Oxidative pathways of chemical toxicity and oxidative stress biomarkers in marine organisms

Unravelling biochemical responses in the species Mytilus galloprovincialis exposed to the antineoplastics ifosfamide and cisplatin under different temperature scenarios

This study investigates the chronic impact of two of the most widely consumed antineoplastic drugs, Ifosfamide (IF) and Cisplatin (CDDP), on the bivalve species Mytilus galloprovincialis under current (17 °C) and predicted warming conditions (21 °C). Accompanying the expected increase in worldwide cancer incidence, antineoplastics detection in the aquatic environment is also expected to rise. Mussels were exposed to varying concentrations of IF (10, 100, 500 ng/L) and CDDP (10, 100, 1000 ng/L) for 28 days. Biochemical analyses focused on metabolic, antioxidant and biotransformation capacities, cellular damage, and neurotoxicity. Results showed temperature-dependent variations in biochemical responses. Metabolic capacity remained stable in mussels exposed to IF, while CDDP exposure increased it at 1000 ng/L for both temperatures. Antioxidant enzyme activities were unaffected by IF, but CDDP activated them, particularly at 21 °C. Biotransformation capacity was unchanged by IF but enhanced by CDDP. Nevertheless, cellular damage occurred at CDDP concentrations above 100 ng/L, regardless of temperature. Integrated biomarker responses highlighted CDDP's greater impact, emphasizing the critical role of temperature in shaping organismal responses and underscoring the complexity of environmental stressor interactions.

Praseodymium and warming interactions in mussels: Comparison between observed and predicted results

Being a crucial element for technological development, praseodymium (Pr) has been increasingly used, leading to a rise in its concentration in aquatic systems. However, its potential threats to organisms remain poorly understood. Besides contamination, organisms are also threatened by climate change-related factors, including warming. It is important to evaluate how climate change-related factors may influence the effects of contaminants. To address this, histopathological and biochemical analyses were performed in adult mussels of Mytilus galloprovincialis, following a 28-day exposure to Pr (10 μg/L) and warming (4 °C increase) separately, and in combination. Additionally, biochemical and physiological alterations were analysed in the sperm of mussels after 30-min exposure to the same treatments. Furthermore, it was used the Independent Action model to predict the interaction between Pr and warming. The results showed, in the case of adults exposed to Pr, an increase in superoxide dismutase (SOD) and glutathione S-transferases (GSTs) activities. However, it was insufficient, leading to histopathological injuries, redox imbalance, and cellular damage. In the case of sperm, Pr induced an increase of mitochondrial activity and respiration rate, in response to the increase in systemic metabolic rate and oxygen demand. Warming increased the metabolism, and induced redox imbalance and cellular damage in adults. In sperm, a rise in temperature induced lipid peroxidation and a decrease in velocity. Warming induced some alterations in how adult mussels responded to Pr, activating catalase instead of SOD, and in addition to GSTs, also activated carboxylesterases. However, it was not enough to avoid redox imbalance and cellular damage. In the case of sperm, the combination induced a decrease in H2O2 production, and higher oxygen demand, which prevented the decrease in motility and velocity. This study highlights the limitations of using models and emphasizes the importance of studying the impacts of emerging contaminants, such as rare earth elements, and their combination with climate change-related factors. Under environmental conditions, chronic exposure to the combined effect of different stressors might generate impacts at higher biological levels. This may affect organisms' respiratory and filtration capacity, nutrient absorption, defence capacity against infections or diseases, and sperm viability, ultimately resulting in reduced growth and reproduction, with consequences at the population level.

Looking beyond the obvious: The ecotoxicological impact of the leachate from fishing nets and cables in the marine mussel Mytilus galloprovincialis

Once in the marine environment, fishing nets and cables undergo weathering, breaking down into micro and nano-size particles and leaching plastic additives, which negatively affect marine biota. This study aims to unravel the ecotoxicological impact of different concentrations of leachate obtained from abandoned or lost fishing nets and cables in the mussel Mytilus galloprovincialis under long-term exposure (28 days). Biochemical biomarkers linked to antioxidant defense system, xenobiotic biotransformation, oxidative damage, genotoxicity, and neurotoxicity were evaluated in different mussel tissues. The chemical nature of the fishing nets and cables and the chemical composition of the leachate were assessed and metals, plasticizers, UV stabilizers, flame retardants, antioxidants, dyes, flavoring agents, preservatives, intermediates and photo initiators were detected. The leachate severely affected the antioxidant and biotransformation systems in mussels' tissues. Following exposure to 1 mg·L-1 of leachate, mussels' defense system was enhanced to prevent oxidative damage. In contrast, in mussels exposed to 10 and 100 mg·L-1 of leachate, defenses failed to overcome pro-oxidant molecules, resulting in genotoxicity and oxidative damage. Principal component analysis (PCA) and Weight of Evidence (WOE) evaluation confirmed that mussels were significantly affected by the leachate being the hazard of the leachate concentrations of 10 mg·L-1 ranked as major, while 1 and 100 mg·L-1 was moderate. These results highlighted that the leachate from fishing nets and cables can be a threat to the heath of the mussel M. galloprovincialis.

Can photoperiod improve growth performance and antioxidant responses of pacu (Piaractus mesopotamicus) reared in recirculation aquaculture systems?

The present study investigated the best photoperiod for culturing pacu (Piaractus mesopotamicus) in recirculation aquaculture systems (RAS) based on its growth performance and hematological and oxidative stress responses. Juveniles (∼ 5 g) were subjected to five treatments (in triplicate): 24 L (light):0D (dark), 15 L: 09D, 12 L:12D, 9 L:15D, and 0 L:24D for 45 days. A total of 225 pacu individuals were randomly distributed among 15 tanks of 210 L (n = 15 per tank). Zootechnical, hematological (glucose, lactate, hematocrit, and hemoglobin), and antioxidant and oxidative stress parameters (glutathione S-transferase (GST), total antioxidant capacity against peroxyl radicals (ACAP), and lipid peroxidation (LPO) were analyzed. The zootechnical parameters (e.g., weight gain, Fulton's condition factor, and specific growth rate) were better and worse with 9 L:15D and 24 L:0D photoperiods, respectively. The hepatosomatic index was higher and lower in the 0 L:24D and 9 L:15D photoperiods. Blood lactate levels and antioxidant and oxidative stress responses were increased in the longest photoperiods (15 L:9D and 24 L:0D). In contrast, the treatments that showed lower oxidative damage (liver, gills, brain, and muscle) were 9 L:15D and 12 L:12D. In conclusion, manipulating artificial light is one way to improve fish growth and health, where the best photoperiod for pacu farming in RAS is 9 L:15D.

Bio-based microplastic polylactic acid exerts the similar toxic effects to traditional petroleum-based microplastic polystyrene in mussels

Microplastics (MPs) have accumulated in the oceans, causing adverse effects on marine organisms and the environment. Biodegradable polylactic acid (PLA) is considered as an excellent substitute for traditional petroleum-based plastics, but it is difficult to degrade completely and easily become MPs in the marine environment. To test the ecological risk of bio-based PLA, we exposed thick-shelled mussels (Mytilus coruscus) to bio-based PLA and petroleum-based polystyrene (PS) (at 102, 104, and 106 particles/L) for 14 days. The significant increase in enzyme activities related to oxidative stress and immune response showed that mussels were under physiological stress after MP ingestion. While enzyme activities of nerve conduction and energy metabolism were significantly disturbed after exposure. Meanwhile, normal physiological activities in respiration, ingestion and assimilation were also suppressed in association with enzyme changes. The negative effects of PS and PLA in mussels were not differentiated, and further integration analysis of integrated biomarker response (IBR) and principal component analysis (PCA) also showed that PLA would induce adverse effects in mussels and ecological risks as PS, especially at environmental concentrations. Therefore, it is necessary to pay more attention to the environmental and ecological risk of bio-based MP PLA accumulating in the marine environment.

Exposure to hull cleaning wastewater induces mortality through oxidative stress and cholinergic disturbance in the marine polychaete Perinereis aibuhitensis

While wastewater and paint particles discharged from the in-water cleaning process of ship hulls are consistently released into benthic ecosystems, their hazardous effects on non-target animals remain largely unclear. In this study, we provide evidence on acute harmful effects of hull cleaning wastewater in marine polychaete Perinereis aibuhitensis by analyzing physiological and biochemical parameters such as survival, burrowing activity, and oxidative status. Raw wastewater samples were collected during ship hull cleaning processes in the field. Two wastewater samples for the exposure experiment were prepared in the laboratory: 1) mechanically filtered in the in-water cleaning system (MF) and 2) additionally filtered with a 0.45 μm filter in the laboratory (LF). These wastewater samples contained high concentrations of metals (zinc and copper) and metal-based booster biocides (copper pyrithione and zinc pyrithione) compared to those analyzed in seawater. Polycheates were exposed to different concentrations of the two wastewater samples for 96 h. Higher mortality was observed in response to MF compared to LF-exposed polychaetes. Both wastewater samples dose-dependently decreased burrowing activity and AChE activity. Drastic oxidative stress was observed in response to the two wastewater samples. MDA levels were significantly increased by MF and LF samples. Significant GSH depletion was observed with MF exposure, while increased and decreased GSH contents were observed in LF-exposed polychaetes. Enzymatic activities of antioxidant components, catalase, superoxide dismutase, and glutathione S-transferase were significantly modulated by both wastewater samples. These results indicate that even filtered hull cleaning wastewater can have deleterious effects on the health status of polychaetes.

