Cellular physiological assessment of bivalves after chronic exposure to spilled Exxon Valdez crude oil using a novel molecular diagnostic biotechnology

Physiological Responses of the Bivalves Mytilus galloprovincialis and Ruditapes decussatus Following Exposure to Phenanthrene: Toxicokinetics, Dynamics and Biomarkers Study

The aim of the current study was to assess the multifaceted effects of the polycylic aromatic hydrocarbon phenanthrene, mainly used in the colouring, explosive, and pharmaceutical industries, on the physiology of two bivalve species with economic value as seafood, namely, the Mediterranean mussel Mytilus galloprovincyalis and the European clam Ruditapes decussatus. The current study assessed how the phenanthrene affected several biomarkers and biometric endpoints in both bivalves, based on an in vivo experiment in silico approach. The bivalves were exposed during four time slots (i.e., 7, 15, 21, and 28 days) to two concentrations of phenanthrene in water (50 µg/L and 100 µg/L). For the clam R. decussatus, an additional contamination of sediment was applied due their typical benthic lifestyle (50 µg/kg and 100 µg/kg). The phenanthrene significantly reduced the ability of bivalves to tolerate desiccation and their Median Lethal Time, and also inhibited the activity of the enzyme acetylcholinesterase in a time-dependent manner. The activity of catalase indicated that bivalves also experienced oxidative stress during the first 21 days of the experiment. The significant decline in catalase activity observed during the last week of the experiment for the mussel M. galloprovincyalis supported a depletion of enzymes caused by the phenanthrene. The phenanthrene has also toxicokinetic and toxicodynamic properties, as assessed by the in silico approach. Overall, the results obtained suggest that the bivalves Ruditapes decussatus and M. galloprovincyalis can be used as a sentinel species in monitoring studies to assess the environmental impact of phenanthene in marine ecosystems. The significance of our findings is based on the fact that in ecotoxicology, little is known about the chronic effects, the simultaneous use of multiple species as bioindicators, and the interactions molecular modelling.

Assessment of the marine ecotoxic state in the Moroccan coastal area Anza-Taghazout following the installation of two wastewater treatment plants: a multibiomarker study using Mytilus galloprovincialis

The aim of the present study is the first to evaluate the ecotoxic state of the marine environment in Anza-Taghazout coasts (Morocco) after installation of two wastewater treatment plants using a natural population of marine bivalves Mytilus galloprovincialis. These coasts are exposed to many discharges generating, thus, different sources of pollutants. These pollutants can modulate the physiological responses of marine bivalves to environmental stress. In this context, a multibiomarker approach consisting of a battery of biomarker evaluation was used to assess the response of these species to stress. In the whole soft tissues of M. galloprovincialis, four biomarkers were evaluated as follows: acetylcholinesterase (AChE), glutathione S-transferase (GST), catalase (Cat), and malondialdehyde activity (MDA). In parallel, physico-chemical parameters were measured in the marine water of Anza-Taghazout within three selected sites: S₁ considered as "hotspot" located at Anza city; S₂ located near of Aourir city; and the third site, S₃ "reference" located in Imouran beach. Our results showed that activities of both glutathione S-transferase and catalase were higher in M. galloprovincialis collected from site S₁, but high values of malondialdehyde and acetylcholinesterase activities were observed successively at S₃ and S₂. Application of integrated biomarker response (IBR) index was suitable for classifying the stress response in the M. galloprovincialis but did not allow to evaluate the level of the xenobiotic exposure in the studied sites. The statistical results did not show any significant differences between the three studied sites, and therefore, S₁ has recently become clean due to the installation of two wastewater treatment plants.

Marine health of the Arabian Gulf: Drivers of pollution and assessment approaches focusing on desalination activities

The Arabian Gulf is one of the most adversely affected marine environments worldwide, which results from combined pollution drivers including climate change, oil and gas activities, and coastal anthropogenic disturbances. Desalination activities are one of the major marine pollution drivers regionally and internationally. Arabian Gulf countries represent a hotspot of desalination activities as they are responsible for nearly 50% of the global desalination capacity. Building desalination plants, up-taking seawater, and discharging untreated brine back into the sea adversely affects the biodiversity of the marine ecosystems. The present review attempted to reveal the potential negative effects of desalination plants on the Gulf's marine environments. We emphasised different conventional and innovative assessment tools used to assess the health of marine environments and evaluate the damage exerted by desalination activity in the Gulf. Finally, we suggested effective management approaches to tackle the issue including the significance of national regulations and regional cooperation.

Stress responses to warming in the mussel Brachidontes rodriguezii (d'Orbigny, 1842) from different environmental scenarios

