Genotoxic damage in Solea senegalensis exposed to sediments from the Sado Estuary (Portugal): Effects of metallic and organic contaminants

Multi-biomarker analysis of sub-chronic PAH mixture effects in fish at environmentally relevant levels

Polycyclic Aromatic Hydrocarbons (PAHs) are persistent pollutants in aquatic ecosystems, occurring as complex mixtures with unpredictable toxicity. Although PAHs are procarcinogenic, their harmful effects require metabolic activation, leading to reactive metabolites and reactive oxygen species (ROS) that can cause DNA damage. This study assessed the toxic effects of individual PAHs (Phenanthrene and Benzo[a]pyrene) and their mixtures (1:2 and 2:1 ratios) on juvenile seabream (Sparus aurata) after 42 days of exposure at 0.2nmol.L-1 . Biomarkers related to oxidative stress, detoxification, and lipid peroxidation were analysed in the liver and gills (e.g., glutathione (GSH), glutathione peroxidase (GPx), glutathione-S-transferase (GST), catalase (CAT), lipoperoxidation (LPO). Liver gene expression (Cytochromes P450 (CYP1A), GST3, tumour protein p53 (TP53) and blood cell DNA damage were also studied. Correlation analyses and Non-Metric Multidimensional Scaling (NMDS) were used to relate treatments and biomarkers. Results suggested differences in organ responses, with the gills generally showing the most significant changes in GSH levels, GST activity, and LPO compared to the control group. DNA repair mechanisms appeared to prevent significant genotoxicity as assessed by the comet assay. However, erythrocytic nuclear anomalies (ENAs) were notably higher in fish exposed to Phe, B[a]P, and the 2:1 B[a]P:Phe mixture compared to the control group. Interestingly, the 2:1 Phe:B[a]P mixture appeared to have an enhanced effect, showing a marked upregulation of GST3 mRNA (up to 7-fold), possibly influenced by the higher proportion of Phe. MDS analysis proved to be a valuable tool in identifying patterns among biological responses, offering insight into how fish cope with PAH exposure and helping to uncover the unpredictable effects of chemical mixtures. This study highlights the need for further research into the interactions of PAH mixtures, employing multi-analysis approach and underscores the importance of revising environmental guidelines to account for their effects.

Ecological quality assessment of estuarine macrobenthic communities using an integrative approach

Macrobenthic communities play a crucial role in the functioning of estuarine ecosystems and serve as bioindicators of environmental quality. This study assessed the ecological quality of an estuarine system using the AMBI and M-AMBI indices. The following parameters were considered: (i) environmental factors (total organic matter, organic carbon, grain size, calcium carbonate), (ii) sediment trace metals (Pb, Zn, Cu, Cr, Co, Ni, Hg, Li, As), (iii) species composition (morphological and molecular identification), and (iv) anthropogenic activities. The results demonstrated notable differences between study areas, reflecting hydrodynamic processes and human activities. The AMBI index indicated that all areas exhibited conditions classified as "slightly disturbed." However, the composition of the ecological groups and M-AMBI results differed according to the identification method. This approach allowed for a more complete understanding of communities, by integrating the influence of anthropogenic activities on the sediment and macrobenthic communities, highlighting the importance of using both identification methodologies.

Differences in biomarker responses and chemical contamination among three flatfish species in the Bay of Seine (NE Atlantic)

To assess the potential of the sole as sentinel species for ecotoxicological monitoring, the present study compares contaminant levels and biological responses with two closely related flatfish species: the common dab and European flounder. Trace metals, organic contaminants and biomarkers were measured in the three flatfish species collected during the same oceanographic cruise in the Bay of Seine (France). Overall, sole showed lower concentrations of Hg, met-Hg, Cd, Zn and PBDE (lw), higher concentrations of Ag, Cu, PFOS (ww), PCBs, p,p'-DDE (lw) and OH-pyrene, a higher ability to metabolize PBDEs and higher genotoxic (Comet, Micronuclei) and neurotoxic (AChE inhibition) alterations. Sole was the species most frequently occurring in the bay and appeared sensitive to chemical contamination. We therefore recommend promoting the use of the common sole for ecotoxicological monitoring.

Brodifacoum Levels and Biomarkers in Coastal Fish Species following a Rodent Eradication in an Italian Marine Protected Area: Preliminary Results

Brodifacoum is the most common rodenticide used for the eradication of invasive rodents from islands. It blocks the vitamin K cycle, resulting in hemorrhages in target mammals. Non-target species may be incidentally exposed to brodifacoum, including marine species. A case study conducted on the Italian Marine Protected Area of Tavolara Island was reported after a rodent eradication using the aerial broadcast of a brodifacoum pellet. Brodifacoum presence and effects on non-target marine organisms were investigated. Different fish species were sampled, and a set of analyses was conducted to determine vitamin K and vitamin K epoxide reductase concentrations, prothrombin time, and erythrocytic nuclear abnormalities (ENA) assay. In all the examined organisms, brodifacoum was not detected. The results obtained showed differences in vitamin K and vitamin K epoxide concentrations among the samples studied, with a positive correlation for three species between vitamin K, vitamin K epoxide, and fish weight. The prothrombin time assay showed a good blood clotting capacity in the fish. Higher abnormality values were recorded for four species. The results of this study suggest that it is possible to hypothesize that the sampled fish were not likely to have been exposed to brodifacoum and that consequently there are no negative issues concerning human consumption.

Impact assessment of a large river on the sediments and fish from its continental shelf: using Solea solea as sentinel in the Ebro river mouth (NW Mediterranean, Spain)

Many studies have been carried out along mighty rivers with heavily industrialized watersheds to evaluate pollutants and their effects on freshwater organisms. However, their impact on marine organisms is virtually unknown. In order to cover this gap, Solea solea, one of the most important commercial fish species, together with sediments, were sampled during 2013-2015 offshore from the Ebro Delta river mouth. Fish health indicators (condition indices, histological tissue alterations, and parasite descriptors) were used to assess the potential effect of pollutants, an issue of particular interest in the area following the dredging activities taking place in the river upstream in 2013. No major histopathological alterations were detected, but perivascular inflammatory foci (PIF) were frequently observed, especially in 2014. The most prevalent and abundant parasites were acanthocephalans and digeneans within the digestive tract and copepods on the gills. Levels of trace metals from sediments and fish muscle were below the effects range median and reference levels accepted for human consumption, respectively. However, the lower levels of the hepatosomatic index, higher numbers of PIF, and variations in the abundance of parasites in 2014 and 2015 could suggest a pollutant exposure during these years. These results warn signs of toxicity, which could be associated with sediment leaks during the dredging activities.

Impact of sewer overflow on public health: A comprehensive scientometric analysis and systematic review

Sewer overflow (SO), which has attracted global attention, poses serious threat to public health and ecosystem. SO impacts public health via consumption of contaminated drinking water, aerosolization of pathogens, food-chain transmission, and direct contact with fecally-polluted rivers and beach sediments during recreation. However, no study has attempted to map the linkage between SO and public health including Covid-19 using scientometric analysis and systematic review of literature. Results showed that only few countries were actively involved in SO research in relation to public health. Furthermore, there are renewed calls to scale up environmental surveillance to safeguard public health. To safeguard public health, it is important for public health authorities to optimize water and wastewater treatment plants and improve building ventilation and plumbing systems to minimize pathogen transmission within buildings and transportation systems. In addition, health authorities should formulate appropriate policies that can enhance environmental surveillance and facilitate real-time monitoring of sewer overflow. Increased public awareness on strict personal hygiene and point-of-use-water-treatment such as boiling drinking water will go a long way to safeguard public health. Ecotoxicological studies and health risk assessment of exposure to pathogens via different transmission routes is also required to appropriately inform the use of lockdowns, minimize their socio-economic impact and guide evidence-based welfare/social policy interventions. Soft infrastructures, optimized sewer maintenance and prescreening of sewer overflow are recommended to reduce stormwater burden on wastewater treatment plant, curtail pathogen transmission and marine plastic pollution. Comprehensive, integrated surveillance and global collaborative efforts are important to curtail on-going Covid-19 pandemic and improve resilience against future pandemics.

