Integrated biomarker responses in oysters Crassostrea gasar as an approach for assessing aquatic pollution of a Brazilian estuary

Exploring the phytotoxicity mechanisms of PET nanoplastics and 6:2 FTSA in water hyacinth under individual and combined exposure scenarios

Due to its similarity in hydrophobic properties to perfluorooctanesulfonic acid (PFOS), 6:2 fluorotelomer sulfonic acid (6:2 FTSA) has emerged as a key substitute for PFOS. Its presence in aquatic environments, along with the coexistence of polyethylene terephthalate (PET), may impact the growth of aquatic plants and ecosystem stability. This study explored the changes in antioxidant defense, photosynthetic system, and metabolic responses of water hyacinths (Eichhornia crassipes) under individual and combined exposure conditions. The results indicated that water hyacinth efficiently accumulated 6:2 FTSA, with notably higher accumulation levels in leaves compared to roots, leading to a more pronounced stress response in leaves. The contents of nitrate, nitrite, ammonium, and the activities of nitrogen assimilation enzymes in leaves increased significantly, which in turn boosted the levels of reactive oxygen species (ROS) scavengers such as glutamic acid and glutathione, as well as antioxidant defense enzymes. Meanwhile, leaf photosynthesis was significantly suppressed due to the resource reallocation. This was corroborated by disruptions in the chloroplast thylakoid structure and alterations in chlorophyll fluorescence parameters. Metabolomics analysis further revealed that the contents of monosaccharides and organic acids decreased markedly, whereas amino acid levels increased significantly, suggesting that water hyacinths prioritized antioxidant defense mechanisms at the expense of growth. Additionally, we observed that the phytotoxic effects of 6:2 FTSA were exacerbated in the presence of PET nanoplastics, with the aforementioned indicators exhibiting synergistic effects. This study provides phenotypic, physiological, metabolic, and transcriptional insights into the toxic effects of the coexistence of PET nanoplastics and 6:2 FTSA on water hyacinths, offering toxicological data (e.g., oxidative stress markers and gene expression profiles) for assessing the environmental risks associated with emerging contaminants and proposing management strategies.

Characterization of acetylcholinesterase and carboxylesterases in the mangrove oyster Crassostrea gasar as biomarkers of exposure to environmental pollutants

Brazil is one of the world's leading consumers of agricultural pesticides, highlighting the urgent need to identify responsive biomarkers as diagnostic and prognostic tools for monitoring aquatic pollution. Acetylcholinesterase (AChE) and carboxylesterases (CbE) are B-esterases enzymes expressed in several organisms. AChE plays an essential role in neural transmission at cholinergic synapses, while CbE are directly involved in the detoxification of organic pollutants, including organophosphorus pesticides. The activities of AChE and CbE in bivalves have not been extensively investigated, despite their suitability as sentinel organisms for environmental monitoring. In this study, we characterized the activities of AChE and CbE in the mangrove oyster Crassostrea gasar, collected from an estuarine system in southern Brazil. We compared enzymatic activities between the gills and the digestive gland, revealing that CbE activity was significantly higher in the digestive gland, while AChE activity did not differ between the two tissues. These results indicate that the digestive gland functions as the primary metabolic organ in C. gasar. Additionally, we observed notable differences in CbE activity depending on the substrate used: ρ-nitrophenyl acetate (ρNPA), ρ-nitrophenyl butyrate (ρNPB), α-naphtyl acetate (αNA), and α-naphtyl butyrate (αNB). Our findings suggest that more lipophilic substrates are metabolized more rapidly in both the digestive gland and gills. These results enhance our understanding of the biotransformation processes and neurotoxicity potential of pesticides in oysters. However, further in vitro validation is needed to confirm the utility of these biomarkers for monitoring environmental pollution in coastal waters.

