Cadmium sulfide quantum dots induce oxidative stress and behavioral impairments in the marine clam Scrobicularia plana.

Cadmium sulfide (CdS) quantum dots have a number of current applications in electronics and solar cells and significant future potential in medicine. The aim of the present study was to examine the toxic effects of CdS quantum dots on the marine clam Scrobicularia plana exposed for 14 d to these nanomaterials (10 µg Cd L(-1) ) in natural seawater and to compare them with soluble Cd. Measurement of labile Cd released from CdS quantum dots showed that 52% of CdS quantum dots remained in the nanoparticulate form. Clams accumulated the same levels of Cd regardless of the form in which it was delivered (soluble Cd vs CdS quantum dots). However, significant changes in biochemical responses were observed in clams exposed to CdS quantum dots compared with soluble Cd. Increased activities of catalase and glutathione-S-transferase were significantly higher in clams exposed in seawater to Cd as the nanoparticulate versus the soluble form, suggesting a specific nano effect. The behavior of S. plana in sediment showed impairments of foot movements only in the case of exposure to CdS quantum dots. The results show that oxidative stress and behavior biomarkers are sensitive predictors of CdS quantum dots toxicity in S. plana. Such responses, appearing well before changes might occur at the population level, demonstrate the usefulness of this model species and type of biomarker in the assessment of nanoparticle contamination in estuarine ecosystems.

Fate and effects of metal-based nanoparticles in two marine invertebrates, the bivalve mollusc Scrobicularia plana and the annelid polychaete Hediste diversicolor.

The objective of this paper is to synthesize results from seven published research papers employing different experimental approaches to evaluate the fate of metal-based nanoparticles (Ag NPs, Au NPs, CuO NPs, CdS NPs, ZnO NPs) in the marine environment and their effects on two marine endobenthic species, the bivalve Scrobicularia plana and the ragworm Hediste diversicolor. The experiments were carried out under laboratory (microcosms) conditions or under environmentally realistic conditions in outdoor mesocosms. Based on results from these seven papers, we addressed the following research questions: (1) How did the environment into which nanoparticles were released affect their physicochemical properties?, (2) How did the route of exposure (seawater, food, sediment) influence bioaccumulation and effects?, (3) Which biomarkers were the most responsive? and (4) Which tools were the most efficient to evaluate the fate and effects of NPs in the marine environment? The obtained results showed that metal-based NPs in general were highly agglomerated/aggregated in seawater. DGT tools could be used to estimate the bioavailability of metals released from NPs under soluble form in the aquatic environment. Both metal forms (nanoparticulate, soluble) were generally bioaccumulated in both species. Among biochemical tools, GST and CAT were the most sensitive revealing the enhancement of anti-oxidant defenses in both species exposed to sub-lethal concentrations of metal-based NPs. Apoptosis and genotoxicity were frequently observed.

Biochemical and behavioural responses of the marine polychaete Hediste diversicolor to cadmium sulfide quantum dots (CdS QDs): waterborne and dietary exposure.

Cadmium sulfide (CdS) quantum dots are widely used in medical imaging. The aim of this study was to examine toxicity effects of CdS engineered nanoparticles (CdS NPs) compared to soluble Cd, on marine ragworms (Hediste diversicolor) exposed for 14 d to these contaminants (10 µg Cd L(-1)) in seawater or via their food (contaminated worm tissue). In our experimental media, Dynamic Light Scattering studies showed that the majority of CdS remained in the nanoscale (1-10 nm) with the exception of few aggregates (100-300 nm). Labile Cd fractions released from CdS NPs were estimated by diffusive gradient in thin films, showing that about 50% of CdS NPs remained in nanoparticulate form. Ragworms accumulated Cd in both soluble Cd and CdS NPs in waterborne exposures only. Greater significant changes of biochemical responses were observed in worms exposed to CdS NPs in seawater compared to contaminated food. Catalase and glutathione-S-transferase activities were the most sensitive biochemical biomarkers responding to both Cd treatments for waterborne exposure. Inductions of CAT were higher in diet-exposed worms to Cd as NPs vs soluble form suggesting a specific "nano" effect. Caspase activities increased in worms exposed to soluble Cd and Cd NPs for the two routes of exposure compared to controls. Defences, may be insufficient to prevent reactive oxygen species generation and the associated apoptosis. Behaviour of invertebrates inside sediment showed impairments of body movements in worms exposed to CdS NPs. This study points out oxidative processes as the main consequences of exposure to Cd based NPs in worms.

