Oxidative stress in the mussel Mytella guyanensis from polluted mangroves on Santa Catarina Island, Brazil

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.

Exploring the Effects of Acute Stress Exposure on Lumpfish Plasma and Liver Biomarkers

This study aimed to expand knowledge on lumpfish stress physiology by investigating the effects of acute stress on primary (i.e., cortisol) and secondary (e.g., metabolites) stress responses, as well as oxidative stress biomarkers, from stress exposure to a recovery phase. The results showed that the lumpfish physiological response to 1 min air exposure is mild, in line with recent studies, and comparable to that described for white sturgeons. Cortisol seems to be the most reliable acute stress biomarker in lumpfish, with a significant increase in plasma 30 min after stress exposure, returning to resting levels 2 h after exposure. In contrast, glucose and lactate were not significantly altered by short-term air exposure. Effects on hepatic energy mobilisation were also detected following the acute stress. This study showed that acute 1 min air exposure seems tolerable, allowing a swift recovery. However, more studies on the impacts of air exposure and repeated acute stressors on lumpfish stress and immune responses are required to develop industry standards for lumpfish health and welfare monitoring.

Role of Citrullus colocynthis and Psidium guajava Mediated Green Synthesized Silver Nanoparticles in Disease Resistance against Aeromonas hydrophila Challenge in Labeo rohita

Green synthesis of metallic nanoparticles is an auspicious method of preparing nanoparticles using plant extracts that have lesser toxicity to animal cells and the host. In the present work, we analyzed the antibacterial activity of Citrullus colocynthis and Psidium guajava-mediated silver nanoparticles (Cc-AgNPs and Pg-AgNPs, respectively) against Aeromonas hydrophila (A. hydrophila) in an in vivo assay employing Labeo rohita (L. rohita). L. rohita were divided into six groups for both Cc-AgNPs and Pg-AgNPs treatments separately: Control, A. hydrophila infected, A. hydrophila + Ampicillin, A. hydrophila + Cc/Pg-AgNPs (25 µg/L), A. hydrophila + Cc/Pg-AgNPs (50 µg/L), and A. hydrophila + Cc/Pg-AgNPs (75 µg/L). Changes in different bio-indicators such as hematological, histological, oxidative stress, and cytokine analysis were observed. Interestingly, the infected fish treated with both types of AgNPs (Cc-AgNPs and Pg-AgNPs) exhibited a higher survival rate than the untreated infected fish and demonstrated signs of recovery from the infection, providing a compelling indication of the positive impact of phytosynthesized AgNPs. Disruptions in hematological and histological parameters were found in the infected fish. Both Cc-AgNPs and Pg-AgNPs showed recovery on the hematological and histological parameters. Analysis of oxidative stress and cytokine markers also revealed provoking evidence of the positive impact of Cc-AgNPs and Pg-AgNPs treatment against disease progression in the infected fish. The major finding of the study was that the higher concentrations of the nanoparticles (50 µg/L in the case of Cc-AgNPs and 75 µg/L in the case of Pg-AgNPs) were more effective in fighting against disease. In conclusion, our work presents novel insights for the use of green-synthesized AgNPs as economic and innocuous antibacterial candidates in aquaculture.

Genotoxicity of surface waters in Brazil

Brazil has abundant surface water resources, huge aquatic biodiversity and is home to 213 million people. Genotoxicity assays are sensitive tools to detect the effects of contaminants in surface waters and wastewaters, as well as to determine potential risks of contaminated waters to aquatic organisms and human health. This work aimed to survey the articles published in 2000-2021 that evaluated the genotoxicity of surface waters within Brazilian territory to unveil the profile and trends of this topic over time. In our searches, we considered articles focused on assessing aquatic biota, articles that conducted experiments with caged organisms or standardized tests in the aquatic sites, as well as articles that transported water or sediment samples from aquatic sites to the laboratory, where exposures were performed with organisms or standardized tests. We retrieved geographical information on the aquatic sites evaluated, the genotoxicity assays used, the percentage of genotoxicity detected, and, when possible, the causative agent of aquatic pollution. A total of 248 articles were identified. There was a trend of increase in the number of publications and annual diversity of hydrographic regions evaluated over time. Most articles focused on rivers from large metropolises. A very low number of articles were conducted on coastal and marine ecosystems. Water genotoxicity was detected in most articles, regardless of methodological approach, even in little-studied hydrographic regions. The micronucleus test and the alkaline comet assay were widely applied with blood samples, mainly derived from fish. Allium and Salmonella tests were the most frequently used standard protocols. Despite most articles did not confirm polluting sources and genotoxic agents, the detection of genotoxicity provides useful information for the management of water pollution. We discuss key points to be assessed to reach a more complete picture of the genotoxicity of surface waters in Brazil.

Exploring the mechanisms underlying the toxicity of boric acid against the land snail, Theba pisana

BACKGROUND

The land snail, Theba pisana, is one of the most important threats facing agriculture around the globe. Boric acid (BOA) is currently used as a safe alternative molluscicide to control land snails in sustainable agriculture, but the mechanisms of toxicity have not yet been investigated. The present study characterizes the lethal and sub-lethal (0.5 and 1 mg g^-1 ) toxic effects of BOA-contaminated food for 14 days by examining physiological, biochemical and histopathological indicators in T. pisana to understand the mechanisms underlying its toxic action.

RESULTS

BOA was found to be lethal against T. pisana with LC₅₀ values of 24.7 and 8.05 mg g^-1 after 3 and 7 days of exposure, respectively. BOA sublethal concentrations led to a significant reduction in food consumption and growth of snails after 14 days of exposure. BOA also caused a significant increase in testosterone levels, whereas an opposite effect was observed in estradiol levels. An increase in progesterone levels in snails in the 0.5 mg g^-1 BOA group and a decrease in the 1 mg g^-1 BOA group were observed after all exposure times. Moreover, the lipid peroxidation level and catalase activity were elevated, whereas acetylcholinesterase activity was inhibited in the treated snails. Alteration in glutathione-S-transferase activity was noticed after exposure to both sublethal concentrations. In addition, BOA induced histopathological alterations in the digestive gland of T. pisana.

CONCLUSION

Our findings provide novel insights into how physiological, biochemical and histopathological alterations can be used to explore the mechanisms underlying BOA toxicity against snails. © 2022 Society of Chemical Industry.

Ecotoxicological Effects of Four Commonly Used Organic Solvents on the Scleractinian Coral Montipora digitata

Organic solvents are often used in aquatic toxicity tests to facilitate the testing of hydrophobic or poorly water-soluble substances such as ultraviolet (UV) filters, pesticides, or polycyclic aromatic hydrocarbons (PAHs). Knowledge of intrinsic effects (i.e., measured as standardized and non-standardized endpoints) of such carrier solvents in non-standardized organisms (i.e., corals), is critical to regulatory processes. Therefore, we exposed the reef-building coral Montipora digitata to the most commonly used carrier solvents ethanol, methanol, dimethyl sulfoxide, and dimethylformamide in the range of 10-100 µL L^-1 for 16 days. The effects on mortality, photobiological, morphological, and oxidative stress markers were evaluated. In our study, all solvents resulted in significant morphological and/or oxidative stress responses, but not in mortality. Moreover, ethanol led to a rapid increase in turbidity, thus questioning its suitability as a carrier solvent in aquatic studies in general. Based on our observations, we could rank the solvent effects as follows: dimethylformamide < dimethyl sulfoxide ≈ methanol ≤ ethanol, with dimethylformamide showing the least and ethanol the most pronounced effects. We conclude that the use of solvents in toxicity studies with corals, particularly by examining non-standardized (e.g., morphological, physiological) endpoints, should be taken with caution and requires further elaboration.

Health-Promoting Additives Supplemented in Inert Microdiets for Whiteleg Shrimp (Penaeus vannamei) Post-Larvae: Effects on Growth, Survival, and Health Status

Dietary additives have the potential to stimulate the whiteleg shrimp immune system, but information is scarce on their use in diets for larval/post-larval stages. The potential beneficial effects of vitamins C and E, β-glucans, taurine, and methionine were evaluated. Four experimental microdiets were tested: a positive control diet (PC); the PC with decreased levels of vitamin C and E as negative control (NC); the PC with increased taurine and methionine levels (T + M); and the PC supplemented with β-glucans (BG). No changes in growth performance and survival were observed. However, post-larvae shrimp fed the NC had lower relative expressions of pen-3 than those fed the PC, suggesting that lower levels of vitamins C and E may impact the shrimp immune status. Lipid peroxidation levels dropped significantly in the BG compared to the PC, indicating that β-glucans improved the post-larvae antioxidant mechanisms. Furthermore, when compared with the NC diet, PL fed with BG showed significant increases in tGSH levels and in the relative expression of crus and pen-3, suggesting a synergistic effect between vitamins C and E and β-glucans. Amongst the additives tested, β-glucans seems to be the most promising even when compared to a high-quality control diet.