The intertidal mussel B. rodriguezii is a representative species from hard bottom substrates where both anthropogenic and natural stressors are present. Pre-exposure to these different stressors can modify the tolerance to additional stressors such as warming. Moreover, this tolerance can vary depending on intraspecific variables such as the organism's sex. The effects of warming and its intraspecific variability in representative coastal species are crucial to understanding the tolerance to future environmental scenarios. The mussels were collected in different environmental scenarios, including low (Control), chemical (Harbour) and natural stressed (Estuary) sites, and then exposed to different water temperatures (10-30 °C) for 14 days. Lethal and sublethal responses were evaluated in different mussel populations. Thus, cumulative death rate, air survival time, heat shock proteins (HSC70/HSP70), total ubiquitin, catalase (CAT), glutathione-s-transferase (GST) and lipid peroxidation (TBARS) were assessed in mussels from different areas and different sexes. The results revealed diminished air survival time and high cumulative mortality rate in mussels collected at the harbour and those exposed to higher temperatures, respectively. The sublethal responses of the field animals showed different patterns according to the different areas investigated. Besides, the results revealed that these differences were also observed between sexes. Regarding the sublethal responses in mussels exposed to warming, the interactive effects of temperature and sites showed a strong influence on all biochemical parameters analyzed (p < 0.001). Therefore, harbour mussels showed a distinct pattern compared to other locations and reflecting the most damaging effects of warming. The influence of sex and its interactions with warming were also crucial in most of the sublethal responses (p < 0.05). Multivariate analysis was performed with all sublethal responses, and the different warming scenarios showed different groups according to the sites. In the predicted warming scenarios, males showed no differences between sites. In contrast to males, females showed differences between sites in the predicted and the worse-case warming scenarios. Our results highlight the importance of compensatory mechanisms in the mussel warming tolerance like HSP70. The influence of sex is also crucial in understanding warming tolerance in mussels chronically exposed to pollutants in their natural environment. Also, lethal endpoints are essential for understanding the non-reversibility signature of the observed biochemical responses.

The Potential Impact of Hydrocarbons on Mussels in Port au Port Bay, Newfoundland

Since 2012, the scallop fishery in Port au Port Bay, Newfoundland, Canada has experienced a drastic decline, while no decline was observed in adjacent St. George's Bay. Local fishermen have raised concerns about an abandoned oil exploration well in the Port au Port Bay. This study investigated the potential impact of petroleum hydrocarbons on sediments and blue mussels [Mytilus edulis] (a proxy organism for scallops) in the area. Sediments from both bays were characterized for their hydrocarbons and compared to potential petroleum hydrocarbon sources. Mussels were analysed for health indices and their ¹⁴C content. The results showed that the concentration of hydrocarbons found in the sediments of the fishing ground was within the range of unpolluted marine sediments and that the hydrocarbons present were likely from a mixture of sources. The health indices of the mussels in Port au Port Bay were similar to the health indices of mussels in St. George's Bay and the ¹⁴C content of the mussels from both bays was modern. These data suggest that the Port au Port fishing ground was not solely contaminated from crude oil leaking from an oil exploration well, that the mussels were not contaminated with petroleum hydrocarbons, and that Port au Port mussels were just as healthy as the mussels of St. George's Bay. Therefore, whatever caused the scallop decline was most likely scallop- and bay-specific. During this study a fast and efficient method for extracting petroleum hydrocarbons from sediment using accelerated solvent extraction with integrated silica gel was developed.

Bioinspired Peptide-Coated Superhydrophilic Poly(vinylidene fluoride) Membrane for Oil/Water Emulsion Separation

Polyvinylidene fluoride (PVDF) membranes are limited in the field of oil-in-water emulsion treatment because the intrinsic hydrophobicity of PVDF can cause serious membrane fouling. Here, a superhydrophilic PVDF membrane (PVDF@PDA-GSH) was fabricated using a facile, versatile, mussel-inspired method. The pristine PVDF membrane was coated with dopamine under mild alkaline conditions by a dip-coating method, followed by addition of glutathione (GSH) via a simple reaction. GSH was successfully coated onto the membrane surface and confirmed by X-ray photoelectron spectroscopy and energy dispersive X-ray spectrometry. Hierarchical surface structure and superhydrophilicity were examined by scanning electron microscopy and contact angle, respectively, giving the PVDF@PDA-GSH membrane excellent wettability and antifouling ability. The water flux of PVDF@PDA-GSH was several-fold higher than conventional filtration membranes, and the oil rejection ratio was nearly 99%. The PVDF@PDA-GSH membrane also showed favorable reusability because the flux recovery ratio (FRR) remained above 90% after five cycles. In general, these results indicated that this modification might provide a good method for the fabrication of superhydrophilic PVDF membranes with good prospects for water filtration applications.

Evaluation of toxicity of Deepwater Horizon slick oil on spat of the oyster Crassostrea virginica

The 2010 explosion of the Deepwater Horizon (DWH) oil rig generated the largest marine oil spill in US history with millions of barrels of crude oil released in the Gulf of Mexico (GoM). The eastern oyster, Crassostrea virginica, is an ecologically and economically important species in the northern GoM. Due to its biological characteristics (sessile, filter feeding), juvenile oysters may have been affected. This study investigated the effects of surface-collected DWH oil prepared as high-energy water-accommodated fraction (HEWAF) on the survival of 2-month-old oyster spat, and evaluated the potential impacts of HEWAF on particle clearance rate and spat tissue. Exposure of oysters to a range of oil/HEWAF (0-7-66-147-908-3450 μg tPAH50 (sum of 50 polycyclic aromatic hydrocarbons) L^-1) resulted in non-dose-dependent mortalities and reduced clearance rates of algal food (Tisochrysis lutea). A morphometric study of the digestive tubules (DGTs) indicated a dose-dependent response to oil exposure on lumen dilation, on epithelium thinning of the DGT, and a significant change in DGT synchrony (LOEC = 66 μg tPAH50 L^-1). This finding suggests that structural changes occurred in the digestive gland of exposed oysters most likely due to an oil-related stress. In addition, histological observations showed that tissues in contact with HEWAF (gills, palp, connective tissue, digestive gland) were adversely impacted at ≥ 7 μg tPAH50 L^-1, and exhibited pathological symptoms typical of an inflammatory response (e.g., hemocyte diapedesis and infiltration, syncytia, epithelium sloughing).

