Adaptation of the bivalve embryotoxicity assay for the high throughput screening of emerging contaminants in Mytilus galloprovincialis

Effects of perfluorooctanoic acid on the nutritional quality of Mytilus edulis

Perfluorooctanoic acid (PFOA), which widely presents in marine environment, may produce some adverse effects to aquatic organism. Mytilus edulis are popular due to their high protein and low fat content in China. However, few studies have investigated the effects of PFOA on the quality of aquatic products. Here, PFOA effects on basic nutritional indices in M. edulis were measured, and possible mechanisms were explored. PFOA caused clear variation in physiological and biochemical indices of M. edulis. The contents of some important proteins, nutrients, and amino acids etc. dropped. Integrating metabolomics data, we speculate PFOA exposure triggered inflammation and oxidative stress in mussels, interfered with the metabolic pathways related to the quality and the transport and absorption pathways of metal ions, and affected the levels of some important elements and metabolites, thus decreasing the nutritional quality of M. edulis. The study provides new insights into PFOA adverse effects to marine organism, and may offer some references for some researchers to assess food quality and ecological risk to pollutants.

Current state of knowledge of environmental occurrence, toxic effects, and advanced treatment of PFOS and PFOA

Per- and polyfluoroalkyl substances (PFAS) are anthropogenic synthetic compounds, with high chemical and thermal stability and a persistent, stable and bioaccumulative nature that renders them a potential hazard for the environment, its organisms, and humans alike. Perfluorooctane sulfonic acid (PFOS) and Perfluorooctanoic acid (PFOA) are the most well-known substances of this category and even though they are phased out from production they are still highly detectable in several environmental matrices. As a result, they have been spread globally in water sources, soil and biota exerting toxic and detrimental effects. Therefore, up and coming technologies, namely advanced oxidation processes (AOPs) and advanced reduction processes (ARPs) are being tested for their implementation in the degradation of these pollutants. Thus, the present review compiles the current knowledge on the occurrence of PFOS and PFOA in the environment, the various toxic effects they have induced in different organisms as well as the ability of AOPs and ARPs to diminish and/or eliminate them from the environment.

A broad-taxa approach as an important concept in ecotoxicological studies and pollution monitoring

Aquatic invertebrates play a pivotal role in (eco)toxicological assessments because they offer ethical, cost-effective and repeatable testing options. Additionally, their significance in the food chain and their ability to represent diverse aquatic ecosystems make them valuable subjects for (eco)toxicological studies. To ensure consistency and comparability across studies, international (eco)toxicology guidelines have been used to establish standardised methods and protocols for data collection, analysis and interpretation. However, the current standardised protocols primarily focus on a limited number of aquatic invertebrate species, mainly from Arthropoda, Mollusca and Annelida. These protocols are suitable for basic toxicity screening, effectively assessing the immediate and severe effects of toxic substances on organisms. For more comprehensive and ecologically relevant assessments, particularly those addressing long-term effects and ecosystem-wide impacts, we recommended the use of a broader diversity of species, since the present choice of taxa exacerbates the limited scope of basic ecotoxicological studies. This review provides a comprehensive overview of (eco)toxicological studies, focusing on major aquatic invertebrate taxa and how they are used to assess the impact of chemicals in diverse aquatic environments. The present work supports the use of a broad-taxa approach in basic environmental assessments, as it better represents the natural populations inhabiting various ecosystems. Advances in omics and other biochemical and computational techniques make the broad-taxa approach more feasible, enabling mechanistic studies on non-model organisms. By combining these approaches with in vitro techniques together with the broad-taxa approach, researchers can gain insights into less-explored impacts of pollution, such as changes in population diversity, the development of tolerance and transgenerational inheritance of pollution responses, the impact on organism phenotypic plasticity, biological invasion outcomes, social behaviour changes, metabolome changes, regeneration phenomena, disease susceptibility and tissue pathologies. This review also emphasises the need for harmonised data-reporting standards and minimum annotation checklists to ensure that research results are findable, accessible, interoperable and reusable (FAIR), maximising the use and reusability of data. The ultimate goal is to encourage integrated and holistic problem-focused collaboration between diverse scientific disciplines, international standardisation organisations and decision-making bodies, with a focus on transdisciplinary knowledge co-production for the One-Health approach.

Intraspecific genetic lineages of a marine mussel show behavioural divergence when exposed to microplastic leachates

Worldwide, microplastic pollution has numerous negative implications for marine biota, exacerbating the effects of other forms of global anthropogenic disturbance. Mounting evidence shows that microplastics (MPs) not only cause physical damage through their ingestion, but also act as vectors for hazardous compounds by leaching absorbed and adsorbed chemicals. Research on the effects of plastic pollution has, however, largely assumed that species respond uniformly, while ignoring intraspecific diversity (i.e., variation within a single species). We investigated the effects of plastic leachates derived from factory-fresh (virgin) and beached microplastics on the behavioural responses of two genetic lineages of the Mediterranean mussel Mytilus galloprovincialis. Through laboratory behavioural experiments, we found that during exposure to leachates from beached microplastics (beached MPLs), Atlantic specimens moved significantly less than Mediterranean individuals in terms of both (i) proportion of individuals responding through movement and (ii) net and gross distances crawled. In contrast, no significant intraspecific differences were observed in the behaviour of either adults or recruits when exposed to MPLs from virgin microplastics (virgin MPLs). Additionally, the reception of cues from three amino acids (L-cysteine, proline and L-leucine) at increasing concentrations (10-5 M to 10-3 M in charcoal-filtered seawater) was tested by electrophysiological analysis using mussels exposed to beached MPLs or control seawater. We found significant intraspecific differences in response to 10-3 M L-cysteine (regardless of treatment) and 10-4 M L-cysteine (in mussels exposed to beached MPLs) and to 10-3 M proline (in mussels exposed to beached MPLs) and 10-5 M L-leucine. Our study suggests that intraspecific variation in a marine mussel may prompt different responses to plastic pollution, potentially triggered by local adaptation and physiological variability between lineages. Our work highlights the importance of assessing the effects of intraspecific variation, especially in environmental sentinel species as this level of diversity could modulate responses to plastic pollution.

Antidepressants and their metabolites primarily affect lysosomal functions in the marine mussel, Mytilus galloprovincialis

Antidepressants widely occur as emerging contaminants in marine coastal waters, with concentrations reported in the low ng/L range. Although at relatively lower levels with respect to other pharmaceuticals, antidepressants - fluoxetine (FLX) in particular - have attracted attention because of their striking effects exerted at low doses on marine invertebrates. In this study, the effects of four antidepressants including FLX, sertraline (SER), and citalopram, as members of the selective serotonin reuptake inhibitor (SSRI) class, and venlafaxine (VEN) as a member of the serotonin and norepinephrine reuptake inhibitor (SNRI) class, were evaluated in the mussel Mytilus galloprovincialis. In addition, the effects of two main metabolites of FLX and VEN, i.e., norfluoxetine (NFL) and O-desmethylvenlafaxine (ODV) respectively, were compared to those of the parent compounds. Eight concentrations of each drug (0.5-500 ng/L range) were tested on the early life stage endpoints of gamete fertilization and larval development at 48 h post fertilization (hpf). Egg fertilization was reduced by all compounds, except for VEN. Larval development at 48 hpf was affected by all SSRIs, but not by SNRIs. The above effects were significant but never exceeded 20 % of control values. Adult mussels were exposed in vivo for 7 days to environmental concentrations of the drugs (0.5, 5, and 10 ng/L) and a battery of eight biomarkers was assessed. Antidepressants primarily targeted lysosomal functions, decreasing haemocyte lysosome membrane stability (up to 70 % reduction) and increasing of the lysosome/cytosol ratio (up to 220 %), neutral lipid (up to 230 %), and lipofuscin (up to 440 %) accumulation in digestive gland. Only SER and NFL significantly affected catalase and glutathione-S-transferase activities in gills and digestive gland. NFL and ODV, were effective and sometimes more active than the parent compounds. All compounds impaired mussel health status, as indicated by the low to high stress levels assigned using the Mussel Expert System.

Toxicity of environmentally relevant concentration of PFAS chemicals in Lumbriculus variegatus (Oligochaeta, Lumbriculidae) - A multi-bioindicator study

PFAS, or per- and polyfluoroalkyl substances, are a family of man-made chemicals found in a variety of products from non-stick cookware and food wrappers to firefighting foams. PFAS are persistent and widely distributed in the environment, including aquatic environments. In this study we examined the impact of PFAS chemicals on the physiological and behavioral endpoints of Lumbriculus variegatus (i.e., blackworms). Lumbriculus variegatus is a species of freshwater annelid worm that plays key roles in shallow freshwater ecosystems. At an environmentally relevant concentration of 1 μg/L, 12-day aqueous exposure to long chain PFAS, including PFOA, PFOS and PFDA, each markedly slowed the pulse rate of the dorsal blood vessel in L. variegatus, indicating a suppressive effect on blood circulation. The mean pulse rate was reduced from 9.6 beats/minute to 6.2 and 7.0 beats/min in PFOA and PFOS, respectively (P < 0.0001). Further, PFOA, PFOS and PFDA reduced the escape responsiveness of L. variegatus to physical stimulation. The percentage of worms showing normal escape behavior was reduced from 99.0% in control to 90.6% in the PFOS exposed group (P < 0.01). In a chronic (4 week) growth study, exposure to overlying water and sediment spiked with PFOA, PFOS or PFDA reduced the total biomass and the number of worms, indicating a suppressive effect on worm population growth. For instance, PFOA and PFDA reduced the total dry biomass by 26.3% and 28.5%, respectively, compared to the control (P < 0.05). The impact of PFAS on blackworm physiology is accompanied by an increase in lipid peroxidation. The level of malondialdehyde (MDA), an indicator of lipid peroxidation, and catalase, a major antioxidant enzyme, were markedly increased in PFOA, PFOS and PFDA exposed groups. Interestingly, exposure to PFHxA, a short chain PFAS, had no detectable effect on any of the measured endpoints. Our results demonstrate that L. variegatus is highly sensitive to the toxic impact of long chain PFAS chemicals as measured by multiple endpoints including blood circulation, behavior, and population growth. Such toxicity may have a detrimental impact on L. variegatus and the freshwater ecosystems where it resides.

