Total thiol redox status as a potent biomarker of PAH-mediated effects on mussels

Biomarker responsiveness in Norwegian Sea mussels, Mytilus edulis, exposed at low temperatures to aqueous fractions of crude oil alone and combined with dispersant

Biological effects of aqueous fractions of a crude oil, alone or in combination with dispersant, were investigated in mussels, Mytilus edulis, exposed at three temperatures (5, 10 and 15 °C). Polycyclic aromatic hydrocarbons (PAHs) tissue concentrations were determined, together with genotoxicity, oxidative stress and general stress biomarkers and the Integrated Biological Response (IBR) index. The bioaccumulation of individual PAHs varied depending on the exposure temperature, with relevant bioaccumulation of phenantrene and fluoranthene at 5 °C and heavier (e.g. 5-rings) PAHs at 15 °C. The values and response profiles of each particular biomarker varied with exposure time, concentration of the oil aqueous fraction and dispersant addition, as well as with exposure temperature. Indeed, PAH bioaccumulation and biomarker responsiveness exhibited specific recognizable patterns in mussels exposed at low temperatures. Thus, genotoxicity was recorded early and transient at 5 °C and delayed but unremitting at 10-15 °C. Catalase activity presented a temperature-dependent response profile similar to the genotoxicity biomarker; however, glutathione-S-transferase responsiveness was more intricate. Lysosomal membrane stability in digestive cells decreased more markedly at 5 °C than at higher temperatures and the histological appearance of the digestive gland tissue was temperature-specific, which was interpreted as the combined effects of PAH toxicity and cold stress. It can be concluded that the profile and level of the biological effects are definitely different at low temperatures naturally occurring in the Arctic/Subarctic region (e.g. 5 °C) than at higher temperatures closer to the thermal optimum of this species (10-15 °C).

Investigating seasonal metal impact on Stramonita haemastoma gastropod along the Algerian East Coast: Understanding through various pollution indicators

The main objective of this study was to assess the impact of environmental pollution on the gastropod Stramonita haemastoma by examining various physiological and biochemical parameters. Trace metal elements (TME) were measured in the snail's foot. Over a one-year period from 2013 to 2014, the study investigated the variations in reduced glutathione, malondialdehyde, metallothionein, glutathione S-transferase, acetylcholinesterase and catalase activities in the foot of the gastropod at three different sites. The results showed spatiotemporal fluctuations in biomarkers, physiological parameters and TME. This integrative approach, being the first of its kind in the region using S. haemastoma as a model organism, represents a means of environmental assessment accessible to all countries allowing the monitoring and conservation of coastal marine environments on a national and international scale and which could be used in marine biomonitoring programs to indicate the impact of pollution and assess the quality of the Algerian coastal marine environment.

Redox control of antioxidants, metabolism, immunity, and development at the core of stress adaptation of the oyster Crassostrea gigas to the dynamic intertidal environment

This review uses the marine bivalve Crassostrea gigas to highlight redox reactions and control systems in species living in dynamic intertidal environments. Intertidal species face daily and seasonal environmental variability, including temperature, oxygen, salinity, and nutritional changes. Increasing anthropogenic pressure can bring pollutants and pathogens as additional stressors. Surprisingly, C. gigas demonstrates impressive adaptability to most of these challenges. We explore how ROS production, antioxidant protection, redox signaling, and metabolic adjustments can shed light on how redox biology supports oyster survival in harsh conditions. The review provides (i) a brief summary of shared redox sensing processes in metazoan; (ii) an overview of unique characteristics of the C. gigas intertidal habitat and the suitability of this species as a model organism; (iii) insights into the redox biology of C. gigas, including ROS sources, signaling pathways, ROS-scavenging systems, and thiol-containing proteins; and examples of (iv) hot topics that are underdeveloped in bivalve research linking redox biology with immunometabolism, physioxia, and development. Given its plasticity to environmental changes, C. gigas is a valuable model for studying the role of redox biology in the adaptation to harsh habitats, potentially providing novel insights for basic and applied studies in marine and comparative biochemistry and physiology.

