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The synthetic hormone 17α ethinyl estradiol (EE2) is a molecule widely used in female contraceptives and recognized as a contaminant of attention (Watch List) in the European Union due to its high consumption, endocrine effects and occurrence in aquatic environments. Its main source of introduction is domestic sewage where it can be associated with other contaminants such as microplastics (MPs). Due to their characteristics, they can combine with each other and exacerbate their isolated effects on biota. This study evaluated the combined effects of microplastics (MPs) and 17α ethinylestradiol (EE2) on two tropical estuarine invertebrate species: Crassostrea gasar and Ucides cordatus. Polyethylene particles were spiked with EE2 and organisms were exposed to three treatments, categorized into three groups: control group (C), virgin microplastics (MPs), and spiked microplastics with EE2 (MPEs). All treatments were evaluated after 3 and 7 days of exposure. Oysters exhibited changes in phase 2 enzymes and the antioxidant system, oxidative stress in the gills, and reduced lysosomal membrane stability after exposure to MPs and MPEs. Crabs exposed to MPs and MPEs after seven days showed changes in phase 1 enzymes in the gills and changes in phases 1 and 2 enzymes in the hepatopancreas, such as disturbed cellular health. The combined effects of microplastics and EE2 increased the toxicity experienced by organisms, which may trigger effects at higher levels of biological organization, leading to ecological disturbances in tropical coastal ecosystems.

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This study aimed to evaluate B[a]P and low-density polyethylene microplastics (MPs) toxicty, alone and in mixture (0.03 to 30 µg L-1 of B[a]P; and 5, 50 and 500 mg L-1 for MPs). Five mg L-1 of MPs is considerably higher than commonly reported environmental concentrations, although it has been reported for marine environments. Individual (sea urchin embryo-larval development and mortality of mysids) and sub-individual responses (LPO and DNA damage in mysids) were assessed. The toxicity increased as the B[a]P concentration increased, and microplastics alone did not cause toxicity. B[a]P toxicity was not modified by the lowest concentration of MPs (5 mg L-1), but at higher MPs concentrations (50 and 500 mg L-1), the effects of B[a]P on sea urchin development and in biomarkers in mysids were diminished. Microplastics interacted with B[a]P in seawater, reducing its toxicity, probably due to adsorption of B[a]P to the surface of microplastics.

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Filter-feeder organisms such as oyster and mussels are exposed to particles like microplastics (MPs). Although widely used to monitor MPs contamination, little is known about their performance as sentinels, which are biological monitors accumulating contaminants without significant adverse effects. This study comparatively evaluated the quantitative and qualitative accumulation of MPs by oysters (Crassostrea brasiliana) and mussels (Perna perna) along a gradient of contamination in a highly urbanized estuarine system of Brazil. In the most contaminated site, both species presented the worst status of nutrition and health, and also one of the highest MPs levels reported for molluscs to date (up to 44.1 particles·g-1). Despite some inter-specific differences, oysters and mussels were suitable and showed an equivalent performance as sentinels, reflecting the gradient condition demonstrated for other contaminants in the region. The similarity in MPs accumulation was also observed for qualitative aspects (polymer composition, sizes, shapes and colors). Particles were mostly <1000 µm, fibrous, colorless and composed by cellulose and polymethyl methacrylate (PMMA). Thus, despite small variations, the usage of C. brasiliana and P. perna is recommended and provides reliable information for environmental levels of microplastics.

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Methods to assess the effects of contaminants on marine organisms typically involve euthanasia to obtain samples, but less invasive techniques may be more appropriate for working with threatened species. In this study, were assessed the biological responses of crabs exposed to microplastics and contaminants of emerging concern. Biochemical and cellular effects (lipid peroxidation, DNA damage, cholinesterase activity, and lysosomal membrane stability) in hemolymph were analyzed in a kinetic study, at 3 and 7 days, in U. cordatus exposed to microplastics spiked with Triclosan (TCS) or 17α-Ethynylestradiol (EE2). The results showed that the contaminants were produced toxic effects in the crabs exposed either to the microplastics alone (oxidative stress, genotoxicity, and neurotoxicity), or to microplastics with TCS or EE2 adsorbed (neurotoxic and cytotoxic). The present study showed the responsiveness of non-lethal analyzes to understanding the biological effects of combined exposure to microplastics and chemical pollution.

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Estuaries in the world are affected by different contamination sources related to urbanisation and port/industrial activities. Identifying the substances responsible for the environmental toxicity in estuaries is challenging due to the multitude of stressors, both natural and anthropogenic. The Toxicity Identification and Evaluation (TIE) is a suitable way of determining causes of toxicity of sediments, but it poses difficulties since its application is labour intensive and time consuming. The aim of this study is to evaluate the diagnosis provided by a TIE based on microscale embryotoxicity tests with interstitial water (IW) to identify toxicants in estuarine sediments affected by multiple stressors. TIE showed toxicity due to different combinations of metals, apolar organic compounds, ammonia and sulphides, depending on the contamination source closest to the sampling station. The microscale TIE was able to discern different toxicants on sites subject to different contamination sources. There is good agreement between the results indicated in the TIE and the chemical analyses in whole sediment, although there are some disagreements, either due to the sensitivity of the test used, or due to the particularities of the use of interstitial water to assess the sediment toxicity. The improvement of TIE methods focused on identifying toxicants in multiple-stressed estuarine areas are crucial to discern contamination sources and subsidise management strategies.