PPCPs in coastal wastewater treatment plant effluent and uptake by Pacific oysters (Crassostrea gigas): Findings from a laboratory experiment

Municipal wastewater treatment plant (WWTP) effluent is a primary source of pharmaceuticals and personal care products (PPCPs) to the marine environment, as most of these compounds are not fully removed during the treatment process. Continual discharge from WWTPs into coastal areas may act as a stressor by continually exposing organisms to a suite of PPCPs. To quantify organismal exposure to PPCP mixtures, we conducted a 12-week lab experiment that exposed Pacific oysters to effluent from two Oregon coastal WWTPs of different discharge capacities (permitted as <1 million gallons/day and >1 million gallons/day; or < or >3.785 million liters/day) at a dilution of 25 %. Composite samples of weekly collected effluent and a subset of freeze-dried oysters from experiment week 12 were analyzed for PPCPs. Though challenges with food availability inhibited our ability to confidently identify effects of the contaminants on growth and fitness, the experiment allowed us to examine uptake of contaminants from effluent into an estuarine bivalve of commercial importance. We detected 30 PPCPs and three alkylphenols in effluent and 13 PPCPs and four alkylphenols in oyster tissue, indicating high rates of release from secondary treatment and significant potential for marine organism exposure to and uptake of PPCPs in rural coastal areas.

Polystyrene Nanoplastics in Aquatic Microenvironments Affect Sperm Metabolism and Fertilization of Mytilus galloprovincialis (Lamark, 1819)

The continuous and unregulated discharge of wastes and pollutants into the aquatic environment has required constant monitoring of the risks incurred by aquatic ecosystems. Alarmism arises from plastic pollution as larger artifacts release nanoscale fragments that can contact free-living stages such as gametes, embryos, and larvae. Specifically, the interaction between spermatozoa, released in water in externally fertilizing species, and the surrounding microenvironment is essential for successful fertilization. Activation and kinematics of movement, proper maintenance of ionic balance, and chemotactism are processes highly sensitive to even minimal perturbations caused by pollutants such as polystyrene nanoplastics. Spermatozoa of Mytilus galloprovincialis (M. galloprovincialis), an excellent ecotoxicological model, undergo structural (plasma membrane ruptures, DNA damage) and metabolic (reduced motility, fertilizing capacity) damage upon exposure to 50 nm amino-modified polystyrene nanoplastics (nPS-NH2). Nanoplastics of larger diameter (100 nm) did not affect sperm parameters. The findings highlighted the negative impact that plastic pollution, related to nanoparticle diameter and concentration, could have on sperm quality and reproductive potential of organisms, altering the equilibrium of aquatic ecosystems.

The effect of interspecific and intraspecific diversity on microplastic ingestion in two co-occurring mussel species in South Africa

Interspecific and intraspecific diversity are essential components of biodiversity with far-reaching implications for ecosystem function and service provision. Importantly, genotypic and phenotypic variation within a species can affect responses to anthropogenic pressures more than interspecific diversity. We investigated the effects of interspecific and intraspecific diversity on microplastic ingestion by two coexisting mussel species in South Africa, Mytilus galloprovincialis and Perna perna, the latter occurring as two genetic lineages. We found significantly higher microplastic abundance in M. galloprovincialis (0.54 ± 0.56 MP items g-1WW) than P. perna (0.16 ± 0.21 MP items g-1WW), but no difference between P. perna lineages. Microbeads were the predominant microplastic (76 % in P. perna, 99 % in M. galloprovincialis) and polyethylene the prevalent polymer. Interspecific differences in microplastic abundance varied across locations, suggesting diverse sources of contamination. We suggest that microplastic ingestion can be species-specific even in organisms that coexist and play similar functional roles within ecosystems.

Occurrence of per- and polyfluorinated alkyl substances in wastewater treatment plants in Northern Italy

Wastewater treatment plants are known to be relevant input sources of per- and polyfluoroalkyl substances (PFAS) in the aquatic environment. This study aimed to investigate the occurrence, fate, and seasonal variability of twenty-five PFAS in four municipal wastewater treatment plants (WWTP A, B, C, and D) surrounding the city of Milan (Northern, Italy). Composite 24-h wastewater samples were collected in July and October 2021 and May and February 2022 from influents and effluents of the four WWTPs. PFAS were detected at concentrations ranging between 24.1 and 66.9 μg L-1 for influent and 13.4 and 107 μg L-1 for effluent wastewater samples. Perfluoropentanoic acid was the most abundant (1.91-30.0 μg L-1) in influent samples, whereas perfluorobutane sulfonic acid predominated (0.80-66.1 μg L-1) in effluent samples. In sludge, PFOA was detected in plant A at concentrations in the range of 96.6-165 ng kg-1 dw in primary sludge samples and 98.6-440 ng kg-1 dw in secondary treatment sludge samples. The removal efficiency of total PFAS varied between 6 % and 96 %. However, an increase of PFAS concentrations was observed from influents to effluents for plant D (during July and October), plant A (during October and May), and plant C (during May) indicating that biotransformation of PFAS precursors can occur during biological treatments. This was supported by the observed increase in concentrations of PFOA from primary to secondary treatment sludge samples in plant A. Moreover, the plant operating at shorter hydraulic retention times (plant D) showed lower removal efficiency (<45 %). Seasonal variation of PFAS in influent and effluent appears rather low and more likely due to pulse release instead of seasonal factors.

The biocide triclosan as a potential developmental disruptor in Mytilus early larvae

The broadly utilized biocide triclosan (TCS) is continuously discharged in water compartments worldwide, where it is detected at concentrations of ng-µg/L. Given its lipophilicity and bioaccumulation, TCS is considered potentially harmful to human and environmental health and also as a potential endocrine disruptor (ED) in different species. In aquatic organisms, TCS can induce a variety of effects: however, little information is available on its possible impact on invertebrate development. Early larval stages of the marine bivalve Mytilus galloprovincialis have been shown to be sensitive to environmental concentrations of a number of emerging contaminants, including EDs. In this work, the effects of TCS were first evaluated in the 48 h larval assay in a wide concentration range (0.001-1,000 μg/L). TCS significantly affected normal development of D-veligers (LOEC = 0.1 μg/L; EC50 = 236.1 μg/L). At selected concentrations, the mechanism of action of TCS was investigated. TCS modulated transcription of different genes involved in shell mineralization, endocrine signaling, ceramide metabolism, and biotransformation, depending on larval stage (24 and 48 h post-fertilization-hpf) and concentration (1 and 10 μg/L). At 48 hpf and 10 μg/L TCS, calcein staining revealed alterations in CaCO3 deposition, and polarized light microscopy showed the absence of shell birefringence due to the mineralized phase. Observations by scanning electron microscopy highlighted a variety of defects in shell formation from concentrations as low as 0.1 μg/L. The results indicate that TCS, at environmental exposure levels, can act as a developmental disruptor in early mussel larvae mainly by interfering with the processes of biomineralization.

Ecological characteristics impact PFAS concentrations in a U.S. North Atlantic food web

This is the first comprehensive study of per- and polyfluoroalkyl substances (PFAS) in a coastal food web of the U.S. North Atlantic, in which we characterize the presence and concentrations of 24 targeted PFAS across 18 marine species from Narragansett Bay, Rhode Island, and surrounding waters. These species reflect the diversity of a typical North Atlantic Ocean food web with organisms from a variety of taxa, habitat types, and feeding guilds. Many of these organisms have no previously reported information on PFAS tissue concentrations. We found significant relationships of PFAS concentrations with respect to various ecological characteristics including species, body size, habitat, feeding guild, and location of collection. Based upon the 19 PFAS detected in the study (5 were not detected in samples), benthic omnivores (American lobsters = 10.5 ng/g ww, winter skates = 5.77 ng/g ww, Cancer crabs = 4.59 ng/g ww) and pelagic piscivores (striped bass = 8.50 ng/g ww, bluefish = 4.30 ng/g ww) demonstrated the greatest average ∑PFAS concentrations across all species sampled. Further, American lobsters had the highest concentrations detected in individuals (∑PFAS up to 21.1 ng/g ww, which consisted primarily of long-chain PFCAs). The calculation of field-based trophic magnification factors (TMFs) for the top 8 detected PFAS determined that perfluorodecanoic acid (PFDA), perfluorooctane sulfonic acid (PFOS), and perfluorooctane sulfonamide (FOSA) associated with the pelagic habitat biomagnified, whereas perfluorotetradecanoic acid (PFTeDA) associated with the benthic habitat demonstrated trophic dilution in this food web (calculated trophic levels ranged from 1.65 to 4.97). While PFAS exposure to these organisms may have adverse implications for ecological impacts via toxicological effects, many of these species are also key recreational and commercial fisheries resulting in potential for human exposure via dietary consumption.