A marine mesocosm study on the environmental fate of silver nanoparticles and toxicity effects on two endobenthic species: the ragworm Hediste diversicolor and the bivalve mollusc Scrobicularia plana.

Silver nanoparticles are widely used in a range of products and processes for their antibacterial properties, electrical and thermal conductivity. The fate and effects of Ag nanoparticles were examined in two endobenthic species (Scrobicularia plana, Hediste diversicolor), under environmentally realistic conditions in outdoor mesocosms exposed to Ag at 10 µg L(-1) in nanoparticulate (Ag NPs) or soluble salt (AgNO3) forms for 21 days. Labile Ag was determined in water and sediment by using diffusive gradient in thin films. Ag levels were equivalent in contaminated Ag NPs mesocosms to those contaminated with the soluble form. Bioaccumulation of Ag was observed for both species exposed to either Ag in the nanoparticulate or ionic forms. Concerning biomarker responses, both soluble and nanoparticulate Ag forms, induced defenses against oxidative stress, detoxification, apoptosis, genotoxicity and immunomodulation. Nevertheless, DNA damages measured by the comet assay in the digestive gland of S. plana, and Phenoloxidase and lysozyme activities in S. plana and H. diversicolor, respectively, were higher in the presence of Ag NPs compared to soluble Ag suggesting a specific nano effect.

Biochemical and behavioural responses of the endobenthic bivalve Scrobicularia plana to silver nanoparticles in seawater and microalgal food.

Because of their bactericidal effects, Ag nanoparticles (Ag NPs) have promising industrial development but could lead to potential ecological risks. The aim of this study was to examine the uptake and effect of silver (soluble or as lactate Ag NPs of 40 nm) at low concentrations (10 µg L(-1)) in the endobenthic bivalve Scrobicularia plana exposed, for 14 days, directly (water) or via the diet (microalgae). The stability of Ag NPs in seawater was examined using dynamic light scattering. Release of soluble Ag from Ag NPs in the experimental media was quantified by using diffusive gradient in thin film. Bioaccumulation of Ag in bivalves was measured by electrothermal atomic absorption spectrometry. Behavioural and biochemical biomarkers were determined in bivalves. Aggregation of Ag NPs and the release of soluble Ag from Ag NPs were observed in the experimental media. For both forms of Ag, bioaccumulation was much more important for waterborne than for dietary exposure. The response of oxidative stress biomarkers (catalase, glutathion S-transferase, superoxide dismutase) was more important after dietary than waterborne exposure to Ag (soluble and NPs). These defences were relatively efficient since they led to a lack of response of damage biomarkers. Burrowing was not affected for bivalves exposed directly or through the diet to both Ag forms but feeding behaviour was impaired after 10 days of dietary exposure. Since no differences of responses to Ag either soluble or nanoparticulate were observed, it seems that labile Ag released from Ag NPs was mainly responsible for toxicity.

A mesocosm study of fate and effects of CuO nanoparticles on endobenthic species (Scrobicularia plana, Hediste diversicolor).