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This study investigated the sublethal effects of environmentally relevant concentrations of DCOIT on the neotropical oyster Crassostrea brasiliana. Gills and digestive glands of animals exposed to increasing concentrations of DCOIT were analyzed for biochemical, cellular, and histopathological responses. Exposure to DCOIT (0.2 to 151 µg L-1) for 120 h triggered oxidative stress in both tissues (through the modulation of GPX, GST, GSH and GR), which led to damage of membrane lipids (increase of LPO and reduction of the NRRT). DCOIT increased histopathological pathologies in gills, such as necrosis, lymphocyte infiltration and epithelial desquamation. This study showed that short term exposure to environmental concentrations of DCOIT causes negative effects on C. brasiliana at biochemical, physiological, and histological levels. Therefore, the use of DCOIT as a booster biocide in antifouling paints should be further assessed, as it may cause environmental hazards to marine organisms.

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Data on the occurrence of cocaine (COC) and benzoylecgonine (BE) in marine environmental compartments are still limited, with few studies reporting superficial water contamination, mainly in tropical zones. In this sense, environmental data of these substances are essential to identify potential polluting sources, as well as their impact in costal ecosystems. The aim of this study was to evaluate the occurrence of COC and BE in seawater, sediment and mussels from a subtropical coastal zone (Santos Bay, São Paulo, Brazil), as well as to determine a field measured Bioaccumulation Factor (BAF). COC and BE were detected in all water samples in concentrations ranging from 1.91 ng·L-1 to 12.52 ng·L-1 and 9.88 ng·L-1 to 28.53 ng·L-1, respectively. In sediments, only COC was quantified in concentrations ranging from 0.94 ng·g-1 to 46.85 ng·g-1. Similarly, only COC was detected in tissues of mussels 0.914 µg·kg-1 to 4.58 µg·kg-1 (ww). The field-measured BAF ranged from 163 to 1454 (L·kg-1). Our results pointed out a widespread contamination by cocaine and its main human metabolite benzoylecgonine in Santos Bay. Mussels were able to accumulate COC in areas used by residents and tourists for bathing, fishing, and harvest, denoting concern to human health. Therefore, our data can be considered a preliminary assessment, which indicates the need to evaluate drugs (including illicit as COC) in environmental and seafood monitoring programs, in order to understand their risks on the ecosystem and human health.

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Urban waste is a complex mixture of different substances, including microplastics and pharmaceuticals and personal care products. Microplastics have a high affinity for hydrophobic substances. One of these substances is triclosan, a bactericide used in a variety of hygiene products. Therefore, microplastics (MPs) may serve as a vector between triclosan and aquatic organisms. The current study sought to evaluate the effects of the interaction between microplastics and triclosan based on a mechanistic approach in which the oyster Crassostrea brasiliana was used as a model. The organisms were exposed to three conditions: the control, microplastic (MP), and microplastic contaminated with triclosan (MPT). The organisms were exposed for 3 or 7 days. After the exposure time, hemolymph was sampled for performing the neutral red retention time assay and, subsequently, the gills, digestive glands, and adductor muscles were dissected for measuring biomarkers responses (EROD, DBF, GST, GPx, GSH, lipid peroxidation, DNA strand breaks, and AChE). Our results demonstrate combined effects of MPs associated with triclosan on oyster physiology and biochemistry, as well as on lysosomal membrane stability. These results contribute to understanding the effects of contaminants of emerging concern and microplastics on aquatic organisms.

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Lead is a priority pollutant introduced in the aquatic environment by different sources commonly located in estuarine regions, such as ports, marinas and industries. Environmental agencies around the world set the maximum allowable concentration of lead in effluents, surface water and sediment, but few studies reported its accumulation and chronic toxicity in mangrove benthic invertebrates using concentrations believed to be safe. In the case of Brazilian mangrove environments, Ucides cordatus is a crab species of choice to be used in bioaccumulation studies. We have assessed biomarkers' responses (DNA strand breaks, micronucleated cells, metallothioneins, enzymatic activity of aminolevulinic acid dehydratase and neutral red retention time) and the total bioaccumulation in six tissues of U. cordatus crabs resident to mangrove areas under different conservation status during a 28-day period bioassay. We also investigated Pb subcellular partition and biomarkers' responses using a supposedly safe concentration (10 µg L-1). During the Pb exposure, the highest concentration of Pb was observed in crab gills. Crabs also showed a high ability to allocate Pb in detoxified forms. Multivariate analysis pointed out that bioaccumulation (total, active and detoxified) is linked to biomarkers. Even in supposedly safe dosage, U. cordatus triggered its defense mechanisms expressing more metallothioneins and presented relevant cyto-genotoxic damage. Our data suggest the development of biological tolerance to Pb in crabs from polluted areas. Our results provided a new insight about lead toxicity even at concentrations considered environmentally safe, which could support new strategies to manage estuarine areas considering their respective conservation status.

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Centropomus undecimalis fish inhabit the highly contaminated Santos-São Vicente Estuarine System (SESS) and could be a good biomonitor of contaminants. This study aimed to investigate the cytogenotoxic potential of superficial water from SESS using C. undecimalis as a biomonitoring model and to validate the use of farmed fish as controls. Using biochemical (DNA damage and Lipid Peroxidation - LPO), cellular (erythrocyte nuclear abnormality - ENA) and tissue (8-OHdG immunoexpression) biomarkers, our results showed fish from SEES had higher LPO concentration in gills and higher frequency of reniform, lobed and total ENA in erythrocytes when compared with control farmed fish. Thus, SESS surface water are cytogenotoxic for blood and gills cells of fishes. C. undecimalis has shown to be a good biomonitor model and farmed fish can be used as control only if livers were not the target organs of study since the dietary food from farmed fish causes steatosis.

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