Detection of genotoxins in the marine environment: adoption and evaluation of an integrated approach using the embryo-larval stages of the marine mussel, Mytilus edulis

Biochemical biomarker profiles of different organs of Phrynops geoffroanus freshwater turtle (Testudines, Chelidae) reveal pollutant effects from an anthropized aquatic environment

Aquatic organisms are often exposed to various chemicals, whose individual components are likely to produce different responses within the organisms and/or interact leading to toxic effects. The Phrynops geoffroanus species ("Geoffroy's side-necked turtle", Schweigger, 1812), a freshwater turtle endemic of South America, is commonly found in polluted rivers that cross the urban area and receive domestic and industrial wastewater effluents. In order to evaluate changes in biochemical biomarker profiles in different organs (liver, heart, lung, pancreas, small and large intestines) of P. geoffroanus from an anthropized aquatic environment, we analyzed the responses of enzymes involved in xenobiotic biotransformation, antioxidant enzymes, and lipid peroxidation levels. Acetylcholinesterase (AChE) activity was also assessed to check for neurotoxic effects. Results revealed that the poor water quality of a highly anthropized stream perturbed the biochemical parameters of free-living freshwater turtles. Compared to animals from the reference site (breeding farm), those from the polluted site presented increased biotransformation activity, antioxidant responses, and lipid peroxidation levels, indicative of oxidative stress. AChE activity was decreased in the pancreas. Alterations of different biomarkers in specific organs indicated differences in susceptibility among different organs of this species. These data contribute to a better understanding of how these animals respond to environmental pollutants, suggesting this species as good sentinel organisms for ecotoxicological studies.

Eco-genotoxicology: A personal reflection

This reflective commentary provides a personal viewpoint of developments, over the last 3 decades, in the relatively new, multidisciplinary field of 'eco-genotoxicology,' also called 'genetic ecotoxicology'. It aims to outline the scope of the subject area in relation to the historical development of the discipline, critically categorising accomplishments made, taking into account the available information. It also recognises limitations of the existing information and difficulties encountered in this challenging field. Where appropriate, the article makes comparisons to the advances made in human genetic toxicology and radiation biology. The article critically covers the applications of prevailing and emerging tools being used in the field, such as omics, in vitro methodologies, modelling approaches, and artificial intelligence (AI). It also identifies potential areas of development and attempts to credit some of the important personal contributions made in this exciting and challenging subject in relation to human and environmental health.

Unraveling the interplay between environmental microplastics and salinity stress on Mytilus galloprovincialis larval development: A holistic exploration

The rise of plastic production has triggered a surge in plastic waste, overwhelming marine ecosystems with microplastics. The effects of climate change, notably changing salinity, have shaped the dynamics of coastal lagoons. Thus, understanding the combined impact of these phenomena on marine organisms becomes increasingly crucial. To address these knowledge gaps, we investigated for the first time the interactive effects of environmental microplastics (EMPs) and increased salinity on the early development of Mytilus galloprovincialis larvae. Morphological assessments using the larval embryotoxicity test revealed larval anomalies and developmental arrests induced by EMPs and increased salinity. Transcriptomic analyses targeting 12 genes involved in oxidative stress, apoptosis, DNA repair, shell formation, and stress proteins were conducted on D-larvae uncovered the potential effects of EMPs on shell biomineralization, highlighting the role of Histidine Rich Glycoproteine (HRG) and tubulin as crucial adaptive mechanisms in Mytilus sp. in response to environmental shifts. Furthermore, we explored oxidative stress and neurotoxicity using biochemical assays. Our findings revealed a potential interaction between EMPs and increased salinity, impacting multiple physiological processes in mussel larvae. Our data contribute to understanding the cumulative effects of emerging anthropogenic pollutants and environmental stressors, emphasizing the need for a holistic approach to assessing their impact on marine ecosystems.

Cellular Responses Induced by Zinc in Zebra Mussel Haemocytes. Loss of DNA Integrity as a Cellular Mechanism to Evaluate the Suitability of Nanocellulose-Based Materials in Nanoremediation

Zinc environmental levels are increasing due to human activities, posing a threat to ecosystems and human health. Therefore, new tools able to remediate Zn contamination in freshwater are highly recommended. Specimens of Dreissena polymorpha (zebra mussel) were exposed for 48 h and 7 days to a wide range of ZnCl2 nominal concentrations (1-10-50-100 mg/L), including those environmentally relevant. Cellulose-based nanosponges (CNS) were also tested to assess their safety and suitability for Zn removal from freshwater. Zebra mussels were exposed to 50 mg/L ZnCl2 alone or incubated with 1.25 g/L of CNS (2 h) and then removed by filtration. The effect of Zn decontamination induced by CNS has been verified by the acute toxicity bioassay Microtox®. DNA primary damage was investigated by the Comet assay; micronuclei frequency and nuclear morphological alterations were assessed by Cytome assay in mussels' haemocytes. The results confirmed the genotoxic effect of ZnCl2 in zebra mussel haemocytes at 48 h and 7-day exposure time. Zinc concentrations were measured in CNS, suggesting that cellulose-based nanosponges were able to remove Zn(II) by reducing its levels in exposure waters and soft tissues of D. polymorpha in agreement with the observed restoration of genetic damage exerted by zinc exposure alone.

Genotoxicity and Epigenotoxicity of Carbazole-Derived Molecules on MCF-7 Breast Cancer Cells

The carbazole compounds PK9320 (1-(9-ethyl-7-(furan-2-yl)-9H-carbazol-3-yl)-N-methylmethanamine) and PK9323 (1-(9-ethyl-7-(thiazol-4-yl)-9H-carbazol-3-yl)-N-methylmethanamine), second-generation analogues of PK083 (1-(9-ethyl-9H-carbazol-3-yl)-N-methylmethanamine), restore p53 signaling in Y220C p53-mutated cancer cells by binding to a mutation-induced surface crevice and acting as molecular chaperones. In the present paper, these three molecules have been tested for mutant p53-independent genotoxic and epigenomic effects on wild-type p53 MCF-7 breast adenocarcinoma cells, employing a combination of Western blot for phospho-γH2AX histone, Comet assay and methylation-sensitive arbitrarily primed PCR to analyze their intrinsic DNA damage-inducing and DNA methylation-changing abilities. We demonstrate that small modifications in the substitution patterns of carbazoles can have profound effects on their intrinsic genotoxic and epigenetic properties, with PK9320 and PK9323 being eligible candidates as “anticancer compounds” and “anticancer epi-compounds” and PK083 a “damage-corrective” compound on human breast adenocarcinoma cells. Such different properties may be exploited for their use as anticancer agents and chemical probes.