Physiological and molecular responses of the copepods Acartia clausi and Acartia tonsa to nickel nanoparticles and nickel chloride

Nickel compounds in dissolved form or as nanoparticles may affect planktonic invertebrates in marine ecosystems. Here, we assessed the physiological (naupliar mortality, egg production, egg hatching success) and molecular (quantitative gene expression) responses of the crustacean copepods Acartia clausi (indigenous Mediterranean species) and Acartia tonsa (model organism in ecotoxicology), to nickel nanoparticles (NiNPs) and nickel chloride (NiCl2), over time. We also measured NPs size and the temporal release of Ni ions in aqueous solution, through dynamic light scattering (DLS) and inductively coupled plasma-mass spectrometry (ICP-MS), respectively. Nauplii of A. clausi were highly vulnerable to NiCl2 in the 48 h acute test, with an EC50 in the range of Ni concentrations measured in polluted waters. Females of both species exhibited a decreased egg production and hatching success after the 4-day exposure to NiNPs. Molecular responses in A. clausi incubated in NiNPs and NiCl2 showed a stronger up- or down-regulation, compared to A. tonsa, of genes associated with detoxification (phospholipid-hydroperoxide glutathione peroxidase, glutathione-S-transferase sigma), oxidative stress (superoxide dismutase), nervous system functioning (acetylcholinesterase), and oogenesis (vitellogenin). In conclusion, new information was here obtained on the effects of different forms of nickel on physiological and molecular responses of A. clausi, that could help to identify biomarker genes of exposure to be used as early-warning indicators. Our results also highlighted the need of employing indigenous copepod species to better evaluate the ecotoxicological impact of pollutants in different geographical area.

Pyraclostrobin induces developmental toxicity and cardiotoxicity through oxidative stress and inflammation in zebrafish embryos

Pyraclostrobin, a typical representative of strobilurin fungicides, is extensively used in agriculture to control fungi and is often detected in water bodies and food. However, the comprehensive toxicological molecular mechanism of pyraclostrobin requires further study. To assess the toxic effects and underlying mechanisms of pyraclostrobin on aquatic organisms, zebrafish embryos were exposed to pyraclostrobin (20, 40, and 60 μg/L) until 96 h post fertilization (hpf). These results indicated that exposure to pyraclostrobin induces morphological alterations, including spinal curvature, shortened body length, and smaller eyes. Furthermore, heart developmental malformations, such as pericardial edema and bradycardia, were observed. This indicated severe cardiotoxicity induced by pyraclostrobin in zebrafish embryos, which was confirmed by the dysregulation of genes related to heart development. Besides, our findings also demonstrated that pyraclostrobin enhanced the contents of reactive oxygen species (ROS) and malondialdehyde (MDA), up-regulated catalase (CAT) activity, but inhibited superoxide dismutase (SOD) activity. Subsequently, the NF-κb signaling pathway was further studied, and the results indicated that the up-regulation of tnf-α, tlr-4, and myd88 activated the NF-κb signaling pathway and up-regulated the relative expression level of pro-inflammatory cytokines, such as cc-chemokine, ifn-γ, and cxcl-clc. Collectively, this study revealed that pyraclostrobin exposure induces developmental toxicity and cardiotoxicity, which may result from a combination of oxidative stress and inflammatory responses. These findings provide a basis for continued evaluation of the effects and ecological risks of pyraclostrobin on the early development of aquatic organisms.

The Interactive Effects of the Anti-Sea Lice Pesticide Azamethiphos and Temperature on Oxidative Damage and Antioxidant Responses in the Oyster Ostrea chilensis

Azamethiphos is used in the salmon industry to treat sea lice and is subsequently discharged into the sea, which may affect non-target species (NTS). A rise in seawater temperature could enhance the sensitivity of NTS. Thus, in the present investigation, the combined effects of azamethiphos (0 µg L-1, 15 µg L-1 and 100 µg L-1) and temperature (12 °C and 15 °C) was assessed over time (7 days) in the gonads and gills of the oyster Ostrea chilensis, assessing its oxidative damage (lipid peroxidation and protein carbonyls) and total antioxidant capacity. Our results indicated that in gonads and gills, lipid peroxidation levels increased over time during exposure to both pesticide concentrations. Protein carbonyl levels in gills increased significantly in all experimental treatments; however, in gonads, only pesticide concentration and exposure time effected a significant increase in protein damage. In both, gill and gonad temperature did not influence oxidative damage levels. Total antioxidant capacity in gonads was influenced only by temperature treatment, whereas in the gills, neither temperature nor azamethiphos concentration influenced defensive responses. In conclusion, our results indicated the time of pesticide exposure (both concentrations) had a greater influence than temperature on the cellular damage in this oyster.

Probiotics an emerging therapeutic approach towards gut-brain-axis oriented chronic health issues induced by microplastics: A comprehensive review

Applications for plastic polymers can be found all around the world, often discarded without any prior care, exacerbating the environmental issue. When large waste materials are released into the environment, they undergo physical, biological, and photo-degradation processes that break them down into smaller polymer fragments known as microplastics (MPs). The time it takes for residual plastic to degrade depends on the type of polymer and environmental factors, with some taking as long as 600 years or more. Due to their small size, microplastics can contaminate food and enter the human body through food chains and webs, causing gastrointestinal (GI) tract pain that can range from local to systemic. Microplastics can also acquire hydrophobic organic pollutants and heavy metals on their surface, due to their large surface area and surface hydrophobicity. The levels of contamination on the microplastic surface are significantly higher than in the natural environment. The gut-brain axis (GB axis), through which organisms interact with their environment, regulate nutritional digestion and absorption, intestinal motility and secretion, complex polysaccharide breakdown, and maintain intestinal integrity, can be altered by microplastics acting alone or in combination with pollutants. Probiotics have shown significant therapeutic potential in managing various illnesses mediated by the gut-brain axis. They connect hormonal and biochemical pathways to promote gut and brain health, making them a promising therapy option for a variety of GB axis-mediated illnesses. Additionally, taking probiotics with or without food can reduce the production of pro-inflammatory cytokines, reactive oxygen species (ROS), neuro-inflammation, neurodegeneration, protein folding, and both motor and non-motor symptoms in individuals with Parkinson's disease. This study provides new insight into microplastic-induced gut dysbiosis, its associated health risks, and the benefits of using both traditional and next-generation probiotics to maintain gut homeostasis.

Can exposure to Gymnodinium catenatum toxic blooms influence the impacts induced by Neodymium in Mytilus galloprovincialis mussels? What doesn't kill can make them stronger?

The presence in marine shellfish of toxins and pollutants like rare earth elements (REEs) poses a major threat to human well-being, coastal ecosystems, and marine life. Among the REEs, neodymium (Nd) stands out as a widely utilized element and is projected to be among the top five critical elements by 2025. Gymnodinum catenatum is a phytoplankton species commonly associated with the contamination of bivalves with paralytic shellfish toxins. This study evaluated the biological effects of Nd on the mussel species Mytilus galloprovincialis when exposed to G. catenatum cells for fourteen days, followed by a recovery period in uncontaminated seawater for another fourteen days. After co-exposure, mussels showed similar toxin accumulation in the Nd and G. catenatum treatment in comparison with the G. catenatum treatment alone. Increased metabolism and enzymatic defenses were observed in organisms exposed to G. catenatum cells, while Nd inhibited enzyme activity and caused cellular damage. Overall, this study revealed that the combined presence of G. catenatum cells and Nd, produced positive synergistic effects on M. galloprovincialis biochemical responses compared to G. catenatum alone, indicating that organisms' performance may be significantly modulated by the presence of multiple co-occurring stressors, such those related to chemical pollution and harmful algal blooms. ENVIRONMENTAL IMPLICATIONS: Neodymium (Nd) is widely used in green technologies like wind turbines, and this element's potential threats to aquatic environments are almost unknown, especially when co-occurring with other environmental factors such as blooms of toxic algae. This study revealed the cellular impacts induced by Nd in the bioindicator species Mytilus galloprovincialis but further demonstrated that the combination of both stressors can generate a positive defense response in mussels. The present findings also demonstrated that the impacts caused by Nd lasted even after a recovery period while a previous exposure to the toxins generated a faster biochemical improvement by the mussels.

Developmental and biochemical markers of the impact of pollutant mixtures under the effect of Global Climate Change

This study investigates the combined impact of microplastics (MP) and Chlorpyriphos (CPF) on sea urchin larvae (Paracentrotus lividus) under the backdrop of ocean warming and acidification. While the individual toxic effects of these pollutants have been previously reported, their combined effects remain poorly understood. Two experiments were conducted using different concentrations of CPF (EC10 and EC50) based on previous studies from our group. MP were adsorbed in CPF to simulate realistic environmental conditions. Additionally, water acidification and warming protocols were implemented to mimic future ocean conditions. Sea urchin embryo toxicity tests were conducted to assess larval development under various treatment combinations of CPF, MP, ocean acidification (OA), and temperature (OW). Morphometric measurements and biochemical analyses were performed to evaluate the effects comprehensively. Results indicate that combined stressors lead to significant morphological alterations, such as increased larval width and reduced stomach volume. Furthermore, biochemical biomarkers like acetylcholinesterase (AChE), glutathione S-transferase (GST), and glutathione reductase (GRx) activities were affected, indicating oxidative stress and impaired detoxification capacity. Interestingly, while temperature increase was expected to enhance larval growth, it instead induced thermal stress, resulting in lower growth rates. This underscores the importance of considering multiple stressors in ecological assessments. Biochemical biomarkers provided early indications of stress responses, complementing traditional growth measurements. The study highlights the necessity of holistic approaches when assessing environmental impacts on marine ecosystems. Understanding interactions between pollutants and environmental stressors is crucial for effective conservation strategies. Future research should delve deeper into the impacts at lower biological levels and explore adaptive mechanisms in marine organisms facing multiple stressors. By doing so, we can better anticipate and mitigate the adverse effects of anthropogenic pollutants on marine biodiversity and ecosystem health.

