Seasonal variability in biomarkers in the bivalves Mytilus edulis and Macoma balthica from the northern Baltic Sea

A multibiomarker approach in clams (Ruditapes philippinarum) for a toxicological evaluation of dredged sediments

The Lagoon of Venice is often dredged for channel maintenance. To avoid harmful consequences to the ecosystem, a proper disposal of bottom sediments requires a preliminary evaluation of its potential toxicity before excavation. Here we evaluated the effects of polluted sediments on clams (Ruditapes philippinarum) using a multibiomarker approach. Bivalves were exposed for 3 and 14 days to five sediment samples collected along a navigation canal between Venice historical centre and the industrial area of Porto Marghera. Immunological, antioxidant, detoxification, and neurotoxicity biomarkers were analysed in haemolymph, gill, and digestive gland. As a control, sediment collected far from pollution sources was used. Two experiments were performed to assess potential seasonal/gametogenic influence in clam sensitivity. A different response of clam biomarkers was observed during the two experiments and among sampling sites. Clams' digestive gland resulted to be the most sensitive tissue analysed showing significant differences among sites in all biomarkers analysed. Greater differences were present due to seasonality rather than exposure. The concentrations of metals and organic pollutants increased from the city centre to the industrial area, highlighting the influence that industrial activities had on the lagoon ecosystem. However, bioaccumulation in clams did not follow the same clear pattern, suggesting low bioavailability of compounds due to relatively high organic matter content. Biomarkers modulation was mainly driven by metals, both present in sediments and bioaccumulated. In comparison, effects of organic pollutants on the biomarkers tested were negligible. Other sources of contamination not investigated (e.g. pesticides) were suggested by neurotoxicity biomarkers alteration.

Spatial and seasonal use of biomarkers in dreissenids: implications for biomonitoring

In addition to pollution, organisms are exposed to natural variations of the biotic and abiotic factors of their environment. A battery of sub-cellular biomarkers has been measured seasonally in several populations of both Dreissena polymorpha and Dreissena rostriformis bugensis. To observe and understand the variability associated with biomarker responses, water physicochemistry, sediment contamination, and internal concentrations of contaminants in soft tissues were also considered. Results evidenced seasonal, inter-specific, and inter-populational variability of the measured responses, highlighting the needs (1) to acquire long-term data on the studied populations and (2) to incorporate environmental parameters and contamination in the interpretation of biological responses. From a biomonitoring perspective, significant relationships were identified between biomarkers, internal concentrations of contaminants in soft tissues, and sediment contamination in D. r. bugensis and, to a lesser extent, in D. polymorpha. The detailed interpretation of each biomarker of the battery measured is complex, but a global analysis of all biomarkers at once allows to obtain this signature of the contamination of the studied sites.

Biomarker responses in mussels (Mytilus trossulus) from the Baltic Sea exposed to water-accommodated fraction of crude oil and a dispersant at different salinities

Oil spills pose significant environmental risks, particularly in cold seas. In the Baltic Sea, the low salinity (from 0 to 2 up to 18) affects the behaviour of the spilled oil as well as the efficiency and ecological impacts of oil spill response methods such as mechanical collection and the use of dispersants. In the present study, mussels (Mytilus trossulus) were exposed under winter conditions (5 °C) to the water-accommodated fraction (WAF) of Naphthenic North Atlantic crude oil prepared by mechanical dispersion or to the chemically enhanced fraction (CEWAF) obtained using the dispersant Finasol OSR 51 at salinities of 5.6 and 15.0. Especially at the lower salinity, high bioaccumulation of polycyclic aromatic hydrocarbons was recorded in mussels in the CEWAF treatments, accompanied by increased biomarker responses. In the WAF treatments these impacts were less evident. Thus, the use of dispersants in the Baltic Sea still needs to be carefully considered.

Variability and distribution of parasites, pathologies and their effect on wild mussels (Mytilus sp) in different environments along a wide latitudinal span in the Northern Atlantic and Arctic Oceans

Histopathological examination in mussels can provide useful information for the diagnosis of ecosystem health status. The distribution of parasites in mussels can be conditioned by several environmental factors, including mussels collecting sites or the presence/absence of other species necessary to complete the complex life cycle of certain parasites. Thus, these variables could not only govern the parasitic burden of mussels but also the presence of pathologies associated to parasitism. The aim of this study was to identify the histopathological alterations which could be indicative of a health status distress along a wide latitudinal span in the Northern Atlantic and Arctic Oceans in mussels of two size-classes sampled in clean and impacted sites. A latitudinal gradient is clearly observed in gamete developmental stages as northern and southern mussels presented different conditions at the same period. Furthermore, mussels of the same size in different latitudes presented differences in the reproductive cycle and the appearance of related pathologies, which probably meant the age of individuals was different. In addition, specific parasitic profiles ruled by latitudinal conditions and the settlement of mussels in the shore (horizontal/vertical) have been demonstrated to be significantly influential in the health condition of mussels. Furthermore, the present work provides the first histological description of Gymnophallus cf. bursicola parasite causing a considerable host response in Tromsø and Iceland plus the report of grave histopathological status that included high prevalence of granulocytomas in Scotland and Germany.

Monitoring metallothionein-like protein concentrations and cholinesterase activity in tropical cup oysters as biomarkers of exposure to metals and pesticides in the southern Caribbean, Colombia

Metallothionein-like protein concentrations (MT) and three functionally defined fractions of cholinesterase activity (ChE) were quantified in gill and digestive gland homogenates of tropical cup oysters from 5 nearshore locations in the Colombian Caribbean and correlated with sediment and tissue metal (9 metals) and pesticide (22 organophosphates, OPs, and 20 organochlorines-OCPs), as well as water physical-chemical parameters (salinity, pH, temperature, and dissolved oxygen). Tissue and sediment pesticide concentrations were below detection limits in all samples, whereas sediment and tissue metal concentrations exceeded environmental thresholds at several locations. Tissue MT and ChE biomarkers varied by a factor of 5-6 between locations. Inhibition of cholinesterase activity was negligible for all 5 sites, despite spatial-temporal variation in ChE activity, consistent with below-detection OP concentrations. Tissue MT and ChE biomarkers correlated with tissue and metal sediment concentrations, yet, statistically significant covariance between biomarkers and water chemistry parameters was also observed, indicating that both, metal concentrations and physical-chemical variables, are likely to be responsible for generating the observed spatial-temporal variations in biomarker patterns.