Sensitivity of eastern oyster (Crassostrea virginica) spermatozoa and oocytes to dispersed oil: Cellular responses and impacts on fertilization and embryogenesis

The 2010 Deepwater Horizon (DWH) oil spill released millions of barrels of oil and dispersant into the Gulf of Mexico. The timing of the spill coincided with the spawning season of Crassostrea virginica. Consequently, gametes released in the water were likely exposed to oil and dispersant. This study aimed to (i) evaluate the cellular effects of acute exposure of spermatozoa and oocytes to surface slick oil, dispersed mechanically (HEWAF) and chemically (CEWAF), using flow-cytometric (FCM) analyses, and (ii) determine whether the observed cellular effects relate to impairments of fertilization and embryogenesis of gametes exposed to the same concentrations of CEWAF and HEWAF. Following a 30-min exposure, the number of spermatozoa and their viability were reduced due to a physical action of oil droplets (HEWAF) and a toxic action of CEWAF respectively. Additionally, reactive oxygen species (ROS) production in exposed oocytes tended to increase with increasing oil concentrations suggesting that exposure to dispersed oil resulted in an oxidative stress. The decrease in fertilization success (1-h), larval survival (24-h) and increase in abnormalities (6-h and 24-h) may be partly related to altered cellular characteristics. FCM assays are a good predictor of sublethal effects especially on fertilization success. These data suggest that oil/dispersant are cytotoxic to gametes, which may affect negatively the reproduction success and early development of oysters.

Intoxication and biochemical responses of freshwater snail Bellamya aeruginosa to ethylbenzene

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

Status of intertidal infaunal communities following the Exxon Valdez oil spill in Prince William Sound, Alaska

Intertidal infaunal communities were sampled in Prince William Sound, Alaska from 1990-2000 to evaluate impacts and recovery from the Exxon Valdez oil spill. Initial findings suggested that the spill and cleanup depressed abundances of all taxonomic groups. By 1992, abundances of major taxonomic categories at disturbed sites had either converged or paralleled populations at Unoiled sites. Abundances of littleneck clams, Leukoma (Protothaca) staminea, slowly increased at Treated sites and converged with Unoiled sites by 2000. Infaunal population differences positively correlated with fine-grained sediments at Treated sites. We believe that sediment fines removal during cleanup, and subsequent slow natural replenishment, impeded the return of the environment to pre-spill conditions. This suggests physical recovery of spill-affected beaches is an important precursor to biological recovery.

Responses of oxidative stress biomarkers and DNA damage on a freshwater snail (Bellamya aeruginosa) stressed by ethylbenzene

Ethylbenzene is classified as a priority pollutant; however, toxicity data, especially those regarding sublethal toxicity, are rarely reported on gastropods. The present work was performed to elucidate the sublethal effects of ethylbenzene using a freshwater snail, Bellamya aeruginosa (Reeve), exposed to ethylbenzene for 21 days followed by a 17-day recovery period. Superoxide dismutase (SOD), catalase (CAT), glutathione S-transferase (GST), reduced glutathione (GSH), and malonyldialdehyde (MDA) were used as biomarkers to evaluate oxidative stress in hepatopancreas of snails. In addition, alkaline comet assay was applied to determine the genotoxicity of ethylbenzene in hepatopancreas of snails. These biomarkers and DNA damage exhibited various responses to ethylbenzene in the tested snails. SOD and CAT activities were almost significantly stimulated during the exposure period. As exposure time was prolonged beyond 7 days, CAT activity gradually became significantly increased at higher doses of ethylbenzene. GSH concentration was positively and linearly related with exposure dose. MDA concentration was significantly greater than that in the control only under the lowest treatment after a 7-day exposure. Alkaline comet assay showed that ethylbenzene could significantly induce DNA damage in hepatopancreas of snails, and there was a good dose- and time-response in DNA damage, indicating potential genotoxicity of ethylbenzene on snails. At the end of the recovery period, the repair of DNA damage was not yet completed, showing that DNA repair requires more time. The findings from this study could indicate that SOD, GST, and GSH seem to be effective oxidative biomarkers for snails exposed to ethylbenzene in the short term. CAT proved to be a valuable discriminating biomarker in subchronic exposure to ethylbenzene, but MDA was not a suitable oxidative biomarker for exposure to ethylbenzene in either the short or long term. Alkaline comet assay was efficient tool with which to evaluate the potential genotoxicity of ethylbenzene.

Sodium arsenite and cadmium chloride induction of proteasomal inhibition and HSP accumulation in Xenopus laevis A6 kidney epithelial cells

Sodium arsenite (NA) and cadmium chloride (CdCl(2)) are relatively abundant environmental toxicants that have multiple toxic effects including carcinogenesis, dysfunction of gene regulation and DNA and protein damage. In the present study, treatment of Xenopus laevis A6 kidney epithelial cells with concentrations of NA (20-30 μM) or CdCl(2) (100-200 μM) that induced HSP30 and HSP70 accumulation also produced an increase in the relative levels of ubiquitinated protein. Actin protein levels were unchanged in these experiments. In time course experiments, the levels of ubiquitinated protein and HSPs increased over a 24h exposure to NA or CdCl(2). Furthermore, treatment of cells with NA or CdCl(2) reduced the relative levels of proteasome chymotrypsin (CT)-like activity compared to control. Interestingly, pretreatment of cells with the HSP accumulation inhibitor, KNK437, prior to NA or CdCl(2) exposure decreased the relative levels of ubiquitinated protein as well as HSP30 and HSP70. A similar finding was made with ubiquitinated protein induced by proteasomal inhibitors, MG132 and celastrol, known to induce HSP accumulation in A6 cells. However, the NA- or CdCl(2)-induced decrease in proteasome CT-like activity was not altered by KNK437 pretreatment. This study has shown for the first time in poikilothermic vertebrates that NA and CdCl(2) can inhibit proteasomal activity and that there is a possible association between HSP accumulation and the mechanism of protein ubiquitination.