Metallic nanoparticles affect uptake of polycyclic aromatic hydrocarbons and impacts in the Mediterranean mussels Mytilus galloprovincialis

The impact of metallic nanoparticles (NPs) on the uptake and toxicity of persistent organic pollutants by marine bivalves was assessed through a comparative laboratory study by exposing mussels to polycyclic aromatic hydrocarbon (PAHs), in the presence and absence of ZnO and TiO₂ NPs. PAHs and NPs concentration was analyzed after 14 days of exposure in mussels by GC/MS and ICP/AES. Furthermore, impact on the physiology and neurotoxicity of PAHs and NPs acting alone or in mixtures were also determined. Our results confirmed the bio-uptake of PAHs and NPs by mussels. In addition, the exposure NPs-PAHs resulted in different bio-uptake profile to that of PAHs alone. The NPs and accumulation of PAHs led to disturbance of essential metals concentration and to different impact profiles in the filtration and respiration capacities as well as in the acetylcholinesterase activity. Antagonist interactions between NPs and PAHs could occur after exposure.

The Role of the Ecotoxicology Applied to Seafood as a Tool for Human Health Risk Assessments Concerning Polycyclic Aromatic Hydrocarbons

Background: Polycyclic aromatic hydrocarbons (PAHs) are persistent pollutants routinely detected in aquatic ecosystems. It is, therefore, necessary to assess the link between deleterious marine biota PAH effects, especially in commercialized and consumed animals, environmental health status, and potential human health risks originating from the consumption of contaminated seafood products. Thus, this review seeks to verify the relationships of ecotoxicological studies in determining effect and safety concentrations on animals routinely consumed by humans. Methods: A total of 52 published studies between 2011 and 2021, indexed in three databases, were selected following the PICO methodology, and information on test animals, evaluated PAH, and endpoints were extracted. Results: Benzo(a)pyrene and phenanthrene were the most investigated PAHs in terms of biomarkers and test organisms, and mussels were the most evaluated bioindicator species, with an emphasis on reproductive responses. Furthermore, despite the apparent correlation between environmental PAH dynamics and effects on aquatic biota and human health, few assessments have been performed in a multidisciplinary manner to evaluate these three variables together. Conclusions: The links between human and environmental sciences must be strengthened to enable complete and realistic toxicity assessments as despite the application of seafood assessments, especially to mussels, in bioassays, the connection between toxicological animal responses and risks associated with their consumption is still understudied.

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.

Feeding regimes modulate biomarkers responsiveness in mussels treated with diclofenac

This study investigated the role of the feeding regime on cellular (lysosomal membrane impairment), oxidative (superoxides and nitric oxides generation, as well as lipid peroxidation) and genotoxic (nuclear abnormalities) biomarkers measured in hemocytes of mussels Mytilus galloprovincialis treated with diclofenac (DCF). Specifically, unfed mussels, or mussels fed ad libitum with algal species Tisochrysis lutea or Tetraselmis suecica (Tiso/DCF- and Tetra/DCF- treated mussels, respectively) were exposed to DCF (20 μgL^-1) for 4 days. The results showed that biomarkers' responsiveness against DCF, were more pronounced in unfed and Tetra/DCF-, rather than Tiso/DCF- treated mussel hemocytes, thus revealing food deprivation, changes in mussel feeding/filtration rate and digestion processes, as potent factors of mussels' immune efficiency and response against DCF. Those findings could provide valuable data for the optimization of mussels' feeding regime during laboratory studies, in order to assess reliably the effects of emerging contaminants on non-target sentinel organisms, such as mussels.

Vulnerability of glutathione-depleted Crassostrea gigas oysters to Vibrio species

Glutathione (GSH) is a major cellular antioxidant molecule participating in several biological processes, including immune function. In this study, we investigated the importance of GSH to oysters Crassostrea gigas immune response. Oysters were treated with the GSH-synthesis inhibitor buthionine sulfoximine (BSO), and the function of immune cells and mortality were evaluated after a bacterial challenge with different Vibrio species. BSO caused a moderate decrease (20-40%) in GSH levels in the gills, digestive gland, and hemocytes. As expected, lower GSH decreased survival to peroxide exposure. Hemocyte function was preserved after BSO treatment, however, oysters became more susceptible to challenges with Vibrio anguillarum, V. alginolyticus, or V. harveyi, but not with V. parahaemolyticus and V. vulnificus, indicating a species-specific vulnerability. Our study indicates that in natural habitats or in mariculture farms, disturbances in GSH metabolism may pre-dispose oysters to bacterial infection, decreasing survival.