Impacts of wildfires in aquatic organisms: biomarker responses and erythrocyte nuclear abnormalities in Gambusia holbrooki exposed in situ

Wildfires are an environmental concern due to the loss of forest area and biodiversity, but also because their role as drivers of freshwater systems contamination by metals. In this context, the fish Gambusia holbrooki was used as a model, deployed for in situ exposure in watercourses standing within a recently burnt area and further assessment of toxic effects. The fish were exposed during 4 days at four different sites: one upstream and another downstream the burnt area and two within the burnt area. Biochemical biomarkers for oxidative stress and damage were assessed. The extent of lipoperoxidative damage was monitored by quantifying malondialdehyde and DNA damage evaluated through erythrocyte nuclear abnormalities observation. Chemical analysis revealed higher metal levels within the burnt area, and exposed fish consistently showed pro-oxidative responses therein, particularly an increase of gill glutathione peroxidase and glutathione reductase activity, the records doubling compared to samples from sites in the unburnt area; also the activity of glutathione-S-transferases comparatively increased (by 2-fold in the liver) in samples from the burnt area, and malondialdehyde was produced twice as much therein and in samples downstream the burnt area reflecting oxidative damage. Consistently, the frequency of erythrocyte nuclear abnormalities was higher at sites within and downstream the burnt area. This study supports the use of sensitive oxidative stress and genotoxicity biomarkers for an early detection of potentially noxious ecological effects of wildfires runoff.

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.

Effects of extreme ambient temperature in European seabass, Dicentrarchus labrax acclimated at different salinities: Growth performance, metabolic and molecular stress responses

Extreme weather events are becoming more intense and frequent as a result of climate change. The modulation of hemato-physiological potential as a compensatory response to extreme warm events combined with different salinities is poorly understood. This study aimed to assess the hemato-physiological and molecular response of European seabass, Dicentrarchus labrax exposed to extreme warm temperature (33 °C) after prior acclimatization at 32 psu, 12 psu, 6 psu, and 2 psu water. Fish were acclimated to 32 psu, 12 psu, 6 psu, and 2 psu followed by 10 days extreme warm (33 °C) exposure. Along with growth performance and survival, hemato-physiological response and molecular response of fish were recorded. Fish held at 32 psu and 2 psu exhibited significantly lower growth performance and survival than those at 12 psu and 6 psu (p < 0.05). Red blood cells (RBC), hematocrit, and hemoglobin content were significantly decreased, while white blood cells (WBC), erythrocytic cellular abnormalities (ECA) and erythrocytic nuclear abnormalities (ENA) were found to increase significantly in 32 psu and 2 psu fish (p < 0.05). Plasma lactate was found to increase significantly in 32 psu fish on day 10 (p < 0.05). Activities of glutathione peroxidase (GPx), glutathione reductase (GR), superoxide dismutase (SOD), catalase (CAT), and TNF-α expression increased significantly in 32 psu and 2 psu fish (p < 0.05). Most of the repeated measured parameters indicated limited acclimation capacity during the extreme warm exposure at all four salinity groups. However, overall results indicate that European seabass acclimatized at 12 psu and 6 psu salinities, can cope better during extreme warm exposure (33 °C).

Technical Updates to the Comet Assay In Vivo for Assessing DNA Damage in Zebrafish Embryos from Fresh and Frozen Cell Suspensions

The Single-Cell Gel Electrophoresis, simply known as the Comet assay, is a sensitive and quick technique used to quantitate DNA damage, widely used to assess the effects of genotoxicants and mutagens in animal cells. Still, performing the assay on peripheral or cultured cells is far more expeditious and cost effective than solid tissue, especially from small biological model like the zebrafish embryo. The current work describes and validates a highly cost-effective protocol of the updated Comet assay designed for zebrafish embryos. Compared with the few previous applications of the Comet assay on this biological model, the present method successfully simplifies the process of cell harvesting and resuspending, producing a much higher yield of viable nucleoids with reduced basal DNA damage, even from a small number of embryos, and compatible with scoring with safe fluorescent dyes. Additionally, the protocol can be just as easily performed on freshly harvested cells of cells frozen in dimethyl sulfoxide (DMSO)-containing physiological buffer, without a significant increase of DNA damage, which is another highly relevant update, especially for researchers handling high numbers of samples.

Acute exposure to environmentally relevant concentrations of benzophenone-3 induced genotoxicity in Poecilia reticulata

The organic UV filter benzophenone-3 (BP-3), widely used in the commercial formulations of sunscreens and personal care products, is considered an emerging pollutant and has been associated with several human and environmental health concerns. However, knowledge about their mode of action and ecotoxicity on aquatic biota is scarce. In this scenario, the objective of this work was to evaluate the genotoxic, mutagenic, and erythrotoxicity effects of BP-3 in the guppy Poecilia reticulata after acute exposure. Adult females of P. reticulata were exposed to three non-lethal and environmentally relevant concentrations of BP-3 (10, 100, and 1000 ng L^-1) during 96 h of exposure, and the somatic parameter [Fulton condition factor (K)], genotoxicity (comet assay), mutagenicity [micronucleus (MN) and erythrocyte nuclear abnormalities (ENA) tests] and erythrotoxicity parameters (such as total cell area and nucleus-cytoplasmic ratio) were analyzed. Results showed that the general physiological condition (K value) of fish was not affected by acute exposure to BP-3. However, BP-3 induced DNA damage at 100 and 1000 ng L^-1 and increased the frequency of total ENA at 1000 ng L^-1, specially lobed nucleus, when compared to control group, indicating its genotoxic and mutagenic effects. Furthermore, the BP-3 did not induce significant changes in the total cell area and nucleus-cytoplasmic ratio. In summary, results showed that the BP-3 at environmentally relevant concentration was genotoxic to freshwater fish P. reticulata, confirming its environmental risk.

Effects of triclosan on early development of Solea senegalensis: from biochemical to individual level

Harmful effects of triclosan (TCS) have been reported on several organisms; however, effects on early life stages of marine vertebrates are limited. Therefore, the objective of this work was to assess the effects of TCS during early development of the flatfish Solea senegalensis after initial characterization of cholinesterases (ChEs) and determination of selected biochemical markers baseline levels. Characterization of ChEs and determination of biochemical markers baseline levels of cholinergic activity, energy metabolism and oxidative stress were analysed in sole at 3 days after hatching (dah) and at the onset and end of metamorphosis. To assess TCS effects, fish were exposed during 96h to 30-500 μg L^-1 TCS until 3 dah. Fish at 13 dah were exposed during 48h to 200-1,500 μg L^-1 TCS and maintained until complete metamorphosis. Effects on survival, malformations, length, metamorphosis progression and biochemical markers were evaluated. The main ChE active form present in sole early life stages is acetylcholinesterase and baseline levels of oxidative stress and energy metabolism biomarkers changed according to fish developmental stage. Triclosan induced malformations (EC₅₀ = 180 μg L^-1 at 3 dah), decreased growth (95 μg L^-1 at 3 dah; 548 μg L^-1 at 24 dah) and affected metamorphosis progression (391 μg L^-1 at 17 dah). Impairment of antioxidant system was observed, with TCS affecting catalase at the end of metamorphosis test, however, no oxidative damage on lipids was detected. Glutathione S-transferase was the most sensitive endpoint during early larval test (LOEC = 30 μg L^-1). Exposure to TCS affected S. senegalensis at individual and sub-individual levels, both at early larval stage and during the critical period of metamorphosis.