Studies of Endocrine Disruptors: Nonylphenol and Isomers in Biological Models

Certain emerging pollutants are among the most widely used chemicals globally, causing widespread concern in relation to their use in products devoted to cleaniness and asepsis. Nonylphenol ethoxylate (NPEOn) is one such contaminant, along with its degradation product, nonylphenol, an active ingredient presents in nonionic surfactants used as herbicides, cosmetics, paints, plastics, disinfectants, and detergents. These chemicals and their metabolites are commonly found in environmental matrices. Nonylphenol and NPEOn, used, are particularly concerning, given their role as endocrine disruptors chemical and possible neurotoxic effects recorded in several biological models, primarily aquatic organisms. Limiting and detecting these compounds remain of paramount importance. The objective of the present review was to evaluate the toxic effects of nonylphenol and NPEOn in different biological models. Environ Toxicol Chem 2023;00:1-12. © 2023 SETAC.

Bioplastic leachates characterization and impacts on early larval stages and adult mussel cellular, biochemical and physiological responses

Bioplastics are promoted as safer alternatives to tackle the long-term persistence of conventional plastics. However, information on the potential release of additives and non-intentionally added substances (NIAS) in the surrounding environment is limited, and biological effects of the leachates have been little studied. Leachates produced from three bioplastics, i.e. compostable bags (CB), bio-polyethylene terephthalate bottles (bioPET) and polylactic acid cups (PLA), and a control polymeric material, i.e. rubber tire (TR), were examined. The chemical nature of bioplastic polyesters PET, PLA and poly (butylene adipate-co-terephthalate) (PBAT) in CB, was confirmed by analytical pyrolysis. Fragments were incubated in artificial sea water for 14 days at 20 °C in darkness and leachate contents examined by GC-MS and HPLC-MS/MS. Catalysts and stabilizers represented the majority of chemicals in TR, while NIAS (e.g. 1,6-dioxacyclododecane-7,12-dione) were the main components of CB. Bisphenol A occurred in all leachates at a concentration range 0.3-4.8 μg/L. Trace metals at concentrations higher than control water were found in all leachates, albeit more represented in leachates from CB and TR. A dose response to 11 dilutions of leachates (in the range 0.6-100%) was tested for biological effects on early embryo stages of Mytilus galloprovincialis. Embryotoxicity was observed in the whole range of tested concentrations, the magnitude of effect depending on the polymers. The highest concentrations caused reduction of egg fertilization (CB, bioPET, TR) and of larvae motility (CB, PLA, TR). TR leachates also provoked larvae mortality in the range 10-100%. Effects on adult mussel physiology were evaluated after a 7-day in vivo exposure to the different leachates at 0.6% concentration. Nine biomarkers concerning lysosomal functionality, neurotransmission, antioxidant and immune responses were assessed. All lysosomal parameters were affected, and serum lysozyme activity inhibited. Harmonized chemical and biological approaches are recommended to assess bioplastic safety and support production of sustainable bioplastics.

Potential disruptive effects of copper-based antifouling paints on the biodiversity of coastal macrofouling communities

The expanded use of copper(I)-based antifouling paints (AF) has increased copper leaching into coastal environments, requiring attention and legislative restrictions for potential long-term effects on benthic populations. The ecological succession of macrofouling communities was analysed on wooden and stainless steel panels coated with four copper(I)-based AF (Paints A-D) immersed for 10 months in the Lagoon of Venice. With the exception of Paint B, which contained only copper(I) compounds and was based on hard-matrix technology, the other paints were based on self-polishing matrices and various booster biocides. The booster content was a mix of TBT compounds for Paint A, dichlofluanid for Paint C, Irgarol 1051, and chlorothalonil for Paint D. The macrofouling communities appeared dissimilar to those on the reference uncoated panels as regard the species richness, the coverage areas, and the biocoenosis structure. Generally, green algae, bryozoans, and barnacles were the most tolerant taxa and a negative species selection occurred for sponges, serpulids, and ascidians. Paints A and D showed the highest performance, and Paint D also prevented molluscs on wood panels. Paints B and C rapidly decreased their efficiency, the first probably due to the insoluble matrix with the highest biocidal leaching rate, and the second due to the presence of a booster with low toxicity. Paint B also inhibited red algae and molluscs, but Paint C did not reveal significant differences in types of species settlements with reference panels.

Current scenario and challenges of plastic pollution in Bangladesh: a focus on farmlands and terrestrial ecosystems

Plastic is considered one of the most indispensable commodities in our daily life. At the end of life, the huge ever-growing pile of plastic waste (PW) causes serious concerns for our environment, including agricultural farmlands, groundwater quality, marine and land ecosystems, food toxicity and human health hazards. Lack of proper infrastructure, financial backup, and technological advancement turn this hazardous waste plastic management into a serious threat to developing countries, especially for Bangladesh. A comprehensive review of PW generation and its consequences on environment in both global and Bangladesh contexts is presented. The dispersion routes of PW from different sources in different forms (microplastic, macroplastic, nanoplastic) and its adverse effect on agriculture, marine life and terrestrial ecosystems are illustrated in this work. The key challenges to mitigate PW pollution and tackle down the climate change issue is discussed in this work. Moreover, way forward toward the design and implementation of proper PW management strategies are highlighted in this study.

Responses of Mytilus galloprovincialis to challenge with environmental isolates of the potential emerging pathogen Malaciobacter marinus

Bacteria of the Arcobacter-like spp. represent emerging foodborne zoonotic pathogens in humans and animals. Their increasing presence in seafood, suggesting higher occurrence in seawater due to marine pollution, is raising some environmental concern. Although Arcobacter is frequently detected in diseased oysters and stressed bivalve species, no data are available so far on its potential pathogenicity or interactions with the immune system of the bivalve host. In this work, responses to challenge with two strains of Malaciobacter marinus IRTA-19-131 and IRTA-19-132, R1 and R2), isolated from adult Crassostrea gigas during a mortality event in 2019 in Spain, were investigated in the mussel Mytilus galloprovincialis. In vivo experiments were performed in larvae (48 h post-fertilization), and in adult mussels at 24 h post-injection, in order to evaluate the pathogenicity for early developmental stages, and the hemolymph immune responses, respectively. Both R1 and R2 were moderately pathogenic to early larvae, with significant decreases in the development of normal D-veligers from 10⁴ and 10³ CFU/mL, respectively. In adults, both strains decreased hemocyte lysosomal membrane stability (LMS), and stimulated extracellular defense responses (ROS production and lysozyme activity). The interactions between mussel hemocytes and M. marinus were investigated in in vitro short-term experiments (30-90 min) using the R1 strain (10⁶-10⁸ CFU/mL). R1 decreased LMS and induced lysosomal enlargement, but not cell detachment or death, and stimulated extracellular ROS production and lysozyme release, confirming in vivo data. Moreover, lysosomal internalization and degradation of bacteria were observed, together with changes in levels of activated mTor and LC3, indicating phagocytic activity. Overall, the results indicate the activation of both extracellular and intracellular immune defenses against M. marinus R1. Accordingly, these responses resulted in a significant hemolymph bactericidal activity, with a large contribution of hemolymph serum. The results represent the first data on the potential pathogenicity of Arcobacter isolated from a shellfish mortality to bivalve larvae and adults, and on their interactions with the immune system of the host.

Bisphenol A acts as developmental agonist in Culex quinquefasciatus Say

Plastic wastes deposited in canals running through Thiruvananthapuram city have created stagnant waters providing breeding sites for mosquitoes. In the present study, plastic waste-derived bisphenol A (BPA) was quantified from four mosquito breeding sites. During summer rain, the concentration of BPA in the stagnant water samples was found to be between 0.86 and 1.14 mg/L, and hence 1 mg/L BPA was considered as the environmentally relevant concentration. In the present study, the effect of BPA on the life cycle and metamorphosis of filarial vector, Culex quinquefasciatus Say was elucidated by rearing larvae in water added with BPA at and above the environmentally relevant concentration viz., 1, 2, and 4 mg/L. The duration required for adult emergence was reduced from 10 to 8.5 days, when the concentration of BPA was increased from 1 to 4 mg/L respectively. Our study revealed that embryonic and larval developments were shortened by BPA treatment. BPA also caused a dose-dependent advancement of 20-hydroxyecdysone (20-E) peaks; phospholipase A₂ induction; and upregulation of ecdysone receptor gene, EcRA, and ecdysone inducible gene E75A, which culminated in early pupation. No significant difference in sanguivory and fecundity was observed in adult mosquitoes treated with 1 mg/L of BPA. Our study reveals that BPA is a developmental agonist of C. quinquefasciatus.

