Immunotoxicity and oxidative stress in the Arctic scallop Chlamys islandica: effects of acute oil exposure

Development of an effective QSAR-based hazard threshold prediction model for the ecological risk assessment of aromatic hydrocarbon compounds

The insufficient hazard thresholds of specific individual aromatic hydrocarbon compounds (AHCs) with diverse structures limit their ecological risk assessment. Thus, herein, quantitative structure-activity relationship (QSAR) models for estimating the hazard threshold of AHCs were developed based on the hazardous concentration for 5% of species (HC5) determined using the optimal species sensitivity distribution models and on the molecular descriptors calculated via the PADEL software and ORCA software. Results revealed that the optimal QSAR model, which involved eight descriptors, namely, Zagreb, GATS2m, VR3_Dzs, AATSC2s, GATS2c, ATSC2i, ω, and Vm, displayed excellent performance, as reflected by an optimal goodness of fit (R2adj = 0.918), robustness (Q2LOO = 0.869), and external prediction ability (Q2F1 = 0.760, Q2F2 = 0.782, and Q2F3 = 0.774). The hazard thresholds estimated using the optimal QSAR model were approximately close to the published water quality criteria developed by different countries and regions. The quantitative structure-toxicity relationship demonstrated that the molecular descriptors associated with electrophilicity and topological and electrotopological properties were important factors that affected the risks of AHCs. A new and reliable approach to estimate the hazard threshold of ecological risk assessment for various aromatic hydrocarbon pollutants was provided in this study, which can be widely popularised to similar contaminants with diverse structures.

Toxic effects of polystyrene nanoplastics and polycyclic aromatic hydrocarbons (chrysene and fluoranthene) on the growth and physiological characteristics of Chlamydomonas reinhardtii

While the toxicity of nano-microplastics and polycyclic aromatic hydrocarbons (PAHs) to aquatic organisms is well-studied, their joint impact on microalgae is less explored. This study focused on single and combined effects of PS-NPs (30 nm; concentrations: 2, 5, 10, and 25 mg/L) and two PAHs (chrysene and fluoranthene at 10, 100 µg/L) for 96 h on the accumulation, growth, photosynthetic parameters, and oxidative stress in the Chlamydomonas reinhardtii. The findings revealed that exposure to increasing concentrations of PS-NPs significantly reduced the growth inhibition ratio and chlorophyll-a content after 96 h. Both PAHs (100 µg/L) + PS-NPs (25 mg/L), significantly reduced the growth inhibition ratio and chlorophyll-a levels. Individual and combined exposures of PS-NPs and PAHs can prompt antioxidant responses like SOD, GPx, and GST, as well as an unaffected level of non-enzymatic antioxidant GSH and diminished CAT activity. Furthermore, both PAHs + PS-NPs triggered ROS levels, resulting in cell membrane damage. However, the reduced oxidative effect of LPO of combined exposures can be attributed to the activation of antioxidant defenses. In addition, the microscopic visualization data shows that PS-NPs adhered to the surface of microalgae. Also, PS-NPs reduced the adsorption of PAHs on the surface of C. reinhardtii. Altogether, this study implied that the influence of coexistent PS-NPs should be considered in the environmental risk assessment of PAHs in aquatic environments.

Autochthonous psychrophilic hydrocarbonoclastic bacteria and its ecological function in contaminated cold environments

Petroleum hydrocarbon (PH) pollution has mostly been caused by oil exploration, extraction, and transportation activities in colder regions, particularly in the Arctic and Antarctic regions, where it serves as a primary source of energy. Due to the resilience feature of nature, such polluted environments become the realized ecological niches for a wide community of psychrophilic hydrocarbonoclastic bacteria (PHcB). In contrast, to other psychrophilic species, PHcB is extremely cold-adapted and has unique characteristics that allow them to thrive in greater parts of the cold environment burdened with PHs. The stated group of bacteria in its ecological niche aids in the breakdown of litter, turnover of nutrients, cycling of carbon and nutrients, and bioremediation. Although such bacteria are the pioneers of harsh colder environments, their growth and distribution remain under the influence of various biotic and abiotic factors of the environment. The review discusses the prevalence of PHcB community in colder habitats, the metabolic processes involved in the biodegradation of PH, and the influence of biotic and abiotic stress factors. The existing understanding of the PH metabolism by PHcB offers confirmation of excellent enzymatic proficiency with high cold stability. The discovery of more flexible PH degrading strategies used by PHcB in colder environments could have a significant beneficial outcome on existing bioremediation technologies. Still, PHcB is least explored for other industrial and biotechnological applications as compared to non-PHcB psychrophiles. The present review highlights the pros and cons of the existing bioremediation technologies as well as the potential of different bioaugmentation processes for the effective removal of PH from the contaminated cold environment. Such research will not only serve to investigate the effects of pollution on the basic functional relationships that form the cold ecosystem but also to assess the efficacy of various remediation solutions for diverse settings and climatic conditions.

Modulation of innate immune responses in the flame scallop Ctenoides scaber (Born, 1778) caused by exposure to used automobile crankcase oils

The used automobile crankcase oils are potential sources of contaminant elements for the coastal-marine ecosystems, affecting mainly the immunological system of organisms that feed by filtration, e. g. scallops. This study examined the effects of a water-soluble fraction of used automobile crankcase oils (WSF-UACO) on innate cellular- and humoral immune responses of the flame scallop Ctenoides scaber. The scallops were exposed to ascending concentrations of 0, 0.001, 0.01, and 0.1 of WSF-UACO under a static system of aquaria during 7 and 13 d. The viability, haemocyte total count (HTC), lysosomal membrane destabilization (LMD), phagocytosis, and protein concentration in hemolymph samples withdrawn taken from the blood sinus as well as lysozyme activity of the digestive gland were measured as immune endpoints. A decrease in cellular immune competence in scallops exposed to WSF-UACO was observed, with significant impairment of viability, HTC, and phagocytosis. LMD index increased about exposure concentrations, and plasma protein concentrations augmented to 0.01 and 0.1% during 13 d. Lysozyme activity increased in scallops exposed to WSF-UVCO during 7 d, to level off in the chronic period. Lysozyme activity and enhanced plasma proteins could act as compensatory responses when cell parameters tend to fall, helping to the regulation of microbial microflora and possible invasion of pathogenic microbes as well as defense against xenobiotics. The results demonstrate that the immunological responses of C. scaber are highly sensitive to the complex chemical mixture of contaminants, and it could be used for evaluating biological risks of hazardous xenobiotics in tropical marine environments. Republic of Ecuador.

Unravelling the molecular mechanism of mutagenic factors impacting human health

Environmental mutagens are chemical and physical substances in the environment that has a potential to induce a wide range of mutations and generate multiple physiological, biochemical, and genetic modifications in humans. Most mutagens are having genotoxic effects on the following generation through germ cells. The influence of germinal mutations on health will be determined by their frequency, nature, and the mechanisms that keep a specific mutation in the population. Early prenatal lethal mutations have less public health consequences than genetic illnesses linked with long-term medical and social difficulties. Physical and chemical mutagens are common mutagens found in the environment. These two environmental mutagens have been associated with multiple neurological disorders and carcinogenesis in humans. Thus in this study, we aim to unravel the molecular mechanism of physical mutagens (UV rays, X-rays, gamma rays), chemical mutagens (dimethyl sulfate (DMS), bisphenol A (BPA), polycyclic aromatic hydrocarbons (PAHs), 5-chlorocytosine (5ClC)), and several heavy metals (Ar, Pb, Al, Hg, Cd, Cr) implicated in DNA damage, carcinogenesis, chromosomal abnormalities, and oxidative stress which leads to multiple disorders and impacting human health. Biological tests for mutagen detection are crucial; therefore, we also discuss several approaches (Ames test and Mutatox test) to estimate mutagenic factors in the environment. The potential risks of environmental mutagens impacting humans require a deeper basic knowledge of human genetics as well as ongoing research on humans, animals, and their tissues and fluids.

