps, from two estuaries of the Portuguese coast, Ria de Aveiro and Tejo. Both estuaries have significant anthropogenic influences from multiple sources (industrial, agricultural and shipping activities), which was evident from sediment chemical characterization concerning metal (copper, zinc, nickel, lead and chromium) and polycyclic aromatic hydrocarbon (PAH) concentrations. Spatial variability in fish responses was observed across species for most biomarkers of exposure [the activities of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), ethoxyresorufin O-deethylase (EROD) and glutathione S-transferase (GST), and metallothionein concentrations (MT)] and effect biomarkers [lipid peroxidation (LPO), RNA to DNA ratio (R:D), protein and lipid content]. In general, the interspecific differences in biomarker responses were greater than the spatial differences, due to differences in the behavior and habitat use of the species. Nevertheless, similarities were also observed considering both chemical load and biomarker responses. In highly polluted sites fish showed in general a significant antioxidant enzyme induction, associated with decreased R:D values, while fish from the least impacted site had little enzyme induction and better condition indices (high R:D and low LPO values). EROD activity was also higher for all species in the Tejo than Ria de Aveiro estuary, despite the generally higher total PAH measured in Ria de Aveiro, most likely due to a higher proportion of 4 and 6-ring PAHs, considered more toxic than low molecular weight PAHs, in the Tejo. In conclusion, this multi-biomarker approach considering multiple species provided improved understanding of the diverse responses and effects of exposure to contaminants and the effective risk it poses for different fish species.

Golden grey mullet and sea bass oxidative DNA damage and clastogenic/aneugenic responses in a contaminated coastal lagoon

Several xenobiotics or their metabolites have redox-cycling properties and potential to induce oxidative stress and DNA damage. The current work aimed to study, under environmental conditions, oxidative DNA damage (8-hydroxy-2'-deoxyguanosine (8-OHdG)) and its association with chromosomal damage measured as erythrocytic nuclear abnormalities (ENAs), in Liza aurata and Dicentrarchus labrax, caught at a costal lagoon (Ria de Aveiro, Portugal) having sites with different contamination profiles. The quantified parameters were also used to assess the lagoon's environmental status. Five critical sites were assessed comparing to a reference site. L. aurata displayed higher 8-OHdG levels and ENAs frequency, respectively, at Laranjo and Vagos. D. labrax 8-OHdG levels were higher at the sites where quantification was possible whereas no differences were found in terms of ENAs. No correlation was found in both species between 8-OHdG and ENAs. Despite no direct linkage between the two biomarkers was found, this study demonstrates species and site dependent genotoxic responses.

Antioxidant responses versus DNA damage and lipid peroxidation in golden grey mullet liver: a field study at Ria de Aveiro (Portugal)

The present work aimed to investigate golden grey mullet (Liza aurata) liver protection versus damage responses at a polluted coastal lagoon, Ria de Aveiro (Portugal), as a tool to evaluate the human impacts on environmental health at five critical sites in Ria de Aveiro (Portugal) in comparison to a reference site (Torreira; TOR). Protection was evaluated by measuring non-enzymatic [total glutathione (GSHt) and non-protein thiols (NPT)] and enzymatic [catalase (CAT), glutathione peroxidase (GPx), glutathione-S-transferase (GST), and glutathione reductase (GR)] antioxidant defenses. Damage was assessed as DNA integrity loss and lipid peroxidation (LPO). No significant differences were found between sites in terms of non-enzymatic defenses (GSHt and NPT). CAT did not display significant differences among sites. However, GPx at Barra (BAR, associated with naval traffic), Gafanha (GAF, harbor and dry-dock activities area), Laranjo (LAR, metal contaminated associated with chlor-alkali plant), and Vagos (VAG, contaminated by polycyclic aromatic hydrocarbons) was significantly lower than the reference site. GST was lower at GAF, Rio Novo do Príncipe (RIO, pulp mill effluent area), LAR, and VAG, whereas GR was lower at RIO. The loss of antioxidant defenses was paralleled by higher LPO levels only at GAF and VAG. However, no DNA integrity loss was found. Results highlight the importance of the adopted multibiomarkers as applied in the liver of L. aurata in coastal water pollution monitoring. The integration of liver antioxidant defense and damage responses can improve the aquatic contamination assessment.