Effect-Based Approach to Assess Nanostructured Cellulose Sponge Removal Efficacy of Zinc Ions from Seawater to Prevent Ecological Risks

To encourage the applicability of nano-adsorbent materials for heavy metal ion removal from seawater and limit any potential side effects for marine organisms, an ecotoxicological evaluation based on a biological effect-based approach is presented. ZnCl2 (10 mg L-1) contaminated artificial seawater (ASW) was treated with newly developed eco-friendly cellulose-based nanosponges (CNS) (1.25 g L-1 for 2 h), and the cellular and tissue responses of marine mussel Mytilus galloprovincialis were measured before and after CNS treatment. A control group (ASW only) and a negative control group (CNS in ASW) were also tested. Methods: A significant recovery of Zn-induced damages in circulating immune and gill cells and mantle edges was observed in mussels exposed after CNS treatment. Genetic and chromosomal damages reversed to control levels in mussels' gill cells (DNA integrity level, nuclear abnormalities and apoptotic cells) and hemocytes (micronuclei), in which a recovery of lysosomal membrane stability (LMS) was also observed. Damage to syphons, loss of cilia by mantle edge epithelial cells and an increase in mucous cells in ZnCl2-exposed mussels were absent in specimens after CNS treatment, in which the mantle histology resembled that of the controls. No effects were observed in mussels exposed to CNS alone. As further proof of CNS' ability to remove Zn(II) from ASW, a significant reduction of >90% of Zn levels in ASW after CNS treatment was observed (from 6.006 to 0.510 mg L-1). Ecotoxicological evaluation confirmed the ability of CNS to remove Zn from ASW by showing a full recovery of Zn-induced toxicological responses to the levels of mussels exposed to ASW only (controls). An effect-based approach was thus proven to be useful in order to further support the environmentally safe (ecosafety) application of CNS for heavy metal removal from seawater.

Moderate temperature elevation increase susceptibility of early-life stage of the Mediterranean mussel, Mytilus galloprovincialis to metal-induced genotoxicity

The present study aims to evaluate the effects of copper and silver alone or along with a moderate temperature increase on embryonic development, DNA integrity and target gene expression levels in early life stages of Mytilus galloprovincialis. For this purpose, upon fertilized embryos were exposed to a sub-lethal concentration of Cu (9.54 μg/L), Ag (2.55 μg/L) and to the mixture of the two metals (Cu (6.67 μg/L) + Ag (1.47 μg/L)) along with a temperature gradient (18, 20 and 22 °C). In all experiments, larvae were exposed to stressors for 48 h except for those designed to DNA damage analysis exposed only for 24 h (before shell formation).Our results showed a significant increase in the percentage of malformed D-larvae (p < 0.05) with increasing temperature and exposure to silver and copper alone or in a mixture. Moreover, metal toxicity increased significantly (p < 0.05) with the temperature rise. Genotoxicity was evaluated using classic and modified with Formamidopyrimidine DNA glycosylase (Fpg) Comet assay. Results suggest that co-exposure to metals and temperature significantly increased DNA damage on mussel larvae with a more accentuated oxidative damage. A significant transcription modulation was observed for genes involved in DNA repair and DNA replication (p53, DNA ligase II and topoisomerase II) when larvae are exposed to a single stressor. However, in the case of multiple stresses, caspase involved in the cell apoptosis pathway was overexpressed. Our study suggests that mussel larvae exposed to a moderate increase in temperature may have a compromised ability to defend against genotoxicity. This is particularly relevant in the context of global warming and thermal pollution.

Oxidative and Cellular Metabolic Stress of Fish: An Appealing Tool for Biomonitoring of Metal Contamination in the Kolkata Wetland, a Ramsar Site

The present study delineate the various biochemical and histopathological tool to evaluate as strong biomarker in the field condition for detection of the least and maximize level of pollution and contamination. We have collected Labeo rohita from 13 different sites from East Kolkata wetland to determine biochemical and histopathological status to analyse metal contamination in the significant biological hot spot EKW. The biochemical marker as antioxidative status, i.e., catalase, superoxide dismutase (SOD), and glutathione-S-transferase (GST) in liver and gill, were remarkably higher (p < 0.01) at some of the sampling sites, but catalase in brain, SOD in kidney, GST in brain and kidney, and neurotransmitter as acetylcholine esterase (AChE) in brain were not significant (p > 0.05) among the sampling sites. The glycolytic enzymes, such as lactate dehydrogenase (LDH) and malate dehydrogenase (MDH) in liver, gill, and muscle, and protein metabolic enzymes, such as alanine amino transferase (ALT) and aspartate amino transferase (AST) in liver, gill, muscle, and kidney, were noticeably higher (p < 0.01) at some of the sampling sites. The histopathology of the liver and gill were altered at different sampling sites, such as blood congestion, leucocyte infiltration with parenchymal vacuolisation, nucleus with blood vessels, hepatocytes granular degeneration, haemorrhage, karyorrhexis, shrink nucleus, and pyknotic nuclei in liver. In the gill, structural changes, such as complete destruction and shortening of secondary gill lamellae, blood vessel in gill arch, curling of secondary gill lamellae, aneurism in gill lamellae, and neoplasia, were observed. Most of the metals were found within the safe limit all along the 13 sampling sites, indicating that fishes are safe for the consumption. Based on our finding, we could recommend that a rational application of biochemical profiles, such as oxidative and metabolic stress parameters, including histopathology to be used as biomarkers for biomonitoring the metal contamination in the aquatic environment.

Integrated Biomarker Responses in Livers of the Pale Chub Zacco platypus for Risk Assessment of a Stream Contaminated by Wastewater Effluents

We evaluated the effects of wastewater effluents on pale chub (Zacco platypus) in a contaminated stream by integrating genotoxic, oxidative stress, histological, and physiological biomarkers. The metal pollution index indicated higher pollution loads at downstream sites (DS1 and DS2) compared with the upstream reference site. Significantly higher nuclear abnormality confirmed the existence of genotoxicity (p < 0.05) at downstream sites. Antioxidant activity (catalase and glutathione S-transferase) and lipid peroxidation levels in livers of Z. platypus were also significantly higher at the DS1 site (p < 0.05). The liver somatic index was also influenced, with abnormal histological alterations in the liver, possibly caused by heavy metal accumulation (Cd, Co, Cr, Mn, Ni, and Pb). The integrated biomarker response value was the highest at DS1 (13.74) followed by DS2 (1.94), indicating that wastewater effluents had the potential to cause adverse effects on Z. platypus inhabiting receiving stream.

The role of dissolved organic carbon concentration and composition on nickel toxicity to early life-stages of the blue mussel Mytilus edulis and purple sea urchin Strongylocentrotus purpuratus

Nickel (Ni) emissions resulting from production and transportation raise concerns about the impact of Ni exposure to marine ecosystems. Ni bioavailability models are established for FW systems, but the influence of chemical parameters (e.g. dissolved organic carbon (DOC)) on Ni toxicity within marine systems is less well understood. To examine the effects of DOC concentration and composition on Ni toxicity, acute toxicity tests were conducted on early life-stages of blue mussels (Mytilus edulis) and sea urchin embryos (Strongylocentrotus purpuratus) in full strength sea water (32 ppt). Nine different field collected samples of water with varying concentration (up to 4.5 mg C/L) and composition of DOC were collected from the east coast of the United States. Organic matter compositional analysis included molecular fluorescence and absorbance spectroscopy. The different DOC sources had different protective effects against embryo toxicity. The control (no DOC) Ni 48 h-EC₅₀ for Mytilus embryos was 133 µg/L (95% confidence interval (C.I.) of 123-144 µg/L), while Strongylocentrotus embryos displayed control 96-h EC₅₀ values of 207 µg/L (167-247 µg/L). The most significantly protective sample had high humic acid concentrations (as determined from fluorescence spectroscopy), which yielded an EC₅₀ of 195 µg/L (169-222 µg/L) for Mytilus, and an EC₅₀ of 394 µg/L (369-419 µg/L) for S. purpuratus. Among all samples, protection was related to both DOC quantity and quality, with fluorescence-resolved humic and fulvic acid concentrations showing the strongest correlations with protection for both species. These data suggest that DOC is protective against Ni toxicity in M. edulis and S. purpuratus, and that accounting for a DOC quality factor will improve predictive toxicity models such as the biotic ligand model.