Molecular and biochemical responses to tributyltin (TBT) exposure in the American oyster: Triggers of stress-induced oxidative DNA damage and prooxidant-antioxidant imbalance in tissues by TBT

Environmental pollution increases due to anthropogenic activities. Toxic chemicals in the environment affect the health of aquatic organisms. Tributyltin (TBT) is a toxic chemical widely used as an antifouling paint on boats, hulls, and ships. The toxic effect of TBT is well documented in aquatic organisms; however, little is known about the effects of TBT on DNA lesions in shellfish. The American oyster (Crassostrea virginica, an edible and commercially important species) is an ideal marine mollusk to examine the effects of TBT exposure on DNA lesions and oxidative/nitrative stress. In this study, we investigated the effects of TBT on 8'-hydroxy-2'-deoxyguanosine (8-OHdG, a biomarker of pro-mutagenic DNA lesion), double-stranded DNA (dsDNA), dinitrophenyl protein (DNP, a biomarker on reactive oxygen species, ROS), 3-nitrotyrosine protein (NTP, a biomarker of reactive nitrogen species, RNS), catalase (CAT, an antioxidant), and acetylcholinesterase (AChE, a cholinergic enzyme) expressions in the gills and digestive glands of oysters. We also analyzed extrapallial (EF) fluid conditions. Immunohistochemical and qRT-PCR results showed that TBT exposure significantly increased 8-OHdG, dsDNA, DNP, NTP, and CAT mRNA and/or protein expressions in the gills and digestive glands. However, AChE mRNA and protein expressions, and EP fluid pH and protein concentrations were decreased in TBT-exposed oysters. Taken together, these results suggest that antifouling biocide-induced production of ROS/RNS results in DNA damage, which may lead to decreased cellular functions in oysters. To the best of our knowledge, the present study provides the first molecular/biochemical evidence that TBT exposure results in oxidative/nitrative stress and DNA lesions in oysters.

Effects of elevated temperature on 8-OHdG expression in the American oyster (Crassostrea virginica): Induction of oxidative stress biomarkers, cellular apoptosis, DNA damage and γH2AX signaling pathways

Global temperature is increasing due to anthropogenic activities and the effects of elevated temperature on DNA lesions are not well documented in marine organisms. The American oyster (Crassostrea virginica, an edible and commercially important marine mollusk) is an ideal shellfish species to study oxidative DNA lesions during heat stress. In this study, we examined the effects of elevated temperatures (24, 28, and 32 °C for one-week exposure) on heat shock protein-70 (HSP70, a biomarker of heat stress), 8‑hydroxy-2'-deoxyguanosine (8-OHdG, a biomarker of pro-mutagenic DNA lesion), double-stranded DNA (dsDNA), γ-histone family member X (γH2AX, a molecular biomarker of DNA damage), caspase-3 (CAS-3, a key enzyme of apoptotic pathway) and Bcl-2-associated X (BAX, an apoptosis regulator) protein and/or mRNA expressions in the gills of American oysters. Immunohistochemical and qRT-PCR results showed that HSP70, 8-OHdG, dsDNA, and γH2AX expressions in gills were significantly increased at high temperatures (28 and 32 °C) compared with control (24°C). In situ TUNEL analysis showed that the apoptotic cells in gill tissues were increased in heat-exposed oysters. Interestingly, the enhanced apoptotic cells were associated with increased CAS-3 and BAX mRNA and/or protein expressions, along with 8-OHdG levels in gills after heat exposure. Moreover, the extrapallial (EP) fluid (i.e., extracellular body fluid) protein concentrations were lower; however, the EP glucose levels were higher in heat-exposed oysters. Taken together, these results suggest that heat shock-driven oxidative stress alters extracellular body fluid conditions and induces cellular apoptosis and DNA damage, which may lead to increased 8-OHdG levels in cells/tissues in oysters.

Dietary Strategies to Modulate the Health Condition and Immune Responses in Gilthead Seabream (Sparus aurata) Juveniles Following Intestinal Inflammation

Simple Summary

Feed additives are known to have biological proprieties that can improve fish health. This work assessed the effect of two feed additives (Phaeodactylum tricornutum extracts rich in β-glucans and curcumin) on the gilthead seabream health condition, and its modulatory effects following dextran sodium sulphate (DSS) administration as a chemical inducer of intestinal inflammation. While minor immune-enhancing changes were observed among fish fed dietary treatments at the end of the feeding trial, after the inflammatory stimulus, the feed additives were able to alleviate, to some extent, the DSS-induced effects at both the intestinal and systemic levels.

Abstract

Several feed additives have proved to be beneficial in eliciting fish health. Β-glucans and curcumin are compounds with immunomodulatory capacities known to increase growth performance, stimulate immunity, improve general health, and enhance disease resistance in fish. The present study aimed to evaluate the effects of dietary Phaeodactylum tricornutum extracts rich in β-glucans and curcumin on gilthead seabream health status prior to and following an intestinal inflammatory stimulus. Three experimental diets were formulated: a practical commercial-type diet (CTRL), a CTRL diet supplemented with 1% microalgae-derived β-glucans extract (BG), and a CTRL diet supplemented with 0.2% of curcumin (CUR). After 30 days of the feeding trial, fish were sampled and subjected to an oral administration of 1% dextran sodium sulphate (DSS) to induce intestinal inflammation. Four groups were considered: a group of fish continued to be fed on the CTRL diet while the remaining groups were exposed to DSS, including CTRL-D (CTRL + DSS), BG-D (BG + DSS), and CUR-D (CUR + DSS), for 6 days. Growth, plasma and gut humoral immunity, liver and gut oxidative stress biomarkers, and intestinal gene expression were evaluated. No significant differences were found in growth after 30 days of feeding; however, seabream fed BG had decreased anti-protease activity and nitric oxide concentration in plasma while those fed CUR had increased mRNA levels of the tnfα, csf1r, and hep genes compared to those fed CTRL. After the inflammatory stimulus, hematocrit was enhanced in fish fed BG-D and CUR-D while red blood cell counts increased in those fed CTRL-D. Superoxide dismutase activity decreased in the intestine of all DSS groups while lipid peroxidation increased in the gut of fish fed CTRL-D and BG-D compared to CTRL. Moreover, the mRNA expression levels of csfr1 and sod decreased in fish fed CTRL-D and BG-D compared to CTRL, respectively. Despite the mild intestinal inflammatory condition induced by DSS, CUR was able to partially ameliorate its effects, improving the hematological profile and assisting against the oxidative stress.

Are tolerance processes limiting the responses of Hediste diversicolor to cadmium exposure? A multimarker approach

Cadmium (Cd) is considered a priority hazardous substance under the European Community Directive 2013/39 due to its ecotoxicity. The ragworm Hediste diversicolor (O.F. Müller, 1776), a common species in estuaries and coastal lagoons, plays an important ecological role in these ecosystems and is a suitable bioindicator of environmental chemical contamination. In this study, H. diversicolor was chosen as an ecotoxicological model with the aim of evaluating the responses to Cd contamination, considering a multi-biomarker approach (mortality, biometry, behaviour, Cd bioaccumulation, oxidative stress and damage, and energy metabolism). Also, the hypothesis of different tolerances resulting in different responses was evaluated, by collecting worms from three systems distinctly impacted by metal contamination (Mondego estuary, Óbidos Lagoon and Sado estuary - Portugal). Animals were exposed under laboratory conditions to cadmium (10, 50 and 100 µg/L), for 10 days. Significant differences were observed in responses amongst worms originating from the different sites. Organisms from the less impacted systems revealed greater effects on mortality, biomass decrease and burrowing behaviour, as well as higher bioaccumulation potential, after exposure to Cd. Biochemical and behaviour impairments were observed as a consequence of Cd exposure, although not in a concentration-dependant manner. The results obtained in this study reinforce the importance of integrating endpoint responses, at the individual and sub-individual levels, to assess potential changes induced by pollutants in the physiological status and fitness of H. diversicolor and help to predict what their ecological consequences might be.

Boat noise impacts Lusitanian toadfish breeding males and reproductive outcome

Anthropogenic noise is a growing threat to marine organisms, including fish. Yet very few studies have addressed the impact of anthropogenic noise on fish reproduction, especially in situ. In this study, we investigated the impacts of boat noise exposure in the reproductive success of wild Lusitanian toadfish (Halobatrachus didactylus), a species that relies on advertisement calls for mate attraction, using behavioural, physiological and reproductive endpoints. Two sets of artificial nests were deployed in the Tagus estuary and exposed to either ambient sound or boat noise during their breeding season. Toadfish males spontaneously used these nests to breed. We inspected nests for occupation and the presence of eggs in six spring low tides (in two years) and assessed male vocal activity and stress responses. Boat noise did not affect nest occupation by males but impacted reproductive success by decreasing the likelihood of receiving eggs, decreasing the number of live eggs and increasing the number of dead eggs, compared to control males. Treatment males also showed depressed vocal activity and slightly higher cortisol levels. The assessment of oxidative stress and energy metabolism-related biomarkers revealed no oxidative damage in noise exposed males despite having lower antioxidant responses and pointed towards a decrease in the activity levels of energy metabolism-related biomarkers. These results suggest that males exposed to boat noise depressed their metabolism and their activity (such as parental care and mate attraction) to cope with an acoustic stressor, consistent with a freezing defensive response/behaviour. Together, our study demonstrates that boat noise has severe impacts on reproductive fitness in Lusitanian toadfish. We argue that, at least fishes that cannot easily avoid noise sources due to their dependence on specific spawning sites, may incur in significant direct fitness costs due to chronic noise exposure.

Accumulation of chemical elements and occurrence of microplastics in small pelagic fish from a neritic environment

The assessment of contaminant exposure in marine organisms often focuses on the most toxic chemical elements from upper trophic level species. Information on mid-trophic level species and particularly on potentially less harmful elements is lacking. Additionally, microplastics have been considered emergent contaminants in aquatic environments which have not been extensively studied in species from mid-trophic levels in food chains. This study aims to contribute to an overall assessment of environmental impacts of such chemicals in a community of small pelagic fish in the North Atlantic. The concentrations of 16 chemical elements, rarely simultaneously quantified (including minerals, trace elements and heavy metals), and the presence of microplastics were analysed in sardines (Sardina pilchardus) and mackerels (Scomber spp. and Trachurus trachurus) sampled along the Portuguese coast. Biochemical stress assessments and stable isotope analyses were also performed. The chemical element concentrations in S. pilchardus, T. trachurus, and Scomber spp. were relatively low and lower than the levels reported for the same species in the North Atlantic and adjacent areas. No clear relationships were found between chemical elements and oxidative damage in fish. However, the concentration of several chemical elements showed differences among species, being related with the species' habitat use, trophic niches, and specific feeding strategies. The presence of plastic pieces in the stomachs of 29% of the sampled fishes is particularly concerning, as these small pelagic fish from mid-trophic levels compose a significant part of the diet of humans and other top predators. This study highlights the importance of multidisciplinary approaches focusing on the individual, including position data, stable isotopes, and oxidative stress biomarkers as complementary tools in contamination assessment of the marine mid-trophic levels in food chains.