Seasonal Liza aurata tissue-specific DNA integrity in a multi-contaminated coastal lagoon (Ria de Aveiro, Portugal)

In this study, the DNA integrity of golden grey mullet (Liza aurata) collected in differently contaminated sites of a coastal lagoon, Ria de Aveiro (Portugal), was assessed, over the period of 1 year, using the DNA alkaline unwinding assay, in four different tissues (gill, kidney, liver and blood) and compared to a reference site. The four tissues displayed different DNA integrity basal levels, clearly affected by seasonal factors. Gill and kidney were, respectively, the most and least sensitive tissues. All sites demonstrated the capacity to interfere with DNA integrity. The sites displaying the highest and lowest DNA damage capability were, respectively, Barra (subject to naval traffic) and Vagos (contaminated with polycyclic aromatic hydrocarbons). In terms of seasonal variability, autumn seems to be the more critical season (more DNA damage) unlike summer when no DNA damage was found in any tissue. Data recommend the continued monitoring of this aquatic system.

Antioxidant system breakdown in brain of feral golden grey mullet (Liza aurata) as an effect of mercury exposure

Although brain has been recognized as a primary target for mercury toxicity in mammals, the effects of this metal in fish brain are scarcely described. Thus, the main objective of this study was to assess the mercury threat to feral fish (Liza aurata) by estimating the antioxidant defenses and peroxidative damage in brain, keeping in mind the association with mercury accumulation. Sampling was carried out in an estuarine area historically affected by discharges from a chlor-alkali industry-Laranjo Basin (Ria de Aveiro, Portugal). Total mercury (T-Hg) in brain increased towards the contamination source, clearly indicating mercury exposure. An overall antioxidant depletion was verified in brain of fish collected at the mercury-contaminated stations, since total glutathione content and the studied antioxidant enzymes (catalase-CAT, glutathione peroxidase-GPx, glutathione-S-transferase-GST and glutathione reductase-GR) significantly decreased. In addition, this breakdown of the redox-defense system was significantly correlated with the accumulated T-Hg levels. Unexpectedly, fish exhibited unaltered lipid peroxidation levels, pointing out a higher propensity of mercury to inhibit enzymes than to oxidatively damage lipids in the brain. Nevertheless, an increased susceptibility of the fish's brain was identified, leaving the organ more vulnerable to oxidative stress-related challenges. Overall, the current findings provide information to better understand mechanisms of mercury neurotoxicity in fish.

Anchoring novel molecular biomarker responses to traditional responses in fish exposed to environmental contamination

The responses of Dicentrarchus labrax and Liza aurata to aquatic pollution were assessed in a contaminated coastal lagoon, using both traditional and novel biomarkers combined. DNA damage, assessed by comet assay, was higher in both fish species from the contaminated sites, whereas levels of cytochrome P450 1A1 gene expression were not significantly altered. The liver histopathological analysis also revealed significant lesions in fish from contaminated sites. Alterations in ras and xpf genes were analysed and additional pollutant-responsive genes were identified. While no alterations were found in ras gene, a downregulation of xpf gene was observed in D. labrax from a contaminated site. Suppression subtractive hybridization applied to D. labrax collected at a contaminated site, revealed altered expression in genes involved in energy metabolism, immune system activity and antioxidant response. The approach and results reported herein demonstrate the utility of anchoring traditional biomarker responses alongside novel biomarker responses.

Monitoring pollution of coastal lagoon using Liza aurata kidney oxidative stress and genetic endpoints: an integrated biomarker approach

Despite the importance of fish kidney in several functions (immune, metabolism and excretion of xenobiotics) its use in coastal water biomonitoring focusing on protection and damage is scarce. Five critical sites in Ria de Aveiro (Portugal; Barra--BAR, Gafanha--GAF, Rio Novo do Principe--RIO; Laranjo--LAR and Vagos--VAG) were assessed in comparison to a reference site (Torreira--TOR), focusing on Liza aurata kidney antioxidant defences versus damage responses. Non protein thiols were higher at RIO (near a former bleached kraft pulp mill effluent) and total glutathione at RIO, LAR (mercury contaminated) and VAG (polycyclic aromatic hydrocarbons contaminated). Catalase and glutathione S-transferase activities were higher at RIO and LAR whereas no differences were found in glutathione peroxidase activity. However, glutathione reductase was higher at BAR (subject to naval traffic), GAF (harbour water area), RIO and LAR. No peroxidative damage was observed despite the decreased DNA integrity at RIO and VAG. The integrated biomarker response index ranked impacted sites as: LAR>RIO>BAR>GAF>VAG>TOR.