Cytogenotoxic effects of fullerene C60 in the freshwater teleostean fish, Anabas testudineus (Bloch, 1792)

In recent years, carbon nanomaterials, including fullerene C₆₀ is regarded as the building block in nanotechnology because of its widespread use in medicine, industry, cosmetics and commercial products. Despite the special properties, several reports have raised public health concerns due to the unknown and practically unexplored toxic effects of nanomaterials. However, there have been relatively few studies regarding the genotoxic responses of fullerene C₆₀in vivo. Genotoxic effects of DMSO-solublized C₆₀ nanomaterial suspension at sublethal concentrations (5 and 10 mg/L) were investigated on adult freshwater fish, Anabas testudineus using micronucleus and comet assays. An assessment of micronucleus induction showed severe cytoplasmic and nuclear abnormalities in erythrocytes, gill and liver cells. Abnormalities in cytoplasm were identified as formation of sticky cells, vacuolated cytoplasm, cytoplasmic degeneration, echinocyte, acanthocyte, anisochromatic cells and abnormal erythrocyte membrane. The nuclear abnormalities included micronucleus, binucleated cells, nuclear buds, irregular nucleus, vacuolated, notched and serrated nucleus in the erythrocytes compared to the control groups. Similarly, significant increase (P < 0.05) in micronucleus frequencies were observed in gill and liver cells. The high frequency of micronucleus was observed in the gill cells followed by liver and erythrocytes, respectively, at both sublethal concentrations, and the severity was duration and concentration-dependent. In comet assay, significant increase (P < 0.05) in DNA damage was observed using the comet parameter, percent tail DNA. The highest level of comet damage with grade 3 was observed in blood, gill and liver cells on increase in duration and concentration when compared to the respective control groups. Thus the results revealed that fullerene C₆₀ nanomaterials may pose risk to aquatic organisms, especially fish, by the induction of genotoxicity. Further studies are warranted to provide new insights on the mechanisms and consequences of C₆₀ nanomaterials interactions with biological membranes.

Source identification of polycyclic aromatic hydrocarbons in soil sediments: Application of different methods

Polycyclic aromatic hydrocarbons (PAHs) are organic compounds that tend to rapidly associate to particulate organic matter in sediments due to their hydrophobic characteristics, inducing toxic, carcinogens and mutagens effects to many living organisms. The monitoring and identification of the sources of PAHs in sediments is relevant especially because they are the main reservoir and secondary source of contamination of aquatic systems. To identify the sources there are different methods for data treatment that complement each other: evaluation of profiles distribution, source-specific diagnostic ratios of PAHs and principal component analysis (PCA). To demonstrate the applicability of these different methods, concentrations of PAHs from sediments of four Portuguese estuarine systems were used: Ria de Aveiro, Tagus River, Sado River and Ria Formosa, in order to identify the sources.

Enteric nervous system analyses: New biomarkers for environmental quality assessment

The gastrointestinal tract (GIT) of fish is a target of contaminants since it can absorb these substances. We evaluated the morphophysiological alterations in the GIT of Sphoeroides testudineus collected in two estuaries presenting differences in their environmental quality (NIA and IA). The intestine was analyzed for histological and neuronal changes; liver and gills for biochemical markers; muscle tissues for neurotoxicity and peripheral blood for genotoxic damage. The results showed alterations in the GIT of the animals collected in the IA, such as muscle tunica and goblet cell density reduction, increased intraepithelial lymphocytes density and changes in neuronal density. Furthermore, changes were observed in MTs and LPO in the gills. Thus, we suggest that TGI is functioning as a barrier that responds to ingested contaminants, in order to reduce their absorption and translocation. Thus, alterations in morphophysiological and enteric neurons in S. testudineus can be used as biomarkers of environmental contamination.

Impacts of the combined exposure to seawater acidification and arsenic on the proteome of Crassostrea angulata and Crassostrea gigas

Proteomic analysis was performed to compare the effects of Arsenic (As), seawater acidification (Low pH) and the combination of both stressors (Low pH + As) on Crassostrea angulata and Crassostrea gigas juveniles in the context of global environmental change. This study aimed to elucidate if two closely related Crassostrea species respond similarly to these environmental stressors, considering both single and combined exposures, to infer if the simultaneous exposure to both stressors induced a differentiated response. Identification of the most important differentially expressed proteins between conditions revealed marked differences in the response of each species towards single and combined exposures, evidencing species-related differences towards each experimental condition. Moreover, protein alterations observed in the combined exposure (Low pH + As) were substantially different from those observed in single exposures. Identified proteins and their putative biological functions revealed an array of modes of action in each condition. Among the most important, those involved in cellular structure (Actin, Atlastin, Severin, Gelsolin, Coronin) and extracellular matrix modulation (Ependymin, Tight junction ZO-1, Neprilysin) were strongly regulated, although in different exposure conditions and species. Data also revealed differences regarding metabolic modulation capacity (ATP β, Enolase, Aconitate hydratase) and oxidative stress response (Aldehyde dehydrogenase, Lactoylglutathione, Retinal dehydrogenase) of each species, which also depended on single or combined exposures, illustrating a different response capacity of both oyster species to the presence of multiple stressors. Interestingly, alterations of piRNA abundance in C. angulata suggested genome reconfiguration in response to multiple stressors, likely an important mode of action related to adaptive evolution mechanisms previously unknown to oyster species, which requires further investigation. The present findings provide a deeper insight into the complexity of C. angulata and C. gigas responses to environmental stress at the proteome level, evidencing different capacities to endure abiotic changes, with relevance regarding the ecophysiological fitness of each species and competitive advantages in a changing environment.

Co-exposure to environmental carcinogens in vivo induces neoplasia-related hallmarks in low-genotoxicity events, even after removal of insult

Addressing the risk of mixed carcinogens in vivo under environmentally-realistic scenarios is still a challenge. Searching for adequate biomarkers of exposure requires understanding molecular pathways and their connection with neoplasia-related benchmark pathologies. Subjecting the zebrafish model to realistic concentrations of two genotoxicants and carcinogens, cadmium and benzo[a]pyrene, isolated and combined, yielded low levels of DNA damage. Altogether, the organisms' mechanisms of DNA repair, oxidative stress and phases I and II were not overwhelmed after two weeks of treatment. Still, transcriptional responses related to detoxification (epoxide hydrolase and UDP-glucuronosyltransferase) were higher in animals subjected to the combination treatment, inclusively following depuration. Nonetheless, inflammation and formation of hyperplasic foci in fish epithelia were more severe in animals exposed to the combined substances, showing slower recovery during depuration. Additionally, the combination treatment yielded unexpected increased expression of a ras-family oncogene homologue after depuration, with evidence for increased tp53 counter-response in the same period. The findings indicate that oncogene expression, cell proliferation and inflammation, may not require noticeable DNA damage to occur. Furthermore, albeit absent proof for neoplasic growth, the removal of chemical insult may promote tissue recovery but does not entirely clear molecular and histopathological endpoints that are commonly associated to neoplasia.

An epidemiological approach to characterise the human exposure pathways in a contaminated estuarine environment

This study's aim was to develop and implement an integrative epidemiologic cross-sectional study that allows identifying and characterising exposure pathways of populations living and working on the shores of a contaminated estuarine environment. Population residing in Carrasqueira, located on the Sado estuary with known contaminated areas was compared to another population on a noncontaminated estuary (Vila Nova de Mil Fontes - VNMF), considered a nonexposed population. Simple random samples of individuals were selected in each study population from the National Health Service Lists: 140 individuals were selected in Carrasqueira and 219 in VNMF. Participation rates were higher in the exposed group (62.5%, n=102 in Carrasqueira and 48.3%, n=100 individuals in VNMF). The same structured questionnaire was used in both populations, including questions on occupational activities, leisure activities, consumption of food (including fish and mollusks from the estuary) and use of water for human intake and agriculture. Results showed that a significantly higher proportion of Carrasqueira participants reported doing tasks in their job that promote direct (48.8% vs 1.2% in VNMF, p-value<0.001) or indirect (30% vs 11.9% in VNMF, p-value=0.004) contact with water from the estuary. Regarding seafood consumption, the exposed population of Carrasqueira had a higher frequency of consumption of cuttlefish (23.5% vs 9% in VNMF, p-value=0.007), sole (22.5% vs 4% in VNMF, p-value<0.001) and clams (18.6% vs 5.0 in VNMF, p-value=0.004). The comparative study design, with exposed and nonexposed populations living on the shores of two different estuaries allowed us to confirm the hypothesis of a higher risk of contamination from the contaminated estuarine environment. The study design and the selection of both populations were adequate for this type of epidemiologic study of potential routes of human contamination in a mixture of contaminated estuarine environment and can be used in other estuarine areas with similar environmental risk.

