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In the marine environment, most bivalve species base their reproduction on external fertilization. Hence, gametes and young stages face many threats, including exposure to plastic wastes which represent more than 80% of the debris in the oceans. Recently, evidence has been produced on the presence of nanoplastics in oceans, thus motivating new studies of their impacts on marine life. Because no information is available about their environmental concentrations, we performed dose-response exposure experiments with polystyrene particles to assess the extent of micro/nanoplastic toxicity. Effects of polystyrene with different sizes and functionalizations (plain 2-μm, 500-nm and 50-nm; COOH-50 nm and NH 2 -50 nm) were assessed on three key reproductive steps (fertilization, embryogenesis and metamorphosis) of Pacific oysters (Crassostrea gigas). Nanoplastics induced a significant decrease in fertilization success and in embryo-larval development with numerous malformations up to total developmental arrest. The NH 2 -50 beads had the strongest toxicity to both gametes (EC 50  = 4.9 μg/mL) and embryos (EC 50  = 0.15 μg/mL), showing functionalization-dependent toxicity. No effects of plain microplastics were recorded. These results highlight that exposures to nanoplastics may have deleterious effects on planktonic stages of oysters, presumably interacting with biological membranes and causing cyto/genotoxicity with potentially drastic consequences for their reproductive success., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

Oysters are a diverse group of marine bivalves that inhabit coastal systems of the world's oceans, providing a variety of ecosystem services, and represent a major socioeconomic resource. However, oyster reefs have become inevitably impacted from habitat destruction, overfishing, pollution and disease outbreaks that have pushed these structures to the break of extinction. In addition, the increased frequency of climate change related events promise to further challenge oyster species survival worldwide. Oysters' early embryonic development is likely the most vulnerable stage to climate change related stressors (e.g. salinity and temperature shifts) as well as to pollutants (e.g. arsenic), and therefore can represent the most important bottleneck that define populations' survival in a changing environment. In light of this, the present study aimed to assess two important oyster species, Crassostrea angulata and Crassostrea gigas embryo-larval development, under combinations of salinity (20, 26 and 33), temperature (20, 24 and 28 °C) and arsenic (As) exposure (0, 30, 60, 120, 240, 480, 960 and 1920 μg. As L -1 ), to infer on different oyster species capacity to cope with these environmental stressors under the eminent threat of climate change and increase of pollution worldwide. Results showed differences in each species range of salinity and temperature for successful embryonic development. For C angulata, embryo-larval development was successful at a narrower range of both salinity and temperature, compared to C. gigas. Overall, As induced higher toxicity to C. angulata embryos, with calculated EC50 values at least an order of magnitude lower than those calculated for C. gigas. The toxicity of As (measured as median effective concentration, EC50) showed to be influenced by both salinity and temperature in both species. Nonetheless, salinity had a greater influence on embryos' sensitivity to As. This pattern was mostly noticed for C. gigas, with lower salinity inducing higher sensitivity to As. Results were discussed considering the existing literature and suggest that C. angulata populations are likely to become more vulnerable under near future predictions for temperature rise, salinity shifts and pollution., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

The combined effects of different salinity and temperature levels on the toxicity of Arsenic (As) were studied on the embryonic development of the oyster Crassostrea gigas. A standardized embryotoxicity test was performed to assess the interactive effects of these stressors, in a full factorial design experiment including a range of salinities (15, 19, 24, 28 and 32), temperatures (16, 20, 24, 28 and 32°C) and As concentrations (100, 300, 600, 1200, 2400µgL -1 ). The embryotoxicity endpoint was about the determination of normal larvae development rates at various conditions, and median effect concentration (EC 50 ) determination for each As exposure condition. Results showed that toxicity induced by As was characterized by retardation of embryonic development observing toxic effects at lower concentrations than previously reported studies. The presence of As in seawater resulted in a narrower range of tolerance to both salinity and temperature. These findings bring new insights on the impacts of a common contaminant on an important shellfish species having a planktonic early life stage development, with potential implications for population survival and ecosystem functioning in a changing environment., (Copyright © 2017 Elsevier Inc. All rights reserved.)