Levels and sources of PAHs in selected sites from Portugal: biomonitoring with Pinus pinea and Pinus pinaster needles

Pine needle samples from two pine species (Pinus pinaster Ait. and Pinus pinea L.) were collected at 29 sites scattered throughout Portugal, in order to biomonitor the levels and trends of 16 polycyclic aromatic hydrocarbons (PAHs). The values obtained for the sum of all PAHs ranged from 76 to 1944 ng/g [dry weight (dw)]. Despite the apparent matrix similarities between both pine species, P. pinaster needles revealed higher mean entrapment levels than P. pinea (748 and 399 ng/g (dw) per site, respectively). The urban and industrial sites have the highest average of PAH incidence [for P. pinea, 465 and 433 ng/g (dw) per site, respectively, and for P. pinaster, 1147 and 915 ng/g (dw)], followed by the rural sites [233 ng/g and 711 ng/g (dw) per site, for P. pinea and P. pinaster, respectively]. The remote sites, both from P. pinaster needles, show the least contamination, with 77 ng/g (dw) per site. A predominance of 3-ring and 4-ring PAHs was observed in most samples, with phenanthrene having 30.1% of the total. Naphthalene prevailed in remote sites. Rainfall had no influence on the PAHs levels, but there was a relationship between higher wind speeds and lower concentrations. PAH molecular ratios revealed the influence of both petrogenic and pyrogenic sources.

Evaluation of DNA damage induced by environmental exposure to mercury in Liza aurata using the comet assay

Mercury (Hg) is one of the major aquatic contaminants even though emissions have been reduced over the years. Despite the relative abundance of investigations carried out on Hg toxicity, there is a scarcity of studies on its DNA damaging effects in fish under realistic exposure conditions. This study assessed the Hg genotoxicity in Golden grey mullets (Liza aurata) at Laranjo basin, a particularly contaminated area of Ria de Aveiro (Portugal) well known for its Hg contamination gradient. (1) Fish were seasonally caught at Laranjo basin and at a reference site (S. Jacinto), and (2) animals from the reference site were transplanted and caged (at bottom and surface), for 3 days, in two different locations within Laranjo basin. Using the comet assay, blood was analyzed for genetic damage and apoptotic cell frequency. The seasonal survey showed greater DNA damage in the Hg-contaminated area for all sampling seasons excluding winter. The temporal variation pattern of DNA lesions was: summer approximately autumn > winter > spring. Fish caged at Laranjo also exhibited greater DNA damage than those caged at the reference site, highlighting the importance of gill uptake on the toxicity of this metal. No increased susceptibility to apoptosis was detected in either wild or caged fish, indicating that mercury damages DNA of blood cells by a nonapoptotic mechanism. Both L. aurata and the comet assay proved to be sensitive and suitable for genotoxicity biomonitoring in mercury-contaminated coastal systems.

Wild juvenile Dicentrarchus labrax L. liver antioxidant and damage responses at Aveiro Lagoon, Portugal

The Aveiro Lagoon, at the north-western coast of Portugal, has been under considerable anthropogenic pressure for the last 5 decades. In order to perform an adequate survey of the effects induced by the contaminants in presence, wild juveniles Dicentrarchus labrax (sea bass) were selected. Thus, sea bass was captured at five sites: Torreira (TOR, as reference site), Gafanha (GAF), Rio Novo Príncipe (RIO), Laranjo (LAR) and Vagos (VAG) in autumn 2005. Liver defence responses such as catalase (CAT), glutathione peroxidase (GPx), glutathione reductase (GR), glutathione S-transferase (GST), total glutathione (GSHt), total non-protein thiols (NP-SH) and metallothioneins (MT) were measured. Liver damage was determined as lipid peroxidation (LPO) and DNA integrity loss. RIO, LAR and VAG presented lower CAT, GR, GST activities and NP-SH and GSHt depletion in comparison to TOR. VAG and LAR showed higher GPx activity when compared to TOR. The highest MT level was found at GAF and VAG. The NP-SH and DNA integrity decreased at GAF compared to TOR. This field study demonstrated that not only antioxidant induction but also inhibitory responses must be considered as a signal of contamination.