A survey of environmental pollutants and cellular-stress markers of Porites astreoides at six sites in St. John, U.S. Virgin Islands

Coral communities along the coast of St. John, U.S. Virgin Islands have exhibited site-specific behavior in declines. In order to determine if these specific coral communities are stressed and whether a pollutant or environmental factor present at this site is a probable stressor, we surveyed six near-shore coral communities in St. John, USVI for environmental pollutants and to determine the cellular physiological condition of the coral, Porites astreoides. The six sites within St. John are Cruz Bay, Caneel Bay, Hawksnest Bay, Trunk Bay, Tektite Reef in Beehive Bay, and Red Point. Red Point was considered the reference site because of its abundance and diversity of species, and it was the furthest removed from down-stream and down-current anthropogenic activities. All sites showed distinct cellular-stress marker patterns, indicating that the physiological condition of each population was different. Populations at Cruz, Hawksnest, Trunk, and Tektite were stressed, as indicated by high levels of DNA lesions and expression of stress proteins. Hawksnest and Tektite were contaminated with polyaromatic hydrocarbons (PAHs), while Cruz was contaminated with semi-volatile organochlorines and nitrogen-based biocides. At least for Hawksnest and Tektite, stress-marker patterns were consistent with an exposure to PAHs. Fecal coliform levels were high in Cruz and Trunk, indicating fecal contamination, as well as consideration for management action. Results from this study serve as a justification for a more thorough and methodical investigation into the stressors responsible for declines of coral populations within St. John. Furthermore, this study supports the argument for the importance of local factors contributing to regional coral reef declines; that not all forces impacting coral are global.

Use of three bivalve species for biomonitoring a polluted estuarine environment

Estuaries are marine areas at great contamination risk due to their hydrodynamic features. PAH are wide and ubiquitous contaminants with a high presence in these marine environments. Chemical analysis of sediments can provide information, although it does not give a direct measure of the toxicological effect of such contaminants in the biota. Samples of Venerupis pullastra, Cerastoderma edule, and Mytilus galloprovincialis were collected from two locations in Corcubión estuary (Norhwest of Spain). The level of PAH in sediment and biota, and its possible origin were assessed. A moderate level of contamination was observed with a predominance of PAH of a pyrogenic origin. Genotoxic damage, measured as single-strand DNA breaks with the comet assay, was evaluated in gill tissue and in hemolymph. The values of DNA damage obtained showed a higher sensitivity of clams and cockles to the pollution load level. These differences among species make us suggest the use of some other species coupled with mussels as an optimal tool for biomonitoring estuarine environments.

Comparison between two bivalve species as tools for the assessment of pollution levels in an estuarian environment

Estuaries are semi-enclosed marine areas with water short residence times. Estuary ecosystems show a higher susceptibility to contamination, as historically these sites are linked to urban and industrial development. Polycyclic aromatic hydrocarbons (PAH) are ubiquitous contaminants present in high quantities in these marine environments. Chemical analyses of sediments provides information regarding PAH pollution levels but not a direct measure of the toxicological effects attributed to these contaminants. Samples of sediments and of two bivalve species, Cerastoderma edule and Mytilus galloprovincialis, were collected from two locations (Corcubión and A Concha) in an estuary from northwestern Spain. The PAH levels in sediment and bivalve species and possible sources were determined. A moderate level and a low level of pyrogenic PAH contamination were observed in Corcubión and in A Concha, respectively. Genotoxic damage was evaluated in gills and hemocytes from mussels and cockles by means of the comet assay. DNA damage measured as DNAt values showed a reliable relationship with pollution load levels of the two sampling sites. The higher sensitivity of C. edule compared to M. galloprovincialis enables one to recommend including another species coupled with mussels for biomonitoring estuarine environments.

Single and combined effects of hypoxia and contaminated sediments on the amphipod Monoporeia affinis in laboratory toxicity bioassays based on multiple biomarkers

In estuaries, hypoxic conditions and pollution are among the major factors responsible for the declines in habitat quality, yet little is known about their combined effects on estuarine organisms. In this study, to investigate single and combined effects of hypoxia and contaminated sediment, the Baltic amphipod Monoporeia affinis was exposed for 5-9 days to four different combinations of oxygen conditions (moderate hypoxia vs. normoxia) and contamination (polluted vs. unpolluted sediments) at environmentally realistic levels. To detect oxidative stress, a suite of biomarkers was used - antioxidant enzymes [superoxide dismutases (SOD), catalase (CAT), and glutathione S-transferases (GST)], acetylcholinesterase (AChE), lipid peroxidation status (TBARS concentration), protein carbonyl content (PCC), and DNA strand breakage (DNA-SB). To assay effects at the organism level, we used RNA:DNA ratio as a proxy for growth and metabolic rate and mortality. There were significant increases in CAT and SOD activities and TBARS levels in response to both moderate hypoxia and contaminated sediment, while GST increased and AChE decreased in response to the contamination only. Significant positive correlations were observed among the antioxidant enzymes and between the enzyme activities and TBARS concentration, suggesting a complex response to the oxidative stress. No significant changes in PCC were recorded in any of the treatments. Furthermore, the negative effect of hypoxia on DNA integrity was significant; with frequency of DNA-SB increasing in animals exposed to hypoxia in contaminated sediment. Despite clear effect at the cellular and biochemical levels, no responses at the organism level were observed. Multivariate analyses of the dataset have allowed us to link exposure factors to individual biomarker responses. Of the potential biomarkers assessed in this study, CAT activity was found to be associated with hypoxia, while SOD, GST and AChE activities appear to predict best the effects of exposure to sediments containing several contaminants (e.g. heavy metals, PCBs and PAHs), and TBARS concentration is particularly indicative of combined effects of hypoxia and contamination. In addition to providing new knowledge on the combined effects of multiple stressors on estuarine organisms, the findings of the present study are also important to understand data from biomonitoring studies in the Baltic Sea and in other regions where multiple stress factors co-occur.