Use of statistical analysis to validate ecogenotoxicology findings arising from various comet assay components

Cirrhinus mrigala, Labeo rohita, and Catla catla are economically important fish for human consumption in Pakistan, but industrial and sewage pollution has drastically reduced their population in the River Chenab. Statistics are an important tool to analyze and interpret comet assay results. The specific aims of the study were to determine the DNA damage in Cirrhinus mrigala, Labeo rohita, and Catla catla due to chemical pollution and to assess the validity of statistical analyses to determine the viability of the comet assay for a possible use with these freshwater fish species as a good indicator of pollution load and habitat degradation. Comet assay results indicated a significant (P < 0.05) degree of DNA fragmentation in Cirrhinus mrigala followed by Labeo rohita and Catla catla in respect to comet head diameter, comet tail length, and % DNA damage. Regression analysis and correlation matrices conducted among the parameters of the comet assay affirmed the precision and the legitimacy of the results. The present study, therefore, strongly recommends that genotoxicological studies conduct appropriate analysis of the various components of comet assays to offer better interpretation of the assay data.

Evaluation of the impact of bioaccumulation of PAH from the marine environment on DNA integrity and oxidative stress in marine rock oyster (Saccostrea cucullata) along the Arabian sea coast

Marine pollution due to oil spills is of great concern globally for their impact on the health of marine ecosystems. We assessed the genotoxic effects and oxidative stress due to genotoxic pollutants accumulated from the ambient marine environment in the tissues of marine rock oyster, Saccostrea cucullata along the Arabian Sea coast around Goa, India. The extent of DNA damage in S. cucullata was determined by comet assay as variation of comet parameter: mean % tail DNA along the coast with respect to that at the reference site (Tiracol, Goa, India). In addition, the oxidative stress responses of rock oysters exposed to marine pollutants such as polycyclic aromatic hydrocarbons (PAHs) were assessed as a function of variation in antioxidant enzyme activities such as glutathione-s-transferase (GST), catalase (CAT) and superoxide dismutase (SOD) along the coast. Spearman correlation analysis showed significant correlation between different components of PAHs (viz., 2-3-PAH, 4-6-PAH and oxy-PAH) in the tissues of the rock oysters and the antioxidant enzyme activities. The antioxidant enzyme activities in S. cucullata increased with increasing concentrations of PAHs in tissues in the following order of sampling sites: Tiracol < Arambol < Betul < Velsao. Among the PAHs, oxy-PAH was found to be most predominant in causing DNA damage in S. cucullata. These results provide an insight into environmental genotoxicity and oxidative stress induced by PAHs along the Arabian Sea coast, India.

Baseline and oxidative DNA damage in marine invertebrates

Anthropogenic pollutants produce oxidative stress in marine organisms, directly or following generation of reactive oxygen species (ROS), potentially resulting in increased accumulation of DNA strand breaks quantified. The aim of this study is to quantify baseline levels of DNA strand breaks in marine species from four phyla and to assess relative sensitivity to oxidative stress as well as ability to recover. DNA strand breaks were determined using a formamidopyrimidine DNA glycosylase (Fpg)-amended comet assay in circulating cells from blue mussel (Mytilus edulis), shore crab (Carcinus maenas), sea star (Asterias rubens), and vase tunicate (Ciona intestinalis). Lymphocytes from Atlantic cod (Gadus morhua) were used as a reference. In addition to immediate analysis, cells from all species were exposed ex vivo to two concentrations of hydrogen peroxide (H₂O₂) at 25 or 250 μM prior to assay. Mean baseline DNA strand breaks were highest for cells from sea star (34%) followed by crab (25%), mussel (22%), tunicate (17%), and cod (14%). Circulating cells from invertebrates were markedly more sensitive to oxidative stress compared to cod lymphocytes. DNA strand breaks exceeded 80% for sea star, crab, and mussel cells following exposure to the lowest H₂O₂ concentration. There was no recovery for cells from any species following 1 hr in buffer. This study provides an in-depth analysis of DNA integrity for ecologically important species representing 4 phyla. Data indicate that circulating cells from invertebrates are more sensitive to oxidative stress than cells from fish as evidenced by DNA strand breaks. Future studies need to address the extent to which DNA strand breaks may exert consequences for body maintenance costs in marine invertebrates.

Imposex and organotin compounds in ports of the Mediterranean and the Atlantic: Is the story over?

Organotin compounds are toxic substances released into the marine environment from antifouling paints. Sixty-two years following their first application and 9years after the complete ban on their use as biocides in 2003 (EC No. 782/2003), their negative impact on mollusks was still evident, as illustrated by imposex (i.e. the masculinization of female gastropods). This phenomenon is widely used to investigate tributyltin (TBT) pollution, with Hexaplex trunculus and Nassarius nitidus being considered as sensitive bioindicators. H. trunculus specimens and sediment samples collected from the ports of Cagliari (Sardinia), El Kantaoui (Tunisia) and Olhão (Portugal), along with N. nitidus individuals from the port of Faro (Portugal), were used for the assessment of imposex intensity and organotin pollution in these areas. High imposex frequency and organotin concentrations (TBT, triphenyltin (TPhT) and their degradation products) were observed, especially in Sardinia, implying that these chemicals remain a significant pollution issue in the specific Mediterranean ports. Moreover, the highly significant relationship established between penis length of imposex-affected females H. trunculus and TBT/TPhT concentrations offers a rapid and nonsacrificial proxy model for assessing the impact of organotins in coastal environments. Finally, the complementary use of more than one TBT bioindicator is advised in order to obtain more accurate results in detailed monitoring studies of TBT pollution.

Studies on biomarkers of oxidative stress and associated genotoxicity and histopathology in Channa punctatus from heavy metal polluted canal

Some investigations were made on the Satha canal water and health of dwelling fish Channa punctatus at Satha village, district Aligarh (U.P). Metal bioaccumulation and induction of biomarkers such as lipid peroxidation (LPO), superoxide dismutase (SOD), catalase (CAT), glutathione S transferase (GST), reduced glutathione (GSH), DNA damage and histopathology are potential indicators of stress in C. punctatus exposed to effluents. In canal water Cr, Mn, Fe and Ni concentrations were exceeding the permissible limits set by both Bureau of Indian standards (BIS) and WHO. Fe (74%) was highly bioavailable and accumulated in all organs (gill, liver, kidney, muscle and integument). The highest metal pollution index (MPI) value of 53 was observed in gills and the lowest 6 in liver tissue. SOD and LPO were significantly higher in all tissues, whereas CAT, GST and GSH levels declined significantly compared to fish from the reference site. Concomitant damage to DNA was observed with significantly higher mean tail length in the exposed fish gill cells (19 μm) and in liver (12.7 μm) compared to reference fish (5 and 4 μm respectively). Histopathology in gill and liver also show significant damage. Therefore, it can be concluded that the sugar mill effluent has the potential to cause oxidative stress, DNA damage and histopathology in C. punctatus. This canal is a prime source of water and fish food to the local residents of the area. Therefore, the consumers may suffer adverse health effects like that in indicator organism.