Does salinity modulates the response of Mytilus galloprovincialis exposed to triclosan and diclofenac?

In the present study Mytilus galloprovincialis mussels were exposed for 28 days to three salinities: 30 (control), 25 and 35. Simultaneously, organisms at each salinity were exposed to either the antimicrobial agent Triclosan (TCS) or the pharmaceutical drug Diclofenac (DIC) at 1 μg/L. Salinity alone and exposure to PPCPs changed mussel's metabolic capacity and oxidative status, but no additive or synergetic effects resulting from the combined exposures were observed. Overall, the metabolic capacity of mussels was decreased when exposed to TCS and DIC under control salinity, which was less pronounced at salinities out of the control level. TCS had a notorious effect over glutathione peroxidase activity while DIC exposure enhanced catalase response. Such defence mechanisms were able to prevent cellular damage but still a clear reduction in GSH/GSSG ratio after PPCPs exposures indicates oxidative stress which could compromise bivalve's performance to further stressing events.

The Photodynamic Properties and the Genotoxicity of Heat-Treated Silicalite-1 Films

We investigated the use of a supported silicalite-1 film (SF) as a promising coating for metallic materials used in the fabrication of prostheses. The role of carbonaceous residua present on high-temperature calcined-SF in generating singlet oxygen for future use as a sterilization method has also been addressed, and the potential genotoxicity of these residua in osteoblast-like cells has been investigated. Calcination of as-synthesized SF induced the appearance of a rather complicated mixture of aliphatic and aromatic species on its outer surface. A series of variously volatile polycyclic aromatic hydrocarbons (PAH), including naphthalene, fluorene, phenanthrene, anthracene, fluoranthene, and pyrene, were identified in micromole concentrations. Irradiation of these PAHs on calcined-SF immersed in air-saturated chloroform led to the formation of very low concentrations of singlet oxygen. However, an increased level of DNA damage was observed on calcined-SF by immunofluorescence staining of phosphorylated histone H2AX analyzed by flow cytometry.

Effects of phenanthrene on different levels of biological organization in larvae of the sediment-dwelling invertebrate Chironomus sancticaroli (Diptera: Chironomidae)

The hydrocarbon phenanthrene is an organic compound commonly found in the environment. In aquatic ecosystems, it is highly toxic to organisms, although little is known about its effects on sediment-dwelling organisms. The purpose of this study was to evaluate phenanthrene effects on biochemical, histological, and ontogenetic levels in larvae of the sediment-dwelling invertebrate Chironomus sancticaroli at acute and chronic exposure. Lethal concentrations were estimated and toxicity (acute-96 h and chronic- 8 d) tests were performed at phenanthrene concentrations from 0.12 to 1.2 mg L^-1. At acute and chronic exposure, we evaluated acetylcholinesterase (AChE), alpha esterase (EST-α), and beta esterase (EST-β) activities as well as histological alterations. In the assays with chronic exposure, effects on larval development were estimated using antennae length (instar estimative) and body length (growth estimative). The EST-α showed a significantly increased activity after 48 h at acute exposure to high concentrations of phenanthrene, while EST-β activity was increased after 48 and 72 h at acute exposure at higher concentrations and at 0.12 mg L^-1 at chronic exposure. At acute exposure, the midgut showed alterations such as brush border disruption, gastric caeca regression, and lumen area reduction; the fat body showed nuclear alteration in the trophocytes, while the Malpighian tubules showed brush border reduction and the salivary glands were subject to cytoplasm vacuolation. At chronic exposure, the same alterations were observed, in addition to vacuolar coalescence in the trophocytes of the fat body. Regarding larval development, a reduction of body length was observed with increasing phenanthrene concentrations. Similarly, molting was delayed; in the control group, all larvae were in the fourth instar, while at higher phenanthrene concentrations, larvae were predominantly in the third instar. Phenanthrene had toxic effects on this chironomid, indicating risks for natural populations.