A protocol for identifying suitable biomarkers to assess fish health: A systematic review

Background

Biomarkers have been used extensively to provide the connection between external levels of contaminant exposure, internal levels of tissue contamination, and early adverse effects in organisms.

Objectives

To present a three-step protocol for identifying suitable biomarkers to assess fish health in coastal and marine ecosystems, using Gladstone Harbour (Australia) as a case study.

Methods

Prior to applying our protocol, clear working definitions for biomarkers were developed to ensure consistency with the global literature on fish health assessment. First, contaminants of concern were identified based on the presence of point and diffuse sources of pollution and available monitoring data for the ecosystem of interest. Second, suitable fish species were identified using fisheries dependent and independent data, and prioritised based on potential pathways of exposure to the contaminants of concern. Finally, a systematic and critical literature review was conducted on the use of biomarkers to assess the health of fish exposed to the contaminants of concern.

Results/Discussion

We present clear working definitions for bioaccumulation markers, biomarkers of exposure, biomarkers of effect and biomarkers of susceptibility. Based on emission and concentration information, seven metals were identified as contaminants of concern for Gladstone Harbour. Twenty out of 232 fish species were abundant enough to be potentially suitable for biomarker studies; five of these were prioritised based on potential pathways of exposure and susceptibility to metals. The literature search on biomarkers yielded 5,035 articles, of which 151met the inclusion criteria. Based on our review, the most suitable biomarkers include bioaccumulation markers, biomarkers of exposure (CYP1A, EROD, SOD, LPOX, HSP, MT, DNA strand breaks, micronuclei, apoptosis), and biomarkers of effect (histopathology, TAG:ST).

Conclusion

Our protocol outlines a clear pathway to identify suitable biomarkers to assess fish health in coastal and marine ecosystems, which can be applied to biomarker studies in aquatic ecosystems around the world.

Frequencies of erythrocyte nuclear abnormalities and of leucocytes in the fish Barbus peloponnesius correlate with a pollution gradient in the River Bregalnica (Macedonia)

Integrated chemical and biomarker approaches were performed to estimate if there is ongoing toxicity in the River Bregalnica, namely connected with the presence of metals. The study was performed in water, sediment, and barbel (Barbus peloponnesius), collected in two seasons, from two suspected polluted and one reference zones. The water analyses revealed higher mean values in polluted sites for most of the examined physicochemical parameters. Metal concentrations (Zn, Cu, Cd, Mn, Pb, and Fe) in water were more or less constant, whereas in sediment, they were higher at the two polluted locations. Condition factor (CF), as a general health indicator, revealed better overall condition in barbel from the reference site. In general, blood parameters revealed higher values in the polluted localities. Irrespective of sex and/or season, the frequency of micronuclei (MN) and vacuolated nuclei (VN) were with higher rates in polluted sites. Similarly, the frequencies of the leucocytes (Le), binuclei (BN), and irregularly shaped nuclei (ISN) were also significantly increased in the polluted localities, but they seemed prone to be influenced by sex and/or season. However, strong positive correlations between blood biomarkers and most water physicochemical parameters and metal in sediment were estimated. Our data support that the River Bregalnica's lower course receives significant genotoxic pollution, likely via metal industry effluents, agricultural runoff, and domestic sewage, and reinforced the utility of MN and other nuclear abnormalities as sensitive and suitable biomarkers for genotoxicity when used in monitoring studies.

Assessment of DNA damage in Ardea cinerea and Ciconia ciconia: A 5-year study in Portuguese birds retrieved for rehabilitation

Over the past decades, the presence of micronucleated blood cells has been used to detect genotoxic effects of xenobiotics in fish, amphibians and birds. This study assessed the frequency of micronuclei (MN) and other nuclear abnormalities in erythrocytes of individuals of Ardea cinerea and Ciconia ciconia retrieved for rehabilitation in order to evaluate the influence of age, temporal and spatial factors on the occurrence of DNA damage in Portuguese wild birds. Blood smears from 65 birds with different life-history backgrounds (e.g. geographic origin, age) were collected between 2007 and 2011 and the frequency of erythrocyte nuclear abnormalities (ENAs) was analysed. Differences in DNA damage between ages were observed to occur in C. ciconia, with chicks displaying significantly higher frequencies of ENAs (both when looking at total ENAs or only MN frequency) than juveniles and adults. Additionally, significant differences in ENAs frequencies were observed between different years and geographic origins, whereas MN frequency alone did not show significant alterations concerning spatial and temporal variations. These results suggest that the assessment of ENAs rather than MN frequency alone may be a useful and valuable tool to complement the evaluation of DNA damage in populations of birds, as prompted by individual life-history traits and environmental factors.

Acute exposure to a quinalphos containing insecticide (convoy) causes genetic damage and nuclear changes in peripheral erythrocytes of silver barb, Barbonymus gonionotus

The present study was aimed to assess the genotoxic effect in fish caused by convoy, an insecticide commercial formulation containing quinalphos, present in the aquatic waterbody. For this purpose a freshwater teleost, silver barb was exposed to sublethal concentrations (25% and 50% of LC₅₀) of convoy and erythrocytic cellular abnormalities (ECA) and erythrocytic nuclear abnormalities (ENA) tests were performed in addition to the commonly used micronucleus (MN) assay using peripheral erythrocytes and DNA contents in the different tissues after 1, 24, 36, 48, and 72 h of exposures. The obtained results indicated that acute exposure of different sub lethal concentrations of convoy to the fish resulted in significant alterations of erythrocytes as well as significant reduction of DNA contents in blood and vital organs and tissues, such as the brain, liver, kidney and muscle. Compared to each treatment excluding control group, frequencies of ECA, ENA, and MN were found to be elevated with exposure time of the doses. From this study, we conclude that convoy is a hazardous chemical to silver barb. Bioassays can be used as a tool for screening aquatic pollution, especially for insecticides.

Comparing the genotoxicity of a potentially carcinogenic and a noncarcinogenic PAH, singly, and in binary combination, on peripheral blood cells of the European sea bass

Research on the toxicological mechanisms of polycyclic aromatic hydrocarbons (PAHs) deemed carcinogenic and noncarcinogenic has mostly been developed for individual compounds even though, in the environment, PAHs invariably occur in mixtures. The present work aimed at understanding the interaction effects of two model PAHs, the potentially carcinogenic benzo[b]fluoranthene (B[b]F) and the noncarcinogenic phenanthrene (Phe) to a marine fish (the sea bass Dicentrarchus labrax). The study endeavoured an ecologically-relevant scenario with respect to concentrations and contaminant matrix, sediments, which are the main reservoirs of these substances in the environment, due to their hydrophobic nature. For the purpose, 28-day laboratorial bioassays with spiked sediments (with individual and combined PAHs at equitoxic concentrations) were conducted. Genotoxicity was determined in peripheral blood through the "Comet" assay and by scoring erythrocytic nuclear abnormalities (ENA). The results showed that exposure to either PAHs induced similar levels of DNA strand breaks, although without a clear dose- or time-response, likely due to the low concentrations of exposure and potential shits in PAH bioavailability during the assays. However, clastogenic/aneugenic lesions were only observed in fish exposed to B[b]F-spiked sediments. Conversely, the combination assays revealed a supra-additive effect especially at chromosome level, linked to concentrations of PAHs in water. A decrease in DNA-strand breakage was observed over time during all assays, revealing some ability of fish to cope with this DNA lesion. Overall, the findings show that low-moderate concentrations of sediment-bound mixed PAHs may significantly increase the hazard of mutagenesis even when the individual concentrations indicate low risk, especially considering that chromosome-level damage is unlikely to be repaired, leading to the fixation of DNA lesions upon prolonged exposures. © 2015 Wiley Periodicals, Inc. Environ Toxicol 31: 1307-1318, 2016.