Applications of biological tools or biomarkers in aquatic biota: A case study of the Tamar estuary, South West England

Biological systems are the ultimate recipients of pollutant-induced damage. Consequently, our traditional reliance on analytical tools is not enough to assess ecosystem health. Biological responses or biomarkers are therefore also considered to be important tools for environmental hazard and risk assessments. Due to historical mining, other anthropogenic activities, and its conservational importance (e.g. NATURA sites, SACs), the Tamar estuary in South West England is an ideal environment in which to examine applications of such biological tools. This review presents a thorough and critical evaluation of the different biological tools used in the Tamar estuary thus far, while also discussing future perspectives for biomarker studies from a global perspective. In particular, we focus on the challenges which hinder applications of biological tools from being more readily incorporated into regulatory frameworks, with the aim of enabling both policymakers and primary stakeholders to maximise the environmental relevance and regulatory usefulness of such tools.

Parental exposure to environmental concentrations of diuron leads to aneuploidy in embryos of the Pacific oyster, as evidenced by fluorescent in situ hybridization

Changes in normal chromosome numbers (i.e. aneuploidy) due to abnormal chromosome segregation may arise either spontaneously or as a result of chemical/radiation exposure, particularly during cell division. Coastal ecosystems are continuously subjected to various contaminants originating from urban, industrial and agricultural activities. Genotoxicity is common to several families of major environmental pollutants, including pesticides, which therefore represent a potential important environmental hazard for marine organisms. A previous study demonstrated the vertical transmission of DNA damage by subjecting oyster genitors to short-term exposure to the herbicide diuron at environmental concentrations during gametogenesis. In this paper, Fluorescent in situ hybridization (FISH) was used to further characterize diuron-induced DNA damage at the chromosomal level. rDNA genes (5S and 18-5.8-28S), previously mapped onto Crassostrea gigas chromosomes 4, 5 and 10, were used as probes on the interphase nuclei of embryo preparations. Our results conclusively show higher aneuploidy (hypo- or hyperdiploidy) level in embryos from diuron-exposed genitors, with damage to the three studied chromosomal regions. This study suggests that sexually developing oysters are vulnerable to diuron exposure, incurring a negative impact on reproductive success and oyster recruitment.

Evaluation of γ-radiation-induced DNA damage in two species of bivalves and their relative sensitivity using comet assay

Ionizing radiation is known to induce genetic damage in diverse groups of organisms. Under accidental situations, large quantities of radioactive elements get released into the environment and radiation emitted from these radionuclides may adversely affect both the man and the non-human biota. The present study is aimed (a) to know the genotoxic effect of gamma radiation on aquatic fauna employing two species of selected bivalves, (b) to evaluate the possible use of 'Comet assay' for detecting genetic damage in haemocytes of bivalves as a biomarker for environmental biomonitoring and also (c) to compare the relative sensitivity of two species of bivalves viz. Paphia malabarica and Meretrix casta to gamma radiation. The comet assays was optimized and validated using different concentrations (18, 32 and 56 mg/L) of ethyl methanesulfonate (EMS), a direct-acting reference genotoxic agent, to which the bivalves were exposed for various times (24, 48 and 72 h). Bivalves were irradiated (single acute exposure) with 5 different doses (viz. 2, 4, 6, 8 and 10 Gy) of gamma radiation and their genotoxic effects on the haemocytes were studied using the comet assay. Haemolymph was collected from the adductor muscle at 24, 48 and 72 h of both EMS-exposed and irradiated bivalves and comet assay was carried out using standard protocol. A significant increase in DNA damage was observed as indicated by an increase in % tail DNA damage at different concentrations of EMS and all the doses of gamma radiation as compared to controls in both bivalve species. This showed a dose-dependent increase of genetic damage induced in bivalves by EMS as well as gamma radiation. Further, the highest DNA damage was observed at 24h. The damage gradually decreased with time, i.e. was smaller at 48 and 72 h than at 24h post irradiation in both species of bivalves. This may indicate repair of the damaged DNA and/or loss of heavily damaged cells as the post irradiation time advanced. The present study reveals that gamma radiation induces single strand breaks in DNA as measured by alkaline comet assay in bivalves and comet assay serves as a sensitive and rapid method to detect genotoxicity of gamma radiation. This study further indicates that both M. casta and P. malabarica exhibit almost identical sensitivity to gamma radiation as measured by DNA damage.

Oceans and Human Health (OHH): a European perspective from the Marine Board of the European Science Foundation (Marine Board-ESF)

The oceans and coastal seas provide mankind with many benefits including food for around a third of the global population, the air that we breathe and our climate system which enables habitation of much of the planet. However, the converse is that generation of natural events (such as hurricanes, severe storms and tsunamis) can have devastating impacts on coastal populations, while pollution of the seas by pathogens and toxic waste can cause illness and death in humans and animals. Harmful effects from biogenic toxins produced by algal blooms (HABs) and from the pathogens associated with microbial pollution are also a health hazard in seafood and from direct contact with water. The overall global burden of human disease caused by sewage pollution of coastal waters has been estimated at 4 million lost person-years annually. Finally, the impacts of all of these issues will be exacerbated by climate change. A holistic systems approach is needed. It must consider whole ecosystems, and their sustainability, such as integrated coastal zone management, is necessary to address the highly interconnected scientific challenges of increased human population pressure, pollution and over-exploitation of food (and other) resources as drivers of adverse ecological, social and economic impacts. There is also an urgent and critical requirement for effective and integrated public health solutions to be developed through the formulation of politically and environmentally meaningful policies. The research community required to address "Oceans & Human Health" in Europe is currently very fragmented, and recognition by policy makers of some of the problems, outlined in the list of challenges above, is limited. Nevertheless, relevant key policy issues for governments worldwide include the reduction of the burden of disease (including the early detection of emerging pathogens and other threats) and improving the quality of the global environment. Failure to effectively address these issues will impact adversely on efforts to alleviate poverty, sustain the availability of environmental goods and services and improve health and social and economic stability; and thus, will impinge on many policy decisions, both nationally and internationally. Knowledge exchange (KE) will be a key element of any ensuing research. KE will facilitate the integration of biological, medical, epidemiological, social and economic disciplines, as well as the emergence of synergies between seemingly unconnected areas of science and socio-economic issues, and will help to leverage knowledge transfer across the European Union (EU) and beyond. An integrated interdisciplinary systems approach is an effective way to bring together the appropriate groups of scientists, social scientists, economists, industry and other stakeholders with the policy formulators in order to address the complexities of interfacial problems in the area of environment and human health. The Marine Board of the European Science Foundation Working Group on "Oceans and Human Health" has been charged with developing a position paper on this topic with a view to identifying the scientific, social and economic challenges and making recommendations to the EU on policy-relevant research and development activities in this arena. This paper includes the background to health-related issues linked to the coastal environment and highlights the main arguments for an ecosystem-based whole systems approach.