Reduction in Toxicity of Polystyrene Nanoplastics Combined with Phenanthrene through Binding of Jellyfish Mucin with Nanoplastics

Mucin (Mu), a biological substance extracted from jellyfish (Aurelia aurita), was used to reduce the toxic effect of polystyrene nanoplastics (PS-NP) combined with phenanthrene (Phe) in the aquatic environment of zebrafish (Danio rerio), among other aquatic organisms. Mu showed a high binding capacity, as it bound to 92.84% and 92.87% of the PS-NPs (concentration of 2.0 mg/L) after 0.5 h and 8 h, respectively. A zebrafish embryo development test was conducted to check for any reduction in toxicity by Mu. When exposed to PS-NP + Mu and PS-NP + Phe + Mu, respectively, the hatching rates were 88.33 ± 20.21% and 93.33 ± 2.89%, respectively; these results were not significantly different from those of the control group. However, the hatching rate with the addition of Mu increased, compared to that of the PS-NP (71.83 ± 13.36%) and Phe (37.50 ± 19.83%) treatments, and the morphological abnormality rate decreased. The presence of Mu was also found to obstruct the absorption of PS-NP and PS-NP + Phe by the zebrafish. When zebrafish embryos were exposed to PS-NP at a concentration of 5.0 mg/L, the hatching rate differed significantly from that of the control group, and the expression of CAT and p53 genes increased significantly, but the expression of Bcl-2 decreased significantly. An mRNA sequence analysis revealed that the gene expression levels of the test group containing Mu were similar to those of the control group. These results infer that Mu can be used as a biological material to collect and remove PS-NPs from aquatic environments and reduce toxicity.

Organic UV Filters Induce Toll-like-Receptors and Related Signaling Pathways in Peripheral Blood Mononuclear Cells of Juvenile Loggerhead Sea Turtles (Caretta caretta)

Simple Summary

Emerging environmental contaminants, such as sunscreen agents, have been broadly identified in marine ecosystems. Thus, the present work aims to investigate whether organic UV filters cause immunotoxic effects in juvenile loggerhead sea turtles (Caretta caretta). We found that loggerhead sea turtles showing high circulating levels of organic UV filters manifested increased expression of genes involved in inflammatory responses, probably due to contaminant-induced oxidative damage.

Abstract

Recent evidence suggests that exposure to organic ultraviolet filters (UV filters) is associated with dysregulated neuroendocrine-immune homeostasis. Marine species are likely to be among the most vulnerable to UV filters due to widespread diffusion of these chemicals in the aquatic environment. In the present study, the effects of UV filter bioaccumulation on toll-like-receptors (TLRs) and related signaling pathways were investigated in peripheral blood mononuclear cells (PBMCs) of juvenile loggerhead sea turtles (Caretta caretta). We found that the expression of both TLR1 and TLR2 was significantly increased in UV-filter exposed turtles compared to control animals. Similarly, the signaling pathway downstream of activated TLRs (i.e., Ras-related C3 botulinum toxin substrate 1 (RAC1), Phosphoinositide 3-kinase (PI3K), serine/threonine-protein kinase (AKT3), and nuclear factor κB (NF-κB)) was significantly up-regulated, leading to an enhanced transcription of pro-inflammatory cytokines. In addition, we demonstrated that high levels of plasma UV filters increased lipid peroxidation in sea turtles’ PBMCs. Our results indicated that UV filters affected the inflammatory responses of PBMCs via modulation of the TLR/NF-κB signaling pathway and provided a new insight into the link between exposure to sunscreen agents and sea turtle health.

Immunotoxicity of Perfluorooctanoic Acid to the Marine Bivalve Species Ruditapes philippinarum

Polyfluorinated alkylated substances are recognized as an important class of pollutants in marine environments. Bivalves are good model organisms for evaluating the toxicity of pollutants and monitoring marine environments. In the present study, immunotoxicity of perfluorooctanoic acid (PFOA) was investigated by measuring biomarkers of the immune profile of Ruditapes philippinarum. In bivalves, hemocytes are an important component of the immune system. Thus, hemocyte proliferation, phagocytosis, cell viability, and immune enzyme activities, which have been applied as marine pollution bioindicators, were identified and observed for changes after exposure to PFOA in R. philippinarum. Based on the integrated biomarker responses method, we selected five biomarkers to evaluate PFOA risk at the multibiomarker level. In addition, the histopathological alterations of hemocytes in bivalves were used as indexes of the response to environmental stress. The subcellular structure of the hemocytes in R. philippinarum changed significantly with PFOA exposure, including hemocyte and nucleus morphological changes, organelle dissolution, cytomembrane and karyotheca swelling, and cytoplasm vacuolization. The present study verifies PFOA immunotoxicity to R. philippinarum at different levels and the integrated assessment of stress levels caused by PFOA in marine environment. Our results will provide new insights into evaluating adverse effects of PFOA and monitoring marine ecosystem. Environ Toxicol Chem 2022;41:426-436. © 2021 SETAC.

The mechanism of apoptosis of Chlamys farreri hemocytes under benzopyrene stress in vitro

Hemocytes are critical to the immune defense system of bivalves, and polycyclic aromatic hydrocarbons (PAHs) can mediate the immunity of bivalves by affecting the apoptosis of hemocytes. However, the underlying mechanism is still unclear. Chlamys farreri, as an important economic bivalve, was selected as the research subject for this experimentation. The hemocytes were exposed to typical PAHs-benzopyrene (B[a]P) in vitro to explore the apoptosis mechanism through detecting oxidative stress and oxidative damage-related indicators, apoptosis pathway factors, and apoptosis rate within 24 h. The results showed that the reactive oxygen species (ROS) and benzo[a]pyrene-7,8-diol-9,10-epoxide (BPDE) content in hemocytes increased significantly under B[a]P exposure, while antioxidant genes, glutathione peroxidase content and total antioxidant capacity all showed a trend of first rising and subsequent falling. B[a]P also caused serious damage to DNA and lysosomal membrane stability. The proapoptotic factors genes in the mitochondrial apoptosis pathway were significantly up-regulated, and the anti-apoptotic gene Bcl-2 was significantly down-regulated. Besides, mitochondrial membrane potential stability was significantly reduced and caspase 9 enzyme activity was significantly improved with the B[a]P stimulation. The factors of death receptor pathway were also significantly up-regulated by B[a]P. Moreover, the expression levels of Mitogen-Activated Protein Kinases were also induced. The gene expression and enzyme activity of the caspase 3 and the apoptosis rate were significantly increased under B[a]P exposure. In conclusion, these results indicated that ROS was induced by B[a]P, and further triggered the oxidative stress and oxidative damage in hemocytes. B[a]P induced hemocyte apoptosis was mediated by both mitochondrial apoptosis pathway and death receptor apoptosis, and the activation of mitochondrial apoptosis pathway was affected by ROS. In addition, BPDE and MAPKs may play important roles in the B[a]P-mediated apoptosis pathway. This study deepens understanding of the apoptosis pathway and the immunotoxicity mechanism in bivalves hemocytes stimulated by persistent organic pollutants.

Antioxidant responses and okadaic acid accumulation in Laeonereis acuta (Annelida) exposed to the harmful dinoflagellate Prorocentrum cf. lima

We evaluated the accumulation of okadaic acid (OA), a diarrhetic toxin, and the antioxidant responses in the marine annelid Laeonereis acuta exposed to the benthic toxigenic dinoflagellate Prorocentrum cf. lima. Nontoxic Tetraselmis sp. was used as a control diet. Living cells of the two algae were supplied as food to animals kept in agar medium for 72 h. To assess the significance of the observed effects, our experimental design treated the algal species (diet), algal cell densities, and exposure time as fixed factors. Responses of the organisms were assessed through oxidative stress biomarkers (glutathione-S-transferase [GST], catalase [CAT], reduced glutathione [GSH] and lipid peroxidation [LPO]). Toxin accumulation was measured by LC-MS/MS in whole-body homogenates after 12, 24 and 72 h of exposure. Worms exposed to the toxigenic dinoflagellate gradually accumulated OA, with toxin levels directly related to the cell density of Prorocentrum cf. lima. Worms fed with Prorocentrum cf. lima exhibited decreased CAT activity, increased LPO levels - both interactively affected by algal species and time - and decreased GSH levels, which were interactively affected by algal species and cell density. Higher LPO levels, along with the inhibition of CAT and GSH, clearly indicated an oxidative stress situation in worms exposed to the toxigenic dinoflagellate. Laeonereis acuta accumulated moderate OA levels and may act as a vector of OA to food webs in estuarine areas under high Prorocentrum cf. lima abundance.