Expression and functional analysis of Fushi Tarazu transcription factor 1 (FTZ-F1) in the regulation of steroid hormones during the gonad development of Fujian Oyster, Crassostrea angulata

Crassostrea angulata, a major shellfish cultivated in Southern China, has experienced a notable surge in commercial value in recent years. Understanding the molecular mechanisms governing their reproductive processes holds significant implications for advancing aquaculture practices. In this study, we cloned the orphan nuclear receptor gene, Fushi Tarazu transcription factor 1 (FTZ-F1), of C. angulata and investigated its functional role in the gonadal development. The full-length cDNA of FTZ-F1 spans 2357 bp and encodes a protein sequence of 530 amino acids. Notably, the amino acid sequence of FTZ-F1 in C. angulata shares remarkable similarity with its homologues in other species, particularly in the DNA-binding region (>90%) and ligand-binding region (>44%). In C. angulata, the highest expression level of FTZ-F1 was observed in the ovary, exhibiting more than a 200-fold increase during the maturation stage compared to the initiation stage (P < 0.001). Specifically, FTZ-F1 was mainly expressed in the follicular cells surrounding the oocytes of C. angulata. Upon inhibiting FTZ-F1 gene expression in C. angulata through RNA interference (RNAi), a substantial reduction in the expression of genes involved in the synthesis of sex steroids in the gonads, including 3β-HSD, Cyp17, and follistatin, was observed. In addition, estradiol (E2) and testosterone (T) levels also showed a decrease upon FTZ-F1 silencing, resulting in a delayed gonadal development. These results indicate that FTZ-F1 acts as a steroidogenic factor, participating in the synthesis and regulation of steroid hormones and thus playing an important role in the reproductive and endocrine systems within oysters.

Transcriptomic investigation and biomarker discovery for zinc response in oysters Crassostrea gasar

In an era of unprecedented industrial and agricultural growth, metal contamination in marine environments is a pressing concern. Sentinel organisms such as the mangrove oyster Crassostrea gasar provide valuable insights into these environments' health. However, a comprehensive understanding of the molecular mechanisms underlying their response to metal exposure remains elusive. To address this gap, we reanalyzed the 454-sequencing data of C. gasar, utilizing an array of bioinformatics workflow of CDTA (Combined De Novo Transcriptome Assembly) to generate a more representative assembly. In parallel, C. gasar individuals were exposed to two concentrations of zinc (850 and 4500 μg L-1 Zn) for 48 h to understand their molecular responses. We utilized Trinotate workflow for the 11,684-CDTA unigenes annotation, with most transcripts aligning with the genus Crassostrea. Our analysis indicated that 67.3% of transcript sequences showed homology with Pfam, while 51.4% and 54.5%, respectively had GO and KO terms annotated. We identified potential metal pollution biomarkers, focusing on metal-related genes, such as those related to the GSH biosynthesis (CHAC1 and GCLC-like), to zinc transporters (ZNT2-like), and metallothionein (MT-like). The evolutionary conservation of these genes within the Crassostrea genus was assessed through phylogenetic analysis. Further, these genes were evaluated by qPCR in the laboratory exposed oysters. All target genes exhibited significant upregulation upon exposure to Zn at both 850 and 4500 μg L-1, except for GCLC-like, which showed upregulation only at the higher concentration of 4500 μg L-1. This result suggests distinct activation thresholds and complex interactions among these genes in response to varying Zn concentrations. Our study provides insights into the molecular responses of C. gasar to Zn, adding valuable tools for monitoring metal pollution in marine ecosystems using the mangrove oyster as a sentinel organism.

Emerging and legacy contaminants on the Brazilian southern coast (Santa Catarina): A multi-biomarker approach in oysters Crassostrea gasar (Adanson, 1757)

Coastal environments, such as those in the Santa Catarina State (SC, Brazil), are considered the primary receptors of anthropogenic pollutants. In this study, our objective was to evaluate the levels of emerging contaminants (ECs) and persistent organic pollutants (POPs) in indigenous Crassostrea gasar oysters from different regions of SC coast in the summer season (March 2022). Field collections were conducted in the São Francisco do Sul, Itajaí, Florianópolis and Laguna coastal zones. We analyzed the bioaccumulation levels of 75 compounds, including antibiotics (AB), endocrine disruptors (ED), non-steroidal anti-inflammatory drugs (NSAIDs), polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs) and pesticides. Furthermore, we assessed biomarker responses related to biotransformation, antioxidant defense, heat shock protection and oxidative damage in oysters' gills. Prevalence of ECs was observed in the central and southern regions, while the highest concentrations of POPs were detected in the central-northern regions of SC. Oysters exhibited an induction in biotransformation systems (cyp2au1 and cyp356a1, sult and GST activity) and antioxidant enzymes activities (SOD, CAT and GPx). Higher susceptibility to lipid peroxidation was observed in the animals from Florianópolis compared to other regions. Correlation analyses indicated possible associations between contaminants and environmental variables in the biomarker responses, serving as a warning related to climate change. Our results highlight the influence of anthropogenic activities on SC, serving as baseline of ECs and POPs levels in the coastal areas of Santa Catarina, indicating more critical zones for extensive monitoring, aiming to conserve coastal regions.