Assessment of seasonal and spatial variation responses of integrated biomarkers in two marine sentinel bivalve species: Agadir Bay (Southern of Morocco)

The present study aims to assess the effects of contamination of the Agadir bay coasts using bivalves as a biomonitoring sentinel species. Seasonal variations of biochemical composition in terms of total protein content and oxidative stress biomarkers including glutathione-S-transferase, malondialdehyde, catalase and acetylcholinesterase were evaluated in the soft tissues of Scrobicularia plana and Donax trunculus specimens. The latter were collected from two sites in Agadir bay during two-year span (2018-2020). The Integrated Biomarker Response Index (IBR) was performed to classify the stress response in both species and to assess the level of exposure to xenobiotics. The data showed maximum annual values of acetylcholinesterase and malondialdehyde for Donax trunculus in Agadir beach (AG) with 6.25 nmol/mn/mg and 3 nmol/mg of protein, respectively. Those of catalase and glutathione-S-transferase for Scrobicularia plana in Oued Souss estuary (OS) were of 4.41 μmol/mn/mg and 14.43 nmol/mn/mg of protein, respectively. The studied species are considered good indicators in aquatic ecosystems.

Multi-biomarker approach and IBR index to evaluate the effects of different contaminants on the ecotoxicological status of Apis mellifera

The honeybee, Apis mellifera L. (Hymenoptera: Apidae), a keystone pollinator of wild plant species and agricultural crops, is disappearing globally due to parasites and diseases, habitat loss, genetic constraints, beekeeper management issues and to the widespread use of pesticides. Besides insecticides, widely studied in this species, honeybees are also exposed to herbicides and fungicides and heavy metals whose lethal and sublethal effects need to be investigated. In this context, our study aimed to evaluate the effects of fungicides and of heavy metals on honeybees and to develop and apply a multi-biomarker approach that include an Integrated Biological Index (IBRv2) to assess the toxicological status of this species. Biomarkers of neurotoxicity (AChE and CaE), metabolic alteration (ALP, and GST) and immune system (LYS, granulocytes) were measured, following honeybees' exposure to cadmium or to a crop fungicide, using the genotoxic compound EMS as positive control. A biomarker of genotoxicity (NA assay) was developed and applied for the first time in honeybees. At the doses tested, all the contaminants showed sublethal toxicity to the bees, highlighting in particular genotoxic effects. The data collected were analyzed by an IBRv2 index, which integrated the seven biomarkers used in this study. IBRv2 index increased with increasing cadmium or fungicide concentrations. The IBRv2 represents a simple tool for a general description of honeybees ecotoxicological health status. Results highlight the need for more in-depth investigations on the effects of fungicides on non-target organisms, such as honeybees, using sensitive methods for the determination of sublethal effects. This study contributes to the development of a multi-biomarker approach to be used for a more accurate ecotoxicological environmental monitoring of these animals.

Biomarker Responses of the Clam Ruditapes decussatus Exposed to a Complex Mixture of Environmental Stressors under the Influence of an Urban Wastewater-Treatment Plant

To evaluate the potential impact of an urban wastewater-treatment plant on Ria Formosa coastal lagoon, a sentinel species, the clam Ruditapes decussatus, was exposed along a gradient of the effluent's dispersal for 1 mo. Three exposure sites were selected to study the responses of 3 biomarkers: electron transport system, acetylcholinesterase, and lipid peroxidation. As complementary data, morphometric measurements, condition index, and lipid and protein content were considered together with in situ physicochemical characterization of the sites (temperature, salinity, pH, and dissolved oxygen). Electron transport system activity levels were between 35.7 and 50.5 nmol O₂ /min g protein, acetylcholinesterase activity levels ranged from 2.6 to 3.8 nmol/min g protein, and lipid peroxidation ranged from 174.7 to 246.4 nmol malondialdehyde/g protein. The exposure sites shaped the response not only of biomarkers but also of "health" parameters (protein, lipids, and condition index). Lipid peroxidation was the most responsive biomarker also associated with electron transport system, especially at the closest site to the urban wastewater-treatment plant. Because of the presence of complex mixtures of contaminants in urban effluents, biomarker responses can provide valuable information in environmental assessment. However, it is vital to identify all biological and ecological factors induced by the natural life cycle of clams. Abiotic factors can mask or overlap the response of biomarkers and should be considered in a multibiomarker approach. Environ Toxicol Chem 2021;40:272-283. © 2020 SETAC.

Biomarker responses and accumulation of polycyclic aromatic hydrocarbons in Mytilus trossulus and Gammarus oceanicus during exposure to crude oil

In the brackish water Baltic Sea, oil pollution is an ever-present and significant environmental threat mainly due to the continuously increasing volume of oil transport in the area. In this study, effects of exposure to crude oil on two common Baltic Sea species, the mussel Mytilus trossulus and the amphipod Gammarus oceanicus, were investigated. The species were exposed for various time periods (M. trossulus 4, 7, and 14 days, G. oceanicus 4 and 11 days) to three oil concentrations (0.003, 0.04, and 0.30 mg L^-1 based on water measurements, nominally aimed at 0.015, 0.120, and 0.750 mg L^-1) obtained by mechanical dispersion (oil droplets). Biological effects of oil exposure were examined using a battery of biomarkers consisting of enzymes of the antioxidant defense system (ADS), lipid peroxidation, phase II detoxification (glutathione S-transferase), neurotoxicity (acetylcholinesterase inhibition), and geno- and cytotoxicity (micronuclei and other nuclear deformities). In mussels, the results on biomarker responses were examined in connection with data on the tissue accumulation of polycyclic aromatic hydrocarbons (PAH). In M. trossulus, during the first 4 days of exposure the accumulation of all PAHs in the two highest exposure concentrations was high and was thereafter reduced significantly. Significant increase in ADS responses was observed in M. trossulus at 4 and 7 days of exposure. At day 14, significantly elevated levels of geno- and cytotoxicity were detected in mussels. In G. oceanicus, the ADS responses followed a similar pattern to those recorded in M. trossulus at day 4; however, in G. oceanicus, the elevated ADS response was still maintained at day 11. Conclusively, the results obtained show marked biomarker responses in both study species under conceivable, environmentally realistic oil-in-seawater concentrations during an oil spill, and in mussels, they are related to the observed tissue accumulation of oil-derived compounds.

Trace elements and oxidative stress in the Ark shell Arca noae from a Mediterranean coastal lagoon (Bizerte lagoon, Tunisia): are there health risks associated with their consumption?

The current study examined the concentrations of ten trace elements (TE) (nickel, chromium, cadmium, iron, zinc, manganese, aluminum, copper, selenium and lead) in the edible tissue of the Ark shell Arca noae (L. 1758) from a Mediterranean coastal lagoon, the Bizerte lagoon during 2013-2014. The analysis of several redox status biomarkers, metallothioneins (MTs), malondialdehyde (MDA), glutathione peroxidase (GPx), reduced glutathione (GSH) and acetylcholinesterase (AChE), was monitored as a response to TE bioaccumulation and environmental parameters variability. Significant differences (p < 0.05) were observed between mean seasonal TE concentrations in A. noae soft tissue. The highest TE concentrations in A. noae soft tissues were recorded during summer, which coincided with the increase of body dry weight (BDW) and the gonad index (GI). During this season, biomarker responses were enhanced, revealing significant increases of MTs, MDA and GSH levels as well as GPx activity in A. noae tissues, while a decrease of AChE activity was observed. The levels of TE analyzed in A. noae and several parameters used to assess the potential human risk (estimated weekly intake, target hazard quotient and target hazard risk) were lower than the permissible limits for safe seafood consumption. Consequently, this shellfish can be considered safe for human consumption. This preliminary study presents prospects for the valorization of this seafood product in Tunisia's food sector. It also gives basal information for future environmental assessment studies in which A. noae could be used as early warning tools in the field of biomonitoring programs and confirms the usefulness of biomarkers to monitor the health status of aquatic organisms.