Assessment of cellular and functional biomarkers in bivalves exposed to ecologically relevant abiotic stressors

An understanding of the complex effects of the environment on biomarkers of bivalve health is essential for aquaculturists to successfully select field culture sites and monitor bivalve health in these sites and in hatcheries. We tested several whole-organism (functional) and cellular-level biomarkers as indicators of health of the cultured, stress-tolerant northern quahog (hard clam) Mercenaria mercenaria. We performed single- and dual-stressor experiments that were consistent with available water quality data from a clam culture area on the Gulf coast of Florida. Clams from the culture area were exposed over a 14-d period to low O2 (hypoxia), elevated temperature, hyposalinity, and a combination of elevated temperature and hyposalinity. There was no clear relationship between the functional and cellular-level biomarkers, with most of the treatment effects being detected at the whole-organism level but not the cellular level. Survival and burial ability were significantly affected by elevated temperature and by the combination of elevated temperature and hyposalinity. Glycogen content decreased over the experiment duration and did not differ significantly among treatments. There were no significant changes in expression patterns of eight stress proteins or in the levels of oxidatively damaged RNA. The results highlight the importance of investigating the effects of multiple stressors in short-term, controlled laboratory conditions and suggest that such cellular-level biomarker assays should be paired with functional biomarkers to better understand the responses of highly stress-tolerant species.

Alterations in glutathione reductase, superoxide dismutase, and lipid peroxidation of tadpoles (Xenopus laevis) exposed to Bonny Light crude oil and its fractions

We determined the effects of sub-lethal levels of Bonny Light crude oil (WC) and its water soluble (WSF) and insoluble (WIF) fractions on malondialdehyde (MDA) and stress enzymes in tadpoles (Xenopus laevis) following two and 4 weeks exposure at different concentrations. We observed that the treatment of tadpoles with WC, WSF, or WIF decreased the weight of tadpoles, increased MDA levels, and increased superoxide dismutase (SOD) and glutathione reductase (GR) at lower concentrations of exposure and decreased the enzymes at higher doses of exposure. We found that the WC had a lesser negative effect on the parameters of tadpoles compared to the WSF. Longer exposure of tadpoles to WC, WSF, or WIF even at lower concentrations resulted in a negative effect on MDA, SOD, and GR activities The study shows that sub-lethal contaminations with WC, WSF, or WIF induces membrane lipid peroxidation and reduce the ability of tadpoles to produce SOD and GR which may have metabolic costs.

Induction of DNA strand breaks in the mussel (Mytilus trossulus) and clam (Protothaca staminea) following chronic field exposure to polycyclic aromatic hydrocarbons from the Exxon Valdez spill

In 2002, 13 years after the Exxon Valdez spill, mussels and clams were examined for lingering oil exposure and damage. Known oil patches were sampled at four locations, and compared to nearby reference areas (same bay), and were also compared to "hot reference" sites to verify the methods used (Cordova harbor and fresh diesel spill at Port Chalmers). Passive samplers deployed for a month at the sites, along with tissue samples, confirmed that the oiled sites were oiled (fingerprinting back to Exxon Valdez oil) and that reference sites were clean. The highest PAH loads were detected in sub-surface interstitial waters at oiled sites. Exposure at the surface was generally low level, and probably intermittent. DNA damage was assessed in blood cells using sensitive comet analyses. DNA strand breakage was detected in both mussels and clams, with the highest level of damage detected at "hot reference" sites of Cordova harbor and Port Chalmers. Bioavailability and DNA damage at the oiled sties was low, indicating there has been substantial progress in recovery from the spill 13 years before, yet low level bioavailability and damage were still detectable.

Assessment of in vivo effects of the prestige fuel oil spill on the mediterranean mussel immune system

A laboratory experiment was carried out to study immune function alteration of the mussel Mytilus galloprovincialis when exposed to the Prestige oil spilled in November 2002 on the northwestern Spanish coast. Mussels were maintained for 4 months in tanks with flowing seawater and with 1, 2, and 0 kg (controls) Prestige fuel oil. Polycyclic aromatic hydrocarbon concentrations, which were determined in gills and digestive glands, were higher in digestive glands. The methylphenantrene and dibenzothiophene profiles confirmed the real exposure of mussels to the fuel oil. Immune data analysis revealed that no differences between fuel-treated and control animals were found in the cellular immune parameters measured (hemocyte viability, phagocytic activity, nitric oxide production, and chemiluminescence emission). In addition, histologic observations did not reveal tissue lesions in any of the samples, probably because of the short time of fuel-oil exposure. In contrast, significant differences were found in serum protein concentration and lysozyme activity between the fuel-treated mussels and controls. However, these humoral immune parameters were dependant on numerous environmental and physiologic factors, so it was difficult to ascertain the real effect of the fuel oil on their variability. Because hemocytes are the primary line of defense of bivalve mollusks, the results obtained in the present study suggest that the mussel immune system was not significantly affected by exposure to the Prestige fuel oil.