Exposure to the Insecticide Sulfoxaflor Affects Behaviour and Biomarkers Responses of Carcinus maenas (Crustacea: Decapoda)

Simple Summary

Sulfoxaflor is an insecticide for which there are few studies regarding its toxicity to non-target organisms. The present study aimed to investigate the acute and sub-lethal effects of sulfoxaflor on Carcinus maenas by addressing survival, behaviour, and biomarkers. Sulfoxaflor affected feed intake and motricity of C. maenas. From the integrated analysis of endpoints, with the increase in concentrations of sulfoxaflor, after seven days, one can notice a lower detoxification capacity, higher lipid peroxidation, and higher motricity effects and lower feed intake. This study aims to contribute to the understanding of the negative impacts of sulfoxaflor on green crabs and increase knowledge of this pesticide toxicity to non-target coastal invertebrates.

Abstract

Sulfoxaflor is an insecticide belonging to the recent sulfoximine class, acting as a nicotinic acetylcholine receptor (nAChRs) agonist. There are few studies regarding sulfoxaflor’s toxicity to non-target organisms. The present study aimed to investigate the acute and sub-lethal effects of sulfoxaflor on Carcinus maenas by addressing survival, behaviour (feed intake and motricity), and neuromuscular, detoxification and oxidative stress, and energy metabolism biomarkers. Adult male green crabs were exposed to sulfoxaflor for 96 h and an LC₅₀ of 2.88 mg L⁻¹ was estimated. All biomarker endpoints were sampled after three (T3) and seven (T7) days of exposure and behavioural endpoints were addressed at T3 and day six (T6). Sulfoxaflor affected the feed intake and motricity of C. maenas at T6. From the integrated analysis of endpoints, with the increase in concentrations of sulfoxaflor, after seven days, one can notice a lower detoxification capacity (lower GST), higher LPO levels and effects on behaviour (higher motricity effects and lower feed intake). This integrated approach proved to be valuable in understanding the negative impacts of sulfoxaflor on green crabs, while contributing to the knowledge of this pesticide toxicity to non-target coastal invertebrates.

Year-round element quantification of a wide-ranging seabird and their relationships with oxidative stress, trophic ecology, and foraging patterns

Multidisciplinary approaches are essential to diligently assess environmental health status of ecosystems. In this study, year-round chemical elements' exposure and impacts were assessed on the wide-ranging Cory's shearwater Calonectris borealis breeding in Berlenga Island, offshore Portugal, North Atlantic Ocean. The aim was to identify potential contamination and oxidative stress sources associated with trophic ecology, habitat and spatial use, and foraging patterns. A set of 20 chemical elements were quantified, along with oxidative stress biomarkers, stable isotope analyses, and GPS tracking data. Birds presented higher accumulation to some non-essential elements along the year (i.e. arsenic, As; cadmium, Cd; mercury, Hg; lead, Pb; and strontium, Sr), in which concentrations were similar or surpassed other procellariform seabird populations all over the world. No significant differences were found for any of the elements between different periods within the breeding season, with exception of Hg. However, a Principal Component Analysis taking into consideration a group of elements showed differences between pre-laying and chick-rearing periods, with overall higher concentrations in the former. Individuals spending more time engaging in an intensive search for food, and in more coastal environments, presented overall higher element concentrations, and particularly Hg. Contrary to expectations, no relationships were found between chemical elements and oxidative stress. On the other hand, spatial use and foraging patterns of Cory's shearwaters influenced their oxidative stress responses. Our results highlight the need for multidisciplinary approaches to deepen understanding of the large-scale vulnerability of bioindicators such as seabirds and, by extension, the overall environmental health of ecosystems in which they rely.

Antioxidant activity of Far Eastern bivalves in their natural habitat

The activities of the key antioxidant enzymes superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GP) and glutathione reductase (GR) as well as levels of reduced glutathione (GSH) and integral antioxidant activity (IAA), were studied in the digestive glands and gills of 14 bivalve species. Species and tissue differences of the antioxidant (AO) systems of the investigated mollusks were discussed in connection with their physiological and biochemical peculiarities. This article describes the role of the AO system of mollusks in adaptation to natural habitat conditions and shows the relationship of AO activity with the maximum habitat depth (MHD) and maximum lifespan (MLS) of these species.

Study on the impacts of chemical and green synthesized (Leucas aspera and oxy-cyclodextrin complex) dietary zinc oxide nanoparticles in Nile tilapia (Oreochromis niloticus)

The present study was designed to evaluate the health effects of dietary nanozinc prepared by two methods: conventional chemical method and green method. The parameters evaluated were the extent of bioaccumulation, antioxidant status, histological, immunological changes and DNA damage in Nile tilapia fed nanozinc feed. Zinc oxide nanoparticles were first prepared by green and chemical methods. Before feed preparation, the in vitro antioxidant activity and antibacterial activity of both types of nanoparticle solutions were tested and the results revealed enhanced activities in green synthesized ZnO NP solution. After the acclimatization period, 420 Nile tilapias were distributed randomly into 21 glass tanks with 20 fish per tank in triplicates. Fish were fed control diet without any ZnO NP and (i) GT1-green synthesized ZnO NP diet at 100 mg/kg, (ii) CT1-chemically synthesized ZnO NP diet at 100 mg/kg, (iii) GT2-green synthesized ZnO NP diet at 200 mg/kg, (iv) CT2-chemically synthesized ZnO NP diet at 200 mg/kg, (v) GT3-green synthesized ZnO NP diet at 400 mg/kg and (vi) CT3-chemically synthesized ZnO NP diet at 400 mg/kg for 60 days. After 60 days, gill and liver samples were collected for analysing oxidative stress, histopathological alterations and bioaccumulation of zinc, whereas serum samples were collected for evaluating immune response. The results revealed that the GT3 diet significantly (P < 0.05) enhanced the level of antioxidant enzymes (CAT, SOD, GPx, GR and GSH) than dietary nanozinc prepared by the chemical method. Similarly, the innate immunological parameters were significantly (P < 0.05) augmented in fish fed GT3 diet. Comparative histological study of liver and gill tissues revealed normal architecture in the tissues of fish fed green synthesized NP-enriched feed, whereas the tissues of fish fed chemically synthesized NP feed exhibited histological alterations. Bioaccumulation of zinc was more in the liver followed by the muscle and least in the gills and DNA damage was more evident in fish fed chemically synthesized ZnO NP-enriched feed. In conclusion, the results suggest that the inclusion of 400 mg/kg GT3 diet in fish diet enhanced the level of antioxidant enzymes, boosted immune response and did not cause histological damage to organs, and therefore, GT3 nanofeed can be recommended for fish health improvement.

Asparagopsis armata Exudate Cocktail: The Quest for the Mechanisms of Toxic Action of an Invasive Seaweed on Marine Invertebrates

Simple Summary

The invasive red seaweed Asparagopsis armata exhibits a strong invasive behavior, producing harmful secondary metabolites that negatively affect the surrounding community. This study addressed the antioxidant defenses, oxidative damage, and a neuronal parameter, as well as the fatty acid composition responses to sublethal concentrations of A. armata released compounds on the marine snail Gibbula umbilicalis and the shrimp Palaemon serratus. Results revealed that the test species had different metabolic responses to the A. armata exudate concentrations tested. Impacts in G. umbilicalis does not seem to arise from oxidative stress or neurotoxicity, while for P. elegans, an inhibition of AChE and the decrease of antioxidant capacity and increase of LPO suggest neurotoxicity and oxidative stress as contributing to the observed toxicity. Additionally, there were different fatty acid profile changes between species, but omega-3 PUFAs ARA and DPA increased in both invertebrates, indicating a common regulation mechanism of inflammation and immunity responses.

Abstract

The seaweed Asparagopsis armata exhibits a strong invasive behavior, producing halogenated compounds with effective biological effects. This study addresses the biochemical responses to sublethal concentrations of A. armata exudate on the marine snail Gibbula umbilicalis whole body and the shrimp Palaemon elegans eyes and hepatopancreas. Antioxidant defenses superoxide dismutase (SOD) and glutathione-S-transferase (GST), oxidative damage endpoints lipid peroxidation (LPO) and DNA damage, the neuronal parameter acetylcholinesterase (AChE), and the fatty acid profile were evaluated. Results revealed different metabolic responses in both species. Despite previous studies indicating that the exudate affected G. umbilicalis’ survival and behavior, this does not seem to result from oxidative stress or neurotoxicity. For P. elegans, the inhibition of AChE and the decrease of antioxidant capacity is concomitant with the increase of LPO, suggesting neurotoxicity and oxidative stress as contributor mechanisms of toxicity for this species. Fatty acid profile changes were more pronounced for P. elegans with a general increase in polyunsaturated fatty acids (PUFAs) with the exudate exposure, which commonly means a defense mechanism protecting from membrane disruption. Nonetheless, the omega-3 PUFAs arachidonic acid (ARA) and docosapentaenoic acid (DPA) increased in both invertebrates, indicating a common regulation mechanism of inflammation and immunity responses.