The role of the macroalgae Ulva lactuca on the cellular effects of neodymium and mercury in the mussel Mytilus galloprovincialis

Rare earth elements (REEs) are increasingly being studied mainly due to their economic importance and wide range of applications, but also for their rising environmental concentrations and potential environmental and ecotoxicological impacts. Among REEs, neodymium (Nd) is widely used in lasers, glass additives, and magnets. Currently, NdFeB-based permanent magnets are the most significant components of electronic devices and Nd is used because of its magnetic properties. In addition to REEs, part of the environmental pollution related to electrical and electronic equipment, fluorescent lamps and batteries also comes from mercury (Hg). Since both elements persist in ecosystems and are continuously accumulated by marine organisms, a promising approach for water decontamination has emerged. Through a process known as sorption, live marine macroalgae can be used, especially Ulva lactuca, to accumulate potential toxic elements from the water. Therefore, the present study aimed to evaluate the cellular toxicity of Nd and Hg in Mytilus galloprovincialis, comparing the biochemical effects induced by these elements in the presence or absence of the macroalgae U. lactuca. The results confirmed that Hg was more toxic to mussels than Nd, but also showed the good capability of U. lactuca in preventing the onset of cellular disturbance and homeostasis disruption in M. galloprovincialis by reducing bioavailable Hg levels. Overall, the biochemical parameters evaluated related to metabolism, antioxidant and biotransformation defences, redox balance, and cellular damage, showed that algae could prevent biological effects in mussels exposed to Hg compared to those exposed to Nd. This study contributes to the advancement of knowledge in this field, namely the understanding of the impacts of different elements on bivalves and the crucial role of algae in the protection of other aquatic organisms.

Hull-cleaning wastewater poses serious acute and chronic toxicity to a marine mysid-A multigenerational study

We conducted a comprehensive assessment involving acute effects on 96-hour survival and biochemical parameters, as well as chronic effects on growth and reproduction spanning three generations of the marine mysid Neomysis awatschensis exposed to filtered wastewater to evaluate the potential impact of ship hull-cleaning wastewater on crustaceans. The analyzed wastewater exhibited elevated concentrations of metals, specifically zinc (Zn) and copper (Cu) and metal-based antifoulants, i.e., Cu pyrithoine (CuPT) and Zn pyrithoine (ZnPT). The results revealed dose-dependent reductions in survival rates, accompanied by a notable increase in oxidative stress, in response to the sublethal values of two wastewater samples: 1) mechanically filtered using the cleaning system (MF) and 2) additionally filtered in the laboratory (LF) for 96 h. Mysids exposed to MF displayed higher mortality than those exposed to LF. Furthermore, mysids subjected to continuous exposure of 0.001% LF across three generations exhibited significant inhibition of the feeding rate, more pronounced growth retardation along with an extended intermolt duration, and a diminished rate of reproduction compared to the control. A noteworthy inhibition of the feeding rate and growth was observed in the first generation exposed only to the LF sample. However, although the reproduction rate was not significantly affected. Collectively, these findings underscore the potential harm posed by sublethal concentrations of wastewater to the health of mysid populations under consistent exposure.

Behavioral and biochemical responses of the marine polychaete Perinereis aibuhitensis to 2-ethylhexyl-4-methoxycinnamate (EHMC) exposure

2-ethylhexyl-4-methoxycinnamate (EHMC) is a commonly used UV filter, and is receiving increasing concerns due to its ubiquitous occurrence in a variety of environmental media and potential adverse effects. This study was aimed to assess the ecotoxicological potentials of EHMC on the marine polychaete Perinereis aibuhitensis. To this end, ragworms were exposed to 2, 20, 200 μg/L EHMC for 14 days and multiple toxicological endpoints were investigated. The results showed that EHMC significantly reduced burrowing rate, but did not affect AChE activity. Exposure to EHMC significantly elevated the activities of SOD and CAT and decreased the levels of lipid peroxidation. Besides, the induction of AKP activity indicated a stimulated immune response in the ragworms when exposed to high concentration of EHMC. Furthermore, the upregulated expression of caspase-8 suggested that EHMC might induce apoptosis in ragworms via the death receptor-mediated extrinsic pathway. Our findings highlight the potential environmental risks of EHMC to marine ecosystems.

The role of warming in modulating neodymium effects on adults and sperm of Mytilus galloprovincialis

The use of rare earth elements (REEs) has been increasing and one of the most used is neodymium (Nd). Being an emergent contaminant, its negative impacts are poorly understood. Aquatic organisms are also threatened by climate change-related factors, as is the case of warming, which can change the effects of REEs. Thus, the impacts of Nd, warming, and the combination of both stressors were studied in adult mussels and sperm of the species Mytilus galloprovincialis, after an exposure period of 28 days (adults) and 30 min (sperm). The effects were evaluated through the analysis of biochemical and histopathological alterations in adults and biochemical and physiological responses given by sperm. The results showed that mussels only activated their biotransformation capacity when exposed to the stressors acting alone, which was insufficient to avoid lipid peroxidation. Furthermore, warming (alone and combined with Nd) also produces damage to proteins. The digestive gland was the most sensitive organ to Nd, presenting several histopathological alterations. In the case of sperm, all stressors induced lipid peroxidation, a higher oxygen demand, and a decrease in velocity, even if the sperm viability was maintained. It seems that warming influenced the effects of Nd to some extent. The present findings contribute significantly to the field of REEs environmental toxicology by offering valuable insights into the impacts of Nd on various biological levels of mussels. Additionally, within the context of climate change, this study sheds light on how temperature influences the effects of Nd. The obtained results indicate that both stressors can potentially compromise the overall health of mussel populations, thereby affecting other species reliant on them for food and habitat. Moreover, this study highlights impaired sperm health, which could adversely affect their reproductive capacity and ultimately lead to population decline.

Does commercial indoxacarb pose ecotoxicological consequences? Employing a multi-marker approach in the model species Theba pisana

Indoxacarb is one of the most extensively used oxadiazine insecticides worldwide, but it may exert detrimental effects on ecosystems, population dynamics, and health. Due to the lack of knowledge on the ecotoxicity of indoxacarb, it is still challenging to assess whether this insecticide poses an ecotoxicological impact on terrestrial environments. Therefore, our study aims to provide novel data on the toxic effects of 28-day dietary exposure to commercial grade indoxacarb at two environmentally relevant concentrations, 0.02 µg/mL and tenfold (0.2 µg/mL) on the model species, Theba pisana. Their effects were studied using a multiple biomarker approach by evaluating physiological, biochemical, and histopathological responses. After 28 days of treatment, indoxacarb at both concentrations significantly reduced the food intake and growth of the treated snails. Also, it caused decreases in lipid peroxidation (LPO)  levels after 7 and 14 days of exposure, whereas an opposite effect occurred after 21 and 28 days. All treated snails were found to exhibit a lower content of glutathione (GSH) after all times of exposure. Moreover, catalase (CAT), glutathione-S-transferase (GST), and glutathione peroxidase (GPx) activities, as well as protein content (PC), were elevated in the treated snails after all time intervals. Post exposure to both realistic indoxacarb concentrations, changes in acetylcholinesterase (AChE) activity between a decrease and an increase were observed. Furthermore, indoxacarb caused histo-architectural changes in the hepatopancreas of T. pisana. Our results demonstrate that, at environmentally relevant concentrations, indoxacarb poses negative consequences for T. pisana, indicating its ecotoxicological impacts.

Regional evaluation of glyphosate pollution in the minor irrigation network

Due to its low cost, its ease of use and to the "mild action" declared for long time by the Control and Approval Agencies towards it, the herbicide Glyphosate, is one of the currently best-selling and most-used agricultural products worldwide. In this work, we evaluated the presence and spread of Glyphosate in the Po River Basin (Northern Italy), one of the regions with the most intensified agriculture in Europe and where, by now for decades, a strong and general loss of aquatic biodiversity is observed. In order to carry out a more precise study of the real presence of this herbicide in the waters, samples were collected from the minor water network for two consecutive years, starting in 2022, at an interval time coinciding with those of the spring and summer crop treatments. In contrast to the sampling strategies generally adopted by Environmental Protection Agencies, a more focused sampling strategy was adopted to highlight the possible high concentrations in minor watercourses in direct contact with cultivated fields. Finally, we investigated the possible consequences that the higher amounts of Glyphosate found in our monitoring activities can have on stress reactions in plant (Groenlandia densa) and animal (Daphnia magna) In all the monitoring campaigns we detected exceeding European Environmental Quality Standard - EQS limits (0.1 μg/L) values. Furthermore, in some intensively agricultural areas, concentrations reached hundreds of μg/L, with the highest peaks during spring. In G. densa and D. magna, the exposition to increasing doses of herbicide showed a clear response linked to metabolic stress. Overall, our results highlight how, after several decades of its use, the Glyphosate use efficiency is still too low, leading to economic losses for the farm and to strong impacts on ecosystem health. Current EU policy indications call for an agroecological approach necessary to find alternatives to chemical weed control, which farms can develop in different contexts in order to achieve the sustainability goals set by the Farm to Fork strategy.

Syringin alleviates bisphenol A-induced spermatogenic defects and testicular injury by suppressing oxidative stress and inflammation in male zebrafish

Syringin (SRG) is a bioactive principle possessing extensive activities including scavenging of free radicals, inhibition of apoptosis, and anti-inflammatory properties. However, its effects on spermatogenic defects and testicular injury as well as the underlying mechanisms are still unclear. This study aims to investigate the protective effect of SRG on testis damage in zebrafish and explore its potential molecular events. Zebrafish testicular injury was induced by exposure to bisphenol A (BPA) (3000 μg/L) for two weeks. Fish were treated with intraperitoneal injection of SRG at different doses (5 and 50 mg/kg bodyweight) for two more weeks under BPA induction. Subsequently, the testis and sperm were collected for morphological, histological, biochemical and gene expression examination. It was found that the administration of SRG resulted in a significant protection from BPA-caused impact on sperm concentration, morphology, motility, fertility rate, testosterone level, spermatogenic dysfunction and resulted in increased apoptotic and reactive oxygen species' levels. Furthermore, testicular transcriptional profiling alterations revealed that the regulation of inflammatory response and oxidative stress were generally enriched in differentially expressed genes (DEGs) after SRG treatment. Additionally, it was identified that SRG prevented BPA-induced zebrafish testis injury through upregulation of fn1a, krt17, fabp10a, serpina1l and ctss2. These results indicate that SRG alleviated spermatogenic defects and testicular injury by suppressing oxidative stress and inflammation in male zebrafish.