Under ice spills of conventional crude oil and diluted bitumen: Physiological resilience of the blue mussel and transgenerational effects

Spillages at sea of diluted bitumen (dilbit) from oil sands have received little attention until now. To our best knowledge, there are no reports on the impact of a severe exposure to dilbit on the Blue mussel (Mytilus edulis). In this study, adult Blue mussels were exposed to one conventional crude oil (Heidrun) and two dilbits (Cold Lake Blend and Access Western Blend) for a period of 7 days in an ice-covered environment and then maintained for three months until the spawning season. The exposed mussels were monitored for aromatic hydrocarbon bioaccumulation, physiological energetic budget, cellular stress, byssus production and gametogenesis. In spring, spawning was induced to characterize breeding success. Bioaccumulation of polycyclic aromatic hydrocarbons (PAHs) was detected after three days of exposure, with higher concentrations of PAHs associated to the conventional oil (5.49 ± 0.12 μg·g^-1 d.w.) compared to both dilbits (0.91 ± 0.02 μg·g^-1; 0.51 ± 0.03 μg·g^-1 d.w.). Despite a fast depuration rate and a good resilience of the exposed mussels, significant negative effects were observed at the cellular, physiological and fitness levels, especially in offspring. Our results suggest a higher toxicity of the diluted bitumen compared to the conventional crude despite the lower bioaccumulation of total PAHs. Dilbit treatments caused evident negative transgenerational effects on unexposed F1 generation.

Combined Effects of Elevated Temperature and Crude Oil Pollution on Oxidative Stress and Apoptosis in Sea Cucumber (Apostichopus japonicus, Selenka)

Currently, global climate change and oil pollution are two main environmental concerns for sea cucumber (Apostichopus japonicus) aquaculture. However, no study has been conducted on the combined effects of elevated temperature and oil pollution on sea cucumber. Therefore, in the present study, we treated sea cucumber with elevated temperature (26 °C) alone, water-accommodated fractions (WAF) of Oman crude oil at an optimal temperature of 16 °C, and Oman crude oil WAF at an elevated temperature of 26 °C for 24 h. Results showed that reactive oxygen species (ROS) level and total antioxidant capacity in WAF at 26 °C treatment were higher than that in WAF at 16 °C treatment, as evidenced by 6.03- and 1.31-fold-higher values, respectively. Oxidative damage assessments manifested that WAF at 26 °C treatment caused much severer oxidative damage of the biomacromolecules (including DNA, proteins, and lipids) than 26 °C or WAF at 16 °C treatments did. Moreover, compared to 26 °C or WAF at 16 °C treatments, WAF at 26 °C treatment induced a significant increase in cellular apoptosis by detecting the caspase-3 activity. Our results revealed that co-exposure to elevated temperature and crude oil could simulate higher ROS levels and subsequently cause much severer oxidative damage and cellular apoptosis than crude oil alone on sea cucumber.

Time-Dependent Naphthalene Toxicity in Anabas testudineus (Bloch): A Multiple Endpoint Biomarker Approach

Polyaromatic compounds are the major, widespread contaminants in the aquatic environment. However, the adverse impacts of these compounds on blood pathophysiology (hematological profiling and serum biochemical responses) are poorly understood. As a consequence, this study was intended to evaluate the toxic effects of naphthalene, one of the polycyclic aromatic hydrocarbons, on the blood pathophysiology of Anabas testudineus using multiple end-point biomarker approach. A. testudineus was exposed to short-term (1 and 5 d) and long-term (10, 15, and 21 d) naphthalene concentrations, that is, T1 (0.71 mg/L indicates 25% of LC₅₀) and T2 (1.42 mg/L indicates 50% of LC₅₀ value). The results disclosed significant decrease in red blood cells, hemoglobin (Hb), packed cell volume, and platelet levels, while other blood parameters, namely, white blood cells, percent lymphocyte, mean cell volume, mean corpuscular Hb, and mean corpuscular Hb concentration showed enhanced levels under naphthalene intoxication. Results were more detrimental under T2 concentration. Cholesterol, glucose, calcium, high-density lipoprotein, and low-density lipoprotein levels gradually increased throughout the different exposure periods under T1 and T2 concentrations, while the triglyceride level gradually decreased during exposure periods. Finally, integrated biomarker responses (IBR) analysis indicated that serum biochemical parameters are more powerful than hematological parameters for determining the naphthalene-induced fish health status. Additionally, the IBR study clearly identified that long-term (>5 d) exposure was more harmful than short-term (<5 d) naphthalene exposure. So, these responses may be derived as biomarkers for monitoring naphthalene pollution in an aquatic ecosystem.

Environmental effects of offshore produced water discharges: A review focused on the Norwegian continental shelf

Produced water (PW), a large byproduct of offshore oil and gas extraction, is reinjected to formations or discharged to the sea after treatment. The discharges contain dispersed crude oil, polycyclic aromatic hydrocarbons (PAHs), alkylphenols (APs), metals, and many other constituents of environmental relevance. Risk-based regulation, greener offshore chemicals and improved cleaning systems have reduced environmental risks of PW discharges, but PW is still the largest operational source of oil pollution to the sea from the offshore petroleum industry. Monitoring surveys find detectable exposures in caged mussel and fish several km downstream from PW outfalls, but biomarkers indicate only mild acute effects in these sentinels. On the other hand, increased concentrations of DNA adducts are found repeatedly in benthic fish populations, especially in haddock. It is uncertain whether increased adducts could be a long-term effect of sediment contamination due to ongoing PW discharges, or earlier discharges of oil-containing drilling waste. Another concern is uncertainty regarding the possible effect of PW discharges in the sub-Arctic Southern Barents Sea. So far, research suggests that sub-arctic species are largely comparable to temperate species in their sensitivity to PW exposure. Larval deformities and cardiac toxicity in fish early life stages are among the biomarkers and adverse outcome pathways that currently receive much attention in PW effect research. Herein, we summarize the accumulated ecotoxicological knowledge of offshore PW discharges and highlight some key remaining knowledge needs.

Effects of graded levels of starch on the non-specific immune responses, antioxidant capacities and intestinal health in Chinese mitten crab, Eriocheir inensis

A 9-week feeding trial was conducted to investigate the effects of graded levels of dietary starch (12%, 17%, 22%, 27% and 32%) on growth, non-specific immune responses, antioxidant capacities, immunity genes expression levels and pathogen resistance in Chinese mitten crab, Eriocheir inensis (initial body weight: 10.5 ± 0.5 g). Results showed that the highest weight gain rate of crabs was obtained in group containing 22% dietary starch. The highest activity of acid phosphatase, phenoloxidase and lysozyme in blood was found in crabs fed with 22-27% dietary starch. Additionally, 17%-27% dietary starch significantly increased the activities of superoxide dismutase and glutathione peroxidase, reduced malondinaldehyde content and then increased the total antioxidant capacities in hepatopancreas of crabs. The highest activity of alanine aminotransferase and aspartate aminotransferase was found in crabs fed with 32% dietary starch, indicating that excess starch had a negative effect on the liver function of crabs. With the dietary starch level increased, the transcription factors gene expression of the pro-inflammatory factors were significantly up-regulated, and the highest ILF2, IL-16, Relish and ADAM10 was found in crabs fed with dietary 32% starch, which may potentially promote the inflammatory response in intestines. Moreover, with the dietary starch increased, the activity of phenoloxidase and lysozyme, as well as the gene expression of crustin, were all increased in crabs after challenge against Citrobacter freundii, which demonstrated that additional dietary starch could provide immune-protection and help crabs improve their resistance against pathogens. In conclusion, these results suggest that adequate dietary starch can increase growth, enhance innate immune responses and promote disease resistance, reduce oxidative stress and inflammatory response in E. inensis. Taken together, 22-27% dietary starch (25.9-30.8% dietary carbohydrate) was suggested as a digestible energy source in crabs feed.