Health effects and risks associated with the occurrence of pharmaceuticals and their metabolites in marine organisms and seafood

Pharmaceuticals and their metabolites are continuously invading the marine environment due to their input from the land such as their disposal into the drains and sewers which is mostly followed by their transfer into wastewater treatment plants (WWTPs). Their incomplete removal in WWTPs introduces pharmaceuticals into oceans and surface water. To date, various pharmaceuticals and their metabolites have been detected in marine environment. Their occurrence in marine organisms raises concerns regarding toxic effects and development of drug resistant genes. Therefore, it is crucial to review the health effects and risks associated with the presence of pharmaceuticals and their metabolites in marine organisms and seafood. This is an important study area which is related to the availability of seafood and its quality. Hence, this study provides a critical review of the information available in literature which relates to the occurrence and toxic effects of pharmaceuticals in marine organisms and seafood. This was initiated through conducting a literature search focussing on articles investigating the occurrence and effects of pharmaceuticals and their metabolites in marine organisms and seafood. In general, most studies on the monitoring of pharmaceuticals and their metabolites in marine environment are conducted in well developed countries such as Europe while research in developing countries is still limited. Pharmaceuticals present in freshwater are mostly found in seawater and marine organisms. Furthermore, the toxicity caused by different pharmaceutical mixtures was observed to be more severe than that of individual compounds.

Physiological Roles of Serotonin in Bivalves: Possible Interference by Environmental Chemicals Resulting in Neuroendocrine Disruption

Contaminants of Emerging Concerns (CECs) are defined as chemicals not commonly monitored in aquatic ecosystems, but with the potential to cause adverse effects on biota. CECs include Endocrine Disrupting Chemicals (EDCs) and Neuro-Endocrine disruptors (NEDs) of vertebrates. However, most invertebrates only rely on neuroendocrine systems to maintain homeostatic processes. Although conserved neuroendocrine components have been characterized in ecologically relevant groups, limited knowledge on invertebrate neuroendocrinology makes it difficult to define EDCs and NEDs in most species. The monoamine serotonin (5-hydroxytryptamine, 5-HT) acts both as a neurotransmitter and as a peripheral hormone in mammals. In molluscs, 5-HT is involved in multiple physiological roles and molecular components of the serotonergic system have been identified. This review is focused on the effects of CECs on the serotonergic system of bivalve molluscs. Bivalves are widespread in all aquatic environments, estuarine and coastal areas in particular, where they are exposed to a variety of chemicals. In bivalves, 5-HT is involved in gametogenesis and spawning, oocyte maturation and sperm motility, regulates heart function, gill ciliary beating, mantle/siphon function, the ''catch'' state of smooth muscle and immune responses. Components of 5-HT transduction (receptors and signaling pathways) are being identified in several bivalve species. Different CECs have been shown to affect bivalve serotonergic system. This particularly applies to antidepressants, among the most commonly detected human pharmaceuticals in the aquatic environment. In particular, selective serotonin reuptake inhibitors (SSRIs) are frequently detected in seawater and in bivalve tissues. Information available on the effects and mechanisms of action of SSRIs on the serotonergic system of adult bivalves is summarized. Data are also reported on the effects of CECs on development of neuroendocrine pathways of early larval stages, in particular on the effects of model EDCs in the marine mussel Mytilus galloprovincialis. Overall, available data point at the serotonergic system as a sensitive target for neuroendocrine disruption in bivalves. The results contribute drawing Adverse Outcome Pathways (AOPs) for model EDCs and SSRIs in larvae and adults. However, basic research on neuroendocrine signaling is still needed to evaluate the potential impact of neuroendocrine disruptors in key invertebrate groups of aquatic ecosystems.

Multi-parameter risk assessment of forty-one selected substances with endocrine disruptive properties in surface waters worldwide

The increasing use of substances with endocrine disruptive properties (EDs) not only impacts aquatic organisms but can also have a direct negative effect on human health. In this comprehensive worldwide review, we collected ecotoxicology and concentration data observed in surface water for 53 high-potency EDs and performed a risk assessment. The compounds were selected from the EU watchlist of priority substances, expanded with new compounds of emerging concern (total 41), where quantifiable data were available for the past three years (2018-2020). The risk quotients ranged from <0.01 for 22 substances to 1974 for tamoxifen. The frequency of samples in which the predicted no-effect concentrations were exceeded also varied, from 1.8% to 92.7%. By using the comprehensive multi-parameter risk assessment in our study, the most current to date, we determined that tamoxifen, imidacloprid, clothianidin, four bisphenols (BPA, BPF, BPS, and BPAF), PFOA, amoxicillin, and three steroid hormones (estriol, estrone, and cyproterone) pose significant risks in the environment. Comparing two structurally very similar bisphenols, BPA and BPB, suggested that the risk from BPB is currently underestimated by at least four orders of magnitude due to the lack of ecotoxicological data availability. The methodological limitations encountered suggest that a standardized methodology for data selection and assessment is necessary, highlighting the fact that some substances are currently under-represented in the field of ecotoxicological research. A new prioritization system is therefore presented, which provides a potential basis for new substances to be included in environmental monitoring lists.

Comparison of Different Commercial Nanopolystyrenes: Behavior in Exposure Media, Effects on Immune Function and Early Larval Development in the Model Bivalve Mytilus galloprovincialis

In the absence of standard methods for the detection/quantification of nanoplastics (NPs) in environmental samples, commercial nanopolymers are utilized as proxies for toxicity testing and environmental risk assessment. In marine species, a considerable amount of data are now available on the effects of nanopolystyrene (PS-NPs) of different size/surface characteristics. In this work, amino modified PS-NPs (PS-NH2) (50 and 100 nm), purchased from two different companies, were compared in terms of behavior in exposure media and of biological responses, from molecular to organism level, in the model marine bivalve Mytilus. Different PS-NH2 showed distinct agglomeration and surface charge in artificial sea water (ASW) and hemolymph serum (HS). Differences in behavior were largely reflected by the effects on immune function in vitro and in vivo and on early larval development. Stronger effects were generally observed with PS-NH2 of smaller size, showing less agglomeration and higher positive charge in exposure media. Specific molecular interactions with HS components were investigated by the isolation and characterization of the NP-corona proteins. Data obtained in larvae demonstrate interference with the molecular mechanisms of shell biogenesis. Overall, different PS-NH2 can affect the key physiological functions of mussels at environmental concentrations (10 µg/L). However, detailed information on the commercial NPs utilized is required to compare their biological effects among laboratory experiments.

Tetrabromobisphenol A acts a neurodevelopmental disruptor in early larval stages of Mytilus galloprovincialis

Tetrabromobisphenol A-TBBPA, a widely used brominated flame retardant detected in aquatic environments, is considered a potential endocrine disruptor-ED for its reproductive/developmental effects in vertebrates. In aquatic invertebrates, the modes of action of most EDs are largely unknown, due to partial knowledge of the mechanisms controlling neuroendocrine functions. In the marine bivalve Mytilus galloprovincialis, TBBPA has been previously shown to affect larval development in the 48 h larval toxicity assay at environmental concentrations. In this work, the effects of TBBPA were further investigated at different times post-fertilization. TBBPA, from 1 μg/L, affected shell biogenesis at 48 hours post fertilization-hpf, as shown by phenotypic and SEM analysis. The mechanisms of action of TBBPA were investigated at concentrations of the same order of magnitude as those found in highly polluted coastal areas (10 μg/L). At 28-32 hpf, TBBPA significantly affected deposition of both the organic matrix and CaCO₃ in the shell. TBBPA also altered expression of shell-related genes from 24 to 48 hpf, in particular of tyrosinase, a key enzyme in shell matrix remodeling. At earlier stages (24 hpf), TBBPA affected the development of dopaminergic, serotoninergic and GABAergic systems, as shown by in situ hybridization-ISH and immunocytochemistry. These data contribute draw adverse outcome pathways-AOPs, where TBBPA affects the synthesis of neutrotransmitters involved in key events (neurodevelopment and shell biogenesis), resulting in phenotypic changes on individuals (delayed or arrested development) that might lead to detrimental consequences on populations.

Assessing the Impact of Chrysene-Sorbed Polystyrene Microplastics on Different Life Stages of the Mediterranean Mussel Mytilus galloprovincialis

The sorption of organic pollutants to marine plastic litter may pose risks to marine organisms, notably for what concerns their intake and transfer through microplastic (MP) ingestion. This study investigated the effects of polystyrene MP loaded with chrysene (CHR) on early-stage and physiological endpoints measured in the Mediterranean mussel Mytilus galloprovincialis. The same concentrations of virgin microplastics (MP) and MP loaded with 10.8 µg CHR/mg (CHR-MP) were administered to mussel gametes/embryos (25 × 103 items/mL) and adults (5⋅× 103 items/L); further treatments included 0.1 mg/L of freely dissolved CHR and a second CHR concentration corresponding to that vehiculated by CHR-MP during exposure (3.78 µg/L and 0.73 ng/L for gamete/embryos and adults, respectively). None of the treatments affected gamete fertilization, while 0.1 mg/L CHR induced embryotoxicity. In adults, CHR-MP and MP similarly affected lysosomal membrane stability and neutral lipids and induced slight effects on oxidative stress endpoints. CHR affected tested endpoints only at 0.1 mg/L, with lysosomal, oxidative stress and neurotoxicity biomarkers generally showing greater alterations than those induced by CHR-MP and MP. This study shows that the CHR sorption on MP does not alter the impact of virgin MP on mussels and may pose limited risks compared to other routes of exposure.