Oxidative stress and histopathological effect of zinc oxide nanoparticles on the garden snail Helix aspersa

Nanoparticles have many applications in medicine and biology but they have adverse toxic effects on the biosystem. Therefore, this study aimed to evaluate the toxicity of zinc nanoparticles (ZnO NPs) on the garden snail Helix aspersa. ZnO NPs were used at different concentrations for 7 days. The biomarkers of the oxidative stress and histopathology of the hepatopancreas were estimated. ZnO NPs significantly (p ≤ 0.05) increased catalase (CAT) with time- and concentration-dependent manner. Glutathione S-transferase (GST) activity was significantly (p ≤ 0.05) increased at the concentrations 35 μg/ml and 45 μg/ml after 1 and 3 days of exposure. The present results recorded also a significant elevation in malondialdehyde (MDA) level (time-/concentration-dependent), it was 3.2 ± 0.1, at concentration 45 μg/ml. ZnO NPs induced significant decrease in glutathione (GSH) content (8.7 ± 0.2 at 45 μg/ml) (p ≤ 0.05) at 7 days. Moreover, ZnO NPs induced histopathological alterations in the digestive gland of Helix aspersa. From these results, such biochemical and histopathological alterations in Helix aspersa is a suitable bioindicator of nanoecotoxicological effects.

Antioxidant defenses of flame scallop Ctenoides scaber (Born, 1778) exposed to the water-soluble fraction of used vehicle crankcase oils

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This paper evaluated effects of a WSF-UVCO on the antioxidant responses of the scallop Lima scabra.

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The antioxidant defenses in L. scabra seem be highly sensitive to low doses of to WSF-UVCO.

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Digestive gland and gill show stronger antioxidant responses in L. scabra exposed to WSF-UVCO.

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L. scabra could be good sensor for screening pollutant impacts along the Caribbean coastline.

Used vehicle crankcase oils are a source of contamination in Caribbean marine environments and may alter the oxidative balance of organism that inhabiting coastal ecosystems. This paper aims to evaluate effects of a water-soluble fraction of used vehicle crankcase oils (WSF-UVCO) on the antioxidant responses of the flame scallop Ctenoides scaber. The organisms were exposed to ascending sublethal concentrations 0, 0.001, 0.01 and 0.1 % of WSF-UVCO in a static system of aquaria during one week. Subsequently activities of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), glutathione reductase (GR) and glutathione-S-transferase (GST) as well as concentrations of reduced glutathione (GSH) and thiobarbituric acid reactive substances (TBARS) were determined in the digestive gland, adductor muscle and gills. SOD, CAT, GST and TBARS increased in digestive gland of organisms exposed to WSF-UVCO at medium and highest concentrations, with a concomitant decrease in GPX and GR activities. In adductor muscle CAT decreased, but GR rose with exposure to 0.01 and 0.1 % WSF-UVCO; in gills, GST rose through all WSF-UVCO concentrations, and SOD, CAT and GR increased only at 0.1 %. The fluctuations in antioxidant enzymes and GST activities point out possible adjustments to control ROS production and detoxification of xenobiotics. These biochemical responses may guarantee the oxidative balance in flame scallop during short term exposure to low concentrations of WSF-UVCO. C. scaber appears suitable as an experimental organism for evaluating biological risks of sublethal exposure to hazardous xenobiotics in tropical marine environments.

Acclimation history modulates effect size of calcareous algae (Halimeda opuntia) to herbicide exposure under future climate scenarios

Tropical marine habitat-builders such as calcifying green algae can be susceptible to climate change (warming and acidification). This study evaluated the cumulative effects of ocean warming (OW), ocean acidification (OA) and the herbicide diuron on the calcifying green algae Halimeda opuntia. We also assessed the influence of acclimation history to experimental climate change conditions on physiological responses. H. opuntia were exposed for 15 days to orthogonal combinations of three climate scenarios [ambient (28 °C, pCO₂ = 378 ppm), 2050 (29 °C, pCO₂ = 567 ppm) and 2100 (30 °C, pCO₂ = 721 ppm)] and to six diuron concentrations (up to 29 μg L^-1). Half of the H. opuntia had been acclimated for eight months to the climate scenarios in a mesocosm approach, while the remaining half were not pre-acclimated, as is current practice in most experiments. Climate effects on quantum yield (ΔF/Fm'), photosynthesis and calcification in future climate scenarios were significantly stronger (by -24, -46 and +26%, respectively) in non-acclimated algae, suggesting experimental bias may exaggerate effects in organisms not appropriately acclimated to future-climate conditions. Thus, full analysis was done on acclimated plants only. Interactive effects of future climate scenarios and diuron were observed for ΔF/Fm', while the detrimental effects of climate and diuron on net photosynthesis and total antioxidant capacity (TAC) were additive. Calcification-related enzymes were negatively affected only by diuron, with inhibition of Ca-ATPase and upregulation of carbonic anhydrase. The combined and consistent physiological and biochemical evidence of negative impacts (across six indicators) of both herbicide and future-climate conditions on the health of H. opuntia highlights the need to address both climate change and water quality. Guideline values for contaminants may also need to be lowered considering 'climate adjusted thresholds'. Importantly, this study highlights the value of applying substantial future climate acclimation periods in experimental studies to avoid exaggerated organism responses to OW and OA.

Assessment of environmental health based on a complementary approach using metal quantification, oxidative stress and trophic ecology of two gull species (Larus michahellis & Larus audouinii) breeding in sympatry

Metal pollution is currently a major issue in marine ecosystems, as organisms, and particularly seabirds, are exposed and accumulating increased levels from several anthropogenic sources. A set of 13 metals were quantified in two gull species breeding in sympatry, and in two distinct colonies separated by ca. 400 km. Oxidative stress was measured, and stable isotope analyses were used to link metal contamination and oxidative stress with the trophic ecology of each species/population. There was a clear segregation of metal contamination between the two species and to a much lesser extent between colonies. Overall, Audouin's gull was the most contaminated species for most metals, once this species relies mainly on fish and other marine resources. The Yellow-legged gull feeds regularly on terrestrial food sources besides fish, which may dilute contamination levels. Oxidative stress responses were related with birds' trophic ecology and foraging habitat, but apparently not with metal contamination.

An integrated omics approach to investigate summer mortality of New Zealand Greenshell™ mussels

BACKGROUND

Green-lipped mussels, commercially known as Greenshell™ mussels (Perna canaliculus Gmelin 1791), contribute > $300 million to New Zealand's aquaculture exports. However, mortalities during summer months and potential pathogenic outbreaks threaten the industry. Thermal stress mechanisms and immunological responses to pathogen infections need to be understood to develop health assessment strategies and early warning systems.

METHODS

P. canaliculus were collected during a mortality event at a commercial aquaculture farm in Firth of Thames, New Zealand. Gill tissues from six healthy and six unhealthy mussels were excised and processed for metabolomic (GC-MS) and label-free proteomic (LC-MS) profiling. Univariate analyses were conducted separately on each data layer, with data being integrated via sparse multiple discriminative canonical correlation analysis. Pathway enrichment analysis was used to probe coordinated changes in functionally related metabolite sets.

RESULTS

Findings revealed disruptions of the tricarboxylic acid (TCA) cycle and fatty acid metabolism in unhealthy mussels. Metabolomics analyses also indicated oxidative stress in unhealthy mussels. Proteomics analyses identified under-expression of proteins associated with cytoskeleton structure and regulation of cilia/flagellum in gill tissues of unhealthy mussels. Integrated omics revealed a positive correlation between Annexin A4 and CCDC 150 and saturated fatty acids, as well as a negative correlation between 2-aminoadipic acid and multiple cytoskeletal proteins.

CONCLUSIONS

Our study demonstrates the ability of using integrative omics to reveal metabolic perturbations and protein structural changes in the gill tissues of stressed P. canaliculus and provides new insight into metabolite and protein interactions associated with incidences of summer mortality in this species.

Microplastics in wild fish from North East Atlantic Ocean and its potential for causing neurotoxic effects, lipid oxidative damage, and human health risks associated with ingestion exposure

Microplastics (MP) pollution has received increased attention over the last few years. However, while the number of studies documentating the ingestion of microplastics by fish has increased, fewer studies have addressed the toxicological effects derived from the ingestion of these small items in wild conditions. Here, MP contamination and effect biomarkers were investigated in three commercially important fish species from the North East Atlantic Ocean. From the 150 analysed fish (50 per species), 49 % had MP. In fish from the 3 species, MP in the gastrointestinal tract, gills and dorsal muscle were found. Fish with MP had significantly (p ≤ 0.05) higher lipid peroxidation levels in the brain, gills and dorsal muscle, and increased brain acetylcholinesterase activity than fish where no MP were found. These results suggest lipid oxidative damage in gills and muscle, and neurotoxicity through lipid oxidative damage and acetylcholinesterase induction in relation to MP and/or MP-associated chemicals exposure. From the 150 fish analysed, 32 % had MP in dorsal muscle, with a total mean (± SD) of 0.054 ± 0.099 MP items/g. Based on this mean and on EFSA recommendation for fish consumption by adults or the general population, human consumers of Dicentrachus labrax, Trachurus trachurus, Scomber colias may intake 842 MP items/year from fish consumption only. Based on the mean of MP in fish muscle and data (EUMOFA, NOAA) of fish consumption per capita in selected European and American countries, the estimated intake of microplastics through fish consumption ranged from 518 to 3078 MP items/year/capita. Considering that fish consumption is only one of the routes of human exposure to microplastics, this study and others in the literature emphasize the need for more research, risk assessment and adoption of measures to minimize human exposure to these particles. Thus, MP pollution and its effects should be further investigated and addressed according to the WHO 'One Health' approach.