Persistent organic pollutants (POPs) are ubiquitous and coexisted in the aquatic environment. Individual and combined toxic effects of benzo[a]pyrene (BaP) and 2,2',4,4'-tetrabromodiphenyl ether (BDE-47) on embryogenesis, and larval survival of the Pacific oyster were investigated. The EC 50 values of BaP, BDE-47 and their mixture on embryogenesis were 18.4, 203.3 and 72.0 µg/L respectively, while the LC 50 values for 96 h larval mortality were 26.8, 244.5 and 108.9 µg/L respectively. The Marking-Dawson additive toxicity indices were -0.02 and -0.19, indicating an additive effect with a trend to antagonism. In addition, DNA strand breaks were also observed in oyster embryos after exposure. Our study suggests that BaP and BDE-47 exposure can cause developmental abnormalities, DNA damage and larval mortality. Furthermore, the toxicity of the mixture is slightly lower than individual pollutant. These data will be helpful to predict the toxicity of organic pollutants, and provide criteria for marine water quality standards.

Phenanthnere (PHE) is a polycyclic aromatic hydrocarbon continuously discarded in the marine environment and bioavailable to many aquatic species. Although studies about PHE toxicity have been documented for adult oysters, the effects on early developmental stages are poorly characterized in bivalves. In this study, the effects of PHE (0.02 and 2.0μg.L -1 ) were evaluated on the embryogenesis and larval development of Crassostrea gigas. Toxicity bioassays, growth and deformities assessment, analysis of shell calcium abundance and transcript levels of genes related to xenobiotic biotransformation (CYP2AU2, CYP30C1), immune system (Cg-Tal) and tissue growth and shell formation (Ferritin, Insulin-like, Cg-Try, Calmodulin and Nacrein) were assayed in D-shape larvae after 24h of PHE exposure. At the highest concentration (2.0μg.L -1 ), PHE decreased the frequency of normal development (19.7±2.9%) and shell size (53.5±2.8mm). Developmental deformities were mostly related to abnormal mantle and shell formation. Lower calcium levels in oyster shells exposed to PHE 2.0μg.L -1 were observed, suggesting effects on shell structure. At this same PHE concentration, CYP30C1, Cg-Tal, Cg-Tyr, Calmodulin were upregulated and CYP2AU2, Ferritin, Nacrein, and Insulin-Like were downregulated compared to control larvae. At the lowest PHE concentration (0.02μg.L -1 ), it was observed a minor decrease in normal larval development (89,6±6%) and the remaining parameters were not affected. This is the first study to provide evidences that exposure to PHE can affect early oyster development at the molecular and morphological levels, possibly threatening this bivalve species., (Copyright © 2017 Elsevier B.V. All rights reserved.)

Kuwait is a country with low rainfall and highly concentrated industrial and domestic effluents entering its coastal waters. These can be both treated and untreated. In this study we sampled a series of coastal and open-sea sites and used a variety of analyses to identify those sites requiring the most attention. We used a high throughput GC-MS screen to look for over 1000 chemicals in the samples. Estrogen and androgen screens assessed the potential to disrupt endocrine activity. An oyster embryo development screen was used to assess biological effect potential. The chemical screen identified sites which had high numbers of identified industrial and domestic chemicals. The oyster screen showed that these sites had also caused high levels of developmental abnormalities with 100% of embryos affected at some sites. The yeast screen showed that estrogenic chemicals were present in outfalls at 2-3 ng/l E2 equivalent, and detectable even in some open water sites., (Crown Copyright © 2015. Published by Elsevier Ltd. All rights reserved.)

The explosion of the Deepwater Horizon (DWH) oil platform resulted in large amounts of crude oil and dispersant Corexit 9500A® released into the Gulf of Mexico and coincided with the spawning season of the oyster, Crassostrea virginica. The effects of exposing gametes and embryos of C. virginica to dispersant alone (Corexit), mechanically (HEWAF) and chemically dispersed (CEWAF) DWH oil were evaluated. Fertilization success and the morphological development, growth, and survival of larvae were assessed. Gamete exposure reduced fertilization (HEWAF: EC201h=1650μg tPAH50L(-1); CEWAF: EC201h=19.4μg tPAH50L(-1); Corexit: EC201h=6.9mgL(-1)). CEWAF and Corexit showed a similar toxicity on early life stages at equivalent nominal concentrations. Oysters exposed from gametes to CEWAF and Corexit experienced more deleterious effects than oysters exposed from embryos. Results suggest the presence of oil and dispersant during oyster spawning season may interfere with larval development and subsequent recruitment., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