The fate and effects of CuO nanoparticles (CuO NPs) were examined in endobenthic species (Scrobicularia plana , Hediste diversicolor), under environmentally realistic conditions in outdoor mesocosms (exposure to Cu at 10 µg L(-1) in particulate (CuO NPs) or soluble salt (CuNO(3)) forms) for 21 days. Labile Cu was determined in water and sediment by using diffusive gradient in thin films. No labile Cu being detected from CuO NPs; the observed effects in invertebrates exposed to CuO NPs were mainly attributed to the toxicity of nanoparticulate rather than dissolved Cu toxicity. Bioaccumulation of CuO NPs was observed in both species. Biomarkers were examined at different levels of biological organization: biochemical markers of defense and damage, biomarkers of genotoxicity (comet assay), and behavioral biomarkers (feeding and burrowing). Behavioral biomarkers, antioxidant defenses (catalase, glutathion S-transferase, metallothionein), and genotoxicity are the most sensitive tools to highlight the effect of soluble or nanoparticulate metal forms. Concerning other biomarkers of defense (superoxide dismutase, lactate dehydrogenase, laccase) and damage (thiobarbituric acid reactive substances, acetylcholinesterase, acid phosphatase), no significant effects were detected. This experiment shows the suitability of mesocosms for studying the environmental effects of nanoparticles.

Fate of isotopically labeled zinc oxide nanoparticles in sediment and effects on two endobenthic species, the clam Scrobicularia plana and the ragworm Hediste diversicolor.

Although it is reported that metal and metal oxide nanoparticles, which are among the most rapidly commercialized materials, can cause toxicity to organisms, their fate in the environment and toxicity to marine organisms are not well understood. In this study, we used a stable isotope labelling approach to trace the fate of nanoparticles (NPs) in sediments and also investigated bio-uptake in two estuarine intra-sedimentary invertebrates Scrobicularia plana and Nereis diversicolor. We selected exposure to 3 mg kg(-1) sediment ZnO NPs since this level is a realistic prediction of the environmental concentration in sediments. 67ZnO NPs (DLS: 21-34 nm, positively charged: 31.3 mV) suspensions were synthesised in diethylene glycol (DEG). We explored the fate of 67ZnO NPs in sediment, 67Zn bioaccumulation and the biochemical (biomarkers of defence and damage) and behavioural (burrowing kinetics and feeding rates) biomarkers in both species to 67ZnO NPs and DEG on its own during a 16 d laboratory exposure. After exposure, 67Zn concentrations in sediment showed higher levels in the upper section (1cm: 2.59 mg kg(-1)) decreasing progressively (2 cm: 1.63 mg kg(-1), 3 cm: 0.90 mg kg(-1), 4 cm: 0.67 mg kg(-1)) to a minimum value at the bottom (5 cm: 0.31 mg kg(-1)). 67Zn bioaccumulation was observed in both organisms exposed to 67ZnO NPs in DEG but no major inter-species differences were found. At the biochemical level, 67ZnO NPs exposure significantly induced increased glutathione-S-transferase activity in worms and catalase activity in clams whereas superoxide dismutase activity and thiobarbituric acid reactive substance levels were not affected in any species. Exposure to DEG on its own leads to a significant increase of metallothionein-like protein levels in clams compared with those exposed to 67ZnO NPs or controls. Burrowing behaviour as well as feeding rate were significantly impaired in both species exposed to 67ZnO NPs. Concerning exposure to DEG on its own, burrowing behaviour impairments were also shown in both species and feeding rate was impaired in bivalves. At environmentally realistic concentration of 67ZnO NPs in sediment, there is no strong evidence for a severe nanoparticle effect since most effects were also observed in the presence of DEG alone.

Size dependent bioaccumulation and ecotoxicity of gold nanoparticles in an endobenthic invertebrate: the Tellinid clam Scrobicularia plana.