In vivo evaluation of oxidative stress and biochemical alteration as biomarkers in glass clover snail, Monacha cartusiana exposed to zinc oxide nanoparticles

Oxidative stress is considered a main commonly reported mechanism of nanoparticles toxicity, so this study aimed to evaluate oxidative stress and biochemical alterations in the haemolymph and digestive gland of snail, Monacha cartusiana exposed to sublethal concentrations of zinc oxide nanoparticles (ZnONPs) for 14 days (d). The results indicated that, ZnONPs induced significant increases in lipid peroxidation (LPO) and lactate dehydrogenase (LDH) in treated animals and did not return to normal levels after recover period. A significant decline of glutathione peroxidase (GPx), glutathione-S-transferase (GST) activities, and glutathione (GSH) content in the haemolymph and digestive gland of snails was observed when compared with control. A significant increase was observed in catalase (CAT), alanine aminotransferase (ALT), and aspartate aminotransferase (AST) activities of treated animals. In general, nano-materials are able to induce oxidative stress in exposed animals. The present findings indicate that, alterations of antioxidant enzyme activities, increase of LPO, LDH, and reducing of GSH content and GST, GPx activities are recognized to oxidative stress and cell damage. This species could be considered a good bioindicator to assess nano-materials exposure.

Assessment of fipronil toxicity to the freshwater midge Chironomus riparius: Molecular, biochemical, and organismal responses

Fipronil is a phenylpyrazole insecticide that entered the market to replace organochlorides and organophosphates. Fipronil impairs the regular inhibition of nerve impulses that ultimately result in paralysis and death of insects. Because of its use as a pest control, and due to runoff events, fipronil has been detected in freshwater systems near agricultural areas, and therefore might represent a threat to non-target aquatic organisms. In this study, the toxicity of fipronil to the freshwater midge Chironomus riparius was investigated at biochemical, molecular, and whole organism (e.g. growth, emergence, and behavior) levels. At the individual level, chronic (28 days) exposure to fipronil resulted in reduced larval growth and emergence with a lowest observed effect concentration (LOEC) of 0.081 μg L^-1. Adult weight, which is directly linked to the flying performance and fecundity of midges, was also affected (LOEC = 0.040 μg L^-1). Additionally, behavioral changes such as irregular burrowing behavior of C. riparius larvae (EC₅₀ = 0.084 μg L^-1) and impairment of adult flying performance were observed. At a biochemical level, acute (48 h) exposure to fipronil increased cellular oxygen consumption (as indicated by the increase of electron transport system (ETS) activity) and decreased antioxidant and detoxification defenses (as suggested by the decrease in catalase (CAT) and glutathione S-transferase (GST) activities). Exposure to fipronil also caused alterations in the fatty acid profile of C. riparius, since high levels of stearidonic acid (SDA) were observed. A comparison between exposed and non-exposed larvae also revealed alterations in the expression of globins, cytoskeleton and motor proteins, and proteins involved in protein biosynthesis. These alterations may aid in the interpretation of potential mechanisms of action that lead to the effects observed at the organism level. Present results show that environmentally relevant concentrations of fipronil are toxic to chironomid populations which call for monitoring of phenylpyrazole insecticides and of their ecological effects in freshwaters. Present results also emphasize the importance of complementing ecotoxicological data with molecular approaches such as proteomics, for a better interpretation of the mode of action of insecticides in aquatic invertebrates.

Cytotoxic effects of persistent organic pollutants on the freshwater snail (Lanistes carinatus) in Kafr El-Zayat, Egypt

Effects of industrial and municipal wastewaters on the freshwater snail, Lanistes carinatus, were evaluated. Concentrations of some chemicals in some effluents were greater than permissible limits promulgated internationally by various jurisdictions. Pesticides and polychlorinated biphenyls (PCBs) observed in tissues of snails collected during summer were greater than those measured in snails collected during winter. Catalase activities observed during autumn were greater than those observed during other seasons. Activities of catalase were greater at all sites near sources of contamination than in snails from the reference site (S6). Lactate dehydrogenase activity was also greater at all sites relative to the location designated as the reference (S6), at which activities did not exceed 8.10 U/L. Patterns of genomic DNA in snails, as determined by use of OPA-02 primer, were significantly different among sites. Location S1 (Belshay village) exhibited 11 bands, followed by S2 (El-Demer zone) and S5 (Rosetta branch) which exhibited 6 bands. In contrast, all sites exhibited greater numbers of bands when the OPA-08 primer was used. Thus, DNA fingerprinting, lactate dehydrogenase, and catalase offer useful biomarkers in ecotoxicology and risk assessment programs.

Neurotoxicity, Behavior, and Lethal Effects of Cadmium, Microplastics, and Their Mixtures on Pomatoschistus microps Juveniles from Two Wild Populations Exposed under Laboratory Conditions-Implications to Environmental and Human Risk Assessment

Microplastics (MPs) were found to modulate the toxicity of other pollutants but the knowledge on the topic is still limited. The goals of this study were to investigate the short-term toxicity of cadmium (Cd) to wild Pomatochistus microps juveniles, the potential modulation of acute Cd toxicity by 1–5 µm polyethylene MPs in this species, and possible differences of sensitivity to Cd and MPs-Cd mixtures between juveniles from two distinct wild populations. Juveniles were collected in the estuaries of Minho (M-est) and Lima (L-est) Rivers (NW Portugal). One 96 h bioassay with M-est juveniles and another one with L-est juveniles were carried out in laboratory conditions. Each bioassay had 12 treatments: control, 5 Cd concentrations, 1 MPs concentration, and 5 MPs-Cd mixtures. No significant differences in Cd-induced mortality between juveniles from distinct estuaries or between juveniles exposed to Cd alone and those exposed to MPs-Cd mixtures were found. The total 96h LC₁₀ and LC₅₀ of Cd alone were 2 mg/L (95% CI: 0–4 mg/L) and 8 mg/L (95% CI: 2–17 mg/L), respectively. Cd alone significantly decreased the post-exposure predatory performance (PEPP) of M-est (≥6 mg/L) and L-est juveniles (≥3 mg/L), and acetylcholinesterase (AChE) activity of M-est juveniles (13 mg/L). MPs alone (0.14 mg/L) significantly reduced the PEPP and AChE activity of L-est juveniles but not of M-est juveniles. MPs-Cd mixtures (3–13 mg/L of Cd + 0.14 mg/L of MPs) significantly inhibited the PEPP of juveniles from both estuaries and AChE of L-est estuary juveniles but not of M-est juveniles. Evidences of toxicological interactions, namely antagonism, between MPs and Cd were found. Overall, the results indicate that MPs modulated the sub-lethal toxic effects of Cd in wild P. microps juveniles, especially neurotoxicity. Moreover, the environmental conditions of the natural habitats to which juveniles were exposed during pre-developmental phases influence the sub-lethal toxicity of Cd, MPs, and their mixtures. The implications to environmental and human risk assessment are discussed and further research is needed.

Toxicity of the insecticides spinosad and indoxacarb to the non-target aquatic midge Chironomus riparius

Spinosad and indoxacarb are two relatively new insecticides mainly used in agriculture to control insect pests. However, at their current application rates, non-target aquatic insect species may also be impacted. In this study, larvae of the non-biting midge Chironomus riparius were exposed in the laboratory to both insecticides and their effects evaluated at the organismal level, using standard ecotoxicological tests, and at the biochemical level, by monitoring specific oxidative stress, neuronal, and energy metabolism biomarkers. Chronic exposure to both insecticides compromised growth and emergence of C. riparius. Short-term exposures revealed alterations at biochemical level that might be related to the toxicological targets of both insecticides. Growth and development time were the most sensitive endpoints at individual level for both pesticides, while at the biochemical level, the electron transport system activity was the most sensitive biomarker for spinosad exposure, suggesting an increase in energy demands associated with the activation of defense mechanisms. Glutathione-S-transferase was the most sensitive biomarker for indoxacarb exposure, underlining the role of this enzyme in the detoxification of indoxacarb. Additionally, changes in lactate dehydrogenase and glutathione peroxidase activities were observed for both insecticides, and evidences of oxidative damage were found for spinosad. This study contributes to the growing knowledge on sublethal effects of novel insecticides on non-target aquatic invertebrates and strengthens the usefulness of biochemical biomarkers to support the interpretation of their potentially deleterious effects on aquatic insects near agricultural fields.

Amitraz toxicity to the midge Chironomus riparius: Life-history and biochemical responses

Acute and chronic toxicity of the formamidine pesticide amitraz to the midge Chironomus riparius was assessed using conventional ecotoxicological tests and biochemical approaches (biomarkers). Amitraz is mainly used as an ectoparasiticide in veterinary medicine, but also in agriculture and apiculture. However, information of amitraz toxicity to non-target invertebrates is limited. Besides the impairment of developmental and emergence rates (reduced larval growth, emergence, and delayed development time) caused by chronic exposure to amitraz, acute exposures induced alterations in the antioxidant enzymes glutathione peroxidase (GPx) and catalase (CAT), and in energetic metabolism biomarkers, lactate dehydrogenase (LDH) and electron transport system (ETS) activities. Moreover, lipid peroxidation (LPO) increased by amitraz exposure. Our results reveal potential secondary effects of amitraz to invertebrates and biomarkers that may aid in the interpretation of sub-lethal toxic responses to amitraz. These results add information concerning the potential outcomes of amitraz exposure to freshwater invertebrates underlining the importance of risk assessment studies of formamidine pesticides.