Biochemical responses of the shore crab (Carcinus maenas) in a eutrophic and metal-contaminated coastal system (Obidos lagoon, Portugal)

A eutrophic and metal-contaminated coastal system (Obidos lagoon, Portugal) was monitored combining water/sediment quality parameters and Carcinus maenas biomarkers (accumulated metals, oxidative stress and biotransformation responses). Two confined branches (Barrosa and Bom-Sucesso) were surveyed and compared with a reference area. Both crab genders from Barrosa exhibited activation of hepatopancreas CAT, GPx and GST, pointing out this area as the major impacted in the lagoon. Females captured at Barrosa were more vulnerable to peroxidative damage while only males showed decreased EROD activity, reinforcing gender specificities. In general, responses were not directly attributed to metals in hepatopancreas, as supported by Principal Component Analysis (PCA). However, higher metals (Ni, Cu, Cd) and nutrients levels registered in Barrosa water were associated with the observed oxidative stress responses by PCA. Despite the difficulty to establish cause-effect relationships due to the co-occurrence of various stressors and their interactions, the adopted integrated monitoring strategy appears to be promising.

Contamination assessment of a coastal lagoon (Ria de Aveiro, Portugal) using defence and damage biochemical indicators in gill of Liza aurata--an integrated biomarker approach

Fish gill importance in toxicants uptake, bioconcentration and excretion allied to meagre knowledge on branchial damage/protection responses substantiate this study. Five critical sites in Ria de Aveiro (Portugal) were assessed in comparison with a reference site (Torreira), focusing on Liza aurata gill antioxidant defences versus damage (oxidative and genetic). Only in Barra fish displayed damage (lipid peroxidation) though no differences were found in antioxidants. In all other sites, except Rio, antioxidant alterations were found. Thus, fish from Gafanha, Laranjo and Vagos showed higher total glutathione, glutathione peroxidase and catalase. Higher glutathione reductase and glutathione S-transferase activity was also found in the first and the last sites, respectively. In Laranjo, metallothionein levels were higher though lower in Gafanha and Vagos. In general, damage was not accompanied by defences weakening confirming that predicting damage based on antioxidants depletion is not straightforward. The integrated biomarker response index ranked sites as: Gafanha>Barra>Laranjo>Vagos>Rio>Torreira.

Histopathological changes and erythrocytic nuclear abnormalities in Iberian green frogs (Rana perezi Seoane) from a uranium mine pond

In spite of their sensitivity to anthropogenic stressors, adults of Rana perezi Seoane were found inhabiting effluent ponds from a uranium mine. Due to the presence of such organisms in this environment, it becomes of paramount importance to assess the damages induced by local contamination on these aquatic vertebrates, in order to integrate this information on a site-specific risk assessment that is being carried out in the area. To attain this purpose an ethically and statistically acceptable number of green frogs were captured in the mine pond (M) and in a pristine river (VR), a few kilometres from the mine. Bioaccumulation of metals and histopathological alterations were evaluated in the liver, kidneys, spleen, lungs and testes of the animals. Simultaneously, blood samples were collected for the evaluation of genotoxic damage on erythrocytes. Animals captured in the M pond showed significantly increased levels of Be, Al, Mn, Fe and U in the liver, as well as Pb and U in the kidney. The liver was the main target organ for the bioaccumulation of Be, Al, Fe and U. However, renal histopathologies were more severe than those of liver. The main tissue alterations recorded in animals from the mine were: a slight increase in melanomacrophagic centers (MMC) in liver, lung and kidneys; dilatation of the renal tubules lumen associated with tubular necrosis. A significantly higher number of erythrocytic abnormalities (lobed, notched and kidney shaped nuclei and micronuclei) were recorded in frogs from M than in frogs from VR, along with a significantly lower frequency of immature erythrocytes. Both observations suggested that the removal of abnormal blood cells might be compromised.