Effects of ocean acidification and polystyrene microplastics on the oysters Crassostrea gigas: An integrated biomarker and metabolomic approach

The adverse impacts of microplastics (MPs) or ocean acidification (OA) on mollusks have been widely reported, however, little is known about their combined effects on mollusks. The oysters Crassostrea gigas were exposed to two sizes of polystyrene MPs with 1 × 104 particles/L (small polystyrene MPs (SPS-MPs): 6 μm, large polystyrene MPs (LPS-MPs): 50-60 μm) at two pH levels (7.7 and 8.1) for 14 days. The antagonistic effects between MPs and OA on oysters were mainly observed. Single SPS-MPs exposure can induce CAT enzyme activity and LPO level in gills, while LPS-MPs exposure alone can increase PGK and PEPCK gene expression in digestive glands. Ocean acidification can increase clearance rate and inhibit antioxidant enzyme activity, whereas combined exposure of OA and SPS-MPs can affect the metabolomic profile of digestive glands. This study emphasized that the potential toxic effects of MPs under the scene of climate change should be concerned.

Integrating pollutant levels and biochemical biomarkers in oysters (Crassostrea rhizophorae and Crassostrea gasar) indicates anthropic impacts on marine environments along the coast of Santa Catarina state, Brazil

This study aimed to carry out a general diagnosis of the contamination of the coastal marine environment of the Santa Catarina state (SC, Brazil) by different classes of environmental pollutants, as well as to evaluate possible adverse effects of the contaminants on biochemical biomarkers of oysters, Crassostrea gasar and Crassostrea rhizophorae. 107 chemicals were evaluated in water, sediment and oyster samples from nine sites along the coastline of SC. We also examined various biochemical biomarkers in the oysters' gills and digestive glands to assess potential effects of contaminants. In general, the northern and central regions of the littoral of SC presented higher occurrences and magnitudes of contaminants than the southern region, which is probably related to higher urbanization of center and northern areas of the littoral. The biomarker analysis in the oysters reflected these contamination patterns, with more significant alterations observed in regions with higher levels of pollutants. Our results may serve as a first baseline for future and more extensive monitoring actions and follow-up of the degree of contamination in the state, allowing for inspection actions and management of areas most affected by marine pollutants.

Integrated biomarker responses: a further improvement of IBR and IBRv2 indexes to preserve data variability in statistical analyses

In biomonitoring and laboratory studies, it is typical to measure a battery of molecular, biochemical, and cytogenetic biomarkers to evaluate the effects of xenobiotics in biota. However, summarizing the results of several biomarkers to inform laypersons and environmental agencies is still a challenge for researchers and environmental specialists. To address this issue, researchers have developed indexes such as the Integrated Biomarker Responses (IBR) and Integrated Biomarker Response version 2 (IBRv2) to summarize all biomarkers responses into a single value. Unfortunately, these indexes do not preserve the original biological variability, which hampers subsequent statistical analyses. In this study, we created new versions of IBR and IBRv2, which preserve individual data variability and can be used in typical statistical analyses. The new Integrated Biomarker Responses individual (IBRi), Integrated Biomarker Responses version 2 individual (IBRv2i) and Weighted Integrated Biomarker Responses version 2 individual (Weighted IBRv2i) indexes correlated with the original IBR and IBRv2 indexes and were able to detect differences among experimental groups in a simulated and case studies. Using the IBRi, IBRv2i, or Weighted IBRv2i indexes is advantageous because they maintain the data variability of the experimental groups and can be analyzed using hypothesis testing statistics like any other parameter. Additionally, this approach can help translate technical scientific terminology into a more accessible language suitable for environmental governmental agencies and decision-makers.