Microcystin-LR (MC-LR) inhibits green algae growth by regulating antioxidant and photosynthetic systems

Microcystins release from bloom-forming cyanobacteria is considered a way to gain competitive advantage in Microcystis populations, which threaten water resources security and aquatic ecological balance. However, the effects of microcystins on microalgae are still largely unclear. Through simulated culture experiments and the use of UHPLC-MS-based metabolomics, the effects of two microcystin-LR (MC-LR) concentrations (400 and 1,600 μg/L) on the growth and antioxidant properties of three algae species, the toxic Microcystis aeruginosa, a non-toxic Microcystis sp., and Chlorella vulgaris, were studied. The MC-LR caused damage to the photosynthetic system and activated the protective mechanism of the photosynthetic system by decreasing the chlorophyll-a and carotenoid concentrations. Microcystins triggered oxidative stress in C. vulgaris, which was the most sensitive algae species studied, and secreted more glycolipids into the extracellular compartment, thereby destroying its cell structure. However, C. vulgaris eliminated reactive oxygen species (ROS) by secreting terpenoids, thereby resisting oxidative stress. In addition, two metabolic pathways, the vitamin B6 and the sphingolipid pathways, of C. vulgaris were significantly disturbed by microcystins, contributing to cell membrane and mitochondrial damage. Thus, both the low (400 μg/L) and the high (1,600 μg/L) MC-LR concentration inhibited algae growth within 3 to 7 days, and the inhibition rates increased with the increase in the MC-LR concentration. The above results indicate that the toxin-producing Microcystis species have a stronger toxin tolerance under longer-term toxin exposure in natural water environments. Thus, microcystins participates in interspecific interaction and phytoplankton population regulation and creates suitable conditions for the toxin-producing M. aeruginosa to become the dominant species in algae blooms.

Understanding baseline levels of physiological stress tolerance from excessive exercise in a holobenthic octopus species, Octopus pallidus

Cephalopods receive a great deal of attention due to their socioeconomically important fisheries and aquaculture industries as well their unique biological features. However, basic information about their physiological responses under stress conditions is lacking. This study investigated the impact of a simple stressor, exercise to exhaustion, on the activity levels of antioxidant enzymes and the concentrations of molecules involved in oxidative stress response in the pale octopus (Octopus pallidus). Eight biochemical assays were measured in the humoral (plasma) and cellular (hemocyte) components of O. pallidus haemolymph, the invertebrate analogue to vertebrate blood. Overall, exercise resulted in an increase in activity of plasma catalase (CAT) and glutathione-S-transferase (GST) and the decrease in activity of plasms glutathione reductase (GR). In the hemocytes, the exercise elicited a different response, with a reduction in the activity of superoxide dismutase (SOD), GR, and glutathione peroxidase (GPX) and a reduction in nitric oxide (NO) concentration. Malondialdehyde (MDA) activity was similar in the plasma and haemocytes in control and exercised treatments, indicating that exercise did not induce lipid peroxidation. These results provide an important baseline for understanding oxidative stress in octopus, with exercise to exhaustion serving as a simple stressor which will ultimately inform our ability to detect and understand physiological responses to more complex stressors.

Biochemical responses in Pacific oysters Magallana gigas (Thunberg, 1793): Tools to evaluate the environmental quality of aquaculture areas

The discharge of sanitary sewage into the bays of the Florianópolis Metropolitan Area (Southern Brazil), has led to the contamination of oyster farms. Consequently, linear alkylbenzenes (LABs) were quantified in the sediment, and the biochemical responses in gills and digestive gland of oysters from six farms were assessed. Our findings revealed elevated levels of LABs in the sediment of the Imaruim and Serraria farms. Additionally, alterations were observed in the antioxidant enzymes: catalase, glutathione peroxidase and superoxide dismutase in both oyster tissue from the Serraria, Santo Antonio de Lisboa and Sambaqui farms. Furthermore, correlation analyses indicated strong and moderate associations between biochemical responses, organic contaminants, and certain physicochemical parameters. Consequently, our results demonstrated the activation of the antioxidant system in oysters, representing a protective response to the presence of sanitary sewage and other contaminants. Therefore, we propose the utilization of biochemical biomarkers for monitoring the environmental quality of farms.

Ocean acidification impact on the uptake of trace elements by mussels and their biochemical effects

This study delves into the intricate interplay between ocean acidification (OA), metal bioaccumulation, and cellular responses using mussels (Mytilus galloprovincialis) as bioindicators. For this purpose, environmentally realistic concentrations of isotopically labelled metals (Cd, Cu, Ag, Ce) were added to investigate whether the OA increase would modify metal bioaccumulation and induce adverse effects at the cellular level. The study reveals that while certain elements like Cd and Ag might remain unaffected by OA, the bioavailability of Cu and Ce could potentially escalate, leading to amplified accumulation in marine organisms. The present findings highlight a significant rise in Ce concentrations within different mussel organs under elevated pCO2 conditions, accompanied by an increased isotopic fractionation of Ce (140/142Ce), suggesting a heightened potential for metal accumulation under OA. The results suggested that OA influenced metal accumulation in the gills of mussels. Conversely, metal accumulation in the digestive gland was unaffected by OA. The exposure to both trace metals and OA affects the biochemical responses of M. galloprovincialis, leading to increased metabolic capacity, changes in energy reserves, and alterations in oxidative stress markers, but the specific effects on other biomarkers (e.g., lipid peroxidation, some enzymatic responses or acetylcholinesterase activity) were not uniform, suggesting complex interactions between the stressors and the biochemical pathways in the mussels.

Effects of Chronic Heat Stress on Growth, Apoptosis, Antioxidant Enzymes, Transcriptomic Profiles, and Immune-Related Genes of Hong Kong Catfish (Clarias fuscus)

Chronic heat stress can have detrimental effects on the survival of fish. This study aimed to investigate the impact of prolonged high temperatures on the growth, antioxidant capacity, apoptosis, and transcriptome analysis of Hong Kong catfish (Clarias fuscus). By analyzing the morphological statistics of C. fuscus subjected to chronic high-temperature stress for 30, 60, and 90 days, it was observed that the growth of C. fuscus was inhibited compared to the control group. The experimental group showed a significant decrease in body weight and body length compared to the control group after 60 and 90 days of high-temperature stress (p < 0.05, p < 0.01). A biochemical analysis revealed significant alterations in the activities of three antioxidant enzymes superoxide dismutase activity (SOD); catalase activity (CAT); glutathione peroxidase activity (GPx), the malondialdehyde content (MDA), and the concentrations of serum alkaline phosphatase (ALP); Aspartate aminotransferase (AST); and alanine transaminase (ALT) in the liver. TUNEL staining indicated stronger apoptotic signals in the high-temperature-stress group compared to the control group, suggesting that chronic high-temperature-induced oxidative stress, leading to liver tissue injury and apoptosis. Transcriptome analysis identified a total of 1330 DEGs, with 835 genes being upregulated and 495 genes being downregulated compared to the control group. These genes may be associated with oxidative stress, apoptosis, and immune response. The findings elucidate the growth changes in C. fuscus under chronic high temperature and provide insights into the underlying response mechanisms to a high-temperature environment.

From the cellular to tissue alterations induced by two rare earth elements in the mussel species Mytilus galloprovincialis: Comparison between exposure and recovery periods

The global effort to achieve carbon neutrality has led to an increased demand for renewable energy technologies and their raw materials, namely rare earth elements (REEs). These elements possess unique properties and are used in various applications. However, the increased use of REE-based technologies has resulted in higher amounts of electronic waste, leading to elevated REEs concentrations found in the aquatic environment, with poorly understood threats to wildlife. Praseodymium (Pr) and europium (Eu) are two REEs that, despite their potential environmental risks, have almost unknown effects on aquatic organisms. Therefore, the present study aimed to assess the impacts of different concentrations of Pr and Eu (0, 10, 20, 40, and 80 μg/L) in the mussel species Mytilus galloprovincialis, as well as their ability to recover from exposure to the highest concentration. Mussels accumulated both elements in a dose-dependent manner, with the accumulation of Pr being higher. Accompanying the increase of metabolism, mussels exposed to Pr not only enhanced the activity of the antioxidant enzymes superoxide dismutase (up to 40 μg/L) and glutathione reductase (at 80 μg/L) but also the activity of the biotransformation enzymes carboxylesterases (CbE's) and glutathione S-transferases (GSTs) (at 80 μg/L). Nevertheless, these defence mechanisms were not sufficient to prevent cellular damage. All the Eu concentrations induced cellular damage, despite an increase in the activity of biotransformation enzymes (CbE's and GSTs) in mussel tissue. According to the histopathology assessment, mussels were not able to recover after exposure to both elements and lower concentrations induced higher injuries in digestive tubules. This study highlights that exposure to Pr and Eu had adverse effects on M. galloprovincialis, even at the lowest tested concentration, which may eventually impact mussels' growth, reproductive capacity, and survival.