DNA damage and lipid peroxidation vs. protection responses in the gill of Dicentrarchus labrax L. from a contaminated coastal lagoon (Ria de Aveiro, Portugal)

The present research work aimed to investigate the damage vs. protection responses in gill of European sea bass (Dicentrarchus labrax) captured at a polluted coastal lagoon, Ria de Aveiro (Portugal), as a tool to evaluate the human impacts on environmental health. Damage was assessed as DNA strand breakage and lipid peroxidation (LPO) whereas protection was evaluated by measuring catalase (CAT), glutathione peroxidase (GPX), glutathione reductase (GR), glutathione S-transferase (GST), total glutathione (GSHt), thiols and metallothioneins (MT). Fish were caught at five locations: Gafanha (GAF), Rio Novo do Príncipe (RIO), Laranjo (LAR) and Vagos (VAG) presenting each a different recognized source of contamination, and Torreira (TOR), assumed as reference site. Among the surveyed sites, gill damage was observed only at GAF, as measured by DNA integrity loss and LPO increase. An overall induction in enzymatic antioxidant protection was perceptible in fish from GAF and VAG, expressed as higher GPX, GR and GST activities. In addition, LAR fish showed elevated GST and CAT activities. Thiols content was higher in all study sites irrespective to the pollution spectrum, whereas GSHt increase was only observed at GAF and VAG. The highest MT level was detected in fish from VAG and the lowest level from RIO suggesting a low contamination degree on this particular site. Globally, the results expressed site-specific response patterns, signalling two critical areas - GAF and VAG. Additionally, a joint analysis (damage vs. protection) allowed the following ordering of surveyed sites according to the contamination degree and risk to fish health; GAF>VAG>LAR>RIO>TOR. D. labrax gill responses demonstrated their efficacy as early warning signals of the contaminants presence. Moreover, the adopted approach, considering simultaneously protection responses and damaging effects, also revealed its usefulness on the pollution extent assessment.

Erythrocytic nuclear abnormalities in wild and caged fish (Liza aurata) along an environmental mercury contamination gradient

Laranjo basin (Aveiro, Portugal) has been subjected to mercury contamination from a chlor-alkali plant, presenting a well-described mercury gradient. This study aims the assessment of mercury genotoxicity in this area by measuring erythrocytic nuclear abnormalities (ENA) frequency in the mullet Liza aurata, and its relation with total mercury concentration (Hg(t)) in blood. Wild fish were seasonally analysed, and, complementarily, fish were caged for 3 days at three locations differing on their distances to the mercury source. The results from Laranjo were compared with those from a reference area (S. Jacinto). Wild fish from Laranjo showed elevated ENA frequency in summer and autumn in concomitance with increased blood Hg(t). Surprisingly, no ENA induction was found in winter, despite the highest blood Hg(t), which may be explained by haematological dynamics alterations, as supported by a decreased immature erythrocytes frequency. Caged fish displayed ENA induction only at the closest site to the contamination source, also showing a correlation with blood Hg(t).

Organ specific antioxidant responses in golden grey mullet (Liza aurata) following a short-term exposure to phenanthrene