Association Between Placental Polycyclic Aromatic Hydrocarbons (PAHS), Oxidative Stress, and Preterm Delivery: A Case-Control Study

Polycyclic aromatic hydrocarbons are known to disturb the antioxidant defense system, which may indirectly contribute to induction of early pregnancy in women. Therefore, the present investigation was designed to offer preliminary information about exposure to PAHs by estimating their placental levels and its association with oxidative stress as well as with preterm birth. Placenta tissue samples were drawn after delivery from 84 healthy pregnant women, recruited at a local nursing home of Agra, India, and levels of PAHs were quantified by gas chromatograph equipped with flame ionization detector. To evaluate redox status biomarkers, malondialdehyde (MDA) and glutathione (GSH) were determined in placenta tissue. Significantly elevated levels of benzo(a)pyrene and MDA while decreasing trend of GSH was found in women with preterm delivery group (study) than women with a full-term delivery group (control). Results demonstrated higher, but statistically insignificant (p > 0.05), levels of naphthalene, anthracene, fluorene, pyrene, benzo(b)fluoranthene, benzo(k)fluoranthene, indeno[1,2,3-cd]pyrene, dibenzo(ah)anthracene, and benzo(ghi)perylene in the study group than the control group. However, higher and lower molecular weight PAHs showed significant correlation for the depletion trend of GSH sights upon an example of oxidative stress mechanism. Because of limited statistical power and absence of controlled confounders, this study does not provide an ample involvement of PAHs with preterm delivery but increased MDA and decreased GSH in cases than controls gives the possible contribution of PAHs to early delivery.

Benzo(a)pyrene Exposure Causes Genotoxic and Biochemical Changes in the Midge Larvae of Chironomus sancticaroli Strixino & Strixino (Diptera: Chironomidae)

Benzo(a)pyrene (BaP) is a carcinogenic polycyclic aromatic hydrocarbon, also found in nature due to human activities. BaP adheres to sediments showing toxic effects on benthic organisms, including midge larvae of the family Chironomidae. We tested for toxic effects of benzo(a)pyrene on Chironomus sancticaroli Strixino & Strixino 1981 using biochemical and genotoxic biomarkers, to identify changes in metabolic and antioxidant pathways, besides neurotoxic and DNA damage. Enzyme activity was compared by exposing larvae to four nominal concentrations (0.47, 2.13, 3.41, and 4.73 μg l^-1) and DNA damage to two concentrations (0.47 and 4.73 μg l^-1), after exposure at 24, 48, 72, and 96 h. BaP caused neurotoxic effect, showing acetylcholinesterase alterations at different treatments. Changes in the biotransformation pathway were detected, with an increased activity of alpha and beta esterase in 48 h and reduction of glutathione-S-transferase activity in all periods at the highest concentrations. Damage to the antioxidant system was observed by the increase of the superoxide dismutase and reduction of the catalase, in 48 h. Genotoxicity was detected by an increased DNA damage at 48 and 72 h. The lowest concentration (0.47 μg l^-1), even presenting low mortality, also altered the biochemical parameters of the larvae. Thus, these results indicate that BaP causes metabolic, neurotoxic, and genotoxic effects on C. sancticaroli, even at low concentrations and short-term exposure. BaP can cause damage of immature invertebrates, and the ecological dynamics can be affected, since these organisms have trophic importance in the aquatic environment.