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

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

Seasonal dynamics of coastal pollution migration in open waters with intensive marine ranching

Mariculture activities have been recognized as one of the major sources of contamination for marine pollutants, such as the excessive discharging of nitrogen and phosphate. The fully understanding of the pollutants emission and transportation is crucial for coastal environment management. However, the influence of such highly dynamic coastal process on the pollutant migration remain unclear, such as the effects of coastal seasonal hydrodynamics on the dissolved pollutant transportation, especially under intensive marine ranching activities in open waters. This study investigated the seasonal transport mechanisms of pollutants released from three typical mariculture methods (floating raft, cage and bottom pond) in the Wangjia Island (WJ), Yellow Sea, China. We have conducted three field surveys to monitor the coastal dynamics and measure the distribution of dissolved pollutants in the ranching area. Results from these field surveys show that the WJ and adjacent area experienced significant degradation in terms of water quality with the development of regional marine ranching. The average of calculated index for eutrophication Ei increases from 0.12 in the non-farming area to 0.78 in the farming area. In order to delineate the impacts area of pollutant transport associated with these highly dynamics of water exchange, a Eulerian passive tracer-tracking module is applied to simulate the pollutant transport processes based on a field scale three-dimensional Finite Volume Coastal Ocean Model (FVCOM). Then after, the impacts of barotropic and baroclinic coastal dynamics on the migration of dissolved pollutants were evaluated. The transport of pollutants was greatly influenced by the different farming modes. The travel distance of pollutants released from the bottom pond farming mode was limited, whereas pollutants from the surface-farming methods were transported over a longer distance. In this study, there are three folders of finding: 1) The migration direction varies with seasons, with a landward direction in winter and an offshore direction in summer; 2) In winter, strong wind (wind speed over 10 m/s) is the dominant factor for water exchange, which is conducive to the dispersion of pollutants in the study area. However, in summer, the thermal stratification controls pollutant migration; 3) The results of breakthrough time illustrate that the pollutants travelled slower during summer, especially for pollutants discharged from the bottom pond farming method. In summary, this study demonstrates that even in open waters with stronger water exchange capacity, the pollutants from intensive marine ranching can still increase the risk of eutrophication. The finding of this study has important implications for the management and regulation of offshore aquaculture activities, particularly for mitigating pollutants from marine ranching.

Field study of metal concentrations and biomarker responses in resident oysters of an estuarine system in southern Brazil

Pollutant exposure is considered an important factor responsible for the decline in marine biodiversity of Latin American coastal ecosystems. This threat has been detected in an estuarine system in southern Brazil, which prompted an investigation into the long-term biological effects of a chronic metal contamination on resident oysters from the Laguna Estuarine System (LES). Here, we present the species- and size-specific variations of biomarker responses (catalase, glucose-6-phosphate dehydrogenase, glutathione S-transferase, and protein carbonylation) in the gills and digestive gland of Crassostrea gigas and Crassostrea gasar. In parallel, concentrations of eight metals (Al, Cd, Cr, Cu, Fe, Mn, Pb, Zn) in soft tissues were measured. Our analyses revealed that the metal levels exhibited decreasing order in both species: Zn > Fe > Al > Cu > Mn > Cd. Except for Cu and Al, metal concentrations did not differ between oyster species. Biomarker results highlighted that C. gasar presented higher antioxidant responses, whereas C. gigas showed increased biotransformation upon exposure to LES pollutants, which varied according to the tissue. However, C. gasar showed a significant higher content of protein carbonylation but was not related to metals. In our research approach, the observation of metals presence and biomarkers-related responses are considered biologically relevant from an ecotoxicological perspective and serve as a baseline for future pollution studies in estuaries of Latin America. Finally, we recommend adopting a suite of biomarkers in both C. gasar and C. gigas, regardless their size and weight, as sentinel organisms in future regional biomonitoring studies in southern Brazil.