Baseline levels of antioxidant activities in Mytilus galloprovincialis along the coast of Cape Town, South Africa

Antioxidant activities in Mytilus galloprovincialis were determined from samples collected at Scarborough, Hout Bay, Green Point, Milnerton and Bloubergstrand in Cape Town, South Africa. Antioxidant enzyme activity was determined by measuring CAT, SOD and GSH. The total antioxidant capacity was measured using FRAP and ORAC, while the content and lipid peroxidation marker levels of CDs and TBARS. Antioxidant activities and responses in mussels varied between sites with significant correlations for 85% and 71% of all antioxidant measurements made for Fe and Zn, respectively. The oxidative stress results reported here are novel for the region and indicated that mussels in Cape Town do not have (relatively) high levels of antioxidant activities as a result of exposure to metals. The research undertaken suggests that antioxidant responses was an appropriate biomarker of exposure to metals but more environmental parameters should be considered when interpreting antioxidant responses in the natural environment.

The influence of short-term experimental fasting on biomarker responsiveness in oil WAF exposed mussels

Mussels are widely used in toxicological experimentation; however, experimental setups are not standardized yet. Although there is evidence of changes in biomarker values during food digestion and depending on the mussel nutritive status, the mode of feeding differs among toxicological experiments. Typically, mussels are fed with different diets in different long-term experiments, while fasting is the most common approach for short-term studies. Consequently, comparisons among experiments and reliable interpretations of biomarker results are often unfeasible. The present investigation aimed at determining the influence of fasting (against feeding with Isochrysis galbana) on biomarkers and their responsiveness in mussels exposed for 96 h to the water accommodated fraction (WAF) of a heavy fuel oil (0%, 6.25%, 12.5% and 25% WAF in sea water). PAH tissue levels in digestive gland and a battery of biomarkers were compared. WAF exposure led to decrease of cytochrome-C-oxidase activity, modulated glutathione-S-transferase activity, augmented lipid peroxidation, inhibited acetyl cholinesterase (AChE) activity, and led to lysosomal enlargement (Vv_LYS and S/V_LYS) and membrane destabilisation, lipofuscin accumulation, and histopathological alterations (Vv_BAS, MLR/MET and CTD ratio) in the digestive gland epithelium; and were integrated as IBR/n (biological response index). Overall, no significant changes were recorded in AChE activity, S/V_LYS and CTD ratio in any experimental treatment, while all the other biomarkers showed significant changes depending on the fasting/feeding condition, the exposure to WAF and/or their interaction. As a result, the integrated biomarker index IBR/n was higher at increasing WAF exposure levels both in fasted and fed mussels albeit the response was more marked in the latter. The response profiles were qualitatively similar between fasted and fed mussels but quantitatively more pronounced in fed mussels, especially upon exposure to the highest concentration (25% WAF). Therefore, it is highly recommended that mussels are also supplied with food during short-term, like during long-term toxicological experiments. This practice would avoid the interference of fasting with biological responses elicited by the tested chemicals and allow for reliable comparison with data obtained in long-term experiments and monitoring programmes.

Physiopathological responses of sole (Solea senegalensis) subjected to bacterial infection and handling stress after probiotic treatment with autochthonous bacteria

This study aimed to evaluate the protective effects of four autochthonous bacteria isolated from juvenile sole (Solea senegalensis) intestine as dietary probiotic supplement against bacterial pathogen infection and handling/transport stressors. Growth performance and immune responses were evaluated after 85 days of feeding trial. Sole (IBW = 16.07 ± 0.11 g) were fed six experimental diets, a control diet (CTRL, without the dietary probiotic supplementation), and five diets supplemented with probiotic bacteria: PB1 (Shewanella hafniensis), PB2 (Enterococcus raffinosus), PB3 (Shewanella hafniensis + Arthrobacter soli), PB4 (Pseudomonas protegens + Arthrobacter soli) and PB5 (Shewanella hafniensis + Arthrobacter soli + Enterococcus raffinosus). All bacteria were selected based on their in vitro antimicrobial activity. After the growth trial, fish were submitted to a stress factor (transport) and then each dietary group was divided in two additional groups: non-infected (placebo) and infected with Photobacterium damselae subsp. piscicida. Immune and antioxidant responses were evaluated at day 10 post-infection. In infection trial A, fish were infected on the same day of transport, whereas in trial B fish were infected after a 7-day recovery from the transport stress. At the end of the feeding trial, fish fed with PB2 and PB4 showed lower final body weight when compared with the other dietary groups. Respiratory burst activity and nitric oxide production were not affected by probiotic supplementation. Fish fed with PB5 presented lower peroxidase activity compared to CTRL. Lysozyme and alternative complement pathway activity (ACH50) showed no significant differences between treatments. The innate immune responses were significantly affected after handling stress and bacterial infection. In trial A, the ACH50 levels of infected fish were significantly lower than the placebo groups. On the other hand, in trial B fish infected with Pdp demonstrated higher ACH50 levels when compared to placebos. Peroxidase levels were strongly modulated by bacterial infection and handling stress. In trials A and B, infection had a clear downgrade effect in peroxidase levels. Lipid peroxidation, catalase, glutathione S-transferase and glutathione reductase were altered by both bacterial infection and transport. Overall, dietary probiotic supplementation did not influence growth performance of sole. The immune and oxidative defenses of sole responded differently to infection depending on the probiotic and the synergy between pathogen infection and transport.

Does exposure to reduced pH and diclofenac induce oxidative stress in marine bivalves? A comparative study with the mussel Mytilus galloprovincialis and the clam Ruditapes philippinarum

CO₂-driven acidification and emerging contaminants, such as pharmaceuticals, pose new threats for the maintenance of natural populations of marine organisms by interfering with their normal biochemical pathways and defences. The combined effects of seawater acidification, as predicted in climate change scenarios, and an emerging contaminant (the non-steroidal anti-inflammatory drug, NSAID, diclofenac) on oxidative stress-related parameters were investigated in the Mediterranean mussel Mytilus galloprovincialis and the Manila clam Ruditapes philippinarum. A flow-through system was used to carry out a three-week exposure experiment with the bivalves. First, the animals were exposed to only three pH values for 7 days. The pH was manipulated by dissolving CO₂ in the seawater to obtain two reduced pH treatments (pH -0.4 units and pH -0.7 units), which were compared with seawater at the natural pH level (8.1). Thereafter, the bivalves were concomitantly exposed to the three experimental pH values and environmentally relevant concentrations of diclofenac (0.00, 0.05 and 0.50 μg/L) for an additional 14 days. The activities of superoxide dismutase, catalase and cyclooxygenase, and lipid peroxidation and DNA strand-break formation were measured in both the gills and digestive gland after 7, 14 and 21 days of exposure to each experimental condition. The results show that the biochemical parameters measured in both the mussels and clams were more influenced by the reduced pH than by the contaminant or the pH*contaminant interaction, although the biomarker variation patterns differed depending on the species and tissues analysed. Generally, due to increases in its antioxidant defence, M. galloprovincialis was more resistant than R. philippinarum to both diclofenac exposure and reduced pH. Conversely, reduced pH induced a significant decrease in COX activity in both the gills and digestive gland of clams, possibly resulting in the increased DNA damage observed in the digestive gland tissue.

An investigation on the seasonal variations of the biomarkers of oxidative stress response and their correlations to Polonium-210 in mussel (Mytilus galloprovincialis) and common sole (Solea solea) from İzmir Bay, Turkey

It is well known that the marine organisms are used as biological indicators for environmental pollution studies. Among these studies, the research on oxidative stress has been increasing in recent years. In this study, mussels (Mytilus galloprovincialis) and fish (Solea solea) samples were collected seasonally from İnciraltı, İzmir, Turkey. This station was in an area where fishing is carried out for human consumption. The relationship between ²¹⁰Po and oxidative stress markers (lipid peroxidation (LPO), H₂O₂ and proline) was investigated in the mussel tissue (digestive gland, gills) and fish tissue (liver, gills) samples. The present study indicated that H₂O₂ accumulated with increasing ²¹⁰Po concentration in mussel samples. Statistically significant correlation were found between H₂O₂ and ²¹⁰Po and LPO and proline in mussel samples. This correlation between LPO and proline can be attributed to common environmental parameters (other than ²¹⁰Po) affecting expression of both LPO and proline levels. There was not a significant correlation between ²¹⁰Po and LPO levels. Similarly, a significant correlation was not found between ²¹⁰Po and proline.

Trace metals and oxidative status in soft tissues of caged mussels (Aulacomya atra) on the North Patagonian coastline

This study investigated metal accumulation and oxidative effects in mantle, gill and digestive gland of the ribbed mussel Aulacomya atra from the Argentinean North Patagonian coastline. Mussels were transplanted over an 18-month period from a site with low anthropogenic impact to a harbor site with higher seawater concentration of aluminum, chromium, copper, manganese, nickel and zinc. Total trace metal concentration in seawater did not change throughout the 18-month transplant in either site. A. atra bioaccumulated metals in digestive gland, gills and mantle at different levels. Digestive gland had the highest concentration of metals, especially towards the end of the transplant experiment in the harbor area. Mussels transplanted to the harbor site experienced an upregulation in their antioxidant system, which likely explains the lack of oxidative damage to lipids despite higher metal accumulation. These results demonstrate that A. atra selectively accumulates metals from the water column and their prooxidant effects depend on the tissue antioxidant defenses and the exposure time.