Oxidative DNA damage may not mediate Ni-induced genotoxicity in marine mussels: assessment of genotoxic biomarkers and transcriptional responses of key stress genes

Nickel (Ni) is a known carcinogenic and mutagenic compound and an important contaminant of aquatic environments. Ni toxicity and its potential impact on aquatic organisms are, however, not well understood. This study used an integrated approach to evaluate genotoxic effects, tissue-specific accumulation and transcriptional profiles of key genes in mussels, Mytilus galloprovincialis, exposed to a range of concentrations of Ni. The genotoxic effects assessed were total and oxidative DNA damage (DNA strand breaks measured using the enzyme modified comet assay), and induction of micronuclei (MN; clastogenic and/or aneugenic effects) using haemocytes as the target cells. Six genes (pgp, mt10, mt20, sod, hsp70 and gst) were selected for transcriptional analysis in the gills based on their key role in the stress response. Following exposure to sublethal concentrations of Ni (0-3600μgL(-1)) for 5 days, mussel haemocytes showed significant genotoxicity at >1800μgL(-1) (4-fold increase for DNA strand breaks and 3-fold increase for MN induction). There was no significant difference between buffer (control) and enzyme treatments which target oxidised DNA bases (formamidopyrimidine glycosylase or endonuclease IIII). This suggested that, in haemocytes, oxidative DNA damage is not a major mechanism for Ni-induced genotoxicity. The expression of mt20 and gst genes in gill was up-regulated at genotoxic concentrations, whilst pgp expression was markedly up-regulated, particularly at 18μgL(-1) Ni (19-fold increase). Pearson's correlation analysis revealed significant associations between % tail DNA and MN induction in haemocytes (r=0.88, p<0.05), and between Ni accumulation in foot (r=0.47, p<0.05) and digestive gland (r=0.41, p<0.05) and induction of MN in the haemocytes. Our results are the first to suggest that Ni-induced genotoxicity in mussel haemocytes may not be a result of oxidative DNA damage, and that multixenobiotic resistance (MXR) may play an important role in Ni detoxification in this species.

Relative sensitivity of two marine bivalves for detection of genotoxic and cytotoxic effects: a field assessment in the Tamar Estuary, South West England

The input of anthropogenic contaminants to the aquatic environment is a major concern for scientists, regulators and the public. This is especially relevant in areas such as the Tamar valley in SW England, which has a legacy of contamination from industrial activity in the nineteenth and twentieth centuries. Following on from previous laboratory validation studies, this study aimed to assess the relationship between genotoxic and cytotoxic responses and heavy metal concentrations in two bivalve species sampled from locations along the Tamar estuary. Adult cockles, Cerastoderma edule, and blue mussels, Mytilus edulis, were sampled from five locations in the Tamar and one reference location on the south Devon coast. Bivalve haemocytes were processed for comet and neutral red retention (NRR) assays to determine potential genotoxic and cytotoxic effects, respectively. Sediment and soft tissue samples were analysed for metal content by inductively coupled plasma mass spectrometry. Sediment concentrations were consistent with the physico-chemical nature of the Tamar estuary. A significant correlation (P = 0.05) was found between total metal concentration in sediment and C. edule soft tissues, but no such correlation was found for M. edulis samples. DNA damage was elevated at the site with highest Cr concentrations for M. edulis and at the site with highest Ni and Pb concentrations for C. edule. Analysis of NRR revealed a slight increase in retention time at one site, in contrast to comet data. We conclude that the comet assay is a reliable indicator of genotoxic damage in the field for both M. edulis and C. edule and discuss reasons for the apparent discrepancy with NRR.

Detection of 8-oxodG in Dreissena polymorpha gill cells exposed to model contaminants

Genotoxic end-points are routinely measured in various sentinel organisms in aquatic environments in order to monitor the impact of water pollution on organisms. As a first step towards the evaluation of oxidative DNA damage (8-oxodG) in organisms exposed to chemical water pollution, we have optimized the association between the comet assay and the hOGG1 enzyme for use on zebra mussel (Dreissena polymorpha) gill cells by in vitro exposure to H₂O₂. Firstly, we observed that in vitro exposure of D. polymorpha gill cells to benzo[a]pyrene (B[a]P, 98.4nM) induced an increase of the Olive Tail Moment (OTM) in both the comet-hOGG1 and comet-Fpg assays, indicating that B[a]P causes oxidative DNA damage. By contrast, methylmethane sulfonate (MMS, 33μM) only induced an increase of the Fpg-sensitive sites, indicating that MMS caused alkylating DNA damage and confirming that hOGG1 does not detect alkylating damage. Thus, the hOGG1 enzyme seems to be more specific towards oxidative DNA damage, such as 8-oxodG than Fpg. Secondly, as was observed in vitro, the in vivo exposure of D. polymorpha to B[a]P (24.6 and 98.4nM) increased oxidative DNA damage in gill cells, whereas only Fpg-sensitive sites were detected in mussels exposed to MMS (240μM). These results show that the comet-hOGG1 assay detects oxidative DNA lesions induced in vitro by H₂O₂ and in vivo with BaP. The comet-hOGG1 assay will be used to detect oxidative DNA lesions (8-oxodG) in mussels exposed in situ.

Metal speciation and toxicity of Tamar Estuary water to larvae of the Pacific oyster, Crassostrea gigas

As part of the PREDICT Tamar Workshop, the toxicity of estuarine waters in the Tamar Estuary (southwest England) was assessed by integration of metal speciation determination with bioassays. High temporal resolution metal speciation analysis was undertaken in situ by deployment of a Voltammetric In situ Profiling (VIP) system. The VIP detects Cd (cadmium), Pb (lead) and Cu (copper) species smaller than 4 nm in size and this fraction is termed 'dynamic' and considered biologically available. Cadmium was mainly present in the dynamic form and constituted between 56% and 100% of the total dissolved concentration, which was determined subsequently in the laboratory in filtered discrete samples. In contrast, the dynamic Pb and Cu fractions were less important, with a much larger proportion of these metals associated with organic ligands and/or colloids (45-90% Pb and 46-85% Cu), which probably reduced the toxicological impact of these elements in this system. Static toxicity tests, based on the response of Crassostrea gigas larva exposed to discrete water samples showed a high level of toxicity (up to 100% abnormal development) at two stations in the Tamar, particularly during periods of the tidal cycle when the influence of more pristine coastal water was at its lowest. Competitive ligand-exchange Cu titrations showed that natural organic ligands reduced the free cupric ion concentration to levels that were unlikely to have been the sole cause of the observed toxicity. Nonetheless, it is probable that the combined effect of the metals determined in this work contributed significantly to the bioassay response.

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.

DNA hypomethylation induced by tributyltin, triphenyltin, and a mixture of these in Sebastiscus marmoratus liver

Tributyltin (TBT) and triphenyltin (TPT) coexist in freshwater and marine environments. However, the effects of TBT, TPT, and a mixture of the two on DNA methylation in marine fish livers and the mechanism involved remain to be elucidated. Previous study have proved that abnormal methylation patterns are induced by the balance of transmethylation reaction including the tissue level of S-adenosylmethionine (SAM), S-adenosylhomocysteine (SAH) or the activity of DNA (cytosine-5) methyltransferase 1 (DNMT1). Therefore, in the present study, we assessed their ability to cause hepatic DNA hypomethylation in Sebastiscus marmoratus liver and the related mechanism. The results showed that TBT, TPT, and a mixture of the two significantly induced DNA hypomethylation in the fish livers in a dose-dependent manner. Using Pearson correlation coefficient analysis, we identified strong linear correlations between S-adenosylhomocysteine, S-adenosylmethionine, or the SAM to SAH ratio and the hepatic genome-wide 5-methylcytosine content of the DNA, but no correlation between the latter and the DNMT1 expression level. It is therefore proposed that the organotins hypomethylation induced in the marine fish livers was due to altering the balance of the substrate and the product in transmethylation reactions.