Aquatic toxicity evaluations of PFOS and PFOA for five standard marine endpoints

Per- and poly-fluoroalkyl substances (PFAS) are emerging contaminants that are coming under increasing scrutiny. Currently, there is a paucity of effects data for marine aquatic life, limiting the assessment of ecological risks and compliance with water quality policies. In the present study, the toxicity of perfluorooctanesulfonic acid (PFOS) and perfluorooctanoic acid (PFOA) to four standard marine laboratory toxicity testing species, encompassing five endpoints, were evaluated: 1) 96-h embryo-larval normal development for the purple sea urchin (Strongylocentrotus purpuratus); 2) 48-h embryo-larval normal development and normal survival for the Mediterranean mussel (Mytilus galloprovincialis); 3) 96-h survival of opossum shrimp (Americamysis bahia); and 4) 24-h light output for the bioluminescent dinoflagellate Pyrocystis lunula. All species were tested using standard United States Environmental Protection Agency (USEPA) and/or American Society for Testing and Materials (ASTM) International protocols. For PFOS and PFOA, the order of species sensitivity, starting with the most sensitive, was M. galloprovincialis, S. purpuratus, P. lunula, and A. bahia. The range of median lethal or median effect concentrations for PFOS (1.1-5.1 mg L^-1) and PFOA (10-24 mg L^-1) are comparable to the relatively few toxicity effect values available for marine species. In addition to providing effects data for PFOA and PFOS, this study indicates these species and endpoints are sensitive to PFAS such that their use will be appropriate for deriving toxicity data with other PFAS in marine ecosystems.

Effects of BαP and TBBPA on multixenobiotic resistance (MXR) related efflux transporter activity and gene expressions in gill cells of scallop Chlamys farreri

The multixenobiotic resistance mechanism (MXR) provides aquatic organisms with the capacity to adapt to polluted environments, which can be inhibited by chemosensitizers. In the present study, the effect of two typical marine persistent organic pollutants, benzo(a)pyrene (BaP) and tetrabromobisphenol A (TBBPA), on the most relevant ABC transporters, ABCB1, ABCC1, and ABCG2 of scallop Chlamys farreri was tested. MXR transporter efflux activity of cultured gill cells of the scallops was evaluated by measuring the intracellular fluorescent intensity of Calcein-AM and rhodamine 123 with flow cytometry. The results showed that ABCB1 and ABCC1 transporters demonstrated increased activity compared with ABCG2 in mediating MXR efflux activity. BaP and TBBPA were able to suppress the efflux transporter activity of ABC transporters significantly, of which BaP revealed block effects by acting on the ABCB1 transporter. Additionally, exposure of BaP and TBBPA only significantly upregulated the expression level of ABCC1 gene. This study demonstrated the promising utility of efflux transporter activity in conjunction with biomarkers such as mRNA levels in identification of chemosensitizer.

Perfluoroalkyl substances in drinking water sources along the Yangtze River in Jiangsu Province, China: Human health and ecological risk assessment

Perfluoroalkyl substances (PFASs) in source water is of growing concern for its adverse effects on human health and wildlife as well. The Yangtze River is the vital drinking water source in Jiangsu Province of China, but little attention has been paid on PFASs. The occurrence, spatial distribution and temporal trend of PFASs in 21 water sources along the Jiangsu section of the Yangtze River was investigated with sampling from 2018 to 2020. Moreover, health risk of PFASs was assessed by estimated intake dose and derived tolerable intake dose, while ecological risk was assessed by selected effect concentration and environmental exposure. PFASs concentrations in source water ranged from 12.0 to 128 ng/L, with perfluorooctanoic acid (PFOA) as the dominated congener. Fluorine chemical industry lead to a great increase of perfluorohexanoic acid (PFHxA) in its nearest water source. The estimated daily intake of PFASs through drinking was 0.54 and 0.82 ng/kg bw/day for adults and children. The major health risk was from perfluorooctane sulfonate (PFOS) and PFOA for their toxicity on liver, reproduction, development and immunity, with the maximum hazard quotient of 0.029 and 0.043 for adults and children in the worst scenario. The ecological risks from PFASs on nine species groups ranged from 2.7 × 10-10 to 5.2. PFOA and Perfluorobutane sulfonate (PFBS) were causing significant risk on wildlife, particularly on worms, mussels, and fish, which may further influence the structure and processes in the foodweb. Overall, PFASs, especially PFOS, PFOA and PFBS, induced considerable risk on human health and aquatic species in some hotspot area. It would be necessary to include them into monitoring in China and develop standards for different protection purposes.

Occurrence and risk assessment of pharmaceuticals and cocaine around the coastal submarine sewage outfall in Guarujá, São Paulo State, Brazil

The aim of this study was to screen and quantify 23 pharmaceutical compounds (including illicit drugs), at two sampling points near the diffusers of the Guarujá submarine outfall, State of São Paulo, Brazil. Samples were collected in triplicate during the high (January 2018) and low (April 2018) seasons at two different water column depths (surface and bottom). A total of 10 compounds were detected using liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS). Caffeine (42.3-141.0 ng/L), diclofenac (3.6-85.7 ng/L), valsartan (4.7-14.3 ng/L), benzoylecgonine (0.3-1.7 ng/L), and cocaine (0.3-0.6 ng/L) were frequently detected (75% occurrence). Orphenadrine (0.6-3.0 ng/L) and atenolol (0.1-0.3 ng/L), and acetaminophen (1.2-1.4 ng/L) and losartan (0.7-3.4 ng/L), were detected in 50% and 25% of the samples, respectively. Only one sample (12.5%) detected the presence of carbamazepine (< 0.001-0.1 ng/L). Unexpectedly a lower frequency of occurrence and concentration of these compounds occurred during the summer season, suggesting that other factors, such as the oceanographic and hydrodynamic regimes of the study area, besides the population rise, should be taken into account. Caffeine presented concentrations above the surface water safety limits (0.01 μg/L). For almost all compounds, the observed concentrations indicate nonenvironmental risk for the aquatic biota, except for caffeine, diclofenac, and acetaminophen that showed low to moderate ecological risk for the three trophic levels tested.

Assessing the Ecological Risks of Per- and Polyfluoroalkyl Substances: Current State-of-the Science and a Proposed Path Forward

Per- and poly-fluoroalkyl substances (PFAS) encompass a large, heterogenous group of chemicals of potential concern to human health and the environment. Based on information for a few relatively well-understood PFAS such as perfluorooctane sulfonate and perfluorooctanoate, there is ample basis to suspect that at least a subset can be considered persistent, bioaccumulative, and/or toxic. However, data suitable for determining risks in either prospective or retrospective assessments are lacking for the majority of PFAS. In August 2019, the Society of Environmental Toxicology and Chemistry sponsored a workshop that focused on the state-of-the-science supporting risk assessment of PFAS. The present review summarizes discussions concerning the ecotoxicology and ecological risks of PFAS. First, we summarize currently available information relevant to problem formulation/prioritization, exposure, and hazard/effects of PFAS in the context of regulatory and ecological risk assessment activities from around the world. We then describe critical gaps and uncertainties relative to ecological risk assessments for PFAS and propose approaches to address these needs. Recommendations include the development of more comprehensive monitoring programs to support exposure assessment, an emphasis on research to support the formulation of predictive models for bioaccumulation, and the development of in silico, in vitro, and in vivo methods to efficiently assess biological effects for potentially sensitive species/endpoints. Addressing needs associated with assessing the ecological risk of PFAS will require cross-disciplinary approaches that employ both conventional and new methods in an integrated, resource-effective manner. Environ Toxicol Chem 2021;40:564-605. © 2020 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC. This article has been contributed to by US Government employees and their work is in the public domain in the USA.

Bisphenol A interferes with first shell formation and development of the serotoninergic system in early larval stages of Mytilus galloprovincialis

Bisphenol A-BPA, a widespread plastic additive, is an emerging contaminant of high concern and a potential endocrine disruptor in mammals. BPA also represents a potential threat for aquatic species, especially for larval stages. In the marine bivalve Mytilus galloprovincialis, BPA has been previously shown to affect early larval development and gene transcription. In this work, the effects of BPA (0.05-0.5-5 μM) were further investigated at different times post fertilization (24-28-32-48 hpf). BPA induced concentration-dependent alterations in deposition of the organic matrix and calcified shell at different larval stages, as shown by double calcofluor/calcein staining, resulting in altered phenotypes at 48hpf. Transcription of Tyrosinase-TYR, that plays a key role in remodelling of the shell organic matrix, and of HOX1, a member of homeobox genes involved in larval shell formation and neurogenesis, were evaluated by In Situ Hybrydization-ISH. BPA altered the spatial pattern of expression of both genes, with distinct effects depending on the concentration and developmental stage. Moreover, BPA affected the time course of mRNA levels for TYR from 24 to 48hpf. BPA impaired development of serotonin-5-HT-immunoreactive neurons at different times pf; at 48hpf, the reduction in the number of serotoninergic neurons was associated with developmental delay and downregulation of the 5-HT receptor-5-HTR. All the effects were observed from the lowest concentration tested, corresponding to detectable BPA levels in contaminated coastal waters. These data demonstrate that BPA interferes with key processes occurring during the first developmental stages of mussels, thus representing a potential threat for natural populations.