Thiol oxidation of hemolymph proteins in oysters Crassostrea brasiliana as markers of oxidative damage induced by urban sewage exposure

Urban sewage is a concerning issue worldwide, threatening both wildlife and human health. The present study investigated protein oxidation in mangrove oysters (Crassostrea brasiliana) exposed to seawater from Balneário Camboriú, an important tourist destination in Brazil that is affected by urban sewage. Oysters were exposed for 24 h to seawater collected close to the Camboriú River (CAM1) or 1 km away (CAM2). Seawater from an aquaculture laboratory was used as a reference. Local sewage input was marked by higher levels of coliforms, nitrogen, and phosphorus in seawater, as well as polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), linear alkylbenzenes (LABs), and fecal steroid in sediments at CAM1. Exposure of oysters to CAM1 caused marked bioaccumulation of LABs and decreased PAH and PCB concentrations after exposure to both CAM1 and CAM2. Protein thiol oxidation in gills, digestive gland, and hemolymph was evaluated. Lower levels of reduced protein thiols were detected in hemolymph from CAM1, and actin, segon, and dominin were identified as targets of protein thiol oxidation. Dominin susceptibility to oxidation was confirmed in vitro by exposure to peroxides and hypochlorous acid, and 2 cysteine residues were identified as potential sites of oxidation. Overall, these data indicate that urban sewage contamination in local waters has a toxic potential and that protein thiol oxidation in hemolymph could be a useful biomarker of oxidative stress in bivalves exposed to contaminants. Environ Toxicol Chem 2017;36:1833-1845. © 2016 SETAC.

Exposure to phenanthrene and depuration: Changes on gene transcription, enzymatic activity and lipid peroxidation in gill of scallops Nodipecten nodosus

Understanding the mechanism of phenanthrene (PHE) biotransformation and related cellular responses in bivalves can be an important tool to elucidate the risks of polycyclic aromatic hydrocarbons (PAHs) to aquatic organisms. In the present study it was analyzed the transcriptional levels of 13 biotransformation genes related to cytochrome P450 (CYP), glutathione S-transferase (GST), sulfotransferase (SULT), flavin-containing monooxygenase and fatty acid-binding proteins by qPCR in gill of scallops Nodipecten nodosus exposed for 24 or 96h to 50 or 200μgL(-1) PHE (equivalent to 0.28 and 1.12μM, respectively), followed by depuration in clean water for 96h (DEP). Likewise, it was quantified the activity of catalase (CAT), glutathione peroxidase (GPx), superoxide dismutase (SOD), glutathione reductase (GR), glucose 6-phosphate dehydrogenase (G6PDH), GST and levels of lipid peroxidation. Increased transcriptional levels of CYP2UI-like, CYP2D20-like, CYP3A11-like, GSTomega-like, SULT1B1-like genes were detected in organisms exposed to PHE for 24 or 96h. In parallel, GR and GPX activities increased after 96h exposure to 200μgL(-1) PHE and G6PDH activity increased after 24h exposure to 50μgL(-1) PHE. This enhancement of antioxidant and phase I and II biotransformation systems may be related to the 2.7 and 12.5 fold increases in PHE bioaccumulation after 96h exposure to 50 and 200μgL(-1) PHE, respectively. Interestingly, DEP caused reestablishment of GPX and GR activity, as well as to the transcript levels of all upregulated biotransformation genes (except for SULT1B1-like). Bioaccumulated PHE levels decreased 2.5-2.9 fold after depuration, although some biochemical and molecular modifications were still present. Lipid peroxidation levels remained lower in animals exposed to 200μgL(-1) PHE for 24h and DEP. These data indicate that N. nodosus is able to induce an antioxidant and biotransformation-related response to PHE exposure, counteracting its toxicity, and DEP can be an effective protocol for bivalve depuration after PHE exposure.

Bioaccumulation of PCB-153 and effects on molecular biomarkers acetylcholinesterase, glutathione-S-transferase and glutathione peroxidase in Mytilus galloprovincialis mussels

In this study, PCB-153 bioaccumulation kinetics and concentration-response experiments were performed employing wild Mytilus galloprovincialis mussels. In addition, the activity of three enzymatic biomarkers: glutathione S-transferase (GST), glutathione peroxidase (GPx) and acetylcholinesterase (AChE), were measured in the mussel gills. The experimental data fitted well to an asymptotic accumulation model with a high bioconcentration factor (BCF) of 9324 L kg(-1) and a very limited depuration capacity, described by a low excretion rate coefficient (Kd = 0.083 d(-1)). This study reports by first time in mussels significant inhibition of GST activity and significant induction of GPx activity as a result of exposure to dissolved PCB-153. In contrast, AChE activity was unaffected at all concentrations and exposure times tested. The effects on both enzymes are time-dependent, which stresses the difficulties inherent to the use of these biomarkers in chemical pollution monitoring programs.