Gold nanoparticles (AuNPs) have important technological applications resulting in an increased potential for release to the environment, and a greater possibility of toxicological effects. The marine bivalve Scrobicularia plana was exposed to AuNPs of size 5, 15 and 40 nm during a 16 d laboratory exposure at 100 µg Au L(-1). After exposure to AuNPs forming aggregates (>700 nm), the clams accumulated Au in their soft tissues. Biochemical (biomarkers) and behavioral (burrowing and feeding) responses were investigated. Au NPs were responsible of metallothionein induction (5, 40 nm), increased activities of catalase (15, 40 nm) and superoxide dismutase (40 nm) and of glutathione S-transferase by the three sizes of AuNPs indicating defense against oxidative stress. Exposure to AuNPs impaired burrowing behavior. However, it must be underlined that these effects were observed at a dose much higher than expected in the environment.

Potential influence of confounding factors (size, salinity) on biomarkers in the sentinel species Scrobicularia plana used in programmes monitoring estuarine quality.

INTRODUCTION: To use biomarkers in monitoring programmes, potential confounding factors must be considered. In the clam Scrobicularia plana, the influence of size and salinity on biomarkers at different levels of biological organisation has been examined. MATERIAL AND METHODS: Biochemical (glutathione-S-transferase, lactate dehydrogenase, acetylcholinesterase, digestive enzymes, metallothionein), physiological (energy reserves) and behavioural (burrowing) responses were compared (a) in specimens of different sizes from the Loire estuary; (b) in specimens from the Belon estuary at two sites with salinities of 30.1 or 11.5. RESULTS: Amongst the biomarkers able to reveal pollution effects, several are influenced by the size of the clams (Ag, Cu, Ni and glycogen concentrations, GST and AChE activities, condition indices). Salinity differences induced variations of the same order of magnitude (GST, AChE) or even higher (lactate dehydrogenase, digestive enzymes in the crystalline style) than contamination-induced variations. In burrowing tests, the number of burrowed specimens was similar at both salinities after an experiment time <3 h. CONCLUSIONS: Size is a factor necessarily but easily controlled. Because the weight may be different in clams of identical size, correction factors may be used to minimise the influence of weight changes on biomarkers. A correction factor taking into account salinity levels can also be used. The protein concentrations in the clams did not differ with salinity, a very favourable outcome since all enzyme activities are classically expressed by reference to total protein concentrations. For burrowing tests, the number of burrowed specimens at a particular time is an endpoint that is preferable to measures of burrowing speed.

Behavioural and biochemical responses of two marine invertebrates Scrobicularia plana and Hediste diversicolor to copper oxide nanoparticles.

Engineered nano-sized Cu oxide particles are extensively used in diverse applications. Because aquatic environments are the ultimate "sink" for all contaminants, it is expected that nanoparticles (NP) will follow the same fate. In this study, two marine invertebrates Scrobicularia plana and Hediste diversicolor were chosen as ecotoxicological models. The aim was to evaluate behavioural (burrowing kinetics, feeding rate) and biochemical (biomarkers) responses of S. plana and H. diversicolor exposed in the laboratory to Cu (10 µg L(-1)) added in natural seawater either in the form of engineered nanoparticles (NPs) of CuO or as dissolved Cu in 2% HNO(3). Exposure was characterized by considering (i) the physico-chemical fate of NP (ii) the fraction of labile Cu in experimental media and (iii) Cu bioaccumulation. Results showed high aggregation of CuO NPs in seawater and no additional bioavailable Cu concentrations. Behavioural impairments were observed in S. plana exposed to CuO NPs or soluble Cu whereas in H. diversicolor, only the exposure to soluble Cu led to a burrowing decrease. No obvious neurotoxicity effects were revealed since in both species, no changes in cholinesterasic activity occurred in response to both forms of Cu exposure. Biomarkers of oxidative-stress catalase and glutathione-S-transferase were enhanced in both species whereas superoxide dismutase was increased only in S. plana exposed to CuO NPs. Metallothionein-like protein was increased in bivalves exposed to both forms of Cu. Since, no detectable release of soluble Cu from CuO NPs occurred during the time of experiment, ecotoxicity effects seem to be related to CuO NPs themselves.