Combined effects of nanoplastics and elevated temperature in the freshwater water flea Daphnia magna

Global warming and nanoplastics (NPs) are critical global issues. Among NPs, one of the most hazardous types of plastics, polystyrene (PS), poses ecotoxicological threats to several freshwater organisms. The degree of toxicity of PS-NPs is strongly influenced by various environmental factors. This study illustrates the combined effects of temperature and PS-NPs on the water flea Daphnia magna. The sensitivity of D. magna to PS-NPs was tested under control (23 °C) and elevated temperatures (28 °C). As a result, increased temperatures influenced the uptake and accumulation of PS-NPs. Co-exposure to both higher temperatures and PS-NPs resulted in a drastic decrease in reproductive performance. The level of oxidative stress was found to have increased in a temperature-dependent manner. Oxidative stress was stimulated by both stressors, leading to increased levels of reactive oxygen species and antioxidant enzyme activity supported by upregulation of antioxidant enzyme-related genes under combined PS-NPs exposure and elevated temperature. In the imbalanced status of intracellular redox, activation of the p38 mitogen-activated protein kinase signaling pathway was induced by exposure to PS-NPs at high temperatures, which supported the decline of the reproductive capacity of D. magna. Therefore, our results suggest that PS-NPs exposure along with an increase in temperature significantly affects physiological processes triggered by damage from oxidative stress, leading to severely inhibited reproduction of D. magna.

Detrimental effects of hull cleaning wastewater on oxidative status, life cycle parameters, and population growth of the monogonont rotifer Brachionus manjavacas

While wastewater discharged from in-water cleaning process of ship hulls on rotifer consistently released into aquatic ecosystem, its detrimental effects on non-target animals are largely unclear. In this study, we provide evidence on detrimental effects of hull cleaning wastewater in the monogonont rotifer Brachionus manjavacas by analyzing biochemical and physiological parameters in its oxidative status, survival, lifespan, growth, fecundity, and population. The wastewater contained high concentrations of metals (Zn and Cu) and metal-based antifoulants (CuPT and ZnPT). Significant oxidative stress was observed in response to two wastewater samples [1) raw wastewater (RW) and 2) mechanical filtrated in the cleaning system (MF)]. Higher detrimental effects in survival, lifespan, fecundity, and population growth for 10 days were measured in the RW-exposed rotifers than those results analyzed in the MF-exposed rotifers. Two growth parameters, lorica length and width were also significantly modulated by both wastewater samples. These results indicate that even filtered hull cleaning wastewater would have deleterious effects on the maintenance of the rotifer population when they exposed constantly.

Fluorene-induced stress in the benthic oligochaete Tubifex tubifex: A multi-biomarker assessment of toxicological pathways and mechanisms under acute and subchronic exposures

This study examined the multifaceted impacts of fluorene exposure on Tubifex tubifex, encompassing acute (survival analysis and behavioral responses) and subchronic exposure regimens (antioxidant enzyme response and histopathology), molecular docking studies, and generalized read-across analysis. Survival analysis revealed concentration-dependent increases in toxicity over varying time intervals, with LC50 values decreasing from 30.072 mg/L at 24 h to 12.365 mg/L at 96 h, emphasizing the time-sensitive and concentration-responsive nature of the stressor. Behavioral responses were both concentration- and duration-dependent. While Erratic Movement and Clumping Tendency exhibited earlier responses (within 24 h) at lower concentrations, the wrinkling effect and mucus secretion) exhibited delayed onset, suggesting intricate regulatory mechanisms underlying adaptability to environmental challenges; moreover, the wrinkling effect was consistently induced at higher concentrations, indicating greater sensitivity to the toxic effects of fluorene. With sublethal environmentally relevant concentrations-1.24 mg/l and 2.47 mg/L i.e., 10% and 20% 96 h, respectively-the antioxidant enzyme response (i.e., upregulation of SOD, CAT, and GST) with increasing fluorene concentration, revealing a nonlinear, hormetic response, suggested adaptive protection at lower doses but inhibition at higher concentrations. Histopathological examination indicated that higher fluorene concentrations caused cellular proliferation, inflammation, and severe tissue damage in the digestive tract and body wall. Molecular docking studies demonstrated robust interactions between fluorene and major stress biomarker enzymes, disrupting their functions and inducing oxidative stress. Interactions with cytochrome c oxidase suggested interference with cellular energy production. Generalized Read-Across (GenRA) analysis unveiled shared toxicity mechanisms among fluorene and its analogs, involving the formation of reactive epoxides and the influence of cytochrome P450 enzymes. The diverse functional groups of these analogs, particularly chlorine-containing compounds, were implicated in toxicity through lipid peroxidation and membrane damage. Adverse outcome pathways and broader consequences for aquatic ecosystem health are discussed.

Size-dependent effects of plastic particles on antioxidant and immune responses of the thick-shelled mussel Mytilus coruscus

Micro-/nano-plastic particles (MNPs) are present in the ocean with potential detrimental impacts on marine ecosystems. Bivalves are often used as marine bioindicators and are ideal to evaluate the threat posed by various-sized MNPs. We exposed the mussel Mytilus coruscus to MNPs with different particle sizes (70 and 500 nm, 5, 10 and 100 μm) for 3, 72 h and 30 days. The antioxidant responses in digestive gland and the hemolymph were then evaluated. The time of exposure played a strong modulating role in the biological response. A 3-hour exposure had no significant impact on the digestive gland. After 72 h, an increase in oxidative stress was observed in the digestive gland, including increased hydrogen peroxide (H2O2) level, catalase (CAT), glutathione peroxidase (GPx) activities and malondialdehyde (MDA) production. After a 30-day exposure, the oxidative stress decreased while lipid peroxidation increased. A 30-day exposure increased hemocyte mortality (HM) and reactive oxygen species (ROS) levels in the hemolymph, while phagocytosis (PA), lysosome content (LC), mitochondrial number (MN) and mitochondrial membrane potential (MMP) significantly decreased. Longer-term exposure to MNPs caused oxidative stress in the digestive gland as well as impaired viability and immunity of hemocytes. Particle size also influenced the response with smaller particles having more severe effects. A depuration for 7 days was enough to reverse the negative effects observed on the digestive gland and hemolymph. This study provides new insights on the effects of small-sized MNPs, especially nanoplastic particles (NPs), on aquatic organisms, and provides a solid theoretical knowledge background for future studies on toxic effects of MNPs.

Yttrium effects on the Mediterranean mussel under a scenario of salinity shifts and increased temperature

Climate change (CC) induces significant worldwide alterations in salinity and temperature, impacting ecosystems and their services. Marine organisms, susceptible to these changes, may experience modified vulnerability to anthropogenic contaminants, including rare-earth elements (REEs) such as yttrium (Y) derived from electronic waste. This study investigated the influence of temperature and salinity changes on the impacts of Y in Mytilus galloprovincialis mussels. Organisms were subjected to Y (0 and 10 μg/L) for 28 days under three salinity scenarios (20, 30 (control), and 40, at a control temperature of 17 °C) or to two temperatures (17 and 22 °C, at the control salinity of 30). Under these conditions, Y bioaccumulation and different biomarkers were evaluated. Results showed that salinity and temperature did not affect Y accumulation, indicating effective detoxification mechanisms and physiological adaptations in the exposed organisms. However, in Y-exposed mussels effects were intensified under decreased salinity, evidenced by increased metabolism, defense enzyme activities, and acetylcholinesterase (AChE) levels. Similar responses occurred under heat stress with enhanced metabolic capacity, AChE activity, and activation of defense mechanisms such as glutathione S-transferases. These defense mechanisms mitigated cellular damage caused by Y, but under the highest temperature and especially lower salinity, Y-exposed mussels exhibited increased oxidative stress and decreased efficiency of activated defense enzymes, resulting in cellular damage compared to their uncontaminated counterpart. The present study sheds light on the effects that interactions between temperature, salinity, and the presence of emerging contaminants like REEs may have on marine organisms. Such assessments are crucial for developing effective strategies to mitigate the impacts of CC and protect the long-term health and resilience of marine ecosystems.

How predicted temperature and salinity changes will modulate the impacts induced by terbium in bivalves?

The threat of climate change, which includes shifts in salinity and temperature, has generated a global concern for marine organisms. These changes directly impact them and may alter their susceptibility to contaminants, such as terbium (Tb), found in electronic waste. This study assessed how decreased and increased salinity, as well as increased temperature, modulates Tb effects in Mytilus galloprovincialis mussels. After an exposure period of 28 days, Tb bioaccumulation and biochemical changes were evaluated. Results indicated no significant modulation of salinity and temperature on Tb accumulation, suggesting detoxification mechanisms and adaptations. Further analysis showed that Tb exposure alone caused antioxidant inhibition and neurotoxicity. When exposed to decreased salinity, these Tb-exposed organisms activated defense mechanisms, a response indicative of osmotic stress. Moreover, increased salinity also led to increased oxidative stress and metabolic activity in Tb-exposed organisms. Additionally, Tb-exposed organisms responded to elevated temperature with altered biochemical activities indicative of damage and stress response. Such responses suggested that Tb effects were masked by osmotic and heat stress. This study provides valuable insights into the interactions between temperature, salinity, and contaminants such as Tb, impacting marine organisms. Understanding these relationships is crucial for mitigating climate change and electronic waste effects on marine ecosystems.

Subcellular effects and lipid metabolism alterations in the gilthead seabream Sparus aurata fed on ovatoxins-contaminated mussels

The marine microalgae Ostreopsis cf. ovata are a well-known producer of palytoxin (PlTXs) analogues, i.e. ovatoxins (OVTXs) among others, which arouse concern for animal and human health. Both in field and laboratory studies, presence of OVTXs, detected in species directly feeding on O. cf. ovata, was frequently correlated with impairment on organisms' physiology, development and behaviour, while similar knowledge is still lacking for animals feeding on contaminated preys. In this study, transfer and toxicity of OVTXs were evaluated in an exposure experiment, in which gilthead seabream Sparus aurata was fed with bivalve mussel Mytilus galloprovincialis, contaminated by a toxic strain of O. cf. ovata. Mussels exposed to O. cf. ovata for 21 days accumulated meanly 188 ± 13 μg/kg OVTXs in the whole tissues. Seabreams fed with OVTX-contaminated mussels started to reject the food after 6 days of contaminated diet. Although no detectable levels of OVTXs were measured in muscle, liver, gills and gastro-intestinal tracts, the OVTX-enriched diet induced alterations of lipid metabolism in seabreams livers, displaying a decreased content of total lipid and fatty acid, together with overexpression of fatty acid biosynthetic genes, downregulation of β-oxidation genes and modulation of several genes related to lipid transport and regulation. Results from this study would suggest the hypothesis that OVTXs produced by O. cf. ovata may not be subject to bioaccumulation in fish fed on contaminated preys, being however responsible of significant biological effects, with important implications for human consumption of seafood products.