Antioxidant Response and Oxidative Stress in the Respiratory Tree of Sea Cucumber (Apostichopus japonicus) Following Exposure to Crude Oil and Chemical Dispersant

Sea cucumber (Apostichopus japonicus) is mainly cultured in the coastal zone, where it is easily threatened by accidental oil spills. Chemical dispersant is one of the efficient oil spill responses for mitigating the overall environmental damage of oil spills. However, the impact of crude oil and chemical dispersants on sea cucumber is less well known. Hence, the present study focused on exploring the antioxidant response and oxidative stress in the respiratory tree of sea cucumber following exposure to GM-2 chemical dispersant (DISP), water-accommodated fractions (WAF), and chemically enhanced WAF (CEWAF) of Oman crude oil for 24 h. Results manifested that WAF exposure caused a significant increase in the reactive oxygen species (ROS) level (5.29 ± 0.30 AU·mgprot−1), and the effect was much more obvious in CEWAF treatment (5.73 ± 0.16 AU·mgprot−1). Total antioxidant capacity (T-AOC), as an important biomarker of the antioxidant defense capacity, showed an increasing trend following WAF exposure (0.95 ± 0.12 U·mgprot−1) while a significant reduction in T-AOC was observed following CEWAF exposure (0.23 ± 0.13 U·mgprot−1). Moreover, we also evaluated the oxidative damage of the macromolecules (DNA, protein, and lipid), and our results revealed that the presence of chemical dispersant enhanced oxidative damage caused by crude oil to sea cucumber.

Toxicities of Polycyclic Aromatic Hydrocarbons for Aquatic Animals

Polycyclic aromatic hydrocarbons (PAHs) are organic compounds that are widely distributed in the air, water, and soil. Recently, the amount of PAHs derived from fuels and from incomplete combustion processes is increasing. In the aquatic environment, oil spills directly cause PAH pollution and affect marine organisms. Oil spills correlate very well with the major shipping routes. Furthermore, accidental oil spills can seriously impact the marine environment toxicologically. Here, we describe PAH toxicities and related bioaccumulation properties in aquatic animals, including invertebrates. Recent studies have revealed the toxicity of PAHs, including endocrine disruption and tissue-specific toxicity, although researchers have mainly focused on the carcinogenic toxicity of PAHs. We summarize the toxicity of PAHs regarding these aspects. Additionally, the bioaccumulation properties of PAHs for organisms, including invertebrates, are important factors when considering PAH toxicity. In this review, we describe the bioaccumulation properties of PAHs in aquatic animals. Recently, microplastics have been the most concerning environmental problem in the aquatic ecosystem, and the vector effect of microplastics for lipophilic compounds is an emerging environmental issue. Here, we describe the correlation between PAHs and microplastics. Thus, we concluded that PAHs have a toxicity for aquatic animals, indicating that we should emphasize the prevention of aquatic PAH pollution.

Partial characterization of the lipidome of the cold-water scallop, Chlamys islandica

Fingerprinting of the main lipid components of the digestive gland of the Icelandic scallop-Chlamys islandica-has been performed by ultra-high-performance liquid chromatography coupled with time of flight high-resolution mass spectrometry, UHPLC-HRMS/ToF. This method allowed the identification of 224 lipids, including phosphatidylcholines (PC), plasmanyl (PC-O)/plasmenyl (PC-P) phosphatidylcholines, lyso-phosphatidylcholines (LPC), and their plasmanyl/plasmenyl forms (LPC-O/LPC-P). Diacylglycerols (DG), triacylglycerols (TG), and cholesteryl esters (CE) were the neutral lipids (NL) analyzed. While all of the lipids showed a strong seasonal dependence in terms of quantity, only NLs presented significant qualitative changes. Principal component analysis (PCA) of TG and DG profiles evidenced a prevalence of low unsaturated TGs and DGs in spring, which were replaced by species with a higher degree of unsaturations in summer. In autumn, long and highly unsaturated TGs constitute the lipid fraction of the digestive gland of the scallop, while DG species offer a mixed profile. This study contributes to the characterization and the elucidation of the lipidome of Chlamys islandica and provides baseline data for further study of the effects of pollutants on the lipidome of the Icelandic scallop, often used as a sentinel species in biomonitoring programs.

Effects of Marine Toxin Domoic Acid on Innate Immune Responses in Bay Scallop Argopecten irradians

Domoic acid (DA) is an amnesic shellfish poisoning toxin produced by some species of the genera Pseudo-nitzschia and Nitzschia. This toxin has harmful effects on various species, especially scallops. This study aimed to investigate the effects of DA exposure on the immune and physical responses of bay scallop, Argopecten irradians. Various immunological and physical parameters were assessed (acid phosphatase (ACP), alkaline phosphatase (ALP), lactate dehydrogenase (LDH), lipid peroxide (LPO), nitric oxide (NO), and the total protein content) in the haemolymph of scallops at 3, 6, 12, 24, and 48 h post-exposure to DA at different concentrations (10, 50, and 100 ng/mL). Moreover, the expression of immune-related genes (CLT-6, FREP, HSP90, MT, PGRP, and PrxV) was assessed. The activities of ACP, ALP, and LDH and the total protein content and LPO increased upon exposure to DA at different concentrations, while NO levels were decreased. Furthermore, immune-related genes were assessed upon DA exposure. Our results showed that exposure to DA negatively impacts immune function and disrupts physiological activities in bay scallops.

Proteomic analysis of oxidized proteins in the brain and liver of the Nile tilapia (Oreochromis niloticus) exposed to a water-accommodated fraction of Maya crude oil

Crude oil (CO) is a super mixture of chemical compounds whose toxic effects are reported in fish species according to international guidelines. In the current study a proteomic analysis of oxidized proteins (ox) was performed on the brain and liver of Nile tilapia exposed to WAF obtained from relevant environmental loads (0.01, 0.1 and 1.0 g/L) of Maya CO. Results have shown that oxidation of specific proteins was a newly discovered organ-dependent process able to disrupt key functions in Nile tilapia. In control fish, enzymes involved on aerobic metabolism (liver aldehyde dehydrogenase and brain dihydrofolate reductase) and liver tryptophan--tRNA ligase were oxidized. In WAF-treated liver specimens, fructose-bisphosphate aldolase (FBA), β-galactosidase (β-GAL) and dipeptidyl peptidase 9 (DPP-9) were detected in oxidized form. oxDPP-9 could be favorable by reducing the risk associated with altered glucose metabolism, the opposite effects elicited by oxFBA and oxβ-GAL. oxTrypsin showed a clear adverse effect by reducing probably the hepatocyte capacity to achieve proteolysis of oxidized proteins as well as for performing the proper digestive function. Additionally, enzyme implicated in purine metabolism adenosine (deaminase) was oxidized. Cerebral enzymes of mitochondrial respiratory chain complex (COX IV, COX5B), of glycosphingolipid biosynthesis (β-N-acetylhexosaminidase), involved in catecholamines degradation (catechol O-methyltransferase), and microtubule cytoskeleton (stathmin) were oxidized in WAF-treated specimens. This response suggests, in the brain, an adverse scenario for the mitochondrial respiration process and for ATP provision as for ischemia/reoxygenation challenges. Proteomic analysis of oxidized proteins is a promising tool for monitoring environmental quality influenced by hydrocarbons dissolved in water.