Bioaccumulation of 4-nonylphenol and effects on biomarkers, acetylcholinesterase, glutathione-S-transferase and glutathione peroxidase, in Mytilus galloprovincialis mussel gilla

Wild marine mussels, Mytilus galloprovincialis showed a moderate bioaccumulation ability when exposed to waterborne 4-nonylphenol (4-NP), with a bioconcentration factor (BCF) of 6850 L Kg(-1) (dry weight). Kinetic and concentration-response experiments were performed and three enzymatic biomarkers in mussel gills were measured: Glutathione S-transferase (GST), glutathione peroxidase (GPx) and acetylcholinesterase (AChE). Exposure of mussels to environmentally relevant concentrations (25-100 μg L(-1)) of 4-nonylphenol significantly inhibited the AChE activity and induced the GST and GPx activities. GST induction was dose dependent whilst GPx activity showed a less consistent pattern, but in both cases the induction remained after a 10 d depuration period. Mussels seem capable of eliminating 4-NP from their tissues through a mechanism involving GST induction.

Bioaccumulation of BDE-47 and effects on molecular biomarkers acetylcholinesterase, glutathione-S-transferase and glutathione peroxidase in Mytilus galloprovincialis mussels

Mussels, Mytilus galloprovincialis, showed a high bioaccumulation ability when exposed to waterborne tetrabromodiphenyl ether (BDE-47), with a bioconcentration factor of 10,900 L Kg(-1) wet weight, and slow depuration rates in clean seawater. Kinetic and concentration-response experiments were performed measuring in the exposed mussel the activities of three molecular biomarkers: glutathione S-transferase (GST), glutathione peroxidase (GPx) and acetylcholinesterase (AChE). The long term (30 days) exposure of mussels to all concentrations (2-15 µg L(-1)) of BDE-47 significantly inhibited the AChE and GST activities, a result that supports the suitability of these biomarkers in marine pollution monitoring programs. However, GPx activity showed a less consistent pattern of response depending on the concentration and the duration of exposure.

Organic pollution and its effects in the marine mussel Mytilus galloprovincialis in Eastern Mediterranean coasts

Persistent chemicals and emerging pollutants are continuously detected in marine waters and biota. Out of these, polycyclic aromatic hydrocarbons (PAHs) and organochlorine pesticides (OCs) are significant contaminants with decades of presence in the marine environment. The Mediterranean Sea is an ecosystem directly affected by a variety of anthropogenic activities including industry, municipal, touristic, commercial and agricultural. The Mediterranean mussel (Mytilus galloprovincialis) is a filter feeder, which presents wide distribution. In this regard, the specific organism was used as a biological indicator for the monitoring and evaluation of pollution in the studied areas with focus on the mentioned chemical groups. Pristine Turkish sites with minimum effect from anthropogenic activities, in contrast with Greek sites which were subjected to heavy industrial and shipping activity, were selected. A gas chromatographic tandem mass spectrometric method (GC-MS/MS) was developed and validated to monitor 34 compounds (16 EPA priority PAHs and 18 OCs). Analyses of mussel samples in 2011 from sites with the limited anthropogenic pollution shores have shown the occurrence of 11 pollutants (6 PAHs, 5 OCs), while in the samples from sites with intensive activity and expected pollution, 12 PAHs and 6 OCs were detected. Biochemical and biological responses studied only in mussels samples from the sites with the highest contamination showed a situation that was under strong seasonal influence. The intensity of the response was also influenced by deployment duration. Noteworthy correlations were detected among biochemical/biological effects and between mussel body burden and these effects. Continuous monitoring of priority pollutants of East Mediterranean Sea is vital both for ecological and human risk assessment purposes.