Micronuclei and Nuclear Abnormalities in Erythrocytes from Barbel Barbus peloponnesius Revealing Genotoxic Pollution of the River Bregalnica

The strong negative anthropogenic pressure on the River Bregalnica resulted in the increase of pollution in the river ecosystem. The aim of this study was to evaluate if aquatic pollutants generate genotoxic effects in barbel (Barbus peloponnesius). Thirty individuals were collected from three localities along the river: one control site and two locations in the middle and lower course of the river with the presence of different pollution sources. Blood smears were stained with May-Grünwald/Giemsa method and the frequency of micronuclei, vacuolated nuclei, binuclei, blebbed nuclei and notched nuclei expressed in per mill was recorded. In fish collected from the control site, the investigated erythrocyte nuclear abnormalities revealed lowest values compared to polluted sites. In general, significantly higher values for erythrocyte deformations, including micronuclei, were noted in the middle and lower part of the river. Significantly higher values of vacuolated and blebbed nuclei were detected in fish from the middle course of the river, while at the lower course the frequencies of occurrence of micronuclei and notched nuclei were significant compared with control site. The middle course of the River Bregalnica has more diverse pollutants compared to the lower course, and consequently the highest frequency of all nuclear deformations was found in barbel from the middle course of the river. Obtained results suggest that pollutants draining into the Bregalnica river ecosystem display a genotoxic effect on the local barbel population.

Assessing genotoxic effects in fish from a marine protected area influenced by former mining activities and other stressors

The goal of the current study was to evaluate different genotoxicity tools in order to assess a marine protected area (MPA) affected by former mining activities and urban settlements. A catfish (Cathorops spixii) was analyzed for genotoxic effects at the (i) molecular and at the (ii) chromosomal levels. Through factor analysis, genotoxicity was found to be linked to levels of metals bioaccumulated and PAH metabolites in the bile. Micronucleus and nuclear alteration were less vulnerable to the effects of confounding factors in mildly contaminated areas since they were more frequently associated with bioaccumulated metals than the DNA analysis. The different genotoxicity responses allowed for the identification of sources of pollution in the MPA. This approach was important for detecting environmental risks related to genotoxic contaminants in a mildly contaminated MPA.

Acute and chronic effects of erythromycin exposure on oxidative stress and genotoxicity parameters of Oncorhynchus mykiss

Erythromycin (ERY) is a macrolide antibiotic used in human and veterinary medicine, and has been detected in various aquatic compartments. Recent studies have indicated that this compound can exert biological activity on non-target organisms environmentally exposed. The present study aimed to assess the toxic effects of ERY in Oncorhynchus mykiss after acute and chronic exposures. The here adopted strategy involved exposure to three levels of ERY, the first being similar to concentrations reported to occur in the wild, thus ecologically relevant. Catalase (CAT), total glutathione peroxidase (GPx), glutathione reductase (GRed) activities and lipid peroxidation (TBARS levels) were quantified as oxidative stress biomarkers in gills and liver. Genotoxic endpoints, reflecting different types of genetic damage in blood cells, were also determined, by performing analysis of genetic damage (determination of the genetic damage index, GDI, measured by comet assay) and of erythrocytic nuclear abnormalities (ENAs). The results suggest the occurrence of a mild, but significant, oxidative stress scenario in gills. For acutely exposed organisms, significant alterations were observed in CAT and GRed activities, and also in TBARS levels, which however are modifications with uncertain biological interpretation, despite indicating involvement of an oxidative effect and response. After chronic exposure, a significant decrease of CAT activity, increase of GPx activity and TBARS levels in gills was noticed. In liver, significant decrease in TBARS levels were observed in both exposures. Comet and ENAs assays indicated significant increases on genotoxic damage of O. mykiss, after erythromycin exposures. This set of data (acute and chronic) suggests that erythromycin has the potential to induce DNA strand breaks in blood cells, and demonstrate the induction of chromosome breakage and/or segregational abnormalities. Overall results indicate that both DNA damaging effects induced by erythromycin may be related to the oxidative damage observed, shown to occur at environmentally relevant concentrations of erythromycin.

Early genotoxic response and accumulation induced by waterborne copper, lead, and arsenic in European seabass, Dicentrarchus labrax

Cu, Pb, and As, which are among the most abundant metals in the aquatic environment, are also among the most health-threatened by causing diverse cellular injuries. The aim of this study was to assess and compare the potential early induction of genotoxic effects after waterborne Cu, Pb, and As exposure in European seabass, Dicentrarchus labrax, a commercial widely cultured fish, using the micronucleus (MN) assay in peripheral blood erythrocytes. Fish were exposed under laboratory conditions to nominal solutions ranging 0-10 mg/L for 24 and 96 h. Furthermore, actual metal ion concentrations were measured by inductively coupled plasma atomic emission spectroscopy (ICP-AES) or differential pulse anodic stripping voltammetry (DPASV) in water and four fish tissues differentially related to environmental exposition and metal accumulation, i.e. the gills, liver, muscle, and brain. Dose-dependent increases of micronuclei (MNi) frequency were observed after these very short exposures; based on measured metal concentrations in water, the genotoxic effect ordered as Cu > As > Pb. Significant genotoxic effect at 0.009 mg/L Cu, 0.57 mg/L Pb, and 0.01 mg/L As was seen. For Cu and Pb these are only slightly higher, but for As it is notably lower than the USEPA criteria of maximum concentration to prevent acute toxicity in aquatic organisms. Furthermore, genotoxicity was differentially related to metal accumulation. MNi frequency correlated positively with the content of Pb in all the organs, with the content of As in liver and gills and only with the content of Cu in the brain. In conclusion, our findings raised environmental concerns because these depicted a genotoxic potential of Cu, Pb, and As after a very short exposure to low but environmentally relevant concentrations, too close to regulatory thresholds. In addition, the MN test in D. labrax could be considered an early biomarker of genotoxicity induced by these metals in fish.

Effects of carcinogenic versus non-carcinogenic AHR-active PAHs and their mixtures: lessons from ecological relevance

Polycyclic aromatic hydrocarbons (PAHs) are priority environmental mutagens and carcinogens that occur in the aquatic environment as mixtures rather than the individual compounds for which guidelines are issued. The present work aimed at understanding the interaction effects between carcinogenic and non-carcinogenic PAHs in a model marine fish (Dicentrarchus labrax) in realistic scenarios. Laboratory assays under ecologically-relevant parameters were conducted for 28 days with sediments spiked with low-moderate concentrations (250-800ngg(-1)) of two model PAHs, phenanthrene (non-carcinogenic) and benzo[b]fluoranthene (carcinogenic to experimental animals). Both PAHs induced hepatic histopathological changes that indicate metabolic failure and inflammation, especially in animals exposed to mixtures. Phenanthrene elicited biochemical changes better related to oxidative stress (lipid peroxidation, glutathione and glutathione S-transferase activity) and CYP function, whereas B[b]F disrupted metabolic responses and defences to toxicological challenge. Conversely, mixed PAHs yielded lesions and responses that, altogether, are compatible with the AHR dependent pathway (the basis of PAH mutagenicity), potentially generating supra-additive effects. Nonetheless, the low, ecologically-relevant, concentrations of PAHs diluted dose and time-response relations. Overall, although seemingly predicting the risk of individual PAHs, environmental guidelines may not apply to mixtures by underestimating adverse effects, which calls for a redefinition of standards when determining the true risk of toxicants under realistic circumstances.

Assessing the environmental genotoxicity risk in the Baltic Sea: frequencies of nuclear buds in blood erythrocytes of three native fish species

Nuclear bud (NB) formation was investigated in blood erythrocytes of 1892 flounder Platichthys flesus, herring Clupea harengus, and eelpout Zoarces viviparus specimens that were collected at 82 sites representing different regions of the Baltic Sea in 2009-2011. This is the first attempt to evaluate the baseline levels of NB and rank the genotoxicity risk for native fish species. NB levels were compared to the previously published micronuclei (MN) data from the same individual fish specimens in order to compare the two methods of genotoxicity assessment and investigate the relationship between MN as the cytogenetic measure of genotoxicity and the DNA damage reflecting NB. In 2009-2011, elevated NB levels in 89.4% of flounder sampling groups indicated high and extremely high genotoxicity risk levels. Herring and eelpout sampling groups showed elevated levels of NB, 74.6 and 45.7%, respectively. In general, herring and eelpout NB measure was more sensitive as the genotoxicity biomarker than MN.