Evaluación preliminar de biomarcadores enzimáticos en caracoles de agua dulce (<i>Pachychilus</i> sp.) del humedal “Ciénaga de Tamasopo”, México

Se determinó la actividad de la enzima acetilcolinesterasa (AChE), el rango de conjugación de glutatión s-transferasa (GST) y la presencia de malondialdehído (MDA), como biomarcadores de exposición a plaguicidas, durante dos temporadas (secas y post-lluvias) en tejidos de macroinvertebrados acuáticos (caracoles de agua dulce -Pachychilus sp.-) residentes del humedal Ciénega de Tamasopo (San Luis Potosí, México). Esto se acompañó con un monitoreo de los parámetros fisicoquímicos en agua del humedal con una sonda multiparamétrica. La actividad de los biomarcadores se determinó en la fracción S12 (fracción post-mitocondrial) de tejidos de Pachychilus sp. mediante métodos de espectrofotometría UV-Visible en un lector de microplacas. Se encontró una menor actividad de AChE (39,0%) y un mayor rango de conjugación de GST (28,5%) seguido de una menor presencia (25,0%) de peroxidación lipídica (MDA) en la temporada de secas en el tejido de los caracoles. Además, se encontraron asociaciones significativas entre el rango de conjugación de GST con el resto los biomarcadores en ambas temporadas, lo cual es el resultado de procesos de desintoxicación en los caracoles. La actividad de los biomarcadores podría estar modulada por la salinidad regulando así la producción de enzimas antioxidantes y la toxicidad de los plaguicidas usados en las áreas agrícolas cercanas a este humedal. Los caracoles del género Pachychilus sp. pueden ser utilizados como como bioindicadores del estado de la salud de los humedales, lo cual puede derivar en el diseño de medidas de gestión para la conservación y manejo sustentable de estos ecosistemas.

In Situ Reproductive Bioassay with Caged Gammarus fossarum (Crustacea): Part 2-Evaluating the Relevance of Using a Molt Cycle Temperature-Dependent Model as a Reference to Assess Toxicity in Freshwater Monitoring

Active biomonitoring approaches are now recognized as relevant for monitoring water contamination and toxicity. Nevertheless, due to the confounding influence of variable and uncontrolled environmental conditions such as temperature, biological markers measured on transplanted individuals to assess water quality are difficult to interpret. The purpose of the present study is to propose a methodology for adapting a laboratory test of chronic sublethal toxicity based on the molting cycle of Gammarus fossarum to in situ assays. To this end, we 1) adapted the molt cycle temperature-dependent model developed in Part 1 (Chaumot et al. 2020, this issue) to the fluctuating temperatures measured in the field; 2) assessed the predictive power of our approach as a "reference value" from gammarids caged in 9 nonimpacted sites at different seasons; and 3) tested the relevance of our tool to interpret in situ reproductive bioassays from 5 upstream/downstream studies and a large-scale deployment in 12 sites. Our approach based on modeling the progress of gammarid molting cycle as a function of temperature appeared to be a relevant and robust tool for interpreting in situ observations in different environmental contexts in time and space. By avoiding using a "reference" or upstream situation as a baseline from which water quality could be assessed, this approach provides a real added value to water quality diagnosis in biomonitoring programs. Environ Toxicol Chem 2020;39:678-691. © 2019 SETAC.

Seasonal and spatial variations in biomarker baseline levels within Arctic populations of mussels (Mytilus spp.)

Climate change and pollution resulting from human activities in the Arctic require reliable monitoring systems in sentinel species. Mytilus spp. are used as sentinel species all around the world. The use of Mytilus spp. in environmental monitoring requires knowledge about natural variations in pollution biomarkers. Seasonal variations in baseline levels of biomarkers were studied over a year in the mussels from both upper and lower littoral zones in Rakkfjorden, Norway, as they underwent their annual reproductive cycle. Spatial variations of these biomarker baseline levels were measured in five mussel populations within a 60-km radius from Rakkfjorden to investigate universality of the results from the specific population of Rakkfjorden at a regional scale. Seasonal variations in biomarker baseline levels were revealed and seemed to be related to the reproductive state of the mussels and the tidal zone. The mussels appeared to be more sensitive to oxidative stress during gametogenesis in autumn and winter, when having lower lysosome membrane stability and lower baseline levels of antioxidant biomarkers. An increase in baseline levels of these biomarkers was reported during spawning in spring, however, it was not possible to reveal whether these changes were due to spawning, or to a higher metabolic activity in mussels in response to elevated water temperature and food abundance. The differences between the tidal zones were reflected in reduced size of the mussels from the upper littoral zone, their late spawning in the season and increased baseline levels of antioxidant biomarkers during the coldest month, indicating a more challenging environment in the upper littoral zone. The spatial study indicated that the biomarker baseline levels measured in Rakkfjorden were no different from the levels measured in the mussels from five other sites and thus, are representative for mussels on a regional scale.

Impact of multiple stressors on biomarker responses in sympatric dreissenid populations

Dreissenid mussels, well-known invaders of the northern hemisphere, also constitute good biomonitors for freshwater quality assessment. Whereas the oldest, Dreissena polymorpha, is relatively well-known, the new invasive, Dreissena rostriformis bugensis, has been very little characterized. The aim of this study was to compare subcellular biomarker responses within these species, by taking into account inter- and intra-specific variability in biomarker responses during a multi-stress assessment. Indeed, due to local environmental conditions and genetic background, biomarker responses can be different between populations of a given species, not only between species. To evaluate these differential responses, we sampled mussels on two sites where they are both present in sympatry (plus another D. r. bugensis population), and we exposed these populations in laboratory to different stressors: thermal stress (12 or 17 °C), dietary stress (fed or unfed), contamination (nickel at 0, 20 and 500 μg L^-1) and exposure duration (0, 4 or 8 days). Results mainly evidenced strong inter-species and inter-population differences, underlining the need to discriminate correctly between the two species and to know well the populations used in biomonitoring. Results also evidenced thermal and food stress-related effects. The numerous data obtained during this multi-stress experiment also highlight the complexity of working on several stressors and analysing the associated results.