Exploring toxicological interactions in a changing sea: The case of the alkaloids caffeine and caulerpin

The bisindolic alkaloid caulerpin (CAU) is a bioactive compound isolated from green algae of the genus Caulerpa that are highly invasive in the Mediterranean Sea. On the other side, the purine alkaloid caffeine (CAF) is one of the most globally consumed psychoactive substances and a widespread anthropogenic water pollutant. Both compounds display a large panel of biological properties and are well known to accumulate in the tissues of aquatic organisms and, in certain circumstances, co-occur in the human diet. On this premise, the present study aimed to investigate possible synergistic interactions between CAU and CAF by using the bivalve Mytilus galloprovincialis as a model organism. Mussels were exposed to CAF via medium while they were fed with food enriched with CAU. After treatments, biochemical analysis confirmed the toxic potential of CAF, with increased AChE activity and lipid peroxidation. Also, histopathological alterations were observed in the gills and digestive tubules. The NMR-based metabolomics analysis detected higher levels of free amino acids under CAF treatments. Conversely, the food administration of CAU did not affect the above toxicological biomarkers. In addition, we did not observe any cumulative effect between CAF and CAU toward increased cellular damage and neurotoxicity. On the other hand, a possible action of CAU in decreasing CAF toxicity could be hypothesized based on our results. This hypothesis is supported by the activity of CAU as an agonist of peroxisome proliferator-activated receptors (PPARs). PPARs mediate xenobiotic detoxification via cytochromes P450, which is involved in CAF metabolism. Overall, the results obtained not only rule out any cumulative adverse effects of CAF and CAU but also encourage further research to evaluate the possible use of CAU, a compound easily obtained through the valorization of biomass from invasive species, as a food additive to improve the clearance of xenobiotics.

Life stage-specific effects of tire particle leachates on the cosmopolitan planktonic copepod Acartia tonsa

Tire wear particles (TWP) are a major source of microplastics in the aquatic environment and the ecological impacts of their leachates are of major environmental concern. Among marine biota, copepods are the most abundant animals in the ocean and a main link between primary producers and higher trophic levels in the marine food webs. In this study, we determined the acute lethal and sublethal effects of tire particle leachates on different life stages of the cosmopolitan planktonic copepod Acartia tonsa. Median lethal concentration (LC50, 48 h) ranged from 0.4 to 0.6 g L-1 depending on the life stages, being nauplii and copepodites more sensitive to tire particle leachates than adults. The median effective concentration (EC50, 48 h) for hatching was higher than 1 g L-1, indicating a relatively low sensitivity of hatching to tire particle leachates. However, metamorphosis (from nauplius VI to copepodite I) was notably reduced by tire particle leachates with an EC50 (48 h) of 0.23 g L-1 and the absence of metamorphosis at 1 g L-1, suggesting a strong developmental delay or endocrine disruption. Leachates also caused a significant decrease (10-22%) in the body length of nauplii and copepodites after exposure to TWP leachates (0.25 and 0.5 g L-1). We tested a battery of enzymatic biomarkers in A. tonsa adult stages, but a sublethal concentration of 50 mg L-1 of tire particle leachates did not cause a statistically significant effect on the measured enzymatic activities. Our results show that tire particle leachates can negatively impact the development, metamorphosis, and survival of planktonic copepods. More field data on concentrations of TWPs and the fate and persistence of their leached additives is needed for a better assessment of the risk of tire particle pollution on marine food webs.

A multibiomarker approach in clams (Ruditapes philippinarum) for a toxicological evaluation of dredged sediments

The Lagoon of Venice is often dredged for channel maintenance. To avoid harmful consequences to the ecosystem, a proper disposal of bottom sediments requires a preliminary evaluation of its potential toxicity before excavation. Here we evaluated the effects of polluted sediments on clams (Ruditapes philippinarum) using a multibiomarker approach. Bivalves were exposed for 3 and 14 days to five sediment samples collected along a navigation canal between Venice historical centre and the industrial area of Porto Marghera. Immunological, antioxidant, detoxification, and neurotoxicity biomarkers were analysed in haemolymph, gill, and digestive gland. As a control, sediment collected far from pollution sources was used. Two experiments were performed to assess potential seasonal/gametogenic influence in clam sensitivity. A different response of clam biomarkers was observed during the two experiments and among sampling sites. Clams' digestive gland resulted to be the most sensitive tissue analysed showing significant differences among sites in all biomarkers analysed. Greater differences were present due to seasonality rather than exposure. The concentrations of metals and organic pollutants increased from the city centre to the industrial area, highlighting the influence that industrial activities had on the lagoon ecosystem. However, bioaccumulation in clams did not follow the same clear pattern, suggesting low bioavailability of compounds due to relatively high organic matter content. Biomarkers modulation was mainly driven by metals, both present in sediments and bioaccumulated. In comparison, effects of organic pollutants on the biomarkers tested were negligible. Other sources of contamination not investigated (e.g. pesticides) were suggested by neurotoxicity biomarkers alteration.

Thermoregulatory response in juvenile Hippocampus erectus: Effect of magnitude and rate of thermal increase on metabolism and antioxidative defence

Behavioural, physiological and biochemical mechanisms constitute the adaptive capacities that allow marine ectotherms to explore the environment beyond their thermal optimal. Limitations to the efficiency of these mechanisms define the transition from moderate to severe thermal stress, and serve to characterise the thermoregulatory response in the zone of thermal tolerance. We selected a tropical population of Hippocampus erectus to describe the timing of the physiological and biochemical mechanisms in response to the following increments in water temperature: (i) 4°C abrupt (26-30°C in <5 min); (ii) 7°C abrupt (26-33°C); (iii) 4°C gradual (1°C every 3 h) and (iv) 7°C gradual (1.5°C every 3 h). The routine metabolic rate (Rrout) of juvenile H. erectus was measured immediately before and after 0.5, 12 and 28 h of being exposed to each thermal treatment. Samples of muscle and abdominal organs were taken to quantify indicators of aerobic and anaerobic metabolism and antioxidant enzymes and oxidative stress at each moment throughout exposure. Results showed a full thermoregulatory response within 0.5 h: Rrout increased in direct correspondence with both the magnitude and rate of thermal increase; peroxidised lipids rapidly accumulated before the antioxidant defence was activated and early lactate concentrations suggested an immediate, yet temporary, reduction in aerobic scope. After 12 h, Rrout had decreased in sea horses exposed to 30°C, but not to 33°C, where Rrout continued high until the end of trials. Within 28 h of thermal exposure, all metabolite and antioxidant defence indicators had been restored to control levels (26°C). These findings testify to the outstanding thermal plasticity of H. erectus and explain their adjustment to rapid fluctuations in ambient temperature. Such features, however, do not protect this tropical population from the deleterious effects of chronic exposure to temperatures that have been predicted for the future.

Recent progress in practical applications of a potential carotenoid astaxanthin in aquaculture industry: a review

Astaxanthin is the main natural C40 carotenoid used worldwide in the aquaculture industry. It normally occurs in red yeast Phaffia rhodozyma and green alga Haematococcus pluvialis and a variety of aquatic sea creatures, such as trout, salmon, and shrimp. Numerous biological functions reported its antioxidant and anti-inflammatory activities since astaxanthin possesses the highest oxygen radical absorbance capacity (ORAC) and is considered to be over 500 more times effective than vitamin E and other carotenoids such as lutein and lycopene. Thus, synthetic and natural sources of astaxanthin have a commanding influence on industry trends, causing a wave in the world nutraceutical market of the encapsulated product. In vitro and in vivo studies have associated astaxanthin's unique molecular features with various health benefits, including immunomodulatory, photoprotective, and antioxidant properties, providing its chemotherapeutic potential for improving stress tolerance, disease resistance, growth performance, survival, and improved egg quality in farmed fish and crustaceans without exhibiting any cytotoxic effects. Moreover, the most evident effect is the pigmentation merit, where astaxanthin is supplemented in formulated diets to ameliorate the variegation of aquatic species and eventually product quality. Hence, carotenoid astaxanthin could be used as a curative supplement for farmed fish, since it is regarded as an ecologically friendly functional feed additive in the aquaculture industry. In this review, the currently available scientific literature regarding the most significant benefits of astaxanthin is discussed, with a particular focus on potential mechanisms of action responsible for its biological activities.

Nano Iron Versus Bulk Iron Forms as Functional Feed Additives: Growth, Body Indices, Hematological Assay, Plasma Metabolites, Immune, Anti-oxidative Ability, and Intestinal Morphometric Measurements of Nile tilapia, Oreochromis niloticus

The current study aimed to compare the utilization efficiency of iron (Fe) feed additives from either bulk or nano sources in Nile tilapia, Oreochromis niloticus diets on growth, haematological, immunity, anti-oxidative, and intestinal topography capacities. Five isonitrogenous and isoenergetic diets were performed; the basal diet served as a control with no Fe added, whereas the experimental diets were shaped by adding bulk-Fe2O3 and nano-Fe2O3 to the basal diet to preserve Fe levels at 0.2 and 0.4 mg kg-1, respectively. Results indicated that superior growth performance was recorded in fish-fed diets supplemented with 0.4 nano-Fe2O3 mg kg-1 diet. In addition, the highest (P ≤ 0.05) survival rate, absorption area of villous (AAV), mucosal to serosal amplification ratio (MSR), and villi parameters (height and width) were noticed in fish fed diet enrichment with either bulk or nano-Fe2O3 source. However, the superiority observed in nano-Fe2O3 fish groups. Also, the highest values of plasma albumin, total protein, high-density lipoprotein cholesterol (HDL-C), white blood cells (WBCs), and lymphocyte absolute count (LYM) (P ≤ 0.05) recorded in fish fed a diet supplemented with nano-Fe2O3 versus the basal diet. Moreover, the highest values of catalase (CAT), glutathione peroxidase (GPx), superoxide dismutase (SOD), and plasma lysozyme activity (P ≤ 0.05) were observed in fish fed 0.4 mg/kg-1 nano-Fe2O3, while the lowest value was recorded in fish fed the control diet. The best value of malondialdehyde activity (P ≤ 0.05) recorded in a fish-fed diet supplemented with 0.4 mg/kg-1 nano-Fe2O3. The current findings emphasize the importance of including Fe to improve fish growth, immunity, antioxidant capabilities, and intestinal structure, primarily with a nano-Fe source, which demonstrated a more effective function in satisfying Nile tilapia dietary Fe requirements and improving the aforementioned parameters.