Evaluation of biometry and blood concentration of heavy metals in free-living Chelonia mydas with and without fibropapillomatosis in southern Brazil

The present study determined the presence of heavy metals in green sea turtles with and without fibropapillomatosis in Itapirubá and Cassino beaches, southern Brazil. The weight, curved length of the carapace and body index were determined and blood was collected to quantify the concentrations of cadmium, lead and mercury. A total of 51 blood samples were analyzed, being 46 positives for at least one of the metals. There was a greater number of juvenile turtles in Itapirubá, larger in size and weight than those in Cassino. No statistical differences were found between metal concentrations between regions or between turtles with and without fibropapillomatosis. There was no significant correlation between metal concentrations, biometric variables and the presence of fibropapilomatose. Metal concentrations were low in both regions, with the highest concentrations being Cd and the lowest Hg.

Modeling integrated biomarker response (IBR) index for the mussel Mytilus galloprovincialis (Lamark 1819) exposed to heavy metal mixture using the CCF design

Marine pollutants such as heavy metals (HMs) are considered among the most copious oxidative stress (OS) inducers in marine organisms which leads to reactive oxygen species (ROS) formation. Complementary to our previous bioassays studies, the present research focuses on Catalase (CAT), Glutathione S-transferase (GST) and Malondialdehyde (MDA) as oxidative stress biomarkers and the integrated biomarker response (IBR) indexes (IBR₁ and IBR₂) as an ecotoxicological assessment tool in Mytilus galloprovincialis using central composite face centered (CCF) design. The oxidative stress biomarkers were measured in adult mussels (45-55 mm) on 3 days-exposed under different sub-lethal concentrations of cadmium (Cd), zinc (Zn), and copper (Cu). Using multiple regressions, ANOVA analysis revealed that experimental data fitted to second-order (quadratic) polynomial equations. The results showed that types, concentrations and metals combinations has a direct effect in CAT and GST activities, MDA level and IBR indexes. Additionally, metal-metal interactions were found synergistic (supra-additive), antagonistic (infra-additive) or zero interaction in the toxicological effect. As necessary, the optimization of the experimental results was done in order to determine the optimal conditions for the oxidative stress responses and IBR indexes. It was demonstrated that the CCF design combined with the multi-biomarker approach and IBR index can be used as an appropriate tool in ecotoxicological modulation and prediction of oxidative stress and antioxidant status by heavy metals in the mussels Mytilus galloprovincialis.

Multi-level responses of oysters Crassostrea virginica for assessing organochlorine pesticides in a Ramsar coastal lagoon in southern Mexico

Organochlorine pesticides (OCPs) have been intensively used without proper regulation and control in Latin America due to the prevalence of diseases and pests, thus posing potential risks to nontarget organisms. Initiatives for ecosystem preservation, such as to designate protected areas, may not be enough to avoid contamination by OCPs, considering that protected areas tend to be permeable to diffuse sources. Here, we investigate multi-level responses of the oyster Crassostrea virginica to OCPs in Laguna de Términos, a RAMSAR coastal lagoon in the southern Gulf of Mexico. For this aim, OCPs occurrence and concentrations in the water, sediment, and in oysters from 3 settlement banks were assessed. Enzymatic and non-enzymatic biochemical biomarkers were quantified in the oysters' mantle and digestive gland, and the human health risk due to oyster consumption was also evaluated. OCPs in water were below detection limits. Fourteen OCPs were detected in sediments (∑OCPs mean of 49 ngg^-1) and 7 in oyster tissues (∑OCPs mean of 121 ngg^-1). The occurrence of OCPs was related to the land uses along the watersheds of the rivers that drain into the lagoon. Biochemical responses were correlated with OCPs (∑HCH, ∑DDT, heptachlor and endosulfan) in sediment, and oyster tissues. OCPs in oyster tissues showed a strong association with pro-oxidant forces and oxidative stress responses (Superoxide dismutase, Catalase, Glutathione Peroxidase, and lipid peroxidation), and neurotoxicity (Acetylcholinesterase), suggesting that the current OCPs contamination exerts significant stress. Our study also shows that the consumption of oysters from the lagoon increases the potential human health risk. Considering that Laguna de Términos is a protected Ramsar site, we suggest that environmental protection measures should be increased and that a monitoring program for OCPs exposure is necessary to assess the effects on this ecosystem.