Antioxidant defense responses in Mytella guyanensis (Lamarck, 1819) exposed to an experimental diesel oil spill in Paranaguá Bay (Paraná, Brazil)

We evaluated the effects of diesel oil on the bivalve Mytella guyanensis using biomarkers of oxidative stress (glutathione S-transferase, glutathione peroxidase, and reduced glutathione) after an experimental in situ spill in a mangrove area in southern Brazil. A linear model was developed for the Multiple Before-After Control-Impact (MBACI) experimental design to assess the significance of biological responses. Control and impacted sites were sampled seven and two days before as well as two and seven days after the spill. With the exception of a late response of reduced glutathione (GSH) levels on day seven, none of the biomarkers were significantly altered by the impact. This result was attributed to the high environmental variability of the experimental sites combined with a low sensitivity of Mytella guyanensis to diesel oil at short time-scales. The high resistance of M. guyanensis suggests that its antioxidant response is triggered only after a medium- to long-term exposure to contaminants.

A light in the darkness: new biotransformation genes, antioxidant parameters and tissue-specific responses in oysters exposed to phenanthrene

Phenanthrene (PHE), a major component of crude oil, is one of the most abundant polycyclic aromatic hydrocarbons (PAHs) in aquatic ecosystems, and is readily bioavailable to marine organisms. Understanding the toxicity of PAHs in animals requires knowledge of the systems for xenobiotic biotransformation and antioxidant defence and these are poorly understood in bivalves. We report, for the first time, new transcripts and tissue-specific transcription in gill and digestive gland from the oyster Crassostrea brasiliana following 24h exposure to 100 and 1000μgL(-1) PHE, a model PAH. Six new cytochrome P450 (CYP) and four new glutathione S-transferase (GST) genes were analysed by means of quantitative reverse transcription PCR (qRT-PCR). Different antioxidant endpoints, including both enzymatic and non-enzymatic parameters, were assessed as potential biomarkers of oxidative stress. GST activity was measured as an indicator of phase II biotransformation. Rapid clearance of PHE was associated with upregulation of both phase I and II genes, with more pronounced effects in the gill at 1000μgL(-1) PHE. After 24h of exposure, PHE also caused impairment of the antioxidant system, decreasing non-protein thiols and glutathione levels. On the other hand, no change in antioxidant enzymes was observed. PHE treatment (100μgL(-1)) significantly decreased GST activity in the gill of exposed oysters. Both CYP and GST were transcribed in a tissue-specific manner, reflecting the importance of the gill in the detoxification of PAHs. Likewise, the antioxidant parameters followed a similar pattern. The data provide strong evidence that these genes play key roles in C. brasiliana biotransformation of PHE and highlight the importance of gill in xenobiotic metabolism.

Aqueous phenanthrene toxicity after high-frequency ultrasound degradation

Given that polycyclic aromatic hydrocarbons (PAHs), such as phenanthrene (PH), possess a potent risk for aquatic biota, a great attempt to develop and apply advanced oxidation processes, such as ultrasound (US), is of great concern nowadays. However, because US PAH-derived toxic intermediates are difficult to detect, the present study investigates aqueous PH toxicity before and after high-frequency US degradation, in hemocytes of mussel Mytilus galloprovincialis. Specifically, cell viability (with the use of neutral red uptake/NRU method), and oxidative-stress indices in terms of superoxide anions, (O2(-)), nitric oxides (NO, in terms of nitrites), lipid peroxidation products (in terms of malondialdehyde/MDA content) and DNA damage (with the use of Comet assay method) were investigated in mussel hemocytes exposed to environmentally relevant concentrations of PH (0.01, 0.1, 1 and 10 μg L(-1)), before and after US treatment for 120 min (at a frequency of 582 kHz). According to the results, the NRU method showed a significant attenuation of PH-induced mortality in US PH-treated hemocytes in all cases. Moreover, the increased levels of O2(-) and NO generation, as well as MDA content measured in PH-treated hemocytes, were drastically decreased after US degradation in any case. Similarly, the disturbance of DNA integrity (in terms of % DNA in tail, OM and TM), was negligible in case of US PH-treated hemocytes. Although further in vitro and in vivo studies are needed, the present study showed for the first time that high frequency US could be applied as a highly efficient and "environmentally friendly" process for degrading low molecular weight PAH, such as PH.