Application of biomarkers to assess the condition of European Marine Sites

A series of European Marine Sites has been designated as Special Areas of Conservation (SAC) in England. The aim of this study was to develop a practical methodology to assess the condition of SACs by applying a suite of biomarkers. Biomarkers were applied to the blue mussel Mytilus edulis and the shore crab Carcinus maenas from the Fal and Helford SAC (Cornwall). Individual biomarkers provided useful diagnostic information on the activity of certain classes of contaminants and an integrated Biomarker Response Index (BRI) was used to achieve a more holistic understanding of the condition of the SAC. The BRI indicated that the general health of both organisms was impacted in the upper part of the SAC (Fal Estuary) which correlated well with known chemical hotspots and sources of contamination. The BRI allows a pragmatic way to prioritise SAC sites that may require further investigative studies.

Genotoxic effects of binary mixtures of xenoandrogens (tributyltin, triphenyltin) and a xenoestrogen (ethinylestradiol) in a partial life-cycle test with Zebrafish (Danio rerio)

A partial life-cycle test with the model fish Danio rerio was performed in order to evaluate the genotoxic potential of binary mixtures of xenoandrogenic (tributyltin--TBT; triphenyltin--TPT) and an estrogenic compound (ethinylestradiol--EE2). Five days post-fertilisation larvae were diet-exposed to environmental relevant concentrations of TBT and TPT (25 ng/g-100 ng/g), and water-exposed to ethinylestradiol (3.5 ng/L) for a four-month period; binary mixtures of TBT plus EE2 and TPT plus EE2 were run in parallel. The erythrocytic nuclear abnormalities (ENA) assay in circulating erythrocytes was used to evaluate genotoxicity in the end of the four-month exposure period. A significant increase (p<0.05, Kruskall-Wallis non-parametric ANOVA) in ENA frequency, in comparison with control animals, was observed in those animals exposed to TBT and TPT (the highest doses only), and to EE2 and the binary mixtures, although neither synergistic nor additive effects of the tested compounds were evident. Overall, the results clearly indicate that chronic exposure to low levels of TBT, TPT, EE2 and binary mixtures of TBT plus EE2 and TPT plus EE2 are genotoxic to zebrafish, which may suggest that wild fish populations may be under increased DNA damage in areas contaminated by these endocrine disrupting chemicals.

Effects of seawater salinity fluctuations on primary tissue culture from the mussel Mytilus galloprovincialis Potential application to the detection of seawater genotoxicity

The present results were obtained in the context of an attempt to develop an in vitro test intended to assess the genotoxicity of seawater. It is based on a short-term culture method of mussel mantle explants that gives mitotic cells in which DNA damage is likely to be detected. Its principle consists of the incorporation of the seawater to be tested in the culture medium. Two factors that influence cell proliferation were studied: (1) salinity of seawater and (2) basic composition of the culture medium i.e. replacement of Eagle's Basal Medium (BME) by Eagle's Minimum Essential Medium (MEM). When culture medium contained BME, a salinity change from 35 per thousand to 28 per thousand (that is the case for coastal or estuarine waters) resulted in a significant reduction of cell proliferation. In contrast, when culture medium was prepared with MEM, the same decrease of salinity did not change significantly the number of metaphase cells obtained. This suggested medium prepared with MEM allowed tissues in culture to better withstand the hypoosmotic shock generated by 28 per thousand seawater. This has been attributed to amino acids the concentration of which being higher in MEM than in BME. Direct and indirect mechanisms of osmoregulation are suggested to explain the observations. These results show that the test proposed could be used to assess the genotoxicity of coastal or estuarine seawater with salinity comprised from 28 per thousand to 35 per thousand, provided that MEM is used.

Development of the in vivo chromosome aberration assay in oyster (Crassostrea gigas) embryo-larvae for genotoxicity assessment

Bioassay methods currently used to assess the toxicity of effluents, transitional and marine waters measure endpoints such as larval immobilisation or mortality, however, they offer limited data regarding important sub-lethal effects, including genotoxicity. The metaphase chromosome aberration (CAb) assay is routinely used in mammalian systems for testing samples for genotoxicity. In the current study, an in vivo CAb test system has been developed and optimised for use with the early (embryo-larval) life stages of the Pacific oyster Crassostrea gigas, a species used routinely in both effluent hazard assessment and marine environmental monitoring programmes. The method was validated with two reference mutagens: Methylmethanesulfonate, a direct acting mutagen; and benzo[a]pyrene an indirect acting reference mutagen.

Cytogenetic and cytotoxic effects in gill cells of the blue mussel Mytilus spp. from different zones of the Baltic Sea

Frequency of micronuclei (MN) and other nuclear abnormalities (nuclear buds, bi-nucleated and fragmented-apoptotic cells) was analysed in gill cells of the blue mussel (Mytilus spp.) from selected coastal sites in the Baltic Sea--Kvädöfjärden (Sweden), Klaipeda-Būtinge zone (Lithuania), Gulf of Gdansk (Poland) and Wismar Bay (Germany). Samples were collected from 650 specimens during bi-annual sampling campaigns in 2001 and 2002. The lowest frequency of MN (0.37 MN/1000 cells) was found in blue mussels from the reference site (Kvädöfjärden). The highest MN values (up to 6.7 MN/1000 cells) were registered in blue mussels from the Gulf of Gdansk in autumn 2001 and 2002, and at Wismar Bay in spring 2001 (up to 5.06 MN/1000 cells). Gradients of MN incidences were observed when comparing the three studied locations in Wismar Bay, and at the Lithuanian coast before the crude oil spill in the Būtinge oil terminal. Moreover, significant seasonal and inter-location differences in the responses were documented (P<0.0001). Nuclear abnormalities were observed most frequently in blue mussels from the Gulf of Gdansk.

Genotoxic, cytotoxic, developmental and survival effects of tritiated water in the early life stages of the marine mollusc, Mytilus edulis

Using an integrated approach linking different levels of biological organisation, the genotoxic, cytotoxic, developmental and survival impact of tritiated water (HTO) were investigated in the embryo-larvae of marine mollusc Mytilus edulis. One-hour-old embryos were exposed to a range of concentrations (0.37-370 kBq ml(-1)) of HTO, which delivered a dose between 0.02 and 21.41 mGy over the exposure period for different end points. Detrimental effects, if any, were monitored at different levels of biological organisation (i.e. DNA, chromosomal, cellular and individual). Genotoxic effects were assessed using molecular and cytogenetic approaches which included analysis of random amplified polymorphic DNA (RAPD), induction of sister chromatid exchanges (SCEs) and chromosomal aberrations (Cabs). Cytotoxic effects were evaluated by determining the proliferative rate index (PRI) of the embryo-larval cells. Developmental and survival effects were also monitored every 24 h up to 72 h. Results in general indicated that HTO significantly increased cytogenetic damage, cytotoxicity, developmental abnormalities and mortality of the embryo-larvae as a function of concentration or radiation dose. The analysis of RAPD profiles also revealed qualitative effects in the HTO exposed population compared to controls. However, while the embryo-larvae showed dose or concentration dependent effects for mortality, developmental abnormalities and induction of SCEs, the dose-dependent effects were not apparent for Cabs and PRI at higher doses. The study contributes to our limited understanding of the impact of environmentally relevant radionuclides on non-human biota and emphasises the need for further investigations to elucidate potentially long term damage induced by persistent, low levels of other radionuclides on commercially and ecologically important species, in order to protect human and ecosystem health.