An integrative assessment to determine the genotoxic hazard of estuarine sediments: combining cell and whole-organism responses

The application of the Comet assay in environmental monitoring remains challenging in face of the complexity of environmental stressors, e.g., when dealing with estuarine sediments, that hampers the drawing of cause-effect relationships. Although the in vitro Comet assay may circumvent confounding factors, its application in environmental risk assessment (ERA) still needs validation. As such, the present work aims at integrating genotoxicity and oxidative DNA damage induced by sediment-bound toxicants in HepG2 cells with oxidative stress-related effects observed in three species collected from an impacted estuary. Distinct patterns were observed in cells exposed to crude mixtures of sediment contaminants from the urban/industrial area comparatively to the ones from the rural/riverine area of the estuary, with respect to oxidative DNA damage and oxidative DNA damage. The extracts obtained with the most polar solvent and the crude extracts caused the most significant oxidative DNA damage in HepG2 cells, as measured by the formamidopyrimidine-DNA glycosylase (FPG)-modified Comet assay. This observation suggests that metals and unknown toxicants more hydrophilic than polycyclic aromatic hydrocarbons may be important causative agents, especially in samples from the rural part of the estuary, where oxidative DNA damage was the most significant. Clams, sole, and cuttlefish responded differentially to environmental agents triggering oxidative stress, albeit yielding results accordant with the oxidative DNA damage observed in HepG2 cells. Overall, the integration of in vivo biomarker responses and Comet assay data in HepG2 cells yielded a comparable pattern, indicating that the in vitro FPG-modified Comet assay may be an effective and complementary line-of-evidence in ERA even in particularly challenging, natural, scenarios such as estuarine environments.

Responses of the European flounder (Platichthys flesus) to a mixture of PAHs and PCBs in experimental conditions

A multibiomarker approach was developed to evaluate the juvenile European flounder responses to a complex mixture of 9 polycyclic aromatic hydrocarbons (PAHs) and 12 polychlorinated biphenyls (PCBs). Exposure was performed through contaminated food pellets displaying: (1) PAH and PCB levels similar to those detected in the heavily polluted Seine estuary, respectively in sediments and in flatfish and (2) ten times these concentrations. Several biomarkers of the immune system (e.g., lysozyme concentration and gene expression of complement component C3 and TNF-receptor), DNA damage (e.g., Comet assay), energetic metabolism (e.g., activity of cytochrome C oxidase), detoxification process (e.g., cytochrome P450 1A1 expression level: CYP1A1; betaine homocysteine methyl transferase expression level: BHMT) were investigated after 14 and 29 days of contamination, followed by a 14-days recovery period. After 29 days of contamination, the detoxification activity (CYP1A1 expression level) was positively correlated with DNA damages; the increase of the BHMT expression level could also be related to the detoxification process. Furthermore, after the recovery period, some biomarkers were still upregulated (i.e., CYP1A1 and BHMT expression levels). The immune system was significantly modulated by the chemical stress at the two concentration levels, and the lysozyme appeared to be the most sensitive marker of the mixture impact.

DNA damage, EROD activity, condition indices, and their linkages with contaminants in female flounder (Platichthys flesus) from the southern Baltic Sea

The Baltic Sea is considered as one of the marine areas most exposed to human impacts. A variety of chemical contaminants pose a threat to the habitants. Female flounder (Platichthys flesus) collected from three locations in the southern Baltic Sea in February 2010 were examined for biomarkers of exposure to genotoxic agents (DNA damage), AhR-active contaminants (ethoxyresorufin-O-deethylase, EROD activity), and somatic condition indexes. Organochlorine contaminants (OCs) and polycyclic aromatic hydrocarbon (PAH) metabolites were also measured in individual flounder to evaluate the biological responses in the context of contaminant burden. The genotoxicity, mildly exceeding a background level, revealed a significant relationship with mono-ortho substituted PCB (m-oPCB). Hepatic EROD activity was highly induced, yet showed no association with any of the contaminants measured other than biliary 1-OH pyrene normalized to pigment absorbance. Significant negative relationships were observed for lipid-based OCs and the gonado-somatic index (GSI) as well as for Ʃm-oPCB concentrations and the condition factor (CF). Principal component analysis (PCA) revealed an overall connection between somatic condition indexes, biomarkers, and chemical variables. Of the three locations, flounder inhabiting the Gulf of Gdańsk had the greatest contaminant burden and appeared to be the most affected. Of great concern is the reduced GSI in this location which can be attributed to the effects of contaminants and warrants further investigation.

Occurrence of aryl hydrocarbon receptor agonists and genotoxic compounds in the river systems in Southern Taiwan

Water and sediment samples from river systems located in Southern Taiwan were investigated for the presence of aryl hydrocarbon receptor (AhR) agonists and genotoxicants by a combination of recombinant cell assays and gas chromatography-mass spectrometry analysis. AhR agonist activity and genotoxic response were frequently detected in samples collected during different seasons. In particular, dry-season water and sediment samples from Erren River showed strong AhR agonist activity (201-1423 ng L(-1) and 1374-5631 ng g(-1) β-naphthoflavone equivalents) and high genotoxic potential. Although no significant correlation was found between AhR agonist activity and genotoxicity, potential genotoxicants in sample extracts were suggested to be causative agents for yeast growth inhibition in the AhR-responsive reporter gene assay. After high performance liquid chromatography fractionation, AhR agonist candidates were detected in several fractions of Erren River water and sediment extracts, while possible genotoxicants were only found in water extracts. In addition, polycyclic aromatic hydrocarbons, the typical contaminants showing high AhR binding affinity, were only minor contributors to the AhR agonist activity detected in Erren River sediment extracts. Our findings displayed the usefulness of bioassays in evaluating the extent of environmental contamination, which may be helpful in reducing the chances of false-negative results obtained from chemical analysis of conventional contaminants. Further research will be undertaken to identify major candidates for xenobiotic AhR agonists and genotoxicants to better protect the aquatic environments in Taiwan.

Determining oxidative and non-oxidative genotoxic effects driven by estuarine sediment contaminants on a human hepatoma cell line

Estuarine sediments may be reservoirs of hydrophilic and hydrophobic pollutants, many of which are acknowledged genotoxicants, pro-mutagens and even potential carcinogens for humans. Still, studies aiming at narrowing the gap between ecological and human health risk of sediment-bound contaminant mixtures are scarce. Taking an impacted estuary as a case study (the Sado, SW Portugal), HepG2 (human hepatoma) cells were exposed in vitro for 48 h to extracts of sediments collected from two areas (urban/industrial and Triverine/agricultural), both contaminated by distinct mixtures of organic and inorganic toxicants, among which are found priority mutagens such as benzo[a]pyrene. Comparatively to a control test, extracts of sediments from both impacted areas produced deleterious effects in a dose-response manner. However, sediment extracts from the industrial area caused lower replication index plus higher cytotoxicity and genotoxicity (concerning total DNA strand breakage and clastogenesis), with emphasis on micronucleus induction. On the other hand, extracts from the rural area induced the highest oxidative damage to DNA, as revealed by the FPG (formamidopyrimidine-DNA glycosylase) enzyme in the Comet assay. Although the estuary, on its whole, has been classified as moderately contaminated, the results suggest that the sediments from the industrial area are significantly genotoxic and, furthermore, elicit permanent chromosome damage, thus potentially being more mutagenic than those from the rural area. The results are consistent with contamination by pro-mutagens like polycyclic aromatic hydrocarbons (PAHs), potentiated by metals. The sediments from the agriculture-influenced area likely owe their genotoxic effects to metals and other toxicants, probably pesticides and fertilizers, and able to induce reactive oxygen species without the formation of DNA strand breakage. The findings suggest that the mixtures of contaminants present in the assayed sediments are genotoxic to HepG2 cells, ultimately providing a useful approach to hazard identification and an effective line-of-evidence in the environmental monitoring of anthropogenically-impacted coastal ecosystems.