Metals in mangrove ecosystems and associated biota: A global perspective

Mangrove forests prevalent along the intertidal regions of tropical and sub-tropical coastlines are inimitable and dynamic ecosystems. They protect and stabilize coastal areas from deleterious consequences of natural disasters such as hurricanes and tsunamis. Although there are reviews on ecological aspects, industrial uses of mangrove-associated microorganisms and occurrence of pollutants in a region-specific manner, there is no exclusive review detailing the incidence of metals in mangrove sediments and associated biota in these ecosystems on a global level. In this review, mangrove forests have been classified in a continent-wise manner. Most of the investigations detail the distribution of metals such as zinc, chromium, arsenic, copper, cobalt, manganese, nickel, lead and mercury although in some cases levels of vanadium, strontium, zirconium and uranium have also been studied. Seasonal, tidal, marine, riverine, and terrestrial components are seen to influence occurrence, speciation, bioavailability and fate of metals in these ecosystems. In most of the cases, associated plants and animals also accumulate metals to different extents and are of ecotoxicological relevance. Levels of metals vary in a region specific manner and there is disparity in the pollution status of different mangrove areas. Protecting these vulnerable ecosystems from metal pollutants is important from environmental safety point of view.

Bioaccumulation and effects of titanium dioxide nanoparticles and bulk in the clam Ruditapes philippinarum

Biochemical and cellular responses to low concentrations of TiO₂ nanoparticles (nTiO_2, 1 and 10 μg/L) and bulk (bTiO₂, 10 μg/L) were evaluated in gills, digestive gland and haemolymph of the clam Ruditapes philippinarum after1, 3 and 7 days' exposure. At 7 days, titanium content was determined in gills and digestive gland. nTiO₂ significantly increased antioxidant enzyme activities in both tissues, and lipid peroxidation in digestive gland at 10 μg/L only, and affected glutathione S-transferase activity. Slighter variations were observed in bTiO₂-treated clams. A significant Ti bioaccumulation was detected in both gills and digestive gland of 10 μg nTiO₂/L-exposed clams. In haemolymph, nTiO₂ affected total haemocyte count, haemocyte proliferation, haemocyte diameter and volume, and induced DNA damage. Overall, this study demonstrated that TiO₂ alters most of the biomarkers measured in clams, although responses were differently modulated depending on tissues and exposure conditions, and indicated that nTiO₂ can be accumulated by bivalves, suggesting a potential risk for filter-feeding animals.

Uptake and effects of the antimicrobial florfenicol, microplastics and their mixtures on freshwater exotic invasive bivalve Corbicula fluminea

Microplastics and antimicrobials are widely spread environmental contaminants and more research on their toxicity is needed. The uptake and effects of the antimicrobial florfenicol, microplastics, and their mixtures on Corbicula fluminea were investigated. Bivalves were exposed for 96h to florfenicol (1.8 and 7.1mg/l), microplastics (0.2 and 0.7mg/l), or mixtures of the two substances. After 96h, all bivalves exposed to antimicrobial treatments had florfenicol in their body (e.g. 2±1μg/g). Microplastics were found in the gut, lumen of the digestive gland, connective tissue, hemolymphatic sinuses, and gills surface of animals. Florfenicol caused a significant inhibition of cholinesterase (ChE) activity (~32%). Animals exposed to 0.2mg/l of microplastics showed ChE activity inhibition (31%), and no other significant alterations. Mixtures caused feeding inhibition (57-83%), significant ChE inhibition (44-57%) and of isocitrate dehydrogenase activity, and increased anti-oxidant enzymes activity and lipid peroxidation levels. Overall, the results indicate that C. fluminea take up florfenicol and microplastics from the water and accumulated or at least retained it in their body for some time; both florfenicol (low ppm range) and microplastics (ppb range) were toxic to C. fluminea, with mixtures containing florfenicol and microplastics being more toxic. Thus, the risk of exposure and toxic effects of florfenicol to C. fluminea and other bivalves, and its predators increase in ecosystems contaminated with the antimicrobial and microplastics, as well as to humans consuming contaminated species from these ecosystems.

Green synthesis of silver nanoparticles using Piper nigrum: tissue-specific bioaccumulation, histopathology, and oxidative stress responses in Indian major carp Labeo rohita

The aim of the present investigation is to assess the sublethal toxicity of biologically synthesized silver nanoparticles (Ag NPs) in Indian major carp Labeo rohita. Ag NPs used in the study were synthesized by using AgNO₃ with aqueous leaf extract of Piper nigrum. Median lethal concentration (LC₅₀) of synthesized Ag NPs was determined for 96 h (25 μg/L); 2.5 μg/L (1/10th LC₅₀) and 5 μg/L (1/5th LC₅₀) were taken as sublethal concentrations to evaluate the toxicity for 35 days. The results of the TEM, SEM, and EDX analyses revealed that Ag NPs were considerably accumulated in the gill, liver, and kidney of fish at both concentrations (2.5 and 5 μg/L). Consequently, the activity of the antioxidant enzymes, SOD and CAT, was significantly (P < 0.05) decreased in the gill, liver, and kidney when compared to the control group during the study period. However, lipid peroxidase (LPO) activity in the gill, liver, and kidney was significantly (P < 0.05) increased, and the result concluded a possible sign of free radical-induced oxidative stress in Ag NP-exposed fish than the sham-exposed individuals. The histopathological study also confirmed the alterations such as degeneration of lamella, lifting of lamellar epithelium, hepatic necrosis, pyknotic nuclei, increased intracellular space, and shrinkage of glomerulus elicited by Ag NPs in the gill, liver, and kidney of Labeo rohita with two different concentrations. The findings of the present study revealed that green synthesis of Ag NPs from Piper nigrum at sublethal concentrations leads to accumulation of Ag, oxidative stress, and histopathological alterations in the target organs of the fish, Labeo rohita.

Assessing the health status of farmed mussels (Mytilus galloprovincialis) through histological, microbiological and biomarker analyses

The Gulf of La Spezia (northern Tyrrhenian Sea, Italy) is a commercially important area both as a shipping port and for mussel farming. Recently, there has been increased concern over environmental disturbances caused by anthropogenic activities such as ship traffic and dredging and the effects they have on the health of farmed mussels. This paper reports the results of microbiological and histological analyses, as well as of measurement of several biomarkers which were performed to assess the health status of mussels (Mytilus galloprovincialis) from four rearing sites in the Gulf of La Spezia. Mussels were collected between October 2015 and September 2016 and histological analyses (including gonadal maturation stage), as well as the presence of pathogenic bacteria (Vibrio splendidus clade, V. aestuarianus and V. harveyi), viruses (Herpes virus and ostreid Herpes virus 1) and protozoa (Marteilia spp., in the summer season only) were carried out on a monthly basis. Conversely, biomarker responses in haemocyte/haemolymph (total haemocyte count, haemocyte diameter and volume, lysozyme and lactate dehydrogenase activities in cell-free haemolymph, and micronuclei frequency) and in gills and digestive gland (cortisol-like steroids and lipid peroxidation levels), were evaluated bimonthly. Microbiological data indicated that mussels contain a reservoir of potentially pathogenic bacteria, viruses and protozoa that in certain environmental conditions may cause a weakening of the immune system of animals leading to mortality episodes. The percentage of parasites detected in the mussels was generally low (9.6% for Steinhausia mytilovum, that is 17 samples out of 177 examined females; 3.4% for Proctoeces maculatus; 0.9% for Mytilicola intestinalis and 2% for ciliated protozoa), while symbiont loads were higher (31% for Eugymnanthea inquilina and Urastoma cyprinae). Interestingly, a previously undescribed haplosporidian was detected in a single mussel sample (0.2%) and was confirmed by in situ hybridization. Cells morphologically similar to Perkinsus sp. trophozoites were observed in 0.7% of the mussels analysed; however, infection with Perkinsus spp. could neither be confirmed by ISH nor by PCR. Different pathological aspects, such as host defence responses and regressive/progressive changes were detected in the gills, digestive glands, gonads and mantle. Only one single case of disseminated neoplasia (0.2%) was observed. As for the biomarker evaluation, the MANOVA analysis revealed the statistically significant effect that the variable "sampling site" had on the biological parameter measured, thus suggesting that the multibiomarker approach was able to differentiate the rearing sites.

Effects of domestic effluent discharges on mangrove crab physiology: Integrated energetic, osmoregulatory and redox balances of a key engineer species

Mangroves are increasingly used as biofiltering systems of (pre-treated) domestic effluents. However, these wastewater discharges may affect local macrofauna. This laboratory study investigates the effects of wastewater exposure on the mangrove spider crab Neosarmatium meinerti, a key engineering species which is known to be affected by waste waters in effluent-impacted areas. These effects were quantified by monitoring biological markers of physiological state, namely oxygen consumption, the branchial cavity ventilation rate, gill physiology and morphology, and osmoregulatory and redox balance. Adults acclimated to clean seawater (SW, 32 ppt) and freshwater (FW, ∼0 ppt) were compared to crabs exposed to wastewater for 5 h (WW, ∼0 ppt). Spider crabs exposed to WW increased their ventilation and whole-animal respiration rates by 2- and 3-fold respectively, while isolated gill respiration increased in the animals exposed to FW (from 0.5 to 2.3 and 1.1 nmol O₂ min^-1 mg DW^-1 for anterior and posterior gills, respectively) but was not modified in WW-exposed individuals. WW exposure also impaired crab osmoregulatory capacity; an 80 mOsm kg^-1 decrease was observed compared to FW, likely due to decreased branchial NKA activity. ROS production (DCF fluorescence in hemolymph), antioxidant defenses (superoxide dismutase and catalase activities) and oxidative damage (malondialdehyde concentration) responses varied according to animal gender. Overall, this study demonstrates that specific physiological parameters must be considered when focusing on crabs with bimodal breathing capacities. We conclude that spider crabs exposed to WW face osmoregulatory imbalances due to functional and morphological gill remodeling, which must rapidly exhaust energy reserves. These physiological disruptions could explain the ecological changes observed in the field.