Dissecting integrated indices of multiple biomarker responses: Think before use

The multiple biomarker approach is an effective tool to study the responses of aquatic organisms to contaminants. Summarizing multiple biomarker responses for facilitated communication of research findings has been aided by some integrated indices. Here we explain how existing integrated indices were built and why they turn out to be the wheel reinvented. We discuss the role of integrated indices in ecological risk assessment and recommend some changes in summarizing multiple biomarker results. Integr Environ Assess Manag 2023;19:302-311. © 2022 The Authors. Integrated Environmental Assessment and Management published by Wiley Periodicals LLC on behalf of Society of Environmental Toxicology & Chemistry (SETAC).

Use of invertebrates to model chemically induced parkinsonism-symptoms

The prevalence of neurological diseases is currently growing due to the combination of several factor, including poor lifestyle and environmental imbalance which enhance the contribution of genetic factors. Parkinson's disease (PD), a chronic and progressive neurological condition, is one of the most prevalent neurodegenerative human diseases. Development of models may help to understand its pathophysiology. This review focuses on studies using invertebrate models to investigate certain chemicals that generate parkinsonian-like symptoms models. Additionally, we report some preliminary results of our own research on a crustacean (the crab Ucides cordatus) and a solitary ascidian (Styela plicata), used after induction of parkinsonism with 6-hydroxydopamine and the pesticide rotenone, respectively. We also discuss the advantages, limits, and drawbacks of using invertebrate models to study PD. We suggest prospects and directions for future investigations of PD, based on invertebrate models.

Molecular changes in oysters Crassostrea gigas (Thunberg, 1793) from aquaculture areas of Santa Catarina Island bays (Florianópolis, Brazil) reveal anthropogenic effects

Anthropogenic activities in coastal regions cause risks to the environmental and human health. Due to the carcinogenic and mutagenic potential, polycyclic aromatic hydrocarbons (PAH) are considered priority for monitoring. Most of the Brazilian production of Crassostrea gigas oysters are placed in the Bays of Santa Catarina Island. The aim of this study was to evaluate molecular responses (phase I and II of biotransformation and antioxidant defense) of C. gigas from six oyster farming areas potentially contaminated by sanitary sewage in Florianópolis Metropolitan (SC, Brazil): Santo Antônio de Lisboa, Sambaqui, Serraria, Caieira, Tapera, Imaruim. We evaluated the transcript levels of CYP1A1-like, CYP2-like, CYP2AU2-like, CYP356A1, GSTA1A-like, GSTO.4A-like, SULT-like, SOD-like and CAT-like by qRT-PCR. Only oysters from Caieira showed levels of thermotolerant coliforms allowed by the law. Chemicals analyses in soft tissues of oysters showed low to average levels of PAH in all monitored areas. Enhanced transcript levels of phase I (CYP1A1-like, CYP3564A1-like, CYP2-like and CYP2AU2-like) were observed in oysters from Serraria and Imaruí, suggesting higher biotransformation activity in these farming areas. Regarding phase II of biotransformation, GSTO.4A-like was up-regulated in oysters from Imaruí compared to Caieira and Santo Antônio de Lisboa. An upregulation of SOD-like and CAT-like were observed in oysters from Imaruí and Serraria, suggesting that oysters from these sites are facing higher prooxidant conditions compared to other areas. By integrating the biological and chemical data it is suggested that human-derived contaminants are affecting the oyster metabolism in some farming areas.

Analysis of Crassostrea gasar transcriptome reveals candidate genes involved in metal metabolism

Oysters have been extensively employed for monitoring of metal pollution in dynamic aquatic ecosystems. Therefore, the use of specific biomarkers can assist in discriminating the ecotoxicological implications of different elements in such complex environments. In this study, we revisited the sequencing data of gills and digestive glands transcripts in the mangrove oyster Crassostrea gasar and generated a reference transcriptome assembly from multiple assemblers, seven in total. Overall, we were able to identify a total of 11,917 transcripts, with 86.6% of them being functionally annotated and 1.4 times more than the first annotation. We screened the annotated transcripts to identify genes potentially involved in metals' transport, storage, and detoxification. Our findings included genes related to Zn distribution in cells (Zn transporters - ZIP, ZnT), metallothionein (MT-I and MT-IV), GSH biosynthesis, Ca⁺ transporter (NCX and ATP2B), and Cu distribution in cells (ATP7, ATOX1, CCS, and laccase-like). These results provided a reference transcriptome for additional insights into the transcriptional profile of C. gasar and other bivalves to better understand the molecular pathways underpinning metal tolerance and susceptibility. The study also provided an auxiliary tool for biomonitoring metal contamination in dynamic environments as estuaries.