Integration of sediment contamination with multi-biomarker responses in a novel potential bioindicator (Sepia officinalis) for risk assessment in impacted estuaries

For the purpose of biomonitoring, species that combine ecological and commercial importance may provide a link between ecological and human health risk. The common cuttlefish, Sepia officinalis, holds both characteristics in south-western Europe, albeit remaining unsurveyed in ecotoxicological studies. Cuttlefish collected from an impacted estuary in SW Portugal and a reference location off the coast were analysed for a battery of biomarker responses in the digestive gland and gills. The contrast to reference animals revealed that biomarker responses, especially those related to oxidative stress, were consistent with sediment contamination by PAHs, even in a situation that combines complex toxicant mixtures, moderate levels of contamination and high ecotoxicological diversity. However, environmental parameters related to the differences between shore and estuarine habitats should not be overruled. Also, digestive gland metallothionein retained significant specificity to metals even though previous studies in the area with clams and fish failed to trigger a conclusive response. The highest net differences in biomarker responses were detected in the gills, likely indicating higher sensitivity to environmental stressors. Still, the digestive gland responses were overall the most consistent with sediment contamination and effectively differentiated between estuarine industrial- and rural-impacted sites. The results indicate that S. officinalis may be a candidate to meet the European Union's requirements for efficient biomonitoring programmes, with the additional importance of being cosmopolitan, abundant, commercially valuable and combining the molluscan biology that has been granting bivalves their high value for biomonitoring with foraging behaviour, thus better able to reflect anthropogenic stressors impacting a wider area than sedentary organisms. Nevertheless, further investigations in unpolluted sites are needed to better evaluate the background levels of biomarker responses in the species.

Comparative DNA damage and oxidative effects of carcinogenic and non-carcinogenic sediment-bound PAHs in the gills of a bivalve

Polycyclic aromatic hydrocarbons (PAHs) regarded as carcinogenic and non-carcinogenic to humans are ubiquitous hydrophobic pollutants that tend to be trapped in aquatic sediments. As a consequence of their acknowledged toxicity and pro-mutagenic or even carcinogenic potential, PAHs are deemed prioritary in biomonitoring programmes. Still, the differences between the toxicity of carcinogenic and non-carcinogenic PAHs are poorly known especially, when aquatic organisms are exposed to ecologically-relevant concentrations of these compounds in sediments. Laboratory bioassays with sediments spiked with phenanthrene (Phe) and benzo[b]fluoranthene (B[b]F), non-carcinogenic and carcinogenic PAH, respectively, were conducted and the effects of exposure (related to DNA damage and oxidative stress) were analyzed in the gills of a burrowing clam, Ruditapes decussatus (Bivalvia, Veneridae). To ensure ecological relevance, two contaminant concentrations (termed "low" and "high") were selected in accordance with available PAH sediment quality guidelines. The results showed that, even in "low" concentrations, both compounds caused a likely genotoxic effect in the gills, which is in accordance with the link between PAHs in water. Glutathione S-transferase activity and glutathione biosynthesis appear to be associated with limited lipid peroxidation even though they were insufficient to prevent higher and faster genotoxicity induced by exposure to the carcinogenic B[b]F, comparative to Phe. Overall the findings indicate that low concentrations of sediment-bound PAHs, carcinogenic or not, may be rendered significantly bioavailable to benthic filter-feeders as to induce genotoxicity, revealing that even PAHs considered non-carcinogenic to humans detain a latent, albeit significant, pro-mutagenic hazard to bivalve molluscs.

Gold-nanobeacons for gene therapy: evaluation of genotoxicity, cell toxicity and proteome profiling analysis

Antisense therapy is a powerful tool for post-transcriptional gene silencing suitable for down-regulating target genes associated to disease. Gold nanoparticles have been described as effective intracellular delivery vehicles for antisense oligonucleotides providing increased protection against nucleases and targeting capability via simple surface modification. We constructed an antisense gold-nanobeacon consisting of a stem-looped oligonucleotide double-labelled with 3'-Cy3 and 5'-Thiol-C6 and tested for the effective blocking of gene expression in colorectal cancer cells. Due to the beacon conformation, gene silencing was directly detected as fluorescence increases with hybridisation to target, which can be used to assess the level of silencing. Moreover, this system was extensively evaluated for the genotoxic, cytotoxic and proteomic effects of gold-nanobeacon exposure to cancer cells. The exposure was evaluated by two-dimensional protein electrophoresis followed by mass spectrometry to perform a proteomic profile and 3-(4,5-Dimethylthiazol-2-Yl)-2,5-Diphenyltetrazolium Bromide (MTT) assay, glutathione-S-transferase assay, micronucleus test and comet assay to assess the genotoxicity. This integrated toxicology evaluation showed that the proposed nanotheranostics strategy does not exhibit significant toxicity, which is extremely relevant when translating into in vivo systems.

Assessment of trophic transfer of benzo(a)pyrene genotoxicity from the post-larval pink shrimp F. brasiliensis to the juvenile Florida pompano T. carolinus

In the present study, the polycyclic aromatic hydrocarbon (PAH) genotoxicity was investigated in a one-step predator-prey relationship with the trophic-related marine species. Florida pompanos were fed for 5 and 10 days with pink shrimp post larvae previously exposed to benzo(a)pyrene (BaP) concentrations. Parent BaP body burden was measured in samples of Farfantepenaeus brasiliensis. BaP metabolites were determined in bile samples of Trachinotus carolinus and DNA damage was assessed through the comet and erythrocyte nuclear abnormalities (ENAs) assays in fish erythrocytes. BaP body burden increased significantly with the PAH concentration in pink shrimp PLs as well as the fish bile BaP metabolites. Both, comet and ENAs assays indicated significant increase on erythrocyte DNA damage of Florida pompanos fed with BaP-exposed pink shrimp on both feeding periods. The trophic route of BaP genotoxicity is discussed as well as the PAH biotransformation as the inducing mechanism for the DNA damages observed.

Impact of remobilized contaminants in Mytilus edulis during dredging operations in a harbour area: bioaccumulation and biomarker responses

Dredging operations in harbours are recurrent to maintain accessibility and navigational depths. One of the main environmental risks of these operations is the remobilization of contaminants trapped in the sediments, rendering them more bioavailable to the biota. However, regulatory policies regarding the contamination risk of dredging chiefly apply to the disposal of dredged materials rather than the direct impact of the procedure itself. In order to assess the ecotoxicological risk of harbour dredging operations in a polluted estuary (the Tagus, W Portugal), the present study compared bioaccumulation and biomarker responses in field-deployed mussels before and after the beginning of operations, complemented by sediment characterization and risk analysis based on standardized sediment quality guidelines. The results revealed a very significant increase in genotoxicity and oxidative stress from the beginning of dredging onwards, which was accompanied by increased bioaccumulation of toxicants, especially polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs). Overall, the results indicate the importance of surveying the direct impacts of these procedures on local contamination, especially considering these sediments had been previously classified as "trace contaminated", according to normative guidelines, and therefore safe for disposal. This study shows the importance of obtaining both chemical and biological data in standard monitoring procedures and that the remobilization of contaminants by dredging operations may be grossly underestimated, which calls for caution when assessing the impact of these activities even in low to moderately polluted areas.