Phenanthrene (Phe) is among the most abundant and ubiquitous polycyclic aromatic hydrocarbons (PAHs) in the aquatic environment as a result of human activities. Even so, the knowledge about its impact on fish health is still limited. In this study, the teleost Liza aurata was exposed to 0.1, 0.3, 0.9 and 2.7 microM Phe concentrations during 16 h. Enzymatic antioxidants such as selenium dependent glutathione peroxidase (GPx), glutathione S-transferase (GST), glutathione reductase (GR) and catalase (CAT), as well as a non-enzymatic antioxidant (glutathione - GSH) were quantified in three target organs - gill, kidney and liver. The lipid peroxidation (LPO) was also assessed as a marker of oxidative damage. GPx activity was decreased in gill (0.1 and 0.9 microM), whereas in the liver it was increased (0.3-2.7 microM). GST activity was decreased in kidney (0.3-2.7 microM) and CAT activity was increased in gill after 0.9 microM exposure. GSH content was significantly increased in gill by the lowest concentration and in liver by all Phe concentrations. Despite the antioxidant defense responses, LPO increased in gill (0.3-2.7 microM), kidney (0.1 microM) and liver (0.1 and 2.7 microM). These results revealed organ specific antioxidant defenses depending on the Phe concentration. Liver demonstrated a higher adaptive competence expressed as antioxidant defenses activation, namely GSH and GPX. The lower vulnerability of the kidney to oxidative damage (compared to gill and liver) seems to be related to its higher antioxidant basal levels. Globally, current data highlight the Phe potential to induce oxidative stress and, consequently, to affect the well-being of fish.

Aspects of the usefulness of five marine pollution biomarkers, with emphasis on MN and lipid content

By using cellular biomarkers, such as the formation of the micronucleus, the morphometric alterations of lipids and the morphometric changes in the lysosomal system, we investigated effects of experimental exposure to phenanthrene, Cu, Cd, and Hg for 15 days in mussels. Concerning micronuclei, the evaluation of the total nuclear abnormalities, instead of the micronucleus only, as a biomarker of marine pollution, indicated more statistically significant differences between the control and the pollutant treated groups. Contrary to the existing knowledge showing that there is an increase in lipid content after pollutant exposure, our results showed that there was a decrease in the amount of lipid, as well as an increase in the number of neutral lipids. Furthermore, although prior studies found that fewer lysosomes formed after pollutant exposure, this was not confirmed by our work, as pollutant treated animals exhibited a decrease in the volume and an increase in the numerical density of lysosomes, compared to control groups.

Antioxidant and biotransformation responses in Liza aurata under environmental mercury exposure - relationship with mercury accumulation and implications for public health

This study was carried out in the Laranjo basin (Ria de Aveiro, Portugal), an area impacted by mercury discharges. Liza aurata oxidative stress and biotransformation responses were assessed in the liver and related to total mercury (Hgt) concentrations. A seasonal fish survey revealed a sporadic increase in total glutathione (GSHt) and elevated muscle Hgt levels, although Hg levels did not exceed the EU regulatory limit. As a complement study, fish were caged for three days both close to the bottom and on the water surface at three locations, and displayed higher Hgt levels accompanied by increased GSHt content and catalase activity as well as EROD activity inhibition. The bottom group displayed higher hepatic Hgt and GSHt contents compared with the surface group. Globally, both wild and caged fish revealed that the liver accumulates higher Hgt concentrations than muscle and, thus, better reflects environmental contamination levels. The absence of peroxidative damage in the liver can be attributed to effective detoxification and antioxidant defense.

Cytochrome P4501A, genotoxic and stress responses in golden grey mullet (Liza aurata) following short-term exposure to phenanthrene

This study represents a first approach to short-term effects of phenanthrene (Phe) in fish. The teleost Liza aurata was exposed to 0.1-2.7microM Phe during 16h. CYP1A induction was assessed as liver ethoxyresorufin-O-deethylase (EROD) activity. Genotoxicity was evaluated in gill and liver as DNA integrity (by alkaline unwinding), whereas in blood the erythrocytic nuclear abnormalities (ENA) frequency was determined. Stress responses were determined as cortisol, glucose and lactate plasma levels. Liver EROD activity was significantly increased by Phe 0.3-2.7microM. Phe genotoxicity in gill was not found, whereas liver DNA integrity significantly decreased after exposure to Phe 0.1 and 0.9microM demonstrating its genotoxicity which did not correlate with liver CYP1A induction. Phe genotoxicity in blood was demonstrated by a significant ENA increase from 0.1 up to 2.7microM. In terms of stress responses, plasma cortisol was significantly increased by Phe 0.3-2.7microM, though plasma glucose was only significantly increased by Phe 0.9 and 2.7microM. The Phe observed effects on L. aurata detected at different levels demonstrate a physiological unbalance and a probable ecological risk to ichthyofauna.