Impact of low doses of tritium on the marine mussel, Mytilus edulis: Genotoxic effects and tissue-specific bioconcentration

Despite growing scientific, public and regulatory concern over the discharge of radioactive substances, no serious attempts have been made to develop a rationale to evaluate the impact of environmentally relevant radionuclides in the aquatic environment. In this study, we have evaluated the genotoxic effects and tissue-specific concentration of tritium (added as tritiated water, HTO) in the adult life stage of the edible mussel, Mytilus edulis. The genotoxic effects were quantified in terms of the induction of: (a) micronuclei (MN), and (b) DNA single-strand breaks/alkali-labile sites using alkaline single-cell gel electrophoresis (Comet assay) in the haemocytes of exposed animals. The assays were optimised and validated using a range of concentrations (18-56 mgl(-1)) of ethylmethane sulfonate (EMS), a direct-acting reference genotoxic agent, over different exposure periods. Mussels were exposed to a series of concentrations of HTO equivalent to a dose range from 12 to 485 muGyh(-1) for 96 h, and different tissues and organs were then extracted and analysed. The study revealed a dose-dependent increase in the response for both the MN test and the Comet assay and for both EMS and HTO. In addition, HTO delivering dose rates below 500 muGyh(-1) was shown to be capable of inducing genetic damage in the haemocytes of these bivalves. The study also showed that inorganic tritium accumulated differentially in mussel tissues in a dose-dependent manner, with the gut accumulating the highest amount of radioactivity, followed by the gill, mantle, muscle, foot and byssus thread. The faeces and pseudo-faeces accumulated least radioactivity over the exposure period. Differential accumulation of radionuclides has significant implications for biomonitoring programmes, for this and other aquatic organisms. The study also suggests that the generic dose limits recommended by the International Atomic Energy Agency for the protection of aquatic biota might not be applicable to all aquatic organisms.

Multi-level assessment of chronic toxicity of estuarine sediments with the amphipod Gammarus locusta: I. Biochemical endpoints

We report on biomarker responses conducted as part of a multi-level assessment of the chronic toxicity of estuarine sediments to the amphipod Gammarus locusta. A companion article accounts for organism and population-level effects. Five moderately contaminated sediments from two Portuguese estuaries, Sado and Tagus, were assessed. Three of them were muddy and two were sandy sediments. The objective was to assess sediments that were not acutely toxic. Three of the sediments met this criterion, the other two were diluted (50% and 75%) with clean sediment until acute toxicity was absent. Following 28-d exposures, the amphipods were analysed for whole-body metal bioaccumulation, metallothionein induction (MT), DNA strand breakage (SB) and lipid peroxidation (LP). Two of the muddy sediments did not cause chronic toxicity. These findings were consistent with responses at organism and population levels that showed higher growth rates and improvement of reproductive traits for amphipods exposed to these two sediments. Two other sediments, one muddy and one sandy, exhibited pronounced chronic toxicity, affecting SB, MT induction (in muddy sediment), survival and reproduction. Potential toxicants involved in these effects were identified. The last sandy sediment exhibited some loss of DNA integrity, however growth was also enhanced. Present results, together with the organism/population-level data, and also benthic communities information, were analysed under a weight-of-evidence approach. By providing evidence of exposure (or lack of it) to contaminants in sediments, the biomarkers here applied assisted in distinguishing toxicants' impacts in test organisms from the confounding influence of other geochemical features of the sediments.

The mutagenic hazards of aquatic sediments: a review

Sediments are the sink for particle-sorbed contaminants in aquatic systems and can serve as a reservoir of toxic contaminants that continually threaten the health and viability of aquatic biota. This work is a comprehensive review of published studies that investigated the genotoxicity of sediments in rivers, lakes and marine habitats. The Salmonella mutagenicity test is the most frequently used assay and accounts for 41.1% of the available data. The Salmonella data revealed mutagenic potency values for sediment extracts (in revertants per gram dry weight) that spans over seven orders of magnitude from not detectable to highly potent (10(5) rev/g). Analyses of the Salmonella data (n=510) showed significant differences between rural, urban/industrial, and heavily contaminated (e.g., dump) sites assessed using TA98 and TA100 with S9 activation. Additional analyses showed a significant positive correlation between Salmonella mutagenic potency (TA98 and TA100 with S9) and PAH contamination (r2=0.19-0.68). The second and third most commonly used assays for the analysis of sediments and sediment extracts are the SOS Chromotest (9.2%) and the Mutatox assays (7.8%), respectively. These assays are frequently used for rapid initial screening of collected samples. A variety of other in vitro endpoints employing cultured fish and mammalian cells have been used to investigate sediment genotoxic activity. Endpoints investigated include sister chromatid exchange frequency, micronucleus frequency, chromosome aberration frequency, gene mutation at tk and hprt loci, unscheduled DNA synthesis, DNA adduct frequency, and DNA strand break frequency. More complex in vivo assays have documented a wide range of effects including neoplasms and preneoplastic lesions in fish and invertebrate exposed ex situ. Although costly and time consuming, these assays have provided definitive evidence linking sediment contamination and a variety of genotoxic and carcinogenic effects observed in situ.

Mutagens in surface waters: a review

A review of the literature on the mutagenicity/genotoxicity of surface waters is presented in this article. Subheadings of this article include a description of sample concentration methods, mutagenic/genotoxic bioassay data, and suspected or identified mutagens in surface waters published in the literature since 1990. Much of the published surface water mutagenicity/genotoxicity studies employed the Salmonella/mutagenicity test with strains TA98 and/or TA100 with and/or without metabolic activation. Among all data analyzed, the percentage of positive samples toward TA98 was approximately 15%, both in the absence and the presence of S9 mix. Those positive toward TA100 were 7%, both with and without S9 mix. The percentage classified as highly mutagenic (2500-5000 revertants per liter) or extremely mutagenic (more than 5000 revertants per liter) was approximately 3-5% both towards TA98 and TA100, regardless of the absence or the presence of S9 mix. This analysis demonstrates that some rivers in the world, especially in Europe, Asia and South America, are contaminated with potent direct-acting and indirect-acting frameshift-type and base substitution-type mutagens. These rivers are reported to be contaminated by either partially treated or untreated discharges from chemical industries, petrochemical industries, oil refineries, oil spills, rolling steel mills, untreated domestic sludges and pesticides runoff. Aquatic organisms such as teleosts and bivalves have also been used as sentinels to monitor contamination of surface water with genotoxic chemicals. DNA modifications were analyzed for this purpose. Many studies indicate that the 32P-postlabeling assay, the single cell gel electrophoresis (comet) assay and the micronucleus test are sensitive enough to monitor genotoxic responses of indigenous aquatic organisms to environmental pollution. In order to efficiently assess the presence of mutagens in the water, in addition to the chemical analysis, mutagenicity/genotoxicity assays should be included as additional parameters in water quality monitoring programs. This is because according to this review they proved to be sensitive and reliable tools in the detection of mutagenic activity in aquatic environment. Many attempts to identify the chemicals responsible for the mutagenicity/genotoxicity of surface waters have been reported. Among these reports, researchers identified heavy metals, PAHs, heterocyclic amines, pesticides and so on. By combining the blue cotton hanging method as an adsorbent and the O-acetyltransferase-overproducing strain as a sensitive strain for aminoarenes, Japanese researchers identified two new type of potent frameshift-type mutagens, formed unintentionally, in several surface waters. One group has a 2-phenylbenzotriazole (PBTA) structure, and seven analogues, PBTA-type mutagens, were identified in surface waters collected at sites below textile dyeing factories and municipal wastewater treatment plants treating domestic wastes and effluents. The other one has a polychlorinated biphenyl (PCB) skelton with nitro and amino substitution group and it was revealed to be 4-amino-3,3'-dichloro-5,4'-dinitrobiphenyl derived from chemical plants treating polymers and dye intermediates. However, the identification of major putative mutagenic/genotoxic compounds in most surface waters with high mutagenic/genotoxic activity in the world have not been performed. Further efforts on chemical isolation and identification by bioassay-directed chemical analysis should be performed.