Carbamazepine-mediated pro-oxidant effects on the unicellular marine algal species Dunaliella tertiolecta and the hemocytes of mussel Mytilus galloprovincialis

This study investigates the pro-oxidant behavior of the antiepileptic drug carbamazepine (CBZ) on the marine algal species Dunaliella tertiolecta and the immune defense-related hemocytes of mussel Mytilus galloprovincialis. A phytotoxicity test, performed in a first step, showed a significant inhibition of the growth rate and the chlorophyll alpha (Chl-α) content in algae after exposure for 24 h to different concentrations of CBZ (1-200 mg L(-1)). On the other hand, the increased levels of lipid peroxidation products, such as MDA, measured in 24 h CBZ-treated cells were attenuated with time (48-96 h), followed by a significant recovery of both the algal growth rate and the Chl-α content in all cases. The latter could be related to the concomitant enhancement of total carotenoids in CBZ-treated algae with time, which in turn could protect algal growth and survival against CBZ-induced oxidative stress. On the other hand, the increased levels of cell death, superoxide anions ((·)O2 (-)), nitric oxides (NO, in terms of nitrites, NO2 (-)) and MDA content observed in mussel hemocytes exposed to environmentally relevant (0.01-1 μg L(-1)) and/or higher (10 and 100 μg L(-1)) concentrations of the drug, clearly indicate the ability of CBZ to induce oxidative effects on cells of non-target species, such as mussels, affecting thus their overall health status. The significant relationships occurred among the tested biological parameters in both bioassays, further reinforce CBZ-mediated pro-oxidant effects on species, widely used in ecotoxicological and toxicological studies and provide a more comprehensive view on its environmental fate and ecotoxicological risk evaluation.

Biochemical biomarker responses of green-lipped mussel, Perna canaliculus, to acute and subchronic waterborne cadmium toxicity

The biochemical responses of the green-lipped mussel, Perna canaliculus, to waterborne cadmium (Cd) were investigated in order to delineate toxic mechanisms, and the impacts of exposure dose and duration, of this important toxicant in a potential sentinel species. Mussels were exposed for either 96 h (acute: 0, 2000, 4000 μgL(-1) Cd) or for 28 d (subchronic: 0, 200, 2000 μgL(-1) Cd), and the digestive gland, gill and haemolymph were examined for impacts. Biochemical responses measured included those associated with metal detoxification (metallothionein-like protein; MTLP), oxidative stress (catalase, lipid peroxidation), cellular homeostasis (alkaline phosphatase, Na(+), K(+)-ATPase; NKA), and energy utilisation (glycogen, haemolymph protein). Following acute exposure, digestive gland glycogen and gill NKA activity were significantly altered by Cd exposure relative to levels in mussels exposed to Cd-free seawater. Subchronic Cd exposure resulted in a significant increase in MTLP levels in both the gill and the digestive gland. This increase was correlated strongly with the levels of Cd accumulation measured in these tissues (R=0.957 for gill, 0.964 for digestive gland). Catalase activity followed a similar pattern, although the correlation with tissue Cd accumulation was not as strong (R=0.907 for gill, 0.708 for digestive gland) as that for MTLP. Lipid peroxidation increased in the digestive gland at Days 7 and 14 at both subchronic Cd levels tested, but this effect had largely dissipated by Days 21 and 28 (with the exception of the 2,000 μgL(-1) group at Day 28). Alkaline phosphatase activity decreased significantly with Cd exposure in both tissues. This effect was observed at both tested concentrations in the gill, but only at the highest concentration for digestive gland. A decrease in digestive gland glycogen levels was observed in Cd-exposed mussels (Days 14 and 21 at 2,000 μgL(-1)), while haemolymph protein levels increased as a result of subchronic Cd exposure. These findings indicated that biochemical responses in Cd-exposed mussels were tissue-specific, dose- and time-dependent, with duration of exposure being the predominant effect. This study shows that biochemical changes in Cd-exposed green-lipped mussels can be linked to tissue metal accumulation and are consistent with previously reported physiological effects. It also suggests that green-lipped mussels are amenable to a multiple biomarker approach and may be of use as a bioindicator species for monitoring coastal metal pollution.