Acute exposure to water-soluble fractions of marine diesel oil: Evaluation of apoptosis and oxidative stress in an ascidian

To understand the mechanisms involved in organisms' responses to toxicity from oil pollution, we studied the effect of acute exposure (24 h) to the marine water-soluble fraction of diesel oil (WFDO) on the ascidian Styela plicata. We evaluated the mortality and behavior by means of the siphon reflex, and the response of blood cells (hemocytes) contained in the pharynx, by means of the production of nitric oxide (NO) and reactive oxygen species (ROS), in addition to the activity of the antioxidant enzyme catalase (CAT). We also correlated oxidative stress with the activation of apoptotic pathways. No mortality occurred 24 h after the ascidians were exposed to 5% and 10% marine WFDO; however, the siphon reflex, a behavioral test based on the time that the animals took to close their siphons, increased. We also observed an inflammatory response, as estimated by the increase in the number of hemocytes in the pharynx. NO and ROS production and CAT activity were reduced, whereas caspase-3, a signaling molecule involved in apoptosis, was activated. This suggests that in ascidians acutely exposed to oil, another mechanism can occur in addition to oxidative stress. Another possibility is that WFDO may directly interact with cellular macromolecules and activate caspase-3, independently of generating oxidative stress. The results showed that components of diesel oil affected a marine organism, which showed reduced ROS production in the pharynx cells, including hemocytes, and activation of apoptotic pathways.

What is the relationship between the bioaccumulation of chemical contaminants in the variegated scallop Mimachlamys varia and its health status? A study carried out on the French Atlantic coast using the Path ComDim model

Increasing activity along the French Atlantic coast has led to chronic pollution with, in particular, mixtures of contaminants such as hydrocarbons, phytosanitary products, PCBs and heavy metals. Based on previous research, pollution biomarkers were used in this study as they can indicate health status when monitoring the impact of pollutants on coastal species such as the marine bivalve Mimachlamys varia. Mollusc bivalves were sampled in March 2016, in open and semi-open areas (a harbour zone), from thirteen sites which differed in terms of their level of pollution, and were located along the Atlantic coast from Brittany down to the Nouvelle-Aquitaine region. First, analyses of heavy metals and organic contaminants (e.g. pesticides, polycyclic aromatic hydrocarbons, polychlorobiphenyl) in the digestive gland of bivalves were performed. Second, biochemical assays were used to study defence biomarkers: oxidative stress with Superoxide Dismutase (SOD), detoxification of organic compounds with Glutathione-S Transferase (GST), lipid peroxidation with Malondialdehyde (MDA), and immune processes with Laccase. In addition to the biochemical assays, a genetic approach was used to measure genetic diversity (haplotype and nucleotide diversity) at each site. Biomarker assays and genetic diversity were correlated with the chemical contaminants in bivalves using the Path-ComDim statistical model. Our results showed specific correlations between biochemical assays in the digestive glands with heavy metal contaminants, and between genetic diversity and organic pollution. Blocks of responses were analysed for correlations in order to develop standardized tools and guidelines that could improve our understanding of the short-term and long-term impact of contaminants on physiological parameters.

Physiological and immunological responses to mass mortality in noble scallop Chlamys nobilis cultured in Nan'ao waters of Shantou, China

The noble scallop Chlamys nobilis has been a commercially important marine cultured bivalve in the Southern Sea of China for decades. Mass mortality events, however, often occur during scallops' cultivation. Mortality of up to 67%-90% was recorded at the beginning of March in 2017 in some culture areas of Nan'ao (Shantou, China), spreading to all scallops within a week. In the present study, in order to investigate the response of the noble scallop at the physiological and molecular level during mass mortality, scallops with different mortalities of 90%, 67%, and 6% were sampled from three sites at Hunter bay, Baisha bay, and Longhai, respectively. Total carotenoids content (TCC), total antioxidant capacity (TAC), malondialdehyde (MDA) content and the expression levels of three immune-related genes (toll-like receptor, C-type lectin receptor and big defensing) in different scallop tissues were determined. The scallops were divided into three groups of sub-health, lesion, and health. TAC, TCC, as well as transcript levels of CnTLR-1, Cnlec-1 and CnBD in sub-health and lesion scallops were all significantly lower (P < 0.05) than those in health scallops, while MDA in sub-health and lesion scallops were significantly higher than those in health scallops (P < 0.05). Similarly, TCC and TAC in lesion scallops were both higher than sub-health scallops. Moreover, significantly positive correlations were found between TCC and TAC (P < 0.05) and between CnTLR-1 and Cnlec-1 (P < 0.05), while significantly negative correlations were found between TCC and CnTLR-1 (P < 0.05), TCC and Cnlec-1 (P < 0.05), TAC and CnBD (P < 0.05), as well as between MDA and Cnlec-1 (P < 0.001). All the results indicate that noble scallops significantly change their physiological and molecular levels when suffering from stress, and that their antioxidant and immune response systems play important defense functions.

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.

Comparative toxicity of Corexit® 9500, oil, and a Corexit®/oil mixture on the eastern oyster, Crassostrea virginica (Gmelin)

Given their particle feeding behavior, sessile nature, and abundance in coastal zones, bivalves are at significant risk for exposure to oil and oil dispersant following environmental disasters like the Deepwater Horizon oil spill. However, the effects of oil combined with oil dispersants on the health of oysters are not well studied. Therefore, eastern oysters (Crassostrea virginica) were exposed in vivo to Corexit^® 9500, crude oil (high-energy water accommodated fraction; HEWAF), and a Corexit^®/oil mixture (chemically-enhanced water accommodated fraction; CEWAF) to evaluate potential toxic effects on immunological (phagocytosis and respiratory burst), physiological (feeding rate), and histological endpoints. Phagocytosis was significantly increased following CEWAF exposure only. Respiratory burst was significantly decreased following Corexit^® exposure, but significantly increased following exposure to the highest concentration of CEWAF. Oyster feeding rates were significantly decreased following exposure to Corexit^®, HEWAF, and CEWAF, and were most sensitive to CEWAF exposure. These modulations of important immunological and physiological functions could result in serious health outcomes for oysters, such as increased parasitism and decreased growth. Our experiments showed that subtle, sub-lethal effects occurred following acute in vivo exposure to Corexit^®, HEWAF, and CEWAF, though oysters were not equally sensitive to the three components. Data from this study can be used for more accurate risk assessment concerning the impact of oil and Corexit^® on the health of oysters.

Estimating the acute impacts of Arctic marine oil spills using expert elicitation

Increasing maritime traffic in the Arctic has heightened the oil spill-related risks in this highly sensitive environment. To quantitatively assess these risks, we need knowledge about both the vulnerability and sensitivity of the key Arctic functional groups that may be affected by spilled oil. However, in the Arctic these data are typically scarce or lacking altogether. To compensate for this limited data availability, we propose the use of a probabilistic expert elicitation methodology, which we apply to seals, anatids, and seabirds. Our results suggest that the impacts of oil vary between functional groups, seasons, and oil types. Overall, the impacts are least for seals and greatest for anatids. Offspring seem to be more sensitive than adults, the impact is greatest in spring, and medium and heavy oils are the most harmful oil types. The elicitation process worked well, yet finding enough skilled and motivated experts proved to be difficult.

Native and exotic oysters in Brazil: Comparative tolerance to hypercapnia

Environmental hypercapnia in shallow coastal marine ecosystems can be exacerbated by increasing levels of atmospheric CO₂. In these ecosystems organisms are expected to become increasingly subjected to pCO₂ levels several times higher than those inhabiting ocean waters (e.g.: 10,000µatm), but still our current understanding on different species capacity to respond to such levels of hypercapnia is limited. Oysters are among the most important foundation species inhabiting these coastal ecosystems, although natural oyster banks are increasingly threatened worldwide. In the present study we studied the effects of hypercapnia on two important oyster species, the pacific oyster C. gigas and the mangrove oyster C. brasiliana, to bring new insights on different species response mechanisms towards three hypercapnic levels (ca. 1,000; 4,000; 10,000 µatm), by study of a set of biomarkers related to metabolic potential (electron transport system - ETS), antioxidant capacity (SOD, CAT, GSH), cellular damage (LPO) and energetic fitness (GLY), in two life stages (juvenile and adult) after 28 days of exposure. Results showed marked differences between each species tolerance capacity to hypercapnia, with contrasting metabolic readjustment strategies (ETS), different antioxidant response capacities (SOD, CAT, GSH), which generally allowed to prevent increased cellular damage (LPO) and energetic impairment (GLY) in both species. Juveniles were more responsive to hypercapnia stress in both congeners, and are likely to be most sensitive to extreme hypercapnia in the environment. Juvenile C. gigas presented more pronounced biochemical alterations at intermediate hypercapnia (4,000µatm) than C. brasiliana. Adult C. gigas showed biochemical alterations mostly in response to high hypercapnia (10,000µatm), while adult C. brasiliana were less responsive to this environmental stressor, despite presenting decreased metabolic potential. Our data bring new insights on the biochemical performance of two important oyster species, and suggest that the duration of extreme hypercapnia events in the ecosystem may pose increased challenges for these organisms as their tolerance capacity may be time limited.