Genotoxicological studies in aquatic organisms: an overview

Substantial progress has been made in the lat two decades to evaluate the impact of physical and chemical genotoxins in aquatic organisms. This overview (a) summarises the major high lights in this stimulating area of research, (b) compares the developments in this field with the developments in mammalian genotoxicological studies, where appropriate, (c) introduces 18 different articles presented in this special issue of Mutation Research in the backdrop of main advances and , (d) hypothesises on future directions of research in this exciting field.

An integrated biomarker-based strategy for ecotoxicological evaluation of risk in environmental management

Environmental impacts by both natural events and man-made interventions are a fact of life; and developing the capacity to minimise these impacts and their harmful consequences for biological resources, ecosystems and human health is a daunting task for environmental legislators and regulators. A major challenge in impact and risk assessment, as part of integrated environmental management (IEM), is to link harmful effects of pollution (including toxic chemicals) in individual sentinel animals to their ecological consequences. This obstacle has resulted in a knowledge-gap for those seeking to develop effective policies for sustainable use of resources and environmental protection. Part of the solution to this problem may lie with the use of diagnostic clinical-type laboratory-based ecotoxicological tests or biomarkers, utilising sentinel animals as integrators of pollution, coupled with direct immunochemical tests for contaminants. These rapid and cost-effective ecotoxicological tools can provide information on the health status of individuals and populations based on relatively small samples of individuals. In the context of ecosystem status or health of the environment, biomarkers are also being used to link processes of molecular and cellular damage through to higher levels (i.e., prognostic capability), where they can result in pathology with reduced physiological performance and reproductive success. Complex issues are involved in evaluating environmental risk, such as the effects of the physico-chemical environment on the speciation and uptake of pollutant chemicals and inherent inter-individual and inter-species differences in vulnerability to toxicity; and the toxicity of complex mixtures. Effectively linking the impact of pollutants through the various hierarchical levels of biological organisation to ecosystem and human health requires a pragmatic integrated approach based on existing information that either links or correlates processes of pollutant uptake, detoxication and pathology with each other and higher level effects. It is further proposed here that this process will be facilitated by pursuing a holistic or whole systems approach with the development of computational simulation models of cells, organs and animals in tandem with empirical data (i.e., the middle-out approach). In conclusion, an effective integrated environmental management strategy to secure resource sustainability requires an integrated capability for risk assessment and prediction. Furthermore, if such a strategy is to influence and help in the formulation of environmental policy decisions, then it is crucial to demonstrate scientific robustness of predictions concerning the long-term consequences of pollution to politicians, industrialists and environmental managers; and also increase stakeholder awareness of environmental problems.

Detection of DNA strand breakage in a marine amphipod by agarose gel electrophoresis: exposure to X-rays and copper

This article describes the leading steps to develop an assay of DNA damage for the marine amphipod Gammarus locusta, using agarose gel electrophoresis (AGE). To test the sensitivity and feasibility of the AGE technique, X-ray assays were performed with naked DNA and with live amphipods. These positive controls demonstrated the effectiveness of the AGE technique to not only discriminate distinct levels of DNA strand breakage in a dose-dependent manner, but also to identify and quantify the type of strand breakage induced. It was also shown that it is possible to detect DNA damage using whole-body DNA extracts from amphipods. To explore the potential of this technique for use in ecotoxicological studies with amphipods, a 96-h waterborne-copper toxicity test was performed. Copper-induced DNA strand breakage was first observed after 24 h of exposure, and was recorded again at 96 h, at a copper concentration of 20 microg l(-1). The absence of strand breakage after 48 h of exposure is discussed in the light of the underlying mechanisms of copper toxicity and DNA repair. These studies demonstrated the feasibility of including DNA damage as a biomarker in ecotoxicological studies with amphipods. Information gained from the use of this biomarker would help with the interpretation of chronic toxicity tests and would contribute to our understanding of the impact of genotoxic insult in marine invertebrates, particularly crustaceans.

Ecogenotoxicology: the evolving field

The occurrence of chemical contaminants with DNA-damaging capacity in the environment represents a threat to human health as well as to the health of the ecosystem. This mini-review describes studies that were aimed to monitor at field conditions, the presence of such environmental toxicants and their DNA-damaging effects in aquatic and terrestrial species, as well as in birds. It is obvious that these studies, in particular are abundantly performed in fish and aquatic invertebrates, have brought forward new information on the levels and genotoxic effects of these compounds which complements data coming from monitoring the abiotic fractions of the ecosystem, thereby demonstrating that the ecogenotoxicological approach is fruitful. However, in order to assess the genotoxic impact on the health of the ecosystem, a second generation type of field studies is required focusing on adverse effects on biodiversity and on survival potency. For this, the application of DNA microarray-based technologies provides new opportunities.

Genotoxic, cytotoxic and developmental effects of tributyltin oxide (TBTO): an integrated approach to the evaluation of the relative sensitivities of two marine species

Adopting an integrated approach the potential genotoxic, cytotoxic and developmental effects of tributyltin oxide (TBTO), a known endocrine-disrupting agent for neogastropods, have been evaluated in two ecologically relevant invertebrates: Mytilus edulis (blue mussel) and Platynereis dumerilli (rag worm). Following determination of the maximum tolerated dose (MTD) in terms of developmental and survival effects, the embryo-larval stages of these organisms were exposed to a range of concentrations of TBTO, and analysed for cytotoxic (proliferation rate index) and genotoxic (sister chromatid exchanges and chromosomal aberrations) effects. The study suggested that: (1) TBTO is both toxic and genotoxic to embryo-larval stages of both species; (2) at comparable concentrations, for developmental and genotoxic effects, P. dumerilii (non-target species) is more sensitive compared to M. edulis (target species); and (3) genotoxic effects are more closely tied with the development and survival of the organisms. The study emphasises the need of the evaluation of genotoxic potential of other endocrine-disrupting agents in different taxonomic groups.