Biomarkers of oxidative stress and health risk assessment of heavy metal contaminated aquatic and terrestrial organisms by oil extraction industry in Ogale, Nigeria

Ogale community in Rivers State, Nigeria is characterized by crude-oil contamination of its land resources. The present study aimed to evaluate the health risk and metal (Cd, Pb, Zn, Cr, and Ni) contamination level of the vegetable (Telfairia occidentalis), snail (Achatina achatina) and the catfish (Clarias gariepinus) collected from Ogale community. Samples collected from Elele Alimini community, a less polluted area was used as control. Oxidative damage was evaluated in tissues of snail and in the liver of catfish. The concentration of most of the tested metals in the food samples collected from the polluted sites were higher than those from the reference sites and in most cases exceeded the acceptable permissible limits. The accumulation of the metals by the food samples followed the order: T. occidentalis > A. achatina > C. gariepinus. The tissues of the snail from the polluted sites showed higher malondialdehyde (MDA) and lower glutathione (GSH) levels, and higher MDA and GSH levels in the fish liver compared to control values. The health risks associated with these metals in terms of dietary intake and target hazard quotients (THQs) showed higher non-carcinogenic effect and carcinogenic risks especially for Pb and Cd from the ingestion of Telfairia occidentalis and Achatina achatina from polluted sites. The health hazards due to metal pollution for the highly-exposed consumers of the food samples, especially in Ogale require attention. The oxidative stress response to accumulation status of metals provides a relevant tool for the assessment of metal pollution.

Biochemical approaches to assess oxidative stress induced by exposure to natural and synthetic dyes in early life stages in zebrafish

Zebrafish early life stages were found to be sensitive to several synthetic dyes widely used in industries. However, as environmental concentrations of such contaminants are often at sublethal levels, more sensitive methods are required to determine early-warning adverse consequences. The aim of this study was to utilize a multibiomarker approach to examine underlying oxidative stress mechanisms triggered by sublethal concentrations of synthetic azo dye Basic Red 51 (BR51), the natural dye erythrostominone (ERY), and its light-degraded product using zebrafish embryos. Biochemical biomarkers included parameters of detoxification and markers of antioxidant system, as well as oxidative damage. Results showed pro-oxidant mechanisms attributed to BR51 and ERY as evidenced by increased glutathione S-transferase (GST) activity, a phase II detoxification enzyme related to reactive oxygen species detoxification. BR51 also elevated total glutathione (GSH+GSSG) levels and catalase activity. However, both dyes induced oxidative damage as evidenced by elevated lipid peroxidation content. In contrast, when the natural dye was photodegraded, no marked effects were observed for all biomarkers assessed. Data indicate that such dyes are pro-oxidants at sublethal concentrations, predominantly involving GSH and/or related enzymes pathway.

Seasonal and ontogenetic changes modulate oxygen consumption and antioxidant defenses in the cutlassfish Trichiurus lepturus (Pisces, Trichiuridae)

Several oxidative stress markers and liver oxygen consumption were measured in different tissues of the marine fish Trichiurus lepturus in late summer and late winter, as well as in juveniles and adult females. Oxygen consumption in liver, superoxide dismutase (SOD) and catalase (CAT) activity in liver, red cells, lens and roe, vitamin E, ubiquinol₁₀, β-carotene in liver, red cells, and roe, as well as contents of reduced glutathione (GSH) and lipoperoxidation (TBARS) in red cells were evaluated. Regarding ontogeny, compared to adult fish, juveniles showed significant higher SOD activity in liver and lens, as well as higher liver contents of vitamin E. In contrast, adult females showed higher contents of vitamin E in roe, ubiquinol₁₀ in liver and roe, and higher GSH levels in red cells, while the other markers remained unchanged. Regarding seasonal changes, no differences were detected in adult females for liver CAT and ubiquinol₁₀, CAT in roe, vitamin E in roe and in red cells, liver and red cell ubiquinol₁₀, and in GSH in red cells. However, and coinciding with the spawning period of late summer, liver oxygen consumption, SOD and CAT activity and ubiquinol₁₀ contents in roe and SOD activity in red cells, and red cell TBARS contents were higher compared to late winter. These temporal antioxidant adjustments of Trichiurus lepturus seem to be parallel to the higher oxygen consumption typical of juvenile forms and also to the intense spawning and foraging activities of adult females in late summer.

Baseline levels of oxidative stress biomarkers in species from a subtropical estuarine system (Paranaguá Bay, southern Brazil)

Offshore petroleum exploration has increased the risks of oil spills in coastal tropical and subtropical habitats. Monitoring tools are needed to assess and protect environmental health. We determined baseline values of antioxidant biomarkers (CAT, SOD, GPx, GST, MDA) for five ecologically relevant species in a subtropical system in southern Brazil. Regional baseline levels are compared with literature data as a basis to eventually test their efficacy as post-spill monitoring tools. Differences in the antioxidant response among species, contamination, and seasons were tested using univariate and multivariate analyses. The bivalves Anomalocardia flexuosa and Crassostrea rhizophorae and the catfish Genidens genidens emerge as suitable sentinel species. Seasonality is the main factor accounting for biomarkers variability, and not background contamination level. However, interactions between season and contamination level are also significant, indicating that biomarkers respond to complex environmental settings, a fact that needs to be fully understood for designing proper monitoring programs.

Temperature rise and microplastics interact with the toxicity of the antibiotic cefalexin to juveniles of the common goby (Pomatoschistus microps): Post-exposure predatory behaviour, acetylcholinesterase activity and lipid peroxidation

The goal of this study was to investigate the toxicity of cefalexin to Pomatoschistus microps juveniles in relation to the presence of microplastics in the water and temperature rise. After acclimatization, groups of wild juveniles were exposed for 96h to artificial salt water (control), microplastics alone (0.184mg/l), cefalexin alone (1.3-10mg/l) and in mixture with microplastics (cefalexin: 1.3-10mg/l; microplastics: 0.184mg/l) at 20 and 25°C. Effect criteria were mortality, post-exposure predatory performance (PEPP), acetylcholinesterase activity (AChE) and lipid peroxidation levels (LPO). At 20°C, concentrations of cefalexin alone≥5mg/l significantly reduced PEPP (up to 56%; 96h-EC₅₀=8.4mg/l), indicating toxicity of the antibiotic to juveniles after short-term exposure to water concentrations in the low ppm range. At 20°C, fish exposed to microplastics alone did not have significant differences in any of the parameters tested relative to the control group but tended to have an inhibition of the PEPP (23%) and AChE (21%); at 25°C, microplastics alone caused mortality (33%) and PEPP inhibition (28%). Thus, microplastics are toxic to P. microps juveniles. At 20°C, under simultaneous exposure to cefalexin and microplastics, the PEPP was significantly reduced (at cefalexin concentrations≥1.25mg/l). Moreover, at 25°C, the toxicity curves of cefalexin (PEPP based), alone and in mixture with microplastics, were significantly different (p<0.05; 96h-EC₅₀ of 3.8 and 5.2mg/l, respectively), and the integrated data analysis indicated significant interactions between the two substances for all biomarkers. Thus, the presence of microplastics in the water influenced the toxicity of cefalexin. The rise of water temperature (from 20°C to 25°C), increased the microplastics-induced mortality (from 8 to 33%), and the inhibitory effects of cefalexin on the PEPP (up to 70%). Significant differences (p<0.05) between the toxicity curves of cefalexin alone at distinct temperatures were found, with a lower 96h-EC₅₀ at 25°C (3.8mg/l) than at 20°C (8.4mg/l). Moreover, at 25°C, increases of AChE activity (14%) and LPO (72%) in fish exposed to the mixture treatment containing the highest cefalexin concentration were found, and the integrated analysis of data indicated significant interactions between cefalexin and temperature for PEPP, and among all stressors for LPO. Thus, the temperature rise increased the toxicity of microplastics and of cefalexin, alone and in mixture with microplastics, to P. microps juveniles. These findings raise concern on the long-term exposure of wild populations to complex mixtures of pollutants, likely decreasing their fitness, and highlight the need of more research on the combined effects of widely used pharmaceuticals, microplastics and temperature increase on wild species to improve environmental and human risk assessments of chemicals and their safe use under a global warming scenario.

Blue sharks (Prionace glauca) as bioindicators of pollution and health in the Atlantic Ocean: Contamination levels and biochemical stress responses

Marine ecosystems are constantly being threatened by contaminants produced by human activities. There is an urge to better understand their impacts on marine organisms and develop reliable tools for biomonitoring studies, while also assessing their potential impacts on human health. Given their position on top of food webs, sharks are particularly susceptible to bioaccumulation, making them potential sentinel species of marine contamination. The main objective of this study was to find suitable biomarkers for future marine pollution biomonitoring studies by correlating biochemical responses with tissue contaminant body burden in blue sharks (Prionace glauca), a species heavily caught and consumed by humans, while also addressing their general health. The chemical contaminants analysed comprised different persistent organic pollutants (POPs) families from polychlorinated compounds to brominated flame retardants (BFRs) and perfluorinated compounds (PFCs) and different trace and heavy metals. Concentrations of some contaminants in sharks' tissues were found to be above the legally allowed limits for human consumption. A canonical correspondence analysis (CCA) was performed and some strong associations were found between biochemical responses and contaminants' accumulation levels. DNA damage and lipid peroxidation levels, as well as the inhibition of the antioxidant enzyme glutathione peroxidase, were the main effects and consequences of contamination. The impact of contamination on these vital macromolecules underlines the suboptimal conditions of the sampled P. glauca, which can ultimately lead to the degradation of core ecological aspects, such as swimming, feeding, and reproduction. It can be concluded that P. glauca demonstrates great potential to be used as environmental sentinel and suitable biomarker candidates were identified in this work. Moreover, this study also highlights the risks that the consumption of blue shark derived products can pose to human health, which is of upmost interest as the sampled organisms were still juveniles and already presented values above regulatory limits.