Seawater Acidification Reduced the Resistance of Crassostrea gigas to Vibrio splendidus Challenge: An Energy Metabolism Perspective

Negative physiological impacts induced by exposure to acidified seawater might sensitize marine organisms to future environmental stressors, such as disease outbreak. The goal of this study was to evaluate if ocean acidification (OA) could reduce the resistance capability of the Pacific oyster (Crassostrea gigas) to Vibrio splendidus challenge from an energy metabolism perspective. In this study, the Pacific oyster was exposed to OA (pH 7.6) for 28 days and then challenged by V. splendidus for another 72 h. Antioxidative responses, lipid peroxidation, metabolic (energy sensors, aerobic metabolism, and anaerobic metabolism) gene expression, glycolytic enzyme activity, and the content of energy reserves (glycogen and protein) were investigated to evaluate the environmental risk of pathogen infection under the condition of OA. Our results demonstrated that following the exposure to seawater acidification, oysters exhibited an energy modulation with slight inhibition of aerobic energy metabolism, stimulation of anaerobic metabolism, and increased glycolytic enzyme activity. However, the energy modulation ability and antioxidative regulation of oysters exposed to seawater acidification may be overwhelmed by a subsequent pathogen challenge, resulting in increased oxidative damage, decreased aerobic metabolism, stimulated anaerobic metabolism, and decreased energy reserves. Overall, although anaerobic metabolism was initiated to partially compensate for inhibited aerobic energy metabolism, increased oxidative damage combined with depleted energy reserves suggested that oysters were in an unsustainable bioenergetic state and were thereby incapable of supporting long-term population viability under conditions of seawater acidification and a pathogen challenge from V. splendidus.

Use of sperm DNA integrity as a marker for exposure to contamination in Palaemon serratus (Pennant 1777): Intrinsic variability, baseline level and in situ deployment

In a previous study, the Comet assay was optimized for Palaemon serratus prawns in order to propose a biomarker for sperm quality in this species. However, better knowledge of its basal level and its natural variability, related to intrinsic biotic and environmental abiotic factors, is required before any relevant use of this biomarker in the field. To fulfill this goal, the present study proceeded in three steps: (i) the temporal variability of DNA integrity was followed monthly in a reference population over a 2-year period, (ii) the correlation between the main intrinsic biotic (i.e. size, weight and molting stage) and abiotic factors (i.e. water temperature) were recorded in the field, and the basal DNA integrity was assessed in order to scrutinize any confounding influence of factors unrelated to toxic response, (iii) the baseline level was used to discriminate biomarker response among different stations displaying contrasting contamination levels. The results of the two-year monitoring in the reference population revealed no correlation between the levels of spermatozoa DNA damage and temperature, body size, weight or molting stage. Only a slight variability between monthly samplings was detected. On the basis of these field-collected data, we defined a reference distribution (i.e. 52.6 ± 5.6 A.U) with a threshold value (i.e. 61.7 A.U). Finally, this threshold value proved its relevance to discriminate among stations with contrasting pollution levels around the Seine Bay. Indeed, the results suggest significant DNA damage in populations nearest the Seine estuary, a major source of contaminants in the Bay, and a lower effect in populations further away from the estuary. The overall conclusion was that the Comet assay on P. serratus spermatozoa could be a useful tool for the monitoring of the toxicological print within sperm and main globally the contamination exposure of crustaceans in marine waters.

Comparison of caged and native blue mussels (Mytilus edulis spp.) for environmental monitoring of PAH, PCB and trace metals

Contaminant bioaccumulation was studied in blue mussels (Mytilus edulis spp.) using the harbor waters of Kristiansand (Norway) as a case study. A suite of chemical contaminants (trace metals, PAHs and PCBs) was analyzed in caged and native mussels as well as in passive samplers (Diffusive Gradients in Thin films (DGT)-devices and silicone rubbers) placed alongside the mussels for estimation of contaminant concentrations in water and uptake rates and bioaccumulation factors (BAFs) in mussels during a six-months deployment period. Estimated logBAFs were in the ranges 2.3-5.5, 3.8-5.2 and 3.2-4.4 for metals, PCBs and PAHs, respectively. Contaminant levels in caged mussels increased rapidly to stable levels for trace metals, whereas for hydrophobic organic contaminants the increase was steady but slow and for many compounds did not reach the levels observed in native mussels. Some key issues related to mussel caging design, such as mussel deployment time and confounding influence from seasonal fluctuations, are discussed herein.

Blue mussels (Mytilus edulis spp.) as sentinel organisms in coastal pollution monitoring: A review

The blue mussel (Mytilus spp.) is widely used as a bioindicator for monitoring of coastal water pollution (mussel watch programs). Herein we provide a review of this study field with emphasis on: the suitability of Mytilus spp. as environmental sentinels; uptake and bioaccumulation patterns of key pollutant classes; the use of Mytilus spp. in mussel watch programs; recent trends in Norwegian mussel monitoring; environmental quality standards and background concentrations of key contaminants; pollutant effect biomarkers; confounding factors; particulate contaminants (microplastics, engineered nanomaterials); climate change; harmonization of monitoring procedures; and the use of deployed mussels (transplant caging) in pollution monitoring. Lastly, the overall state of the art of blue mussel pollution monitoring is discussed and some important issues for future research and development are highlighted.

Comparative study of acetylcholinesterase and glutathione S-transferase activities of closely related cave and surface Asellus aquaticus (Isopoda: Crustacea)

The freshwater isopod crustacean Asellus aquaticus has recently been developed as an emerging invertebrate cave model for studying evolutionary and developmental biology. Mostly morphological and genetic differences between cave and surface A. aquaticus populations have been described up to now, while scarce data are available on other aspects, including physiology. The purpose of this study was to advance our understanding of the physiological differences between cave A. aquaticus and its surface-dwelling counterparts. We sampled two surface populations from the surface section of the sinking Pivka River (central Slovenia, Europe), i.e. locality Pivka Polje, and locality Planina Polje, and one cave population from the subterranean section of the sinking Pivka River, i.e. locality Planina Cave. Animals were sampled in spring, summer and autumn. We measured the activities of acetylcholinesterase (AChE) and glutathione S-transferase (GST) in individuals snap-frozen in the field immediately after collection. Acetylcholinesterase is likely related to animals’ locomotor activity, while GST activity is related to the metabolic activity of an organism. Our study shows significantly lower AChE and GST activities in the cave population in comparison to both surface A. aquaticus populations. This confirms the assumption that cave A. aquaticus have lower locomotor and metabolic activity than surface A. aquaticus in their respective natural environments. In surface A. aquaticus populations, seasonal fluctuations in GST activity were observed, while these were less pronounced in individuals from the more stable cave environment. On the other hand, AChE activity was generally season-independent in all populations. To our knowledge, this is the first study of its kind conducted in A. aquaticus. Our results show that among closely related cave and surface A. aquaticus populations also physiological differences are present besides the morphological and genetic. These findings contribute to a better understanding of the biology of A. aquaticus and cave crustaceans in general.