Redox proteomics in the blue mussel Mytilus edulis: carbonylation is not a pre-requisite for ubiquitination in acute free radical-mediated oxidative stress

Mytilus edulis was exposed under controlled conditions to a panel of model pro-oxidants (H(2)O(2), CdCl(2) and menadione) for 24h. Protein extracts of gill, mantle and digestive gland were analysed by immunoblotting in sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) separations. Immunoblotting revealed extensive and comparable levels of protein carbonylation across the pro-oxidant panel with approximately 1.5-fold higher levels in gill than digestive gland. Ubiquitination in gill was modest in response to H(2)O(2), but increased in response to menadione and CdCl(2). High ubiquitination levels were found for all pro-oxidants in digestive gland with levels comparable to the highest found in gill. Two-dimensional (2D) SDS-PAGE confirmed specific targeting of individual proteins by ubiquitin against a generally stable protein expression signature. Spot matching suggested that carbonylation is not a pre-requisite for ubiquitination. While gill showed consistently higher constitutive levels of glutathione transferase, glucose 6-phosphate dehydrogenase and glutathione reductase activity, pro-oxidant treatment had only modest effect on these enzymes and on the ratio of reduced/oxidised glutathione. In digestive gland, this latter ratio was higher than in gill and increased in response to menadione and CdCl(2). Ubiquitination may provide a marker for acute onset of oxidative stress in bivalves.

Increased expression of stress proteins in the surf clam Donax variabilis following hydrogen sulfide exposure

Endogenous free radical production and resulting oxidative damage may result from exposure to hypoxia, hyperoxia, or hydrogen sulfide. Previous investigations of sulfide-induced oxidative damage have produced conflicting results, perhaps because these studies utilized species presumably adapted to sulfide. We examined the effects of sulfide, hypoxia and hyperoxia on the surf clam Donax variabilis to test whether these stressors induce a cellular response to oxidative stress. These clams inhabit high-energy sandy beaches and are unlikely to have specific adaptations to these stressors. In duplicate flow-through experiments performed in fall and spring, clams were exposed to normoxia (22 kPa P(O(2))), hypoxia (10 kPa), hyperoxia (37 kPa), or sulfide with normoxia ( approximately 100 mumol L(-1), 22 kPa respectively) for 24 h. We quantified whole-animal expression of three antioxidants (Cu/Zn and Mn superoxide dismutases, glutathione peroxidase), a lipid peroxidation marker (4-hydroxy-2E-nonenol-adducted protein), a DNA repair enzyme (OGG1-m), four heat shock proteins (small Hsp, Hsp60, Hsp70, and mitochondrial Hsp70), ubiquitin, and actin. Clams exposed to sulfide showed upregulation of the greatest number of stress proteins and the pattern was consistent with a cellular response to oxidative stress. Furthermore, there was a marked seasonality, with greater stress protein expression in clams from the spring.

Bioindicators in monitoring long term genotoxic impact of oil spill: Haven case study

The evaluation of long term impact and risk of oil spill is a complex process involving chemical analyses and development of the ecosystem-based toxicology. An integrated biomarker approach using different bioindicators, mussels, oysters and fish with different feeding habits was applied to evaluate the long term risk from Haven oil spill along the Ligurian coast (Italy). Mussels were caged for a period of 4 weeks and fish were caught in the impacted and reference area. Caged oysters were also analyzed in different area of the wreck. DNA damage and micronuclei (MN) frequency were evaluated in gill cells of bivalves. DNA single strand breaks were measured in hepatocytes and MN were measured in fish erythrocytes. The results revealed an increase in MN frequency (more than 10 times the level at the reference site) in caged mussels from Arenzano compared to the reference area after an interval of 4 months from the accident. No increase in DNA damage and a significant increase in MN frequency were recorded in caged mussels (mean value 10.15 vs 5.3) and in benthic fish Mullus barbatus (2.5 vs 0.7) in a further sampling in 1998. Statistically significant increase of DNA damage and MN frequency was observed in caged oysters in different areas of the wreck in a biomonitoring carried out in 2001.

Evolutionary toxicology: population-level effects of chronic contaminant exposure on the marsh frogs (Rana ridibunda) of Azerbaijan

We used molecular methods and population genetic analyses to study the effects of chronic contaminant exposure in marsh frogs from Sumgayit, Azerbaijan. Marsh frogs inhabiting wetlands in Sumgayit are exposed to complex mixtures of chemical contaminants, including petroleum products, pesticides, heavy metals, and many other industrial chemicals. Previous results documented elevated estimates of genetic damage in marsh frogs from the two most heavily contaminated sites. Based on mitochondrial DNA (mtDNA) control region sequence data, the Sumgayit region has reduced levels of genetic diversity, likely due to environmental degradation. The Sumgayit region also acts as an ecological sink, with levels of gene flow into the region exceeding gene flow out of the region. Additionally, localized mtDNA heteroplasmy and diversity patterns suggest that one of the most severely contaminated sites in Sumgayit is acting as a source of new mutations resulting from an increased mutation rate. This study provides an integrated method for assessing the cumulative population impacts of chronic contaminant exposure by studying both population genetic and evolutionary effects.