Lightsticks are artifacts used as attractors in a type of commercial fishery, known as surface longline gear. Despite the excessive use, the contamination risks of these devices have not yet been properly investigated. This research aimed to fill up this gap by determining the chemical composition and the toxicity of lightsticks recently activated, compared to those one year after activation and to the ones collected on the beaches. The analyzes were carried out by Gas Chromatography coupled with Mass Spectrometry (GC-MS). Additionally, the variations in composition and the toxicity of their sea Water Soluble Fractions (WSF) were evaluated based on the WSF-effects of Crassostrea rhizophorae embryonic development. The GC-MS analysis made possible the identification of nineteen substances in the water soluble fraction of the lightsticks, such as dibutyl phthalate (DBP) and dimethyl phthalate (DMP). The value of the WSF-effective concentration (EC50) was in an average of 0.35%. After one year of the lightsticks activation, the toxicity was even higher (0.65%). Furthermore, other substances, also present in the lightsticks-WSF caused persistent toxicity even more dangerous to the environment than DBP and DMP. This essay discusses their toxicity effects and possible environment damages., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

The brevetoxin-producing dinoflagellate, Karenia brevis, adversely affects many shellfish species including the commercially and ecologically important bivalve molluscs, the northern quahog (=hard clam) Mercenaria mercenaria and eastern oyster Crassostrea virginica, in the Gulf of Mexico, USA. This study assessed the effects of exposure of these bivalves to K. brevis during their early development. In separate experiments, embryos of 2-4 cell stage of M. mercenaria and C. virginica were exposed to both whole and lysed K. brevis cells isolated from Manasota Key, Florida. Low bloom concentrations of 500 to 3000 cells mL(-1) were simulated for 96 h. Shell length, percent abnormality (and normality), and percent mortality of resulting larvae were measured. Percentages were recorded after 6, 24, and 96 h of exposure; larval shell length was measured at 24 and 96 h. For both quahogs and oysters, the effects of exposing embryos to K. brevis on all larval responses were generally dose- and time-dependent. Percent mortalities and abnormalities of both clam and oyster embryos increased significantly after only 6h of exposure to whole cells of K. brevis. For clams, these parameters were significantly higher in whole and lysed treatments (at 3000 cells mL(-1)) than in controls. Percent mortalities of oysters were significantly higher in the whole-cell treatment (3000 cells mL(-1)) than under control conditions. After 24h of exposure, mean larval shell length of both bivalve species was significantly reduced relative to controls. This was evident for clam larvae in both the lysed treatment at 1500 cells mL(-1) and in whole and lysed treatments at 3000 cells mL(-1), and for oyster larvae in the lysed treatment at 3000 cells mL(-1). After 96 h, both species exposed to the lysed cell treatment at 3000 cells mL(-1) had significantly smaller larvae compared to those in the control. Overall, lysed cells of K. brevis had a more pronounced effect on shell length, percent abnormality, and mortality in both clams and oysters than did whole cells. Given the fact that blooms of K. brevis overlap with the spawning periods of these two bivalves, and that cells of this naked dinoflagellate are readily lysed by wave action, these results suggest that exposure to K. brevis during the early life history stages of clams and oysters could adversely affect their population recruitment. Further, the presence of whole or lysed cells of K. brevis in hatcheries could have a major negative impact on production., (Copyright © 2014 Elsevier B.V. All rights reserved.)

Camamu Bay, an Environmentally Protected Area, may be affected by the pressures of tourism and oil exploration in the adjacent continental platform. The current quality of the mangrove sediments was evaluated by porewater bioassays using embryos of Crassostrea rhizophorae and by an analysis of benthic macrofauna and its relationships with organic compounds, trace metals and bioavailability. Porewater toxicity varied from low to moderate in the majority of the samples, and polychaetes dominated the benthos. The Grande Island sampling station (Station 1) presented more sandy sediments, differentiated macrobenthic assemblages and the highest metal concentrations in relation to other stations and guideline values, and it was the only station that indicated a possible bioavailability of metals. The origin of the metals (mainly barium) is most likely associated with the barite ore deposits located in the Grande and Pequena islands. These results may be useful for future assessment of the impact of oil exploration in the coastal region., (Copyright © 2010 Elsevier Inc. All rights reserved.)