Biochemical and behavioral effects of zinc oxide nanorods on the freshwater mussel Potomida littoralis

Our study aimed to investigate the impact of nano-zinc oxide (nZnO), a widely used pollutant in industry, pharmaceuticals, and personal care products, on the behavior and oxidative stress of freshwater mussels (Potomida littoralis) an indicator species and also a model non-target organism in ecotoxicology. To this end mussels were exposed to nZnO (50 and 100 µg/L) and Zn2+ from ZnSO4 (50 and 100 µg/L) for 7 days. ZnSO4 was used for comparison purposes and to determine if the toxicity of nZnO was due to the release of ions into the aquatic environment. We evaluated changes in oxidative stress markers, including catalase (CAT), glutathione-S-transferase (GST), acetylcholinesterase (AChE), and malondialdehyde (MDA) levels, on the mussel gills and digestive glands. Additionally, the effect of nZnO on the filtration rate of bivalves was studied. The findings showed that the mussel tissue's different parameters were significantly affected by exposure to various concentrations of nZnO, causing changes in their behavior that led to a decrease in filtration rate. Additionally, noteworthy increments were observed in CAT activity, AChE activity, and MDA levels, whereas GST activity displayed a decreasing trend, implying that oxidative stress contributes to the toxicity of nZnO. The purpose of this review is to present a framework for comprehending the toxicological impacts of nanoparticles from an environmental standpoint. Additionally, it includes novel information about the connections between nanoparticles (NPs) and bivalve species.

Synergistic effects of microplastic and lead trigger physiological and biochemical impairment in a mangrove crab

Microplastics (MP) are vectors for other environmental contaminants, such as metals, being a considerable problem, especially in the aquatic ecosystem. To investigate the combined effects of MP (high density polyethylene) with lead (Pb), we exposed the mangrove fiddler crab Minuca vocator to Pb (50 mg L-1), and MP (25 mg L-1) alone and in mixture, for 5 days. We aimed to determine Pb and MP bioaccumulation, as well as physiological (oxygen consumption and hemolymph osmolality) and biochemical (superoxide dismutase, catalase, glutathione peroxidase, and lipid peroxidation) traits effects. Co-exposure of MP and Pb significantly increased the bioaccumulation of Pb, but reduced MP tissue accumulation. Regarding the physiological traits, increasing osmolality and oxygen consumption rates compared to the control were observed, particularly in the combined Pb and MP exposure. As to biochemical traits, the combination of Pb and MP induced the most significant responses in the enzymatic profile antioxidant enzyme activity. The catalase (CAT), glutathione peroxidase (GPx), and dismutase superoxide (SOD) decreased compared to individual exposure effects; the combination of MP and Pb had a synergistic effect on promoting lipid peroxidation (LPO). The co-exposure of MP and Pb acted synergistically when compared to the effects of the isolated compounds. Due to the increasing MP contamination in mangroves, more severe physiological and biochemical effects can be expected on mangrove crabs exposed to metal contamination.

Acute and chronic effects of triclosan on the behavior, physiology, and multigenerational characteristics of the water flea Moina macrocopa

Triclosan, a chlorinated biphenyl ether is widely used in industrial products and cosmetics due to its antibiotic activity. Although relatively levels of triclosan have been detected in aquatic ecosystems, limited information is available regarding the acute and chronic impacts of triclosan on aquatic invertebrates, especially planktonic crustaceans. In this study, we analyzed the acute (24 h) and chronic (14 days exposure across three generations) effects of different concentrations of triclosan [1/10 of the no observed effect concentration (NOEC), the NOEC, and 1/10 of the LC50] calculated from the 24 h acute toxicity value, on the water flea Moina macrocopa. In the acute exposure experiment, the 1/10 LC50 value of triclosan significantly reduced survival, feeding rate, thoracic limb activity, heart activity, and acetylcholinesterase activity. In response to the 1/10 LC50 value, intracellular reactive oxygen species increased along with elevated levels of malondialdehyde and glutathione. Enzymatic activities of catalase, superoxide dismutase, glutathione peroxidase, and glutathione reductase were significantly increased by the 1/10 LC50 value, suggesting active protection of the antioxidant defense system against oxidative stress. Chronic exposure to the 1/10 NOEC and NOEC values revealed multigenerational adverse impacts of triclosan. The second generation was found to be the most sensitive to triclosan, as the NOEC value significantly reduced the survival rate, body length, and the number of neonates per brood, along with a delayed hatching period. Taken together, these results indicate that even sublethal levels of triclosan can have detrimental effects on the water flea population's maintenance through intergenerational toxicity.

Toxic effects and mechanisms of cationic blue SD-GSL on Chlorella vulgaris before and after the biological decolorization process

Biodegradation is regarded as an efficient way to decolorize azo dyes. However, the changes in the algal toxicity of azo dyes during biodecolorization are still unclear. In this study, the physiological responses of Chlorella vulgaris to the hydrophobic and hydrophilic components of cationic blue SD-GSL (a typical monoazo dye) and its biodecolorization products were investigated. The toxicity of each component to Chlorella vulgaris and the sources of the toxicity were analyzed. The cationic blue SD-GSL components inhibited the algal cell division and superoxide dismutase (SOD) activity at all concentrations, and inhibited the synthesis of chlorophyll-a (Chl-a) at concentrations >100 mg/L, whereas increased the malondialdehyde (MDA) content. The hydrophobic and hydrophilic components of its biodecolorization products had enhanced inhibition rates on cell density (10.7% and 15.6%, respectively), Chl-a content (31.2% and 8.4%, respectively), and SOD activity (13.5% and 1.9%, respectively) of Chlorella vulgaris, and further stimulated an increase in MDA content (4.4% and 7.0%, respectively), indicating that the biodecolorization products were more toxic than the pristine dye. Moreover, the toxic effect of hydrophobic components on Chlorella vulgaris was stronger than that of hydrophilic components. The sensitivity sequence of Chlorella vulgaris to the toxicity of cationic blue SD-GSL and its biodecolorization product components was: Chl-a synthesis > SOD activity > cell division. SUVA analysis and 3D-EEM analysis revealed that the enhanced algal toxicity of the biodecolorization products of cationic blue SD-GSL was attributed to the aromatic compounds, which were mainly concentrated in the hydrophobic components. UPLC-Q-TOF-MS was used to verify dye biodecolorization byproducts. The information obtained from this study helps to understand the decolorization products toxicities of the biologically treated azo dyes, thereby providing new insights into the environmental safety of textile wastewater after traditional biological treatment.

The combined effects of phenanthrene and micro-/nanoplastics mixtures on the cellular stress responses of the thick-shell mussel Mytilus coruscus

Pollution with complex mixtures of contaminants including micro- and nano-plastics (MNPs) and organic pollutants like polycyclic aromatic hydrocarbons (PAH) poses a major threat to coastal marine ecosystems. Toxic mechanisms of contaminant mixtures are not well understood in marine organisms. We studied the effects of single and combined exposures to polycyclic aromatic hydrocarbon phenanthrene (Phe) and MNPs mixture with sizes of 70 nm, 5 μm and 100 μm on the immune health and oxidative stress parameters in the thick-shell mussel Mytilus coruscus. Immune cells (hemocytes) were more sensitive to the pollutant-induced oxidative stress than the gills. In hemocytes of co-exposed mussels, elevated mortality, lower lysosomal content, high production of reactive oxygen species (ROS) and decrease mitochondrial were found. Disparate responses of antioxidant enzymes in the hemolymph (e.g. increased superoxide dismutase (SOD) activity without a corresponding increase in catalase (CAT) in Phe exposures and an increase in CAT without a change in SOD in MNPs exposures) suggests misbalance of the antioxidant defense in the pollutant-exposed mussels. Gill lacked pronounced oxidative stress response showing a decline in ROS and antioxidant levels. Tissue-specific single and combined effects of Phe and MNPs suggest variation in bioavailability and/or different sensitivity to these pollutants in the studied tissues. Notably, the combined effects of MNPs and Phe were additive or antagonistic, showing that MNPs do not enhance and occasionally mitigate the toxic effects of Phe on the hemocytes and the gills of the mussels. Overall, our study sheds light on the impact of long-term exposure to MNPs and Phe mixtures on mussels, showing high sensitivity of the immune system and modulation of the Phe toxicity by MNPs co-exposure. These findings that may have implications for understanding the impacts of combined PAH and MNPs pollution on the health of mussel populations from polluted coastal habitats.