Biomarkers in environmental and human health risk assessment

Marine pollution is a major threat to human and environmental health. Given the complexity of function of marine and coastal ecosystems, it is unlikely that a balanced view of the nature and extent of risk will easily be achieved if human and environmental risk assessments continue to be conducted in isolation. Here, the integration of assessment protocols is advocated as a holistic means of improving risk management. Biomarkers can provide the common conceptual framework and measurable endpoints necessary for successful integration. Examples are given of the ways in which suites of biomarkers encompassing molecular change, cellular pathology and physiological impairment can be developed and adapted for human and ecological scenarios. By placing a greater emphasis on the health status of impacted biota, it is more likely that risk assessment will develop the efficiency, reliability and predictive power to adapt to the unforeseen environmental threats that are an inevitable consequence of human development and global change.

The ECOMAN project: A novel approach to defining sustainable ecosystem function

The ECOMAN was initiated in 2001 by the University of Plymouth, UK, Plymouth Marine Laboratory and the Department of the Environment, Fisheries and Rural Affairs (DEFRA) to address the need for more pragmatic assessment techniques linking environmental degradation with its causes. The primary aim of the project was to develop an evidence-based approach in which suites of easy-to-use, cost-effective and environmentally valid biological responses (biomarkers) could be used together to assess the health of coastal systems through the general condition of individuals. A range of sub-lethal endpoints, chosen to reflect successive levels of biological organisation (molecular, cellular, physiological), was evaluated in common coastal organisms showing different feeding types (filter feeding, grazing, predation) and habitat requirements (estuary, rocky shore). Initially, the suite of biomarkers was used in laboratory studies to determine the relative sensitivities of key species within different functional groups to common contaminants. These results were then validated in field studies performed in a range of ecosystems exhibiting different degrees/signatures of contamination. Here, an example is provided of a field study in the Humber Estuary, UK, which illustrates how multivariate statistical analysis can be used to identify patterns of response to discriminate between contaminated and clean sites. The use of a holistic, integrated approach of this kind is advocated as a practical means of assessing the impact of chemical contamination on organismal health and of ranking the status of marine ecosystems.

Significance of cytochrome P450 system responses and levels of bile fluorescent aromatic compounds in marine wildlife following oil spills

The relationships among cytochrome P450 induction in marine wildlife species, levels of fluorescent aromatic compounds (FAC) in their bile, the chemical composition of the inducing compounds, the significance of the exposure pathway, and any resulting injury, as a consequence of exposure to crude oil following a spill, are reviewed. Fish collected after oil spills often show increases in cytochrome P450 system activity, cytochrome P4501A (CYP1A) and bile fluorescent aromatic compounds (FAC), that are correlated with exposure to polycyclic aromatic hydrocarbons (PAH) in the oil. There is also some evidence for increases in bile FAC and induction of cytochrome P450 in marine birds and mammals after oil spills. However, when observed, increases in these exposure indicators are transitory and generally decrease to background levels within one year after the exposure. Laboratory studies have shown induction of cytochrome P450 systems occurs after exposure of fish to crude oil in water, sediment or food. Most of the PAH found in crude oil (dominantly 2- and 3-ring PAH) are not strong inducers of cytochrome P450. Exposure to the 4-ring chrysenes or the photooxidized products of the PAH may account for the cytochrome P450 responses in fish collected from oil-spill sites. The contribution of non-spill background PAH, particularly combustion-derived (pyrogenic) PAH, to bile FAC and cytochrome P450 system responses can be confounding and needs to be considered when evaluating oil spill effects. The ubiquity of pyrogenic PAH makes it important to fully characterize all sources of PAH, including PAH from natural resources, e.g. retene, in oil spill studies. In addition, such parameters as species, sex, age, ambient temperature and season need to be taken into account. While increases in fish bile FAC and cytochrome P450 system responses, can together, be sensitive general indicators of PAH exposure after an oil spill, there is little unequivocal evidence to suggest a linkage to higher order biological effects, e.g. toxicity, lesions, reproductive failure.

Shifting the paradigm of coral-reef 'health' assessment

Coral reefs are in crisis. Globally, our reefs are degrading at an accelerating rate and present methodologies for coral-reef 'health' assessment, although providing important information in describing these global declines, have been unable to halt these declines. These assessments are usually employed with no clear purpose and using uncorrelated methods resulting in a failure to prevent or mitigate coral reef deterioration. If we are to ever successfully intervene, we must move beyond the current paradigm, where assessments and intervention decisions are based primarily on descriptive science and embrace a paradigm that promotes both descriptive and mechanistic science to recognize a problem, and recognize it before it becomes a crisis. The primary methodology in this alternative paradigm is analogous to the clinical and diagnostic methodologies of evidence-based medicine. Adopting this new paradigm can provide the evidence to target management actions on those stressors currently impacting reef ecosystems as well as providing a means for proactive management actions to avert irreversible habitat decline.

Cellular diagnostics and coral health: declining coral health in the Florida Keys

Coral reefs within the Florida Keys are disappearing at an alarming rate. Coral cover in the Florida Keys National Marine Sanctuary declined by 38% from 1996 to 2000. In 2000, populations of Montastraea annularis at four sites near Molasses Reef within the Florida Keys National Marine Sanctuary and one reef within Biscayne National Park were sampled on a quarterly basis. Anecdotal observations showed corals at Alina's Reef in Biscayne National Park appeared healthy in March, but experienced an acute loss of coral cover by August. Cellular Diagnostic analysis indicated that Alina's Reef corals were in distress: they had been afflicted with a severe oxidative damaging and protein-denaturing stress that affected both the corals and their symbiotic zooxanthellae. This condition was associated with a significant xenobiotic detoxification response in both species, reflecting probable chemical contaminant exposure. These results demonstrate that applying a Cellular Diagnostic approach can be effective in helping to identify stress and its underlying causes, providing diagnostic and prognostic biomarkers of coral health.