Chronic environmental stress enhances tolerance to seasonal gradual warming in marine mussels

In global climate change scenarios, seawater warming acts in concert with multiple stress sources, which may enhance the susceptibility of marine biota to thermal stress. Here, the responsiveness to seasonal gradual warming was investigated in temperate mussels from a chronically stressed population in comparison with a healthy one. Stressed and healthy mussels were subjected to gradual temperature elevation for 8 days (1°C per day; fall: 16–24°C, winter: 12–20°C, summer: 20–28°C) and kept at elevated temperature for 3 weeks. Healthy mussels experienced thermal stress and entered the time-limited survival period in the fall, became acclimated in winter and exhibited sublethal damage in summer. In stressed mussels, thermal stress and subsequent health deterioration were elicited in the fall but no transition into the critical period of time-limited survival was observed. Stressed mussels did not become acclimated to 20°C in winter, when they experienced low-to-moderate thermal stress, and did not experience sublethal damage at 28°C in summer, showing instead signs of metabolic rate depression. Overall, although the thermal threshold was lowered in chronically stressed mussels, they exhibited enhanced tolerance to seasonal gradual warming, especially in summer. These results challenge current assumptions on the susceptibility of marine biota to the interactive effects of seawater warming and pollution.

Investigating heritability of cadmium tolerance in Chironomus riparius natural populations: A physiological approach

Physiological responses allow populations to cope with metal contamination and can be involved in the evolution of tolerance under historical metal contamination scenarios. Here we investigate physiological aspects that might be underlying the heritable high tolerance to cadmium (Cd) in two Chironomus riparius populations collected from historically metal contaminated sites in comparison to two populations from reference sites. To evaluate differences in the physiological response to short-term Cd exposure, protein expression profiles, metallothioneins [MTs] and several antioxidant defences such as total glutathione (GSH_t), catalase (CAT) and glutathione-S-transferases [GSTs], were measured in all four populations reared for at least 8 generations under laboratory clean conditions. Cd-induced oxidative damage in lipids and energy related parameters (energy consumption and energy reserves) were also assessed. Results showed two major gradients of protein profiles according to Cd concentration and population tolerance. Furthermore, Cd-tolerant populations showed higher baseline levels of MTs and GSH_t while Cd-sensitive populations, collected from reference sites, showed significant induction of GSH_t levels with Cd exposure that were nonetheless insufficient to avoid increased oxidative damage to lipids. Cd exposure had no clear effects on the antioxidant enzymes or energy reserves but triggered a general increase in energy consumption. Finally, energy consumption was higher in Cd-tolerant populations across experimental conditions. Altogether, results demonstrate that inherited Cd-tolerance in these midge populations is related, at least in part, with different constitutive levels and plasticity of different defence mechanisms confirming the validity of using multiple physiological traits when studying evolution of tolerance.

Characterization of a genotoxicity biomarker in three-spined stickleback (Gasterosteus aculeatus L.): Biotic variability and integration in a battery of biomarkers for environmental monitoring

As a large array of hazardous substances exhibiting genotoxicity are discharged into surface water, this work aimed at assessing the relevance of adding a genotoxicity biomarker in a battery of biomarkers recently developed in the model fish three-spined stickleback (Gasterosteus aculeatus). First the confounding influence of gender, body length, and season (used as a proxy of age and of the fish reproductive status, respectively) on the level of primary DNA damage in erythrocytes was investigated in wild sticklebacks. Then, the genotoxity biomarker was included in a large battery of biomarkers assessing xenobiotic biotransformation, oxidative stress and neurotoxicity, and implemented in five sites. Gender, age and reproductive status did not influence DNA damage level in fish from the reference site. A significant relationship between the level of primary DNA damage and fish length (as a proxy of age also correlated to the season) was highlighted in the contaminated site. Among all biomarkers investigated in the field, the level of DNA damage was one of the four most discriminating biomarkers with EROD, catalase activity and the level of lipid peroxidation representing together 75.40% of the discriminating power in sampled fish. The level of DNA damage was correlated to the EROD activity and to the level of peroxidation, which mainly discriminated fish from sites under urban pressure. Finally, Integrated Biomarker Response indexes (IBRv2), which were calculated with the whole biomarker response dataset exhibited higher values in the Reveillon (9.62), the Scarpe and Rhonelle contaminated sites (5.11 and 4.90) compared with the two reference sites (2.38 and 2.55). The present work highlights that integration of a genotoxicity biomarker in a multiparametric approach is relevant to assess ecotoxicological risk in freshwater aquatic organisms.

Effect of nutritive status on Mytilus galloprovincialis pollution biomarkers: Implications for large-scale monitoring programs

Biomarkers have been extensively used in monitoring programs with the aim of assessing the biological effects of pollutants on marine organisms and determining environmental status. Data obtained from these programs are sometimes difficult to interpret due to the large amount of natural variables affecting biological processes, which could act as confounding factors on biomarker responses. The main aim of this work was to identify the effect of one of these variables, the food availability, and consequently, the mussel nutritive status, on biomarker responses. For that purpose, mussels (Mytilus galloprovincialis) were conditioned to three different food rations for 2 months in order to create three mussel nutritive statuses and afterwards, each status was exposed to three nominal concentrations of fluoranthene (FLU) for 3 weeks. A battery of biomarkers was considered in this study to cover a wide range of organism responses, both physiological (scope for growth - SFG) and biochemical (superoxide dismutase - SOD, catalase - CAT, glutathione reductase - GR, glutathione peroxidase - GPx, glutathione-S-transferase - GST and phenoloxidase - PO activities, and lipid membrane peroxidation - LPO). The results obtained, evidenced that most of the studied biomarkers (SFG, SOD, CAT, GPx, and PO) were strongly affected by mussel nutritive status, showing higher values at lower status, whereas the effect of toxicant was not always evident, masked by the nutritive status effect. This paper demonstrates that toxicants are not the only source of variability modulating pollution biomarkers, and confirms nutritive status as a major factor altering biochemical and physiological biomarkers.

Integrated biomarker assessment of the effects of tailing discharges from an iron ore mine using blue mussels (Mytilus spp.)

The blue mussel (Mytilus spp.) has been used to assess the potential biological effects of the discharge effluent from the Sydvaranger mine, which releases its tailings into Bøk fjord at Kirkenes in the north of Norway. Metal bioaccumulation and a suite of biomarkers were measured in mussels positioned for 6 weeks at varying distances from the discharge outlet. The biomarkers used included: stress on stress (SS); condition index (CI); cellular energy allocation (CEA); micronuclei formation (MN); lysosomal membrane stability (LMS), basophilic cell volume (VvBAS); and neutral lipid (NL) accumulation. The individual biomarkers were integrated using the integrated biological response (IBR/n) index. The accumulation of Fe was significantly higher in mussels located closer to the discharge outlet, indicating that these mussels had been exposed to the suspended mine effluent. The IBR/n results were in good agreement with the location of the mussels in relation to the distance from the discharge outlet and expected exposure to the mine effluent. Several biomarkers showed responses resulting in higher IBR/n values of analysed mussels within a 3 km distance from the tailing discharge.