Hydrocarbon exposure effect on energetic metabolism and immune response in Crassostrea virginica

Crassostrea virginica was exposed to different light crude oil levels to assess the effect on transcriptomic response and metabolic rate. The exposure time was 21 days, and levels of 100 and 200 μg/L were used, including a control. The most significant difference among treatments was the overexpression of several genes associated with energy production, reactive oxygen species (ROS) regulation, immune system response, and inflammatory response. Also, a hydrocarbon concentration-related pattern was identified in ROS regulation, with a gene expression ratio near 1.8:1 between 200 and 100 μg/L treatments. Statistical analysis showed no interaction effect for metabolic rate; however, significant differences were found for oil concentration and time factors, with a higher oxygen consumption at 200 μg/L. Our findings provide novel information about the metabolic response of C. virginica during hydrocarbons exposure. In addition, our results point out which biological processes should be investigated as targets for searching bioindicators.

Biomarkers for pollution in caged mussels from three reservoirs in Bulgaria: A pilot study

The mussel-watch concept was firstly proposed in 1975, which was later adopted by several international monitoring programs worldwide. However, for the very first time, a field experiment with caged mussels was performed in three reservoirs in Bulgaria to follow the harmful effects of sub-chronic pollution (30 days) of metals, trace, and macro-elements, as well as some organic toxicants, such as polybrominated diphenyl ethers and chlorinated paraffins. Therefore, we studied the biometric indices, histochemical lesions in the gills, biochemical changes in the digestive glands (antioxidant defense enzymes, such as catalase, glutathione reductase, and glutathione peroxidase; metabolic enzymes, such as lactate dehydrogenase, alanine aminotransferase, and aspartate aminotransferase, and the neurotransmitter cholinesterase), in addition to the DNA damage in the Chinese pond mussel, Sinanodonta woodiana (Lea, 1834) in Kardzhali, Studen Kladenets and Zhrebchevo reservoirs in Bulgaria. Significant correlation trends between the pollution levels, which we reported before, and the biomarker responses were established in the current paper. Overall, we found that both tested organs were susceptible to pollution-induced oxidative stress. The different alterations in the selected biomarkers in the caged mussels compared to the reference group were linked to the different kinds and levels of water pollution in the reservoirs, and also to the simultaneously conducted bioaccumulation studies.

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The effects of water pollution in caged mussels from three large dam reservoirs in Bulgaria were assessed.

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A cocktail of different inorganic and organic toxicants was measured both in waters and mussels for the first time.

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Different biomarker responses (cellular to individual) were also followed in gills and digestive glands of the transplants.

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Correlation trends between the pollution levels and the applied biological tools were established.

Nanoparticles as vectors of other contaminants in estuarine suspended sediments: Natural and real conditions

Studding the behaviour and danger of nanoparticles (NPs, minerals and amorphous phases) in the estuarine ecosystem is presently incomplete by the lack of measureable description of NPs in the ecological conditions, such as suspended-sediments (SS). In the last years, several works have revealed the toxic consequences of ultra-fine and nanoparticulate compounds on diverse systems, raising apprehensions over the nanocontaminants behaviour and destiny in the numerous ecological partitions. The general objective of the manuscript is to explain the geochemical conditions of the LES (Laguna estuarine system, southern Brazil) suspended sediments covering an area around the main South American coal plant, enhancing the creation of future public policies for environmental recovery projects. Subsequently the discharge of nanoparticles and toxic element (TE) in the ecosystem, NPs react with several constituents of the nature and suffers active alteration progressions. Contamination coming from engineering actions, wastewater, are something identifiable, however when these contaminations are accompanied by other contamination sources (e.g. mining and farming) the work gets defaulted. By combining material about the concentration of TE contaminants and NPs occurrences, this work offers novel visions into contaminant contact and the possible effects of such exposure on estuarine systems in Brazil. The results presented here will be useful for different areas of estuaries around the world.