Genotoxicity of sediment extracts of the Berre lagoon (France)

To evaluate the genotoxic risk that contaminated sediment could constitute for benthic organisms, three contaminated (VA, VC and VN) and one uncontaminated (RN) sediment samples were collected in the Berre lagoon (France). Potentially bioavailable contaminants in sediments were obtained using sediment extraction with synthetic seawater adjusted to pH 4 or pH 6, simulating the range of pH prevailing in the digestive tract of benthic organisms. The genotoxic activities of these extracts were evaluated by three short-term bioassays: the Salmonella mutagenicity test using the Salmonella typhimurium strain TA102, the alkaline comet assay and the micronucleus assay on the Chinese Hamster Ovary cells CHO-K1. Results of the Salmonella mutagenicity assay detected a mutagenic response for RN extract at pH 6, and for VA extract at pH 4. Results of the comet and micronucleus assays detected low genotoxic/clastogenic activities for VA and VC extracts at pH 6 and higher activities for RN, VA and VC extracts at pH 4. To identify if metals (Al, Fe, Mn, As, Cd, Co, Cr, Cu, Hg, Ni, Pb and Zn) were involved in these genotoxic activities, their concentrations were determined in the extracts, and their speciation was assessed by thermodynamic calculations. Results showed that extracts from sites VA, VC and VN generally presented the highest trace metal contents for both extractants, while the site RN presented lower trace metal contents but the highest Fe and Mn contents. Thermodynamic calculations indicated that Fe, Mn, As and in a lower extend Co, Ni and Zn were mainly present under free forms in extracts, and were consequently, more likely able to induce a genotoxic effect. Results globally showed no correspondence between free metal contents and genotoxic activities. They suggested that these positive results could be due to uncharacterized compounds, acting as direct genotoxic agents or enhancing the genotoxic properties of analyzed metals.

Chemical composition and genotoxicity assessment of sanitary landfill leachate from Rovinj, Croatia

Chemical analysis and an in vitro approach were performed to assess elemental composition and genotoxic effects of the samples of landfill leachate taken from Lokva Vidotto sanitary landfill the official landfill for Rovinj town, Croatia. Two samples of landfill leachate were collected and analyzed in order to evaluate macro, micro and trace elements by atomic absorption spectroscopy, energy dispersive X-ray spectrometry and colorimetry. Genotoxicity of sanitary landfill leachate was evaluated in human lymphocytes by the use of the micronucleus test and comet assay. Samples were characterized with relatively low concentrations of heavy metals while organic component level exceeded upper permissible limit up to 39 times. Observed genotoxic effects should be connected with high concentrations of ammonia nitrogen, which exceeded permissible limit up to 180 times. Leachate samples of both sanitary landfills increased the frequency of micronuclei, nucleoplasmic bridges and nuclear buds. Increase of DNA damage in human lymphocytes was also detected by virtue of measuring comet assay parameters. All parameters showed statistically significant difference compared to negative control. Increased micronucleus and comet assay parameters indicate that both samples of sanitary landfill leachate are genotoxic and could pose environmental and human health risk if discharged to an aquatic environment.

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.

Can the integration of multiple biomarkers and sediment geochemistry aid solving the complexity of sediment risk assessment? A case study with a benthic fish

Surveying toxicity of complex geochemical media as aquatic sediments often yields results that are either difficult to interpret or even contradictory to acknowledged theory. Multi-level biomarkers were investigated in a benthic fish exposed to estuarine sediments through laboratory and in situ bioassays, to evaluate their employment either in ecological risk assessment or in more mechanistic approaches to assess sediment-bound toxicity. Biomarkers reflecting lesions (such as genotoxicity or histopathology), regardless of their low or absent specificity to contaminants, are efficient in segregating exposure to contaminated from uncontaminated sediments even when classical biomarkers like CYP1A and metallothionein induction are inconclusive. Conversely, proteomics and gene transcription analyses provided information on the mechanics of toxicity and aided explaining response variation as a function of metabolic imbalance and impairment of defences against insult. In situ bioassays, although less expedite and more affected by confounding factors, produced data better correlated to overall sediment contamination.

A multidisciplinary weight of evidence approach for classifying polluted sediments: Integrating sediment chemistry, bioavailability, biomarkers responses and bioassays

Evaluation of chemical bioavailability and onset of biological alterations is fundamental to assess the hazard of environmental pollutants, particularly when associated to sediments which need to be removed. In the present work, five sediment samples were collected from the Venice Lagoon and data from sediment chemistry were integrated with those of bioaccumulation of chemicals in European eel (Anguilla anguilla) exposed under laboratory conditions, responses of a wide battery of biomarkers, and standardized ecotoxicological bioassays. The overall results were elaborated within a recently developed, software-assisted weight of evidence (WOE) model which provides synthetic indices for each of considered line of evidence (LOE), before a general evaluation of sediment hazard. Levels of chemicals in sediments were not particularly elevated when compared to sediment quality guidelines of Venice Protocol. On the other hand, bioavailability was evident in some samples for Cd, Cu, Zn and, especially, polycyclic aromatic hydrocarbons. The ecotoxicological approach provided further evidence on the biological and potentially harmful effects due to released contaminants, and oxidative-mediated responses appeared of primary importance in modulating sublethal responses and the onset of cellular alterations. Biomarkers variations were sensitive, and more evident variations included significant changes of cytochrome P450 biotransformation pathway, antioxidant responses, onset of oxidative damages, lysosomal membrane stability and genotoxic effects. The results obtained from the battery of bioassays indicated that responses measured at organism level were in general accordance but less marked compared to the onset of sublethal changes measured through biomarkers. Overall this study revealed differences when comparing evaluations obtained from different LOEs, confirming the importance of considering synergistic effects between chemicals in complex mixtures. Compared to a qualitative pass-fail approach toward normative values, the proposed WOE model allowed a quantitative characterization of sediment hazard and a better discrimination of on the basis of various types of chemical and biological data.

In vivo and in vitro exposures for the evaluation of the genotoxic effects of lead on the Neotropical freshwater fish Prochilodus lineatus

In the present study, in vivo and in vitro exposures were used to assess the genotoxicity of lead (Pb) to the freshwater fish Prochilodus lineatus. The comet assay using blood, liver and gill cells, and the occurrence of micronuclei (MN) and other erythrocytic nuclear abnormalities (ENA) were used to assess the genotoxic potential of lead in vivo. Metallothionein content (MT) was measured in fish liver in order to evaluate the protection of fish against Pb toxicity. Fish erythrocytes were exposed to Pb in vitro (1, 3 and 6 h) and the number of viable cells, DNA integrity, using the comet assay, and lysosomal membrane stability, measured by the neutral red retention assay (NRRA) were analyzed. The results of the comet assay after in vivo toxicity tests (6, 24 and 96 h) showed that Pb was genotoxic for all the three tissues analyzed after 96 h exposure. A significant increase in liver MT content was observed after 6 and 24 h of Pb exposure. MN frequency did not increase after Pb exposures, but the frequency of the other ENA, such as kidney-shaped nuclei, segmented nuclei and lobed nuclei, showed a significant increase after 24 and 96 h, indicating that ENA is a better biomarker for Pb exposure than MN alone after short-term exposures. The results of the comet assay performed with erythrocytes in vitro exposed to lead confirmed its genotoxic effect and showed that DNA damage increased with increasing exposure time. Moreover, the NRRA clearly indicated that Pb induces a destabilization of the lysosomal membrane. These results demonstrate the potential genotoxicity and cytotoxicity of lead after acute exposures.

Estuarine ecological risk based on hepatic histopathological indices from laboratory and in situ tested fish

Juvenile Senegalese soles were exposed through 28-day laboratory and field (in situ) bioassays to sediments from three sites of the Sado estuary (W Portugal): a reference and two contaminated by metallic and organic contaminants. Fish were surveyed for ten hepatic histopathological alterations divided by four distinct reaction patterns and integrated through the estimation of individual histopathological condition indices. Fish exposed to contaminated sediments sustained more damage, with especial respect to regressive changes like necrosis. However, differences were observed between laboratory- and field-exposed animals, with the latest, for instance, exhibiting more pronounced fatty degeneration and hepatocellular eosinophilic alteration. Also, some lesions in fish exposed to the reference sediment indicate that in both assays unaccounted variables produced experimental background noise, such as hyaline degeneration in laboratory-exposed fish. Still, the field assays yielded results that were found to better reflect the overall levels of contaminants and physico-chemical characteristics of the tested sediments.