What are the effects of PFAS exposure at environmentally relevant concentrations?

The group of synthetic chemicals known as poly and per-fluoroalkyl substances (PFAS) are currently of high concern to environmental regulators and the public due to their widespread occurrence, resistance to degradation and reported toxicity. However, little data exists on the effects of exposure to PFAS at environmentally relevant concentrations and this hampers the effective management of these compounds. This paper reviews current research on the occurrence and ecotoxicology of PFAS at environmentally relevant doses to assess their potential biological impacts. Hazard Quotient (HQ) analysis was undertaken as part of this assessment. Most PFAS detected in the environment were found to have a HQ risk value of <1 meaning their reported concentrations are below their predicted no effect concentration. This indicates many reported toxic effects of PFAS are, theoretically, unlikely to occur outside the laboratory. However, lack of information on new PFAS as well as their precursors and degradation products, coupled with lack of knowledge of their mixture toxicity means our understanding of the risks of PFAS is incomplete, especially in regard to sub-lethal and/or chronic effects. It is proposed that the development of molecular markers for PFAS exposure are needed to aid in the development of environmental PFAS regulations that are effective in fully protecting the environment.

Insight into the microbial communities associated with first larval stages of Mytilus galloprovincialis: Possible interference by estrogenic compounds

The microbiota, the host-associated community of microbes, play important roles in health status and whole body homeostasis of all organisms, including marine species. In bivalves, the microbiota composition has been mainly investigated in adults, whereas little information is available during development. In this work, the microbiota composition of the first larval stages of Mytilus galloprovincialis was evaluated by 16S rRNA gene-based profiling, at 24 and 48 hours post fertilization in comparison with those of eggs and sperm. The main genera detected in both larvae (Vibrio, Pseudoalteromonas, Psychrobium, Colwellia) derived from eggs. However, a clear shift in microbiota was observed in developing larvae compared to eggs, both in terms of core microbiome and relative abundance of different genera. The results provide a first insight into the composition of the microbial communities associated with gametes and early larvae of mussels. Moreover, the impact on larval microbiome of estrogenic chemicals that potentially affect Mytilus early development, 17βestradiol-E₂, Bisphenol A-BPA and Bisphenol F-BPF (10 μg/L), was investigated. Exposure to estrogenic chemicals leads to changes in abundance of different genera, with distinct and common effects depending on the compound and larval stage. Both potential pathogens (Vibrio, Arcobacter, Tenacibaculum) and genera involved in xenobiotic biotransformation (Oleispira, Shewanella) were affected. The effects of estrogenic compounds on larval microbiome were not related to their developmental effects: however, the results address the importance of evaluating the impact of emerging contaminants on the microbiota of marine invertebrates, including larval stages, that are most sensitive to environmental perturbations.

Application of Biomarker Tools Using Bivalve Models Toward the Development of Adverse Outcome Pathways for Contaminants of Emerging Concern

As contaminant exposures in aquatic ecosystems continue to increase, the need for streamlining research efforts in environmental toxicology using predictive frameworks also grows. One such framework is the adverse outcome pathway (AOP). An AOP framework organizes and utilizes toxicological information to connect measurable molecular endpoints to an adverse outcome of regulatory relevance via a series of events at different levels of biological organization. Molecular endpoints or biomarkers are essential to develop AOPs and are valuable early warning signs of the toxicity of pollutants, including contaminants of emerging concern. Ecological risk-assessment approaches using tools such as biomarkers and AOPs benefit from identification of molecular targets conserved across species. Bivalve models are useful in such approaches and integral to our understanding of ecological and human health risks associated with contaminant exposures. We discuss the value of using biomarker approaches in bivalve models to meet the demands of twenty-first-century toxicology. Environ Toxicol Chem 2020;39:1472-1484. © 2020 SETAC.

Anti-inflammatory drugs in the marine environment: Bioconcentration, metabolism and sub-lethal effects in marine bivalves

Pharmaceuticals such as non-steroidal anti-inflammatory drugs (NSAIDs) have been found in the marine environment. Although there is a large body of evidence that pharmaceutical drugs exert negative impacts on aquatic organisms, especially in the freshwater compartment, only limited studies are available on bioconcentration and the effects of NSAIDs on marine organisms. Bivalves have a high ecological and socio-economic value and are considered good bioindicator species in ecotoxicology and risk assessment programs. Therefore, this review summarizes current knowledge on the bioconcentration and the effects of three widely used NSAIDs, diclofenac, ibuprofen and paracetamol, in marine bivalves exposed under laboratory conditions. These pharmaceutical drugs were chosen based on their environmental occurrence both in frequency and concentration that may warrant their inclusion in the European Union Watch List. It has been highlighted that ambient concentrations may result in negative effects on wild bivalves after long-term exposures. Also, higher trophic level organisms may be more impacted due to food-chain transfer (e.g., humans are shellfish consumers). Overall, the three selected NSAIDs were reported to bioconcentrate in marine bivalves, with recognized effects at different life-stages. Immune responses were the main target of a long-term exposure to the drugs. The studies selected support the inclusion of diclofenac on the European Union Watch List and highlight the importance of extending research for ibuprofen and paracetamol due to their demonstrated negative effects on marine bivalves exposed to environmental realistic concentrations, under laboratory conditions.

Chemical composition and ecotoxicity of plastic and car tire rubber leachates to aquatic organisms

Synthetic polymer-based materials are ubiquitous in aquatic environments, where weathering processes lead to their progressive fragmentation and the leaching of additive chemicals. The current study assessed the chemical content of freshwater and marine leachates produced from car tire rubber (CTR), polypropylene (PP), polyethylene terephthalate (PET), polystyrene (PS) and polyvinyl chloride (PVC) microplastics, and their adverse effects on the microalgae Raphidocelis subcapitata (freshwater) and Skeletonema costatum (marine) and the Mediterranean mussel Mytilus galloprovincialis. A combination of non-target and target chemical analysis revealed a number of organic and metal compounds in the leachates, including representing plasticizers, antioxidants, antimicrobials, lubricants, and vulcanizers. CTR and PVC materials and their corresponding leachates had the highest content of tentatively identified organic additives, while PET had the lowest. The metal content varied both between polymer leachates and between freshwater and seawater. Notable additives identified in high concentrations were benzothiazole (CTR), phthalide (PVC), acetophenone (PP), cobalt (CTR, PET), zinc (CTR, PVC), lead (PP) and antimony (PET). All leachates, except PET, inhibited algal growth with EC₅₀ values ranging from 0.5% (CTR) and 64% (PP) of the total leachate concentration. Leachates also affected mussel endpoints, including the lysosomal membrane stability and early stages endpoints as gamete fertilization, embryonic development and larvae motility and survival. Embryonic development was the most sensitive parameter in mussels, with EC₅₀ values ranging from 0.8% (CTR) to 65% (PET) of the total leachate. The lowest impacts were induced on D-shell larvae survival, reflecting their ability to down-regulate motility and filtration in the presence of chemical stressors. This study provides evidence of the relationship between chemical composition and toxicity of plastic/rubber leachates. Consistent with increasing contamination by organic and inorganic additives, the leachates ranged from slightly to highly toxic to mussels and algae, highlighting the need for a better understanding of the overall impact of plastic-associated chemicals on aquatic ecosystems.

Phenotypical and molecular changes induced by carbamazepine and propranolol on larval stages of Mytilus galloprovincialis

The possible impact of carbamazepine (CBZ) and propranolol (PROP), two widespread pharmaceuticals in the aquatic environment, were investigated on morphology and gene transcription of early larvae of Mytilus galloprovincialis. Pharmaceuticals were first tested in a wide concentration range (from 0.01 to 1000 μg/L) through the 48-hpf embryotoxicity assay. The results showed that both compounds significantly affected embryo development from environmental concentrations. Although similar EC₅₀ were obtained, (≅ 1 μg/L) CBZ induced a progressive increase in embryo malformations, whereas PROP apparently showed greater impacts in terms of arrested development and embryo mortality at higher concentrations (>10 μg/L). Transcriptional analyses of 17 genes involved in different physiological functions in mussels and/or in their response to environmental contaminants, were performed at 24 and 48 h pf at two selected concentrations of CBZ and PROP (0.01 and 1 μg/L). Both compounds induced down-regulation of shell-specific and neuroendocrine related transcripts, while distinct effects were observed on antioxidant, lysosomal, and immune-related transcripts, also depending on the larval stage investigated. The results demonstrate that CBZ and PROP can affect development and gene transcription in mussel early larvae at environmental concentrations.

Mytilidae as model organisms in the marine ecotoxicology of pharmaceuticals - A review

Growing production and consumption of pharmaceuticals is a global problem. Due to insufficient data on the concentration and distribution of pharmaceuticals in the marine environment, there are no appropriate legal regulations concerning their emission. In order to understand all aspects of the fate of pharmaceuticals in the marine environment and their effect on marine biota, it is necessary to find the most appropriate model organism for this purpose. This paper presents an overview of the ecotoxicological studies of pharmaceuticals, regarding the assessment of Mytilidae as suitable organisms for biomonitoring programs and toxicity tests. The use of mussels in the monitoring of pharmaceuticals allows the observation of changes in the concentration and distribution of these compounds. This in turn gives valuable information on the amount of pharmaceutical pollutants released into the environment in different areas. In this context, information necessary for the assessment of risks related to pharmaceuticals in the marine environment are provided based on what effective management procedures can be developed. However, the accumulation capacity of individual Mytilidae species, the bioavailability of pharmaceuticals and their biological effects should be further scrutinized.