European Atlantic: the hottest oil spill hotspot worldwide

Oil spills caused by maritime transport of petroleum products are still an important source of ocean pollution, especially in main production areas and along major transport routes. We here provide a historical and geographic analysis of the major oil spills (>700 t) since 1960. Spills were recorded from several key marine ecosystems and marine biodiversity hotspots. The past four decades have been characterized by an overall decrease in the number of accidents and tones of oil spilled in the sea, but this trend was less distinct in the European Atlantic area. Recent black tides from the Erika and Prestige vessels provided new evidence for the high risk of accidents with serious ecological impact in this area, which according to our analysis is historically the most important oil spill hotspot worldwide. The English Channel and waters around Galicia in Spain were the areas with most accidents. Maritime transport in European Atlantic waters has been predicted to continue increasing. Together with our own results this suggests that, in addition to measures for increased traffic safety, deployment of emergency capacities in the spill hotspot areas may be crucial for a sustainable conservation of sea resources and ecosystems.

Evaluation of PAH bioaccumulation and DNA damage in mussels (Mytilus galloprovincialis) exposed to spilled Prestige crude oil

We analyzed the hydrocarbon composition of the Prestige oil as it reached the shores, its solubility in sea water, its bioaccumulation, and the genotoxic damage associated to oil exposure, using Mytilus galloprovincialis as sentinel organism. Mussels were exposed to two oil volumetric ratios (1:500 and 2:500) for 12 days. Great concentrations of total polycyclic aromatic hydrocarbons (TPAH) have been obtained, being in general higher in the samples from the dose of 1:500, both in sea water (55.14 vs. 41.96 microg/l) and mussel tissue (16,993.80 vs. 17,033.00 microg/kg), probably due to the great tendency of these compounds to link to particles in water. Comet assay results reflected an increase in the DNA damage associated to oil exposure, higher in the mussels exposed to the higher aqueous TPAH content. In the view of our results, the importance of the evaluation of biodisponibility, bioaccumulation and DNA damage in the assessment of the effects of xenobiotic pollutants to marine environments could be highlighted.

Bioavailability of PAHs: effects of soot carbon and PAH source

The bioavailability of 38 individual polycyclic aromatic hydrocarbon (PAH) compounds was determined through calculation of biota-sediment-accumulation factors (BSAF). BSAF values were calculated from individual PAH concentrations in freshwater mussel, marine clam, and sediment obtained from field and laboratory bioaccumulation studies. Sediment that was amended with different types of soot carbon (SC) was used in some of the bioaccumulation experiments. BSAF values for petrogenic PAH were greater than those for pyrogenic PAH (e.g., 1.57 +/- 0.53 vs 0.25 +/- 0.23, respectively), indicating that petrogenic PAH are more bioavailable than pyrogenic PAH (p < 0.05). This trend was consistent among marine and freshwater sites. Increased SC content of sediment resulted in a linear decrease in the bioavailability of pyrogenic PAHs (r2 = 0.85). The effect of increasing SC content on petrogenic PAH was negligible. SC was considered as an additional sorptive phase when calculating BSAF values, and using PAH-SC partition coefficients from the literature, we obtained unreasonably large BSAF values for all petrogenic PAH and some pyrogenic PAH. This led us to conclude that a quantitative model to assess bioavailability through a combination of organic carbon and soot carbon sorption is not applicable among field sites with a wide range of soot carbon fractions and PAH sources, at least given our current knowledge of PAH-SC partitioning. Our data offer evidence that many factors including analysis of a full suite of PAH analytes, PAH hydrophobicity, sediment organic carbon content, sediment soot carbon content, and PAH source are importantto adequately assess PAH bioavailability in the environment.

Differential sensitivity of three marine invertebrates to copper assessed using multiple biomarkers

Understanding how biomarkers relate to each other on exposure to particular contaminants in different species is key to their widespread application in environmental management. However, few studies have systematically used multiple biomarkers in more than a single species to determine the variability of sublethal effects of a particular contaminant. In this study, three marine invertebrates, the shore crab Carcinus maenas, the common limpet Patella vulgata and the blue mussel Mytilus edulis, were exposed over 7 days in the laboratory to environmentally realistic concentrations of the priority pollutant copper. A combination of molecular, cellular and physiological biomarkers was measured in each organism to detect the toxic effects of copper. Biomarkers included lysosomal stability (neutral red retention), neurotoxicity (acetylcholinesterase activity), metabolic impairment (total haemolymph protein), physiological status (heart rate) and induction of protective metallothionein proteins. P. vulgata was the most sensitive to copper with significant effects measured in all biomarkers at concentrations of 6.1 microg Cu l(-1). In C. maenas, cellular and neurotoxic endpoints were affected significantly only at 68.1 microg Cu l(-1). Exposure to copper also induced metallothionein production in crabs. Over a 7-day exposure period, M. edulis was the most tolerant species to copper with significant effects being observed at the cellular level only at 68.1 microg Cu l(-1) . In all three species, cellular and neurotoxic pathways were more sensitive to disruption than physiological processes (protein and heart rate). Results illustrate how a suite of biomarkers applied to different sentinel species can provide a 'diagnosis of stress', whereby, effects at the molecular level can be used to interpret the level of physiological impairment of the organism.