Effects of phenanthrene on early development of the Pacific oyster Crassostrea gigas (Thunberg, 1789)

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.

Pre-acclimation to low copper mitigated immunotoxic effects in spleen and head-kidney of large yellow croaker (Pseudosciaena crocea) when exposed subsequently to high copper

The hypothesis tested in this study was that Cu pre-acclimation would mitigate high Cu induced immunotoxic effects in large yellow croaker Pseudosciaena crocea. To the end, fish were pre-acclimation to 0 and 84μg CuL^-1 for 48h and then exposed to 0 and 420μg CuL^-1 for another 48h. Survival rate, Cu content, ROS, NO, activities and mRNA levels of inflammatory genes (iNOS and COX-2), and gene expressions of transcription factor NF-κB and its inhibitor IκBα were determined in spleen and head-kidney of large yellow croaker. Cu pre-acclimation significantly reduced mortality of fish exposed to 420μg CuL^-1. Cu pre-acclimation triggered the up-regulation of both enzyme activities and express levels of iNOS and COX-2 in spleen under 420μg CuL^-1 exposure, resulting in remarkable reduction of Cu content and ROS in this tissue. Contrast to spleen, iNOS activity remained unchanged but the mRNA level of iNOS increased, and the mRNA level of COX-2 remained constant though COX-2 activity enhanced in head-kidney, suggesting iNOS and COX-2 may be modulated by Cu at a post-transcriptional level. In this process, NF-κB/IκBα signaling molecules may play a vital role in the transcriptional activation of inflammatory genes in both spleen and head-kidney. In conclusion, low Cu pre-acclimation alleviated high Cu induced immunotoxicity in spleen and head-kidney of large yellow croaker by enhancing the activities and mRNA levels of inflammatory genes.

Exposure to seismic air gun signals causes physiological harm and alters behavior in the scallop Pecten fumatus

Seismic surveys map the seabed using intense, low-frequency sound signals that penetrate kilometers into the Earth's crust. Little is known regarding how invertebrates, including economically and ecologically important bivalves, are affected by exposure to seismic signals. In a series of field-based experiments, we investigate the impact of exposure to seismic surveys on scallops, using measurements of physiological and behavioral parameters to determine whether exposure may cause mass mortality or result in other sublethal effects. Exposure to seismic signals was found to significantly increase mortality, particularly over a chronic (months postexposure) time scale, though not beyond naturally occurring rates of mortality. Exposure did not elicit energetically expensive behaviors, but scallops showed significant changes in behavioral patterns during exposure, through a reduction in classic behaviors and demonstration of a nonclassic "flinch" response to air gun signals. Furthermore, scallops showed persistent alterations in recessing reflex behavior following exposure, with the rate of recessing increasing with repeated exposure. Hemolymph (blood analog) physiology showed a compromised capacity for homeostasis and potential immunodeficiency, as a range of hemolymph biochemistry parameters were altered and the density of circulating hemocytes (blood cell analog) was significantly reduced, with effects observed over acute (hours to days) and chronic (months) scales. The size of the air gun had no effect, but repeated exposure intensified responses. We postulate that the observed impacts resulted from high seabed ground accelerations driven by the air gun signal. Given the scope of physiological disruption, we conclude that seismic exposure can harm scallops.

Antioxidant defenses in polar cod (Boreogadus saida) and responsiveness toward dietary crude oil exposure

Increasing anthropogenic activities in the Arctic pose the risk for accidental oil spills but our knowledge of ecotoxicological effects is still limited for Arctic organisms. This study aimed to provide insights in baseline levels of antioxidants in polar cod (Boreogadus saida) from different Arctic locations and investigate the susceptibility of this species to oxidative stress during a 32 day dietary crude oil exposure. Baseline levels of individual antioxidants and total oxyradical scavenging capacity (TOSC) varied among different Arctic fjords. Upon crude oil exposure, dose- and time-dependent polycyclic aromatic hydrocarbons (PAHs) biotransformation was evident through hepatic ethoxyresorufine-O-deethylase activity, glutathione S-transferase mRNA expression and biliary PAH metabolites. Changes in the activity of individual antioxidants and TOSC was, however, slight and transient upon exposure. In conclusion, biotransformation was clearly induced by the sub-lethal levels of crude oil in polar cod, while the antioxidant defense responded with high variability.

Combination of polycyclic aromatic hydrocarbons and temperature exposure: In vitro effects on immune response of European clam (Ruditapes decussatus)

Marine organisms are subjected to various biotic and abiotic factors such as changes of temperature and pollutants [e.g. polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), and heavy metals, which may affect their defense mechanisms. In this context, the aim was to evaluate the combined effects of temperature (20 and 30 °C) and PAHs (fluorene, phenanthrene and pyrene) at two concentrations (10^-5 and 10^-3 mg mL^-1) on the immune responses of the European clam Ruditapes decussatus were after 24 h of in vitro exposure. Total haemocyte count, cell viability, phenoloxidase, lysozyme, alkaline phosphatase, esterase, antibacterial and agglutinating activities were measured. Exposure to high temperatures resulted in lower phosphatase alkaline activity and higher haemocyte viability and antibacterial and haemagglutinating activities, compared with the values recorded for clams maintained at low temperature. Only pyrene induced a significant decrease in haemocyte lysozyme (at 20 and 30 °C) and esterase (at 30 °C) activities. The total haemocyte count was increased by phenanthrene and pyrene at 20 °C and at 30 °C, respectively. Alkaline phosphatase activity increased when haemocytes were exposed to pyrene at 30 °C but decreased in the presence of fluorene at 20 °C. Furthermore, haemocyte viability was low in the presence of pyrene and fluorene at 20 °C and 30 °C, respectively, but was unaffected by phenanthrene. Antibacterial activity was significantly increased and no-significantly affected by the presence of pyrene and fluorene at 20 °C and 30 °C, respectively. The present study demonstrates the strong effect of PAHs and high temperature on haemocyte viability and other important immune functions, including phosphatase alkaline and antibacterial activities. Furthermore, changes in the immune parameters of European clam resulting from high temperatures may modulate the effects of PAHs and vice versa.

Preparing for the unprecedented - Towards quantitative oil risk assessment in the Arctic marine areas

The probability of major oil accidents in Arctic seas is increasing alongside with increasing maritime traffic. Hence, there is a growing need to understand the risks posed by oil spills to these unique and sensitive areas. So far these risks have mainly been acknowledged in terms of qualitative descriptions. We introduce a probabilistic framework, based on a general food web approach, to analyze ecological impacts of oil spills. We argue that the food web approach based on key functional groups is more appropriate for providing holistic view of the involved risks than assessments based on single species. We discuss the issues characteristic to the Arctic that need a special attention in risk assessment, and provide examples how to proceed towards quantitative risk estimates. The conceptual model presented in the paper helps to identify the most important risk factors and can be used as a template for more detailed risk assessments.

Effects of dispersed oil exposure on biomarker responses and growth in juvenile wolfish Anarhichas denticulatus

This study evaluated the sensitivity of the wolfish Anarhichas denticulatus exposed to crude oil, comparing the effects of mechanically dispersed versus chemically dispersed oil using sub-lethal endpoints. To test the toxicity of this controversial technique, two experiments involving exposure of the organisms for 48 h were conducted. The first experiment assessed the effects of oil exposure on biomarker responses. The second experiment monitored the growth of juveniles over 5 weeks after exposure. Overall, this study demonstrated that polycyclic aromatic hydrocarbon (PAH) biliary metabolites, ethoxyresorufin-O-deethylase (EROD), and acetylcholinesterase (AChE) are appropriate biomarkers to assess exposure of A. denticulatus. Growth rate, both in length and weight, was significantly higher in control compared to oil exposure treatments. The lack of differences between chemically and mechanically dispersed oils in biomarker response and growth suggests that dispersant application is no more toxic than the natural oil dispersion. The results indicate the potential for population-level effects resulting from exposure to oil.