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

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

Effects of environmentally relevant concentrations of metallic compounds on the flatfish Scophthalmus maximus: biomarkers of neurotoxicity, oxidative stress and metabolism

Flatfish species, such as the turbot (Scophthalmus maximus), are common targets for toxic effects, since they are exposed through the food chain (ingestion of contaminated preys) and are in direct contact with the waterborne contaminant and sediments. Furthermore, these fish species live in close proximity to interstitial water that frequently dissolves high amounts of contaminants, including metals. Despite this significant set of characteristics, the present knowledge concerning flatfish contamination and toxicity by metals is still scarce. To attain the objective of assessing the effects of metals on a flatfish species, S. maximus specimens were chronically exposed to lead, copper and zinc, at ecologically relevant concentrations, and biochemical (oxidative stress: catalase and glutathione S-transferases activities, and lipid peroxidation; neurotoxicity: cholinesterase activity) parameters were assessed on selected tissues (gills and liver). Copper had no significant effects on all tested parameters; lead was causative of significant increases in liver GSTs activities and also in lipoperoxidation of gill tissue; exposure to zinc caused a significant increase in catalase activity of gill tissue. None of the tested metals elicited noteworthy effects in terms of neurotoxicity. The obtained results showed that only the metal lead is of some environmental importance, since it was able to cause deleterious modifications of oxidative nature at relevant concentrations.

The Gooseneck Barnacle (Pollicipes pollicipes) as a candidate sentinel species for coastal contamination

The assessment of toxic effects caused by complex mixtures of contaminants in the marine environment requires previous validation of toxicological criteria, which may include biomarker end points with distinct biological meanings. This is the case of oxidative stress/phase II detoxification (glutathione-S-transferases activity), oxidative damage (thiobarbituric acid reactive substances), and neurotransmission (cholinesterase activity), which are likely to be affected after toxic insults by common marine pollutants. The main purpose of the present study was to assess potential biological alterations in the mollusk species Pollicipes pollicipes (gooseneck barnacle) caused by human contamination and seasonality, during a period of 1 year, in three different areas of the North Atlantic shore of Portugal. Our results indicate that fluctuations of the mentioned biomarkers were strongly related to seasonality, but they may also suffer influence by the already documented patterns of chemical contamination. Organisms collected in contaminated sampling sites (urban areas and oil refinery) showed greater levels of metabolic enzymes and increased levels of lipid peroxidation. These alterations were more evident during the summer, and, in some cases, spring months, suggesting an association between the presence of chemical stressors and temperature-dependent seasonal physiological fluctuations, which contribute to the modulation of the toxic response. In general terms, P. pollicipes was shown to be a promising organism in coastal biomonitoring programs, with an adequate sensitivity toward contamination and/or seasonal fluctuations. However, it is of the utmost importance to consider seasonal fluctuations in physiological parameters that modulate the toxic response. These factors can ultimately compromise the development and interpretation of data from marine biomonitoring programs if a thorough characterization of biological responses is not previously performed.

A multibiomarker approach to the assessment of pollution impacts in two Baltic Sea coastal areas in Sweden using caged mussels (Mytilus trossulus)

Blue mussels (Mytilus trossulus) were transplanted in cages for three months in two Swedish coastal areas in the Bothnian Sea (northern Baltic Sea) to investigate the interactions between analysed environmental chemicals and biological responses. A wide array of biological parameters (biomarkers) including antioxidant and biotransformation activity, geno-, cyto- and neurotoxic effects, phagocytosis, bioenergetic status and heart rate were measured to detect the possible effects of contaminants. Integrated Biomarker Response index and Principal Component Analysis performed on the individual biological response data were able to discriminate between the two study areas as well as the contaminated sites from their respective local reference sites. The two contaminated sites outside the cities of Sundsvall (station S1) and Gävle (station G1) were characterised by different biomarker response patterns. Mussels at station S1 showed a low condition index, increased heart rate recovery time and phagocytosis activity coinciding with the highest tissue concentrations of some trace metals, polycyclic aromatic hydrocarbons and organotins. At station G1 the highest organochlorine pesticide concentration was recorded as well as elevations in glutathione S-transferase activity, thiamine content and low lysosomal membrane stability. Significant variability in the geno- and cytotoxic responses and bioenergetic status was also observed at the different caging stations. The results obtained suggest that different chemical mixtures present in the study areas cause variable biological response patterns in organisms.

The integrated biomarker response revisited: optimization to avoid misuse

The growing need to evaluate the quality of aquatic ecosystems led to the development of numerous monitoring tools. Among them, the development of biomarker-based procedures, that combine precocity and relevance, is recommended. However, multi-biomarker approaches are often hard to interpret, and produce results that are not easy to integrate in the environmental policies framework. Integrative index have been developed, and one of the most used is the integrated biomarker response (IBR). However, an analysis of available literature demonstrated that the IBR suffers from a frequent misuse and a bias in its calculation. Then, we propose here a new calculation method based on both a more simple formula and a permutation procedure. Together, these improvements should rightly avoid the misuse and bias that were recorded. Additionally, a case study illustrates how the new procedure enabled to perform a reliable classification of site along a pollution gradient based on biomarker responses used in the IBR calculations.

Physiological responses of the European cockle Cerastoderma edule (Bivalvia: Cardidae) as indicators of coastal lagoon pollution

Physiological responses can be used as effective parameters to identify environmentally stressful conditions. In this study, physiology changes such as oxygen consumption, clearance rate, survival in air, condition index and energy reserves were measured on natural populations of cockles collected from different sites at Ria de Aveiro, Portugal. At those sites, sediment samples were collected for Hg concentration analysis. Cockles were used for the evaluation of both the Hg concentration and physiological response. Mercury was detected in the cockle tissue and in the sediment collected from the sampling points both nearby and distant from the main mercury contamination source. The energy content was negatively correlated with both Hg concentration in cockle tissues and survival in air. Nonetheless, the energy content was positively correlated with the condition index, and there was a positive correlation between the survival in air test and the tissue mercury concentration. A PCA-factor analysis explained 86.8% of the total variance. The principal factor (62.7%) consisted of the air survival, the Hg in soft tissues (positive) and the condition index (negative). The second factor (24.1%) consisted of a negative correlation between the oxygen consumption and the clearance rate. Due to their sensitivity to environmental conditions, the physiological responses of cockles can be used to assess the ecological status of aquatic environments. More effort should be invested in investigating the effects of environmental perturbations on cockle health once they are a good reporter organism.