We previously found that embryonic development of the bivalve species was highly vulnerable to xenobiotic chemicals, damaging the coastal ecosystem integrity To further assess their potential damage to ecosystem, the xenobiotic composition of the sediment elutriates from two representative industrialized Korean coasts, Pohang and Ulsan, were determined with gas chromatography/mass spectrometry (GC/MS). The presumed critical dilution of the elutriate was then exposed to early life stages of the Pacific oyster (Crassostrea gigas), embryonic development and metamorphic stage to first spat, at which they were believably more vulnerable by the chemical exposure. The early life damage by the xenobiotic exposure was apparently significant by the significant degree of pollution. Here, we indicated their potential damages to the Pacific oyster

Bioassays are routinely employed for sediment quality assessment. In order to be able to effectively use Bioassays responses in regulatory and management frameworks, toxicity scores, which rank toxicity data in defined classes that are continuous and difficult to interpret, should be reliable and suitable tools to support decisions about the presence or absence of toxicity in tested samples and on how toxic a sample is. A statistical approach is needed to define thresholds for toxicity scores. The Minimum Significance Difference (MSD) criterion allowed the evaluation of toxicity thresholds for each test-matrix and organism pair, based on large sets of experimental data. The MSD values were normalized with respect to the control, ranked in ascending order, and the 90th percentile was identified; the Toxicity Threshold (TT) was calculated by subtracting the 90th percentile from 100 and the Toxicity Limit (TL) was estimated as the percentage of control response multiplied by TT. Taking into account sample responses normalized with respect to control (S), when S > TL, the sample is considered nontoxic; when S

The effects of humic acid (HA) on copper speciation and its subsequent toxicity to the sensitive early life stages of the Pacific oyster (Crassostrea gigas) are presented. Differential pulse anodic stripping voltammetry with a hanging mercury drop electrode was used to measure the copper species as labile copper (LCu; free ion and inorganic copper complexes) and total copper (TCu) with respect to increasing HA concentration. The TCu and LCu 50% effect concentrations (EC50s) in the absence of HA were 20.77 microg/L (95% confidence interval [CI], 24.02-19.97 microg/L) and 8.05 microg/L (95% CI, 9.6-5.92 microg/L) respectively. A corrected dissolved organic carbon (DOC) concentration (HA only) of 1.02 mg/L was required to significantly increase the TCu EC50 to approximately 41.09 microg/L (95% CI, 44.27-37.52 microg/L; p < 0.05), almost doubling that recorded when DOC (as HA) was absent from the test media. In contrast, the LCu EC50 was unaffected by changes in DOC concentration and was stable throughout the corrected DOC concentration range. The absence of change in the LCu EC50, despite increased HA concentration, suggests that the LCu fraction, not TCu, was responsible for the observed toxicity to the oyster embryo. This corresponds with the current understanding of copper toxicity and supports the free-ion activity model for copper toxicity.

Wood is widely used in the development of freshwater, estuarine and marine coastlines. Timbers last according to their content of naturally occurring preservatives (mostly phenols and aldehydes), produced to prevent decay from biotic agents. When untreated woods are exposed to aquatic media, leachates are generated with likely toxic effects on the target environment. The potential impact on saltwaters of leachates from some untreated timbers of both native and tropical species has been assessed. The leaching procedure was set up considering British Standard test methods for paints and OECD guidelines for wood preservatives emission scenarios. Toxicity was monitored via the acute toxicity test with the brine shrimp Artemia franciscana and the sub-chronic embryotoxicity test with the oyster Crassostrea gigas. Brine shrimps evidenced no toxic effects while oysters discriminated well among leachates: the tropical wood species showed similar or relatively lower toxic effects than the native ones according to both leaching cycles (24 and 72 h). The ecotoxicological data have been integrated with some physical and chemical parameters.

Methodological research was carried out to evaluate the discriminatory capability of three toxicity bioassays toward different elutriation ratios (1:4, 1:20, 1:50, and 1:200 sediment:water ratios). Samples from six sampling stations of the Lagoon of Venice have been investigated. The toxicity bioassay results (sea urchin Paracentrotus lividus Lmk sperm cell and embryo toxicity bioassays and bivalve mollusk Crassostrea gigas Thunberg embryo toxicity bioassays) have shown that elutriates generated from the widely used 1:4 ratio were less toxic than those from intermediate ratios (1:20 and 1:50).