Transcriptional response of four C1q domain containing protein (C1qDC) genes from Venerupis philippinarum exposed to the water soluble fraction of No.0 diesel oil

As pattern recognitionreceptors, the C1q-domain-containing (C1qDC) proteins play an important role in the pathogen recognition and complement pathway activation. In the present study, four novel C1q domain containing proteins (designated as VpC1qDC1, VpC1qDC2, VpC1qDC3 and VpC1qDC4) were cloned and characterized from clam Venerupis philippinarum. The four VpC1qDCs all possessed the conserved features critical for the fundamental structure and function of the C1q family. The four VpC1qDCs genes showed differential response profiles after exposure to the water soluble fraction of No.0 diesel oil (WSFD). More notably, VpC1qDC1 and VpC1qDC3 were more sensitive to low concentration of WSFD, as their mRNA level changed by higher magnitudes. In addition, VpC1qDC2 and VpC1qDC4 displayed notable increases with larger amplitude to high concentration of WSFD. All these results suggested that the transcriptional response of VpC1qDCs genes were probably a protective mechanism of the cell to oils pollution. The diverse expression patterns of VpC1qDCs demonstrated that VpC1qDC1 and VpC1qDC3 were sensitive responders to environmental stress in V. philippinarum.

Marine Toxin Okadaic Acid Affects the Immune Function of Bay Scallop (Argopecten irradians)

Okadaic acid (OA) is produced by dinoflagellates during harmful algal blooms and is a diarrhetic shellfish poisoning toxin. This toxin is particularly problematic for bivalves that are cultured for human consumption. This study aimed to reveal the effects of exposure to OA on the immune responses of bay scallop, Argopecten irradians. Various immunological parameters were assessed (total hemocyte counts (THC), reactive oxygen species (ROS), malondialdehyde (MDA), glutathione (GSH), lactate dehydrogenase (LDH), and nitric oxide (NO) in the hemolymph of scallops at 3, 6, 12, 24, and 48 h post-exposure (hpe) to different concentrations of OA (50, 100, and 500 nM). Moreover, the expression of immune-system-related genes (CLT-6, FREP, HSP90, MT, and Cu/ZnSOD) was also measured. Results showed that ROS, MDA, and NO levels and LDH activity were enhanced after exposure to different concentrations of OA; however, both THC and GSH decreased between 24-48 hpe. The expression of immune-system-related genes was also assessed at different time points during the exposure period. Overall, our results suggest that exposure to OA had negative effects on immune system function, increased oxygenic stress, and disrupted metabolism of bay scallops.

First evidence of marine diesel effects on biomarker responses in the Icelandic scallops, Chlamys islandica

The decrease of ice cover in polar areas is expected to lead to an increase in ship traffic. In this context, the risk associated with exposure of the aquatic environment to oil-related chemicals from spills and/or accidental fuel discharges from ships will increase in the near future, potentially causing negative impacts on sensitive Arctic species. This study investigated for the first time the biomarker responses of the Icelandic scallops (Chlamys islandica) to marine diesel exposure. Antioxidant response, neurotoxic effect, gonad maturation, and lipid content were assessed in male and female scallops, Chlamys islandica after a 7-day exposure to marine diesel. At the end of exposure, results showed an inhibition of acetylcholinesterase activity in Icelandic scallops exposed to high concentration of diesel. At the end of exposure, results showed an increase in naphthalene residues in hemolymph, together with an inhibition of AChE activity in Icelandic scallops exposed to high concentration of diesel. In addition, alteration of the escape capacity was observed suggesting effects on behavior responses. Overall, this study contributes to the better knowledge of physiological effects of marine diesel in Arctic marine organisms.

Biological effects of mechanically and chemically dispersed oil on the Icelandic scallop (Chlamys islandica)

This study aimed to simulate conditions in which dispersant (Dasic NS) might be used to combat an oil spill in coastal sub-Arctic water of limited depth and water exchange in order to produce input data for Net Environmental Benefit Analysis (NEBA) of Arctic and sub-Arctic coastal areas. Concentration dependent differences in acute responses and long-term effects of a 48h acute exposure to dispersed oil, with and without the application of a chemical dispersant, were assessed on the Arctic filter feeding bivalve Chlamys islandica. Icelandic scallops were exposed for 48h to a range of spiked concentrations of mechanically and chemically dispersed oil. Short-term effects were assessed in terms of lysosomal membrane stability, superoxide dismutase, catalase, gluthatione S-transferases, glutathione peroxidases, glutathione reductase, glutathione, total oxyradical scavenging capacity, lipid peroxidation and peroxisomal proliferation. Post-exposure survival, growth and reproductive investment were followed for 2 months to evaluate any long-term consequence. Generally, similar effects were observed in scallops exposed to mechanically and chemically dispersed oil. Limited short-term effects were observed after 48h, suggesting that a different timing would be required for measuring the possible onset of such effects. There was a concentration dependent increase in cumulative post-exposure mortality, but long-term effects on gonadosomatic index, somatic growth/condition factor did not differ among treatments.

Short-Term and Long-Term Biological Effects of Chronic Chemical Contamination on Natural Populations of a Marine Bivalve

Understanding the effects of chronic chemical contamination on natural populations of marine organisms is complex due to the combined effects of different types of pollutants and environmental parameters that can modulate the physiological responses to stress. Here, we present the effects of a chronic contamination in a marine bivalve by combining multiple approaches that provide information on individual and population health. We sampled variegated scallops (Mimachlamys varia) at sites characterized by different contaminants and contamination levels to study the short and long-term (intergenerational) responses of this species to physiological stress. We used biomarkers (SOD, MDA, GST, laccase, citrate synthase and phosphatases) as indicators of oxidative stress, immune system alteration, mitochondrial respiration and general metabolism, and measured population genetic diversity at each site. In parallel, concentration of 14 trace metals and 45 organic contaminants (PAHs, PCBs, pesticides) in tissues were measured. Scallops were collected outside and during their reproductive season to investigate temporal variability in contaminant and biomarker levels. Our analyses revealed that the levels of two biomarkers (Laccase-type phenoloxidase and malondialdehyde) were significantly correlated with Cd concentration. Additionally, we observed significant seasonal differences for four of the five biomarkers, which is likely due to the scallop reproductive status at time of sampling. As a source of concern, a location that was identified as a reference site on the basis of inorganic contaminant levels presented the same level of some persistent organic pollutants (DDT and its metabolites) than more impacted sites. Finally, potential long-term effects of heavy metal contamination were observed for variegated scallops as genetic diversity was depressed in the most polluted sites.

Effect of dispersed crude oil on the feeding activity, retention efficiency, and filtration rate of differently sized blue mussels (Mytilus edulis)

The use of physiological response endpoints in environmental monitoring represents an opportunity to provide an integrated picture of health status and ecological fitness of individuals, and may provide an indication of potential longer term effects on aquatic organisms in the environment. The feeding behavior response sensitivity of blue mussels (Mytilus edulis) of differing size to dispersed crude oil (DCO) was investigated in a lab exposure experiment. The ability of mussels to recover following a single exposure was also investigated, as well as the response to consecutive exposures, in order to assess the utility of employing the same individuals in chronic environmental monitoring. Feeding physiology was assessed by measuring retention efficiency and filtration rate of individual mussels in a live-algae feeding assay. In addition, the percentage of mussels actively filtering during testing was calculated. The feeding physiology parameters were sensitive and able to discriminate exposed mussels from controls. Further, data indicated that larger mussels appear more suitable in environmental monitoring, as these animals showed both sensitivity and an ability to adapt and recover from exposure while remaining sensitive to subsequent treatments. Smaller mussels were also sensitive to the measured endpoints, even if these animals suffered higher rates of mortality during the exposure. Finally, when exposed to the high concentration of DCO, mussels displayed a tendency to close the valves and terminate filtration.