Review on methods for determination of metallothioneins in aquatic organisms

One aspect of environmental degradation in coastal areas is pollution from toxic metals, which are persistent and are bioaccumulated by marine organisms, with serious public health implications. A conventional monitoring system of environmental metal pollution includes measuring the level of selected metals in the whole organism or in respective organs. However, measuring only the metal content in particular organs does not give information about its effect at the subcellular level. Therefore, the evaluation of biochemical biomarker metallothionein may be useful in assessing metal exposure and the prediction of potential detrimental effects induced by metal contamination. There are some methods for the determination of metallothioneins including spectrophotometric method, electrochemical methods, chromatography, saturation-based methods, immunological methods, electrophoresis, and RT-PCR. In this paper, different methods are discussed briefly and the comparison between them will be presented.

Human exposure, biomarkers, and fate of organotins in the environment

Organotin compounds result from the addition of organic moieties to inorganic tin.Thus, one or more tin-carbon bonds exist in each organotin molecule. The organo-tin compounds are ubiquitous in the environment. Organotin compounds have many uses, including those as fungicides and stabilizers in plastics, among others in industry. The widespread use of organotins as antifouling agents in boat paints has resulted in pollution of freshwater and marine ecosystems. The presence of organotin compounds in freshwater and marine ecosystems is now understood to be a threat, because of the amounts found in water and the toxicity of some organotin compounds to aquatic organisms, and perhaps to humans as well. Organotin com-pounds are regarded by many to be global pollutants of a stature similar to biphenyl,mercury, and the polychlorinated dibenzodioxins. This stature results from the high toxicity, persistence, bioaccumulation, and endocrine disruptive features of even very low levels of selected organotin compounds.Efforts by selected governmental agencies and others have been undertaken to find a global solution to organotin pollution. France was the first country to ban the use of the organotins in 1980. This occurred before the international maritime organization (IMO) called for a global treaty to ban the application of tributyltin (TBT)-based paints. In this chapter, we review the organotin compounds with emphasis on the human exposure, fate, and distribution of them in the environment. The widespread use of the organotins and their high stability have led to contamination of some aquatic ecosystems. As a result, residues of the organotins may reach humans via food consumption. Notwithstanding the risk of human exposure, only limited data are available on the levels at which the organotins exist in foodstuffs consumed by humans. Moreover, the response of marine species to the organotins, such as TBT, has not been thoroughly investigated. Therefore, more data on the organotins and the consequences of exposure to them are needed. In particular, we believe the following areas need attention: expanded toxicity testing in aquatic species, human exposure, human body burdens, and the research to identify biomarkers for testing the toxicity of the organotins to marine invertebrates.

Acetylcholinesterase activity in Gammarus fossarum (Crustacea Amphipoda) Intrinsic variability, reference levels, and a reliable tool for field surveys

The appropriate use of an enzyme activity as a biomarker requires good knowledge of its basal level and its natural variability related to intrinsic biotic and environmental abiotic factors. In view of using whole-body acetylcholinesterase (AChE) activity in Gammarus fossarum as a reliable biomarker of exposure to anti-cholinesterase agents in aquatic ecosystems, (i) the effects of the main biotic (sex, reproductive status, and weight) and abiotic (water temperature) factors on the basal activity level of this enzyme were measured in the laboratory and (ii) the spatio-temporal variability of basal enzyme activity was followed in wild populations over a 1-year period. The results show no direct effect of sex. However, significant differences in AChE activity were observed between females depending on gonadal and embryonic development. A strong negative correlation between the AChE activity levels and organism body weight was observed. Indeed, AChE activity decreases drastically during the early life stages and tends to stabilise in larger individuals. These reports led us to select a standard organism (male; weight range, 15-20mg) to minimise inter-individual variability. No effect of temperature on basal AChE activity was observed in the laboratory for the tested range (6-24 degrees C). Similarly, no spatio-temporal change relative to season or the physico-chemical characteristics of the water (such as conductivity and temperature) was recorded during the field survey. On the basis of field-collected data, we defined the standard organism having a reference activity level with minimal and maximal threshold values. Finally, the value of AChE activity normalisation by protein contents is discussed.

Metallothionein coding sequence identification and seasonal mRNA expression of detoxification genes in the bivalve Corbicula fluminea

The aim of this study was to identify a metallothionein (MT) coding sequence from the freshwater bivalve Corbicula fluminea and to measure the seasonal transcriptional pattern of MT in parallel with several detoxification genes: superoxide dismutase (SOD), catalase (CAT), glutathione S-transferases (GST) and glutathione peroxidases (GPx), in the digestive gland and the gills of this bivalve during a 1-year period. We identified a C. fluminea MT complete cDNA sequence using RT-PCR and RACE-PCR. The amino acid sequence deduced from the coding sequence encodes for a protein of 73 amino acids containing 21 cysteine residues. This protein exhibits high identities and similarities with the MT sequences of numerous bivalves. MT, SOD, CAT, pi-GST and Se-GPx expression patterns did not exhibit major seasonal variations. A slight increase of MT was observed in July. Therefore, the mRNA expression of these five genes could be used as biomarkers for monitoring studies.

Translational responses of Mytilus galloprovincialis to environmental pollution: integrating the responses to oxidative stress and other biomarker responses into a general stress index

Heavy metals are commonly associated with the generation of reactive oxygen species (ROS), which may cause oxidative damage to several cellular macromolecules and organelles. In an attempt to correlate biomarker responses to oxidative stress, caged mussels (Mytilus galloprovincialis) were exposed for 30 days in a relatively clean site and two areas (Stations 1 and 2) unevenly polluted by heavy metals in Gulf of Patras (Greece). Three periods of caging were: one in winter, the second in spring, and the third in autumn. Heavy metal content was determined in digestive glands of the exposed mussels as a measure of metal pollution, metallothionein content as an adaptive and detoxifying index, lysosomal membrane stability as a biomarker of general stress, superoxide radical production and lipid peroxidation as indicators of oxidative stress, and micronucleus frequency in gill cells as an index of chromosomal damage. Considering that protein-synthesizing machinery is one of the candidate targets for ROS, the in vivo activity of ribosomes in digestive glands was also tested. Compared with the reference samples, mussels transplanted to Station 1 showed increased levels of heavy metals and metallothionein in digestive glands, lower lysosomal membrane stability, higher values in oxidative stress indices, reduced activity of ribosomes, and increased chromosomal damage in gill cells. In addition, run-off ribosomes isolated from mussels transplanted to Station 1 were less efficient at initiating protein synthesis in a cell-free system than those from mussels in the reference site. Mussels transplanted to Station 2 exhibited similar but less pronounced responses. Statistical analysis revealed a strong positive correlation of ribosomal activity with lysosomal membrane stability, as well as a significant negative correlation with the oxidative stress indices, metallothionein content, micronucleus frequency, and the digestive gland content in Cr, Cu and Mn. Integration of all the measured biomarker responses into one general "stress index" demonstrated a clear distinction between the sampling sites, allowing classification along a pollution gradient (reference site<Station 2<Station 1), independently from the season. Moreover, this analysis allowed us to compare responses between sampling campaigns and showed that the biomarker responses show best integration in winter. It was also evident that climatic or metabolic changes could modulate bioavailability of pollutants and priming of cellular defence processes.