Hydrogen Peroxide Stress Induced in the Marine Cyanobacterium Synechococcus aeruginosus and Phormidium valdarianum

Biochemical markers against hydrogen peroxide-induced oxidative stress were developed in marine cyanobacteria under standard laboratory conditions. To find out the ability to cope with different concentrations of hydrogen peroxide, two species of marine cyanobacteria including unicellular and filamentous forms were exposed for shorter duration. Synechococcus aeruginosus and Phormidium valderianum tolerated hydrogen peroxide by showing the highest growth of Superoxide dismutase in Synechococcus aeruginosus and Phormidium valderianum, catalase in Synechococcus aeruginosus, peroxidase in Synechococcus aeruginosus and Phormidium valderianum, Glutathione S-transferase in Synechococcus aeruginosus and Phormidium valderianum which were identified as biochemical markers of oxidative stress against H2O2 in marine cyanobacteria. Synechococcus aeruginosus showed new isoforms for Superoxide dismutase, catalase, peroxidase, Glutathione peroxidase, and Glutathione S-transferase and Phormidium valderianum for Superoxide dismutase, peroxidase, and Glutathione S-transferase. Synechococcus aeruginosus is suggested as the indicator species for biochemical markers against hydrogen peroxide in marine cyanobacteria. Peroxidase is suggested as biochemical enzyme marker. The present investigated on these new isoenzymes were identified as biochemical markers for oxidative stress.

Combined impact of elevated temperature and zinc oxide nanoparticles on physiological stress and recovery responses of Scylla serrata

Global climate change is the major cause behind unexpected fluctuations in temperature. In recent years, application of nanotechnology also has become widespread and nanomaterials are constantly being released into aquatic environments, posing a potential risk to various organisms and ecosystems. The lack of detailed understanding of how multiple stressors work, and how they differ from single stressors, impede to assess their combined effect on aquatic organisms and ecosystems. The prime aim of the current investigation is to decipher the toxicity of ZnO-NP after simultaneous exposure to a global environmental stressor, elevated temperature for 14 days, followed by a 7 days recovery period, on the eco-physiological responses of mud crab Scylla serrata collected from Sundarbans. Physiological energetics such as ingestion, assimilation, absorption, respiration, and excretion rates were measured to determine the Scope for growth (SfG). Additionally, we assessed various biomarkers from different levels of biological organisation (antioxidant, detoxification defence mechanisms, and lipid peroxidation levels) of the species. Combined stress attenuated the SfG in crabs which deteriorated further in the recovery phase. Oxidative stress also exacerbated under coalesced stress condition. Recovery was not observed in crabs with increased lipid peroxidation level under combined stress conditions. Elevated temperature disturbed the energy budget of crabs as mirrored by diminished energy left for compensatory actions under added metal stress, ultimately sensitizing the animals to ZnO NP pollutants. The current results advocate future ocean temperature to aggravate the impact of metal NP pollution and induce oxidative damage in S. serrata.

Induced swimming modified the antioxidant status of gilthead seabream (Sparus aurata)

Swimming has relevant physiological changes in farmed fish, although the potential link between swimming and oxidative stress remains poorly studied. We investigated the effects of different medium-term moderate swimming conditions for 6 h on the antioxidant status of gilthead seabream (Sparus aurata), analyzing the activity of enzymes related to oxidative stress in the liver and skeletal red and white muscle. Forty fish were induced to swim individually with the following conditions: steady low (SL, 0.8 body length (BL)·s-1), steady high (SH, 2.3 BL·s-1), oscillating low (OL, 0.2-0.8 BL·s-1) and oscillating high (OH, 0.8-2.3 BL·s-1) velocities, and a non-exercised group with minimal water flow (MF, < 0.1 BL·s-1). All swimming conditions resulted in lower activities of superoxide dismutase (SOD), glutathione reductase (GR), and glutathione-S-transferase (GST) in the liver compared to the MF group, while steady swimming (SL and SH) led to higher reduced glutathione/oxidized glutathione ratio (GSH/GSSG) compared to the MF condition. Swimming also differently modulated the antioxidant enzyme activities in red and white muscles. The OH condition increased lipid peroxidation (LPO), catalase (CAT) and glutathione peroxidase (GPx) activities in the red muscle, decreasing the GSH/GSSG ratio, whereas the SL condition led to increased GSH. Oscillating swimming conditions (OL and OH) led to lower CAT activity in the white muscle, although GPx activity was increased. The GSH/GSSG ratio in white muscle was increased in all swimming conditions. Liver and skeletal muscle antioxidant status was modulated by exercise, highlighting the importance of adequate swimming conditions to minimize oxidative stress in gilthead seabream.

Transgenerational effects of microplastics on Nrf2 signaling, GH/IGF, and HPI axis in marine medaka Oryzias melastigma under different salinities

Little information is available on the toxicity of microplastics (MPs) under different salinities in aquatic organisms. Consequently, the effects of larvae exposure to 180 μg/L MPs with 5.0 μm diameter on growth, antioxidant capacity and stress response were investigated in exposed F1 larvae and unexposed F2 larvae in marine medaka Oryzias melastigma at 5 ‰ and 25 ‰ salinities. Poor growth performance of F1 and F2 larvae and F1 adult fish was merely found under high salinity, as well as changes in the growth hormone/insulin-like growth factor-I (GH/IGF). Although malondialdehyde (MDA) content and antioxidant capacity remained constant in F1 larvae under high salinity, MPs increased MDA content and reduced antioxidant capacity in F2 larvae. Contrarily, MDA and antioxidant capacity increased in F1 and F2 larvae under low salinity. The mRNA expression levels of genes in the NF-E2-related factor 2 (Nrf2) pathway were dysregulated. Cortisol levels in the whole body increased in F1 larvae and recovered to the control level under low salinity while cortisol levels declined in F1 larvae and increased in F2 larvae under high salinity, which was related to the transcriptional regulation of the hypothalamus-pituitary-interrenal (HPI) axis genes. To summary, the present study determined the toxic effects of MPs on growth, antioxidant capacity, and stress response by disturbing Nrf2, HPI, and GH/IGF signaling in exposed larvae and unexposed offspring of marine medaka in a salinity-dependent manner. For the first time, our results highlight the interference effects of salinity on MPs toxicity in fish.

The influence of temperature on the effects of lead and lithium in Mytilus galloprovincialis through biochemical, cell and tissue levels: Comparison between mono and multi-element exposures

Lead (Pb) and lithium (Li) are metals which have been detected in the environment and, at high concentrations, can induce toxic effects that disturb the growth, metabolism or reproduction of organisms along the entire trophic chain. The impacts of these metals have scarcely been investigated using marine bivalves, especially when acting as a mixture. The present study aimed to investigate the influence of temperature on the ecotoxicological effects caused by Pb and Li, acting alone and as a mixture, on the mussel species Mytilus galloprovincialis after 28 days of exposure. The impacts were evaluated under actual (17 °C) and projected (+4 °C) warming conditions, to understand the influence of temperature rise on the effects of the metals (both acting alone or as a mixture). The results obtained showed that the increased temperature did not influence the accumulation of metals. However, the biomarkers evaluated showed greater responses in mussels that are exposed to metals under increased temperature (21 °C). The IBR index showed that there is a comparable toxic effect of Li and Pb separately, while exposure to a mixture of both pollutants causes a significantly higher stress response. Overall, the results obtained revealed that temperature may cause extra stress on the mussels and exposure to the metal mixture caused the greatest impacts compared to each metal acting alone.

Can temperature rise change the impacts induced by e-waste on adults and sperm of Mytilus galloprovincialis?

Nowadays, it is of utmost importance to consider climate change factors, such as ocean warming, since the risk of negative impacts derived from increased surface water temperature is predicted to be high to the biodiversity. The need for renewable energy technologies, to reduce greenhouse gas emissions, has led to the increasing use of rare earth elements (REEs). Dysprosium (Dy) is widely used in magnets, motors, electrical vehicles, and nuclear reactors, being considered a critical REE to technology due to its economic importance and high supply risk. However, the increasing use of this element contributes to the enrichment of anthropogenic REEs in aquatic systems. Nevertheless, the information on the potential toxicity of Dy is limited. Moreover, the effects of pollutants can be amplified when combined with climate change factors. Thus, this study aimed to assess the effects of Dy (10 μg/L) in the species Mytilus galloprovincialis under actual (17 °C) and predicted warming conditions (21 °C). The Dy concentration in contaminated mussels was similar between temperatures, probably due to the detoxification capacity in individuals under these treatments. The combined stressors affected the redox balance, but higher impacts were caused by Dy and warming acting alone. In terms of cellular damage, although Dy acting alone was prejudicial to mussels, warming and both stressors acting together induced higher levels of LPO and PC. The histopathological effects of Dy in the digestive tubules were independent of the temperature tested. Regarding effects on sperm, only warming induced cellular damage, while both stressors, alone and together, impaired sperm movement. Overall, this study highlights that warming might influence the effects induced by Dy, but greater impacts were caused by the element. Eventually, the tested stressors may have consequences on mussels' reproduction capacity as well as their growth, abundance, and survival.

Responses of Mytilus galloprovincialis in a Multi-Stressor Scenario: Effects of an Invasive Seaweed Exudate and Microplastic Pollution under Ocean Warming

Microplastic pollution, global warming, and invasive species are known threats to marine biota, but the impact of their simultaneous exposure is still not well understood. This study investigated whether the toxic effects posed by the invasive red seaweed Asparagopsis armata exudate (2%) to the mussel Mytilus galloprovincialis are amplified by a 96 h exposure to increased temperature (24 °C) and polyethylene microplastics (PE-MPs, 1 mg/L). Biochemical (neurotoxicity, energy metabolism, oxidative stress, and damage) and physiological (byssal thread production) responses were evaluated. The number of produced byssus greatly decreased under concomitant exposure to all stressors. The antioxidant defences were depleted in the gills of mussels exposed to temperature rises and PE-MPs, regardless of exudate exposure, preventing oxidative damage. Moreover, the heat shock protein content tended to decrease in all treatments relative to the control. The increased total glutathione in the mussels' digestive gland exposed to 24 °C, exudate, and PE-MPs avoided oxidative damage. Neurotoxicity was observed in the same treatment. In contrast, the energy metabolism remained unaltered. In conclusion, depending on the endpoint, simultaneous exposure to A. armata exudate, PE-MPs, and warming does not necessarily mean an amplification of their single effects. Studies focusing on the impact of multiple stressors are imperative to better understand the underlying mechanisms of this chronic exposure.