Biomarker modulation associated with marine diesel contamination in the Iceland scallop (Chlamys islandica)

The decrease of ice cover in the Arctic will lead to an increase of ship traffic in the upcoming decades. Consequently, oil pollution is expected. In this context, the goals of this study were to evaluate the biological impact of marine diesel contamination and, on this basis, to determine analytical tools of interest (biomarkers) for future biomonitoring of diesel spills. Using a 7-day contamination protocol, this study investigated biochemical modulations in the digestive gland of the Iceland scallop (Chlamys islandica). Incorporation of contaminants was verified assessing haemolymph metabolites. Results showed a response of glutathione-S-transferase to contamination suggesting detoxification processes and the suitability of such a tool for diesel spill biomonitoring. The lack of modulation of superoxide dismutase activity and lipid peroxidation suggests no oxidative stress and the unsuitability of these molecular tools for biomonitoring.

The immune system and its modulation mechanism in scallop

Scallops are a cosmopolitan family of bivalves, and some of them are highly prized as dominant aquaculture species. In the past decades, there have been increasing studies on the basic biology and immunology of scallops, and this review summarizes the research progresses of immune system and its modulation mechanism in scallop. As invertebrate, scallops lack adaptive immunity and they have evolved an array of sophisticated strategies to recognize and eliminate various invaders by employing a set of molecules and cells. It is evident that basic immune reactions such as immune recognition, signal transduction, and effector synthesis involved in immune response are accomplished in a variety of ways. They rely upon an extensive repertoire of phagocytosis, apoptosis and encapsulation of the circulating hemocytes for eliminating invasive pathogens, as well as the production of immune effectors that are active against a large range of pathogens or sensitive for the environmental stress. Furthermore, the molecular constitutions, metabolic pathways and immunomodulation mechanisms of the primitive catecholaminergic, cholinergic, enkephalinergic system and NO system in scallop are also discussed, which can be taken as an entrance to better understand the origin and evolution of the neuroendocrine-immune regulatory network in lower invertebrates.

Immunotoxicological effects of environmental contaminants on marine bivalves

Coastal areas are complex environments frequently contaminated by numerous pollutants that represent a potential threat to marine organisms, especially bivalves. These pollutants may have major ecological consequences. Although effects of different environmental contaminants on the immune system in marine bivalves have been already reported, a few of reviews summarizes these effects. The main purpose of this chapter relies on summarizing recent body of data on immunotoxicity in bivalves subjected to contaminants. Immune effects of heavy metals, pesticides, HAP, PCB and pharmaceuticals are presented and discussed and a particular section is devoted to nanoparticle effects. A large body of literature is now available on this topic. Finally, the urgent need of a better understanding of complex interactions between contaminants, marine bivalves and infectious diseases is noticed.

Assessment of immunotoxicity of dibutyl phthalate using live zebrafish embryos

This study set out to understand the immune-toxic effects of dibutyl phthalate (DBP) using transgenic, albino or AB line zebrafish. Zebrafish embryos were exposed to different concentrations of DBP, and the immune cells formation, phagocytosis ability were measured after a short-term exposure to DBP for 6 h post-fertilization (hpf) to 72 or 96 hpf. Exposure to DBP was found to inhibit the neutrophils and macrophage formation in a concentration-dependent manner. The ability of macrophage phagocytosis was all decreased after exposure to DBP, indicating the occurrence of immunotoxicity. The respiratory burst was induced, and the transcription levels of T/B cell-related genes rag1/2 were up-regulated. The overall results indicate that DBP in aquatic environment greatly influence the immune system in fish, and zebrafish embryos can serve as a reliable model for the developmental immunotoxicity of toxic-chemicals.

In situ evaluation of oxidative stress and immunological parameters as ecotoxicological biomarkers in a novel sentinel species (Mimachlamys varia)

Although the variegated scallop Mimachlamys varia seems to be a suitable sentinel species for contaminant monitoring, no study has identified biomarkers in this species. In order to fill this gap, this study conducted an in situ biomarker approach. M. varia were collected in contaminated and uncontaminated areas and responsiveness of oxidative stress and immunological biomarkers was evaluated in the digestive gland. In parallel, 14 trace element concentrations were evaluated in the same organ. Superoxide dismutase activity and malondialdehyde content responded efficiently to in situ contamination when a certain degree of contamination was reached. Laccase-type phenoloxidase showed a high sensitivity but saturation of the response was highlighted for the highest contaminations. Additionally, correlations were found between biomarkers and trace element concentrations. Taken together, results showed that biomarker approach conducted in the digestive gland of M. varia represents a sensitive analytical tool to highlight ecotoxicological issues in coastal marine ecosystems.

The detoxification process, bioaccumulation and damage effect in juvenile white shrimp Litopenaeus vannamei exposed to chrysene

This study aimed to evaluate the effect of chrysene (CHR) on detoxification enzymes, bioaccumulation and effect of CHR on biomolecule damage in different organs of the juvenile white shrimp Litopenaeus vannamei. In this study, juvenile white shrimp L. vannamei were exposed to CHR for 21 days at four different concentrations as 0, 0.3, 2.1 and 14.7 μg/L. Results showed that CHR bioaccumulation increased rapidly at first then reached a plateau. The activities of aryl hydrocarbon hydroxylase (AHH), 7-ethoxyresorufin O-deethylase (EROD), epoxide hydrolase (EH), glutathione-S-transferase (GST), sulfotransferase (SULT) and uridinediphosphate glucuronyltransferase (UGT) were induced and then became stable gradually. Moreover, 2.1 and 14.7 μg/L CHR treatments increased activity of superoxide dismutase (SOD) in gills and hepatopancreas, while total antioxidant capacity (T-AOC) and GSH/GSSG were suppressed after CHR exposure. Additionally, lipid peroxidation (LPO) levels, protein carbonyl (PC) contents and DNA damage were induced throughout the exposure period, and different trends were detected with time of exposure. Overall, these novel findings of CHR bioaccumulation and resulted toxicity demonstrate that CHR could affect the physical status of L. vannamei. This study will form a solid basis for a realistic extrapolation scientific data for aquaculture water monitoring and food security.

Effect of seawater desalination and oil pollution on the lipid composition of blue mussels Mytilus edulis L. from the White Sea

A study on the effect oil pollution under normal and reduced salinity had on blue mussels Mytilus edulis L. from the White Sea in an aquarium-based experiment and in the natural habitat revealed a change in gill total lipids as a compensatory response. The cholesterol concentration and the cholesterol/phospholipids ratio in gills were found to reflect the impact of the environmental factors (oil pollution and desalination), and evidence adaptive changes in the cell membrane structure. An elevated content of storage lipids (chiefly triacylglycerols) in the mussels in the aquarium experiment indicates, first of all, the uptake and accumulation of oil products in gill cells under both normal and reduced seawater salinity, while high triacylglycerols level in gill littoral mussels from 'control' biotope in the Gulf of Kandalaksha is primarily associated with the mussel׳s pre-spawning period.

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.

Adsorption of soluble oil from water to graphene

The toxicity of soluble oil to the aquatic environment has started to attract wide attention in recent years. In the present work, we prepare graphene according to oxidation and thermal reduction methods for the removal of soluble oil from the solution. Characterization of the as-prepared graphene are performed by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, Raman spectra, Brunauer-Emmett-Teller, X-ray photoelectron spectroscopy, and contact angle analysis. The adsorption behavior of soluble oil on graphene is examined, and the obtained adsorption data are modeled using conventional theoretical models. Adsorption experiments reveal that the adsorption rate of soluble oil on graphene is notably fast, especially for the soluble diesel oil, which could reach equilibrium within 30 min, and the kinetics of adsorption is perfectly consistent with a pseudo-second-order model. Furthermore, it is determined that the adsorption isotherm of soluble diesel oil with graphene fit the Freundlich model best, and graphene has a very strong adsorption capacity for soluble diesel oil in the solution. These results demonstrate that graphene is the material that provided both good adsorptive capacity and good kinetics, implying that it could be used as a promising sorbent for soluble oil removal from wastewater.