Effects of salinity and temperature on the expression of enzymatic biomarkers in Eurytemora affinis (Calanoida, Copepoda)

In order to establish effective enzymatic biomarkers that could provide in situ early warning of contaminant exposure in estuarine ecosystems, the potential effects of the principal abiotic factors (temperature and salinity) were investigated on common biomarkers, the acetylcholinesterase (AChE) and the glutathione S-transferase (GST) in Eurytemora affinis. Short term salinity stress effects simulated during an experimental tide indicated that enzymatic activities of this species are characterized by maximum expression related to an optimal salinity range (between 5 and 15 psu). Moreover, longer time exposure to various salinity tanks confirmed the effects of this factor on both AChE and GST activities. Therefore, optimal AChE activity was measured at 10 psu, while optimal GST activity was measured at 5 psu. Furthermore, significant effects of temperature were also recorded, particularly for AChE expression (slight effects were measured on GST expression) with an optimal condition at 11 degrees C. These experiments indicated a more pronounced effect of salinity over temperature especially on the AChE expression and confirmed the need to standardize sampling procedures in relation with environmental parameters for biomonitoring studies based on enzymatic analyses.

Development of mussel mRNA profiling: Can gene expression trends reveal coastal water pollution?

Marine bivalves of the genus Mytilus are intertidal filter-feeders commonly used as biosensors of coastal pollution. Mussels adjust their functions to ordinary environmental changes, e.g. temperature fluctuations and emersion-related hypoxia, and react to various contaminants, accumulated from the surrounding water and defining a potential health risk for sea-food consumers. Despite the increasing use of mussels in environmental monitoring, their genome and gene functions are largely unexplored. Hence, we started the systematic identification of expressed sequence tags and prepared a cDNA microarray of Mytilus galloprovincialis including 1714 mussel probes (76% singletons, approximately 50% putatively identified transcripts) plus unrelated controls. To assess the potential use of the gene set represented in MytArray 1.0, we tested different tissues and groups of mussels. The resulting data highlighted the transcriptional specificity of the mussel tissues. Further testing of the most responsive digestive gland allowed correct classification of mussels treated with mixtures of heavy metals or organic contaminants (expression changes of specific genes discriminated the two pollutant cocktails). Similar analyses made a distinction possible between mussels living in the Venice lagoon (Italy) at the petrochemical district and mussels close to the open sea. The suggestive presence of gene markers tracing organic contaminants more than heavy metals in mussels from the industrial district is consistent with reported trends of chemical contamination. Further study is necessary in order to understand how much gene expression profiles can disclose the signatures of pollutants in mussel cells and tissues. Nevertheless, the gene expression patterns described in this paper support a wider characterization of the mussel transcriptome and point to the development of novel environmental metrics.

Evidence of an altered protective effect of metallothioneins after cadmium exposure in the digenean parasite-infected cockle (Cerastoderma edule)

The aim of the present study was to analyse the relation between parasitism and subsequent metallothioneins (MT) in the case of metal contamination. Experimental exposure of parasitized and unparasitized cockles (Cerastoderma edule) to cadmium (Cd) was performed, with the cockle as first or second intermediate host of 2 digenean species. After 7 days of Cd exposure in microcosms, cockles infected as first intermediate host byLabratrema minimusexhibited metal concentrations in tissues double that in uninfected cockles. Jointly, MT concentrations of parasitized cockles were not modified in comparison with uninfected individuals in which concentrations were increased 4·3-fold compared with controls. In cockles experimentally infected as the second intermediate host byHimasthla elongata, cadmium concentrations significantly increased again in parasitized cockles compared with uninfected individuals in contaminated conditions. Simultaneously, MT concentrations in healthy cockles increased, whereas they significantly decreased in parasitized individuals. Therefore, the presence of digenean parasites in Cd-exposed cockles leads to a maintenance or a decrease in MT concentrations compared with healthy individuals, whereas Cd accumulation in tissues is significantly increased. These experiments indicate a significant alteration of the protective effect of metallothioneins towards metals which could consequently enhance cockle vulnerability. Moreover, these results highlight the limit of the use of MT as a biomarker of metal pollution in field monitoring if parasitism is not taken into account.

Molecular Biomarkers: their significance and application in marine pollution monitoring

This paper presents an overview of the significance of the use of molecular biomarkers as diagnostic and prognostic tools for marine pollution monitoring. In order to assess the impact of highly persistent pollutants such as polychlorinated biphenyls (PCB), polychlorinated dibenzo-dioxins (PCDD), polychlorinated dibenzo-furans (PCDF), polynuclear aromatic hydrocarbons (PAH), tributyltin (TBT) and other toxic metals on the marine ecosystem a suite of biomarkers are being extensively used worldwide. Among the various types of biomarkers, the following have received special attention: cytochrome P4501A induction, DNA integrity, acetylcholinesterase activity and metallothionein induction. These biomarkers are being used to evaluate exposure of various species of sentinel marine organisms (e.g. mussels, clams, oysters, snails, fishes, etc.) to and the effect of various contaminants (organic xenobiotics and metals) using different molecular approaches [biochemical assays, enzyme linked immuno-sorbent assays (ELISA), spectrophotometric, fluorometric measurement, differential pulsed polarography, liquid chromatography, atomic absorption spectrometry]. The induction of the biotransformation enzyme, cytochrome P4501A in fishes (Callionymus lyra, Limanda limanda, Serranus sp., Mullus barbatus) and mussels (Dreissena polymorpha) by various xenobiotic contaminants such as PCBs, PAHs, PCDs is used as a biomarker of exposure to such organic pollutants. The induction of cytochrome P4501A is involved in chemical carcinogenesis through catalysis of the covalent bonding of organic contaminants to a DNA strand leading to formation of DNA adduct. Measurement of the induction of cytochrome P4501A in terms of EROD (7-ethoxy resorufin O-deethylase) activity is successfully used as a potential biomarker of exposure to xenobiotic contaminants in marine pollution monitoring. In order to assess the impact of neurotoxic compounds on marine environment the evaluation of acetylcholinesterase activity in marine organisms is used as a biomarker of exposure to neurotoxic agents such as organophosphorus, carbamate pesticides etc. Metallothioneins (MTs) are induced by toxic metals such as Cd, Hg, and Cu by chelation through cysteine residues and are used in both vertebrates and invertebrates as a biomarker of metal exposure. The measurement of the levels of DNA integrity in marine organisms such as Sea stars (Asterias rubens) from the North Sea and the marine snails (Planaxis sulcatus) from the Arabian Sea along the Goa coast exposed to environmental xenobiotic contaminants clearly indicated the extent and the nature of pollution at the sampling sites along coastal environment.