Estrogenic compounds as exogenous modulators of physiological functions in molluscs: Signaling pathways and biological responses

Molluscs have been widely utilized to evaluate the effects of estrogenic compounds, one of the most widespread classes of Endocrine Disrupting Chemicals-EDCs. However, knowledge on steroid signaling and metabolism in molluscs has considerably increased in the last decade: from these studies, a considerable debate emerged on the role of 'natural' steroids in physiology, in particular in reproduction, of this invertebrate group. In this work, available information on the effects and mechanisms of action of estrogens in molluscs will be reviewed, with particular emphasis on bivalves that, widespread in aquatic ecosystems, are most likely affected by exposure to estrogenic EDCs. Recent advances in steroid uptake and metabolism, and estrogen receptors-ERs in molluscs, as well as in estrogen signaling in vertebrates, will be considered. The results so far obtained with 17β-estradiol and different estrogenic compounds in the model bivalve Mytilus spp., demonstrate specific effects on immune function, development and metabolism. Transcriptomic data reveal non genomic estrogen signaling pathways in mussel tissues that are supported by new observations at the cellular level. In vitro and in vivo data show, through independent lines of evidence, that estrogens act through non-genomic signaling pathways in bivalves. In this light, regardless of whether molluscs synthesize estrogens de novo or not, and despite their ERs are not directly activated by ligand binding, estrogens can interact with multiple signaling components, leading to modulation of different physiological functions. Increasing knowledge in endocrine physiology of molluscs will provide a framework for a better evaluation and interpretation of data on the impact of estrogenic EDCs in this invertebrate group.

Inhibition of growth in juvenile manila clam Ruditapes philippinarum: Potential adverse outcome pathway of TBBPA

Tetrabromobisphenol A (TBBPA) is ubiquitous and its contents showing an increasing trend in the coastal environment. In order to investigate the effects of TBBPA on marine bivalves, juvenile manila clams Ruditapes phillipinarum were exposed to TBBPA for 28 days. The results showed that shell growth rate of juvenile clams after exposure to 62.5-1000 μg L^-1 TBBPA for 28 d were significantly inhibited (p < 0.05). Then in order to link the changes in filtration rate, mRNA expression of insulin-like growth factor homologue (IGF) and tissue thyroid hormone (TH) contents to growth, juvenile clams were exposed to 62.5 and 500 μg L^-1 TBBPA for 14 days. The transcriptional levels of neuroendocrine signals (NPF and insulin homologue) associated with filter feeding regulation, and genes of TH synthesis-related enzymes were also examined. The results showed that filtration rates was significantly reduced to 44.1% and 14% of controls after 14 d of exposure. In parallel, exposure to TBBPA significantly increased the expression levels of insulin which may elicit the filter feeding inhibition. TBBPA exposure caused alterations in tissue content of THs and mRNA expression of TH synthesis-related enzymes. However, the data showed increased T₃ content, T₃/T₄ ratio and mRNA expression of IGF. These data demonstrated that the most important key event of TBBPA could be linked to growth impairment in juveniles was the reduction of filtration rate. These results provide a robust framework towards revealing the underlying mechanism of the growth inhibition caused by TBBPA on bivalves and understanding the adverse outcome pathway across taxonomic phyla.

In vivo immunomodulatory and antioxidant properties of nanoceria (nCeO2) in the marine mussel Mytilus galloprovincialis

Cerium nanoparticles (nCeO₂) are increasingly utilized in a wide variety of industrial, environmental and biomedical applications, and are therefore expected to be released in the aquatic environment. Due to its peculiar redox properties, nCeO₂ may present unique hazards to environmental and human health. Previous data showed that in the hemocytes of the marine bivalve Mytilus galloprovincialis, in vitro exposure to a particular type of nCeO₂ (9 nm, characterized by negative ζ-potential, high H₂O₂ scavenging capacity and Ce³⁺/Ce⁴⁺ surface ratio) reduced basal ROS production, lysosomal membrane stability and phagocytic activity in the presence of hemolymph serum; the effects observed were partly ascribed to the formation of a SOD-protein corona in the hemolymph. In this work, the in vivo effects of this type of nCeO₂ were investigated in mussels exposed to 100 μg/L nCeO₂ for 96 h; several lysosomal, immune, inflammatory and antioxidant biomarkers were measured at cellular (hemocytes) and tissue (gills, digestive gland) level. Molecular responses were evaluated in hemocytes and digestive gland by determining expression of 11 selected genes related to known biological functions. The results show specific immunomodulatory and antioxidant effects of nCeO₂ at different levels of biological organization in the absence of Cerium tissue accumulation. These data further support the redox mechanisms at the basis of the physiological effects of nCeO₂. Finally, in order to evaluate the possible impact at the whole organism level, the effects of nCeO₂ were evaluated in the 48 h embryotoxicity assay in a wide concentration range. However, nCeO₂ exposure resulted in a small reduction in normal embryo development. Overall, the results demonstrate that in mussels nCeO₂ can selectively modulate different physiological processes at different levels of biological organization.

Moderate temperature elevation increase susceptibility of early-life stage of the Mediterranean mussel, Mytilus galloprovincialis to metal-induced genotoxicity

The present study aims to evaluate the effects of copper and silver alone or along with a moderate temperature increase on embryonic development, DNA integrity and target gene expression levels in early life stages of Mytilus galloprovincialis. For this purpose, upon fertilized embryos were exposed to a sub-lethal concentration of Cu (9.54 μg/L), Ag (2.55 μg/L) and to the mixture of the two metals (Cu (6.67 μg/L) + Ag (1.47 μg/L)) along with a temperature gradient (18, 20 and 22 °C). In all experiments, larvae were exposed to stressors for 48 h except for those designed to DNA damage analysis exposed only for 24 h (before shell formation).Our results showed a significant increase in the percentage of malformed D-larvae (p < 0.05) with increasing temperature and exposure to silver and copper alone or in a mixture. Moreover, metal toxicity increased significantly (p < 0.05) with the temperature rise. Genotoxicity was evaluated using classic and modified with Formamidopyrimidine DNA glycosylase (Fpg) Comet assay. Results suggest that co-exposure to metals and temperature significantly increased DNA damage on mussel larvae with a more accentuated oxidative damage. A significant transcription modulation was observed for genes involved in DNA repair and DNA replication (p53, DNA ligase II and topoisomerase II) when larvae are exposed to a single stressor. However, in the case of multiple stresses, caspase involved in the cell apoptosis pathway was overexpressed. Our study suggests that mussel larvae exposed to a moderate increase in temperature may have a compromised ability to defend against genotoxicity. This is particularly relevant in the context of global warming and thermal pollution.

The Multixenobiotic resistance system as a possible protective response triggered by microplastic ingestion in Mediterranean mussels (Mytilus galloprovincialis): Larvae and adult stages

The emerging paradigm on plastic pollution in marine environments is that microsize particles (MPs) have far more subtle effects than bigger fragments, given their size range overlapping with that of particles ingested by filter-feeders. The impacts include gut blockage, altered feeding and energy allocation, with knock-on effects on widespread physiological processes. This study investigated whether ingestion of polystyrene MPs (PS-MPs) triggers protective processes in marine mussels. The Multixenobiotic resistance (MXR) system is a cytoprotective mechanism acting as an active barrier against harmful xenobiotics and a route of metabolite detoxification. Both larvae and adults were employed in laboratory experiments with different concentrations of 3-μm PS-MPs (larvae), and 3-μm and 45-μm PS-MPs (adults) matching size range of planktonic food through the mussel lifecycle. Embryos grown in the presence of 3-μm PS-MPs showed significant reduction of MXR activity and down-regulation of ABCB and ABCC transcripts encoding the two main MXR-related transporters P-glycoprotein and the Multidrug resistance-related protein, respectively. In adults, effects of PS-MPs were assessed in haemocytes and gills, which showed different modulation of MXR activity and ABCB/ABCC expression according to MP size (haemocyte and gills) or particle concentration (haemocyte). These data showed that modulation of MXR activity is part of a generalized response triggered by particle ingestion.

Perfluorooctanoic acid exposure induces apoptosis in SMMC-7721 hepatocellular cancer cells

To better understand the toxicological activities of perfluorooctanoic acid (PFOA), we examined the effects of PFOA on apoptosis and its molecular mechanism in SMMC-7721 hepatoma cells. Cell viability was evaluated by MTT assay and apoptosis was determined by flow cytometry. Western blot and quantitative real-time PCR were used to examine the protein and gene expressions of Bax and Bcl-2. Our results showed that PFOA inhibited SMMC-7721 cell growth and induced apoptosis. PFOA treatment increased Bax expression and increased Bcl-2 expression at both gene and protein levels. Our study demonstrated that PFOA had toxic effects on SMMC-7721 cells, such as inhibiting cell proliferation and inducing apoptosis. Furthermore, we showed that PFOA-mediated induction of apoptosis involved inducing Bax and decreasing Bcl-2 expression as a molecular mechanism of its toxicological effects.

Responses of Mytilus galloprovincialis to challenge with the emerging marine pathogen Vibrio coralliilyticus

Vibrio coralliilyticus has emerged as a coral pathogen of concern throughout the Indo-Pacific reef. The interest towards understanding its ecology and pathogenic potential has increased since V. coralliilyticus was shown to be strongly virulent also for other species; in particular, it represents a serious threat for bivalve aquaculture, being one of the most important emerging pathogen responsible for oyster larval mortalities worldwide. V. coralliilyticus has a tightly regulated temperature-dependent virulence and it has been related to mass mortalities events of benthic invertebrates also in the temperate northwestern Mediterranean Sea. However, no data are available on the effects of V. coralliilyticus in the mussel Mytilus galloprovincialis, the most abundant aquacultured species in this area. In this work, responses of M. galloprovincialis to challenge with V. coralliilyticus (ATCC BAA-450) were investigated. In vitro, short term responses of mussel hemocytes were evaluated in terms of lysosomal membrane stability, bactericidal activity, lysozyme release, ROS and NO production, and ultrastructural changes, evaluated by TEM. In vivo, hemolymph parameters were measured in mussels challenged with V. coralliilyticus at 24h p.i. Moreover, the effects of V. coralliilyticus on mussel early embryo development (at 48 hpf) were evaluated. The results show that both in vitro and in vivo, mussels were unable to activate immune response towards V. coralliilyticus, and that challenge mainly induced lysosomal stress in the hemocytes. Moreover, V. coralliilyticus showed a strong and concentration-dependent embryotoxicity. Overall, the results indicate that, although M. galloprovincialis is considered a resistant species to vibrio infections, the emerging pathogen V. coralliilyticus can represent a potential threat to mussel aquaculture.

Diclofenac affects early embryo development in the marine bivalve Mytilus galloprovincialis

Diclofenac-DCF, one of the most widely prescribed non-steroidal anti-inflammatory drug, is globally detected in environmental compartments. Due to its occurrence in freshwater and potential impact on aquatic organisms, it has been added to the watch list of chemicals in the EU Water Directive; consequently, research on the impact of DCF in model aquatic organisms has great regulatory implications towards ecosystem health. DCF is also detected in coastal waters at concentrations from ng/L to 1 μg/L, as well as in marine organisms, such as the mussel Mytilus. Increasing evidence indicates that environmental concentrations of DCF have multiple impacts in adult mussels. Moreover, in M. galloprovincialis, DCF has been shown to affect early embryo development. The developmental effects of DCF in mussels were further investigated. DFC (1 and 10 μg/L) was added at different times post-fertilization (30 min and 24 hpf) and the effects were compared in the 48 hpf embryotoxicity assay. Shell mineralization and morphology were investigated by polarized light microscopy, X-Ray Spectrometry-XRD and Scanning Electron Microscopy-SEM. Transcriptional profiles of 12 selected genes physiologically regulated across early embryo development were assessed at 24 and 48 hpf. DCF induced shell malformations, irrespectively of concentration and time of exposure. DCF phenotypes were characterized by convex hinges, undulated edges, fractured shells. However, no changes in biomineralization were observed. DCF affected gene transcription at both times pf, in particular at 1 μg/L. The most affected genes were those involved in early shell formation (CS, CA, EP) and biotransformation (ABCB, GST). The results confirm that Mytilus early development represents a significant target for environmental concentrations of DCF. These data underline how the standard embryotoxicity assay, in combination with a structural and transcriptomic approach, represents a powerful tool for evaluating the early impact of pharmaceuticals on mussel embryos, and identification of the possible underlying mechanisms of action.

Nanoplastics impaired oyster free living stages, gametes and embryos

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 NH₂-50 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 NH₂-50 beads had the strongest toxicity to both gametes (EC₅₀ = 4.9 μg/mL) and embryos (EC₅₀ = 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.

The impact of propranolol, 17α-ethinylestradiol, and gemfibrozil on early life stages of marine organisms: effects and risk assessment

Pharmaceuticals are ubiquitously detected in the marine environment at the ng-μg/L range. Given their biological activity, these compounds are known to induce detrimental effects on biota at relatively low exposure levels; however, whether they affect early life stages of marine species is still unclear. In this study, a set of bioassays was performed to assess the effects of propranolol (PROP), 17-α ethinylestradiol (EE2), and gemfibrozil (GEM) on gamete fertilization and embryonic development of mussels (Mytilus galloprovincialis) and sea urchins (Paracentrotus lividus), and on the survival of seabream (Sparus aurata) larvae. Treatments of PROP (500, 5000, 50,000 ng/L), EE2 (5, 50, 500 ng/L), and GEM (50, 500, 5000 ng/L) were selected to encompass levels comparable or superior to environmental concentrations. Obtained data were tested for dose-response curve fitting and the lowest EC₁₀/LC₁₀ used to calculate risk quotients (RQs) based on the MEC/PNEC. No alteration was induced by PROP on the mussel gamete fertilization, while inhibitory effects were observed at environmental levels of EE2 (500 ng/L) and GEM (5000 ng/L). Fertilization was significantly reduced in sea urchin at all PROP and EE2 dosages. The 48-h exposure to all pharmaceuticals induced the onset of morphological abnormalities in either mussel or sea urchin embryos. Alterations were generally observed at environmentally relevant dosages, except for PROP in mussels, in which alterations occurred only at 50,000 ng/L. A decreased survival of seabream larvae was recorded after 96-h exposure to PROP (all treatments), EE2 (50-500 ng/L), and GEM (500 ng/L). A median RQ > 1 was obtained for all pharmaceuticals, assigning a high risk to their occurrence in marine environments. Overall, results showed that current levels of contamination by pharmaceuticals can impact early stages of marine species, which represent critical junctures in the resilience of coastal ecosystems.

Uptake and transcriptional effects of polystyrene microplastics in larval stages of the Mediterranean mussel Mytilus galloprovincialis

The widespread occurrence of microplastics (MP) in the marine environment is cause of increasing concerns about the safety of the exposed ecosystems. Although the effects associated to the MP uptake have been studied in most marine taxa, the knowledge about their sub-lethal impacts on early life stages of marine species is still limited. Here, we investigated the uptake/retention of 3-μm polystyrene MP by early stages of the Mediterranean mussel Mytilus galloprovincialis, and the related effects on gut clearance, feeding efficiency, morphological and transcriptional parameters involved in embryo-larval development. Uptake measurements were performed on larvae at 48 h, 3, 6 and 9 days post fertilization (pf) after exposure to a range of 50-10,000 particles mL^-1. At all tested pf periods, treatments resulted in a significant and linear increase of MP uptake with increasing concentrations, though levels measured at 48 h pf were significantly lower compared to 3-9 d pf. Ingested MP were retained up to 192 h in larvae's gut, suggesting a physical impact on digestive functions. No change was noted between the consumption of microalgae Nannochloropsis oculata by larvae when administered alone or in the presence of an identical concentration (2000 items mL^-1) of MP. The exposure to 50-10,000 MP mL^-1 did not alter the morphological development of mussel embryos; however, transcriptional alterations were observed at 50 and 500 MP mL^-1, including the up-regulation of genes involved in shell biogenesis (extrapallial protein; carbonic anhydrase; chitin synthase) and immunomodulation (myticin C; mytilin B), and the inhibition of those coding for lysosomal enzymes (hexosaminidase; β-glucorinidase; catepsin-L). In conclusion, though not highlighting morphological or feeding abnormalities, data from this study revealed the onset of physical and transcriptional impairments induced by MP in mussel larvae, indicating sub-lethal impacts which could increase their vulnerability toward further environmental stressors.

Effects of nanosilver on Mytilus galloprovincialis hemocytes and early embryo development

Silver nanoparticles (AgNP), one of the main nanomaterials for production and use, are expected to reach the aquatic environment, representing a potential threat to aquatic organisms. In this study, the effects of bare AgNPs (47 nm) on the marine mussel Mytilus galloprovincialis were evaluated at the cellular and whole organism level utilizing both immune cells (hemocytes) and developing embryos. The effects were compared with those of ionic Ag⁺(AgNO₃). In vitro short-term exposure (30 min) of hemocytes to AgNPs induced small lysosomal membrane destabilization (LMS EC₅₀ = 273.1 μg/mL) and did not affect other immune parameters (phagocytosis and ROS production). Responses were little affected by hemolymph serum (HS) as exposure medium in comparison to ASW. However, AgNPs significantly affected mitochondrial membrane potential and actin cytoskeleton at lower concentrations. AgNO₃ showed much higher toxicity, with an EC₅₀ = 1.23 μg/mL for LMS, decreased phagocytosis and induced mitochondrial and cytoskeletal damage at similar concentrations. Both AgNPs and AgNO₃ significantly affected Mytilus embryo development, with EC₅₀ = 23.7 and 1 μg/L, respectively. AgNPs caused malformations and developmental delay, but no mortality, whereas AgNO₃ mainly induced shell malformations followed by developmental arrest or death. Overall, the results indicate little toxicity of AgNPs compared with AgNO₃; moreover, the mechanisms of action of AgNP appeared to be distinct from those of Ag⁺. The results indicate little contribution of released Ag⁺ in our experimental conditions. These data provide a further insight into potential impact of AgNPs in marine invertebrates.