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New evidence regarding the risks that microplastics (MP) ingestion pose to human and wildlife health are being revealed with progress made in ecotoxicological research. However, comprehensive and realistic approaches that evaluate multiple physiological responses simultaneously are still scarce despite their relevance to understand whole-organism effects. To address this information gap, we performed an experiment to assess the effects of MP on freshwater fish physiology from the molecular to the organismal level. Using a model species of global commercial importance (Cyprinus carpio) and MP type (recycling industry fragments), size (range between 125-1000 µm), and two concentrations of environmental relevance (0.75 and 8.25 µg/L). Experimental design included 5 blocks containing 3 treatment levels each one: control, low, and high MP concentration, with 6 fish each aquarium (5 blocks x 3 treatments x 6 fish per aquarium = 90 fish). Our results suggest that, under the experimental conditions applied, MP exposure did not cause adverse effects at the morphological (variation in size of gut), metabolic (variation of standard metabolic rate), or ecological (growth performance) levels. Nonetheless, we observed an increased frequency of micronucleated cells with increasing MP concentration (df = 42, t-value = 3.68, p-value < 0.001), showing the potential genotoxicity of MP, which can clearly harm fish health in long-term. Thus, despite being a highly resistant species, exposure to MP may generate negative effects in juvenile C. carpio at cellular or subcellular levels. Our findings highlight that the manifestation of MP effects may vary over time, emphasizing the need for future studies to consider longer exposure durations in experimental designs.

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Pollution by metals is a matter of concern around the world. In recent decades, the high population growth in urban centers has significantly magnified the entry of these pollutants into aquatic ecosystems. The Amazon region, intense migratory flow, gold mining, and industrialization have been considered the main driving forces for increasing metal pollution. Thus, the main aim of this study is to conduct, for the first time, an Ecological Risk Assessment (ERA) based on metal concentrations measured in the sediment and water of several aquatic environments from the Amazon basin, based on the risk quotient values (RQ = measured environmental concentration - MEC/predicted no effect concentration - PNEC). In addition, the metal contamination factor (CF) was estimated. Although metal concentrations in water were generally low, these values were far above the limits established by current national legislation in many areas, showing higher concentrations for the metals Co, Pb, Cr, Cu, and Ni. Concentrations of Mn, Cu, Ba, Pb, Co, Ni, Cr, Zn, Cd, and As were especially high in the sediment for several evaluated environments. The ERA for the water compartment revealed that 56% of the studied areas presented high risk (RQ > 1) for aquatic biota. In the sediment, 66% of the sites presented a high risk and 40% medium risk (RQ = 0.1-1). The CF indicated that 49% of the sampling points had high contamination and only 24%, had low contamination. These results reveal that monitoring studies in the Amazon region, provides important information so that public policies for the preservation of water resources can be strengthened in the Amazon.

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The main aimed of this study was to provide information on microplastics present in the freshwater of fish farm ponds. In addition, the study showes a relationship between the seasonal, spatial distribution and the amount of microplastics found. This study was conducted in 35 fish farms located in the Rondônia state, Brazil, the sample collects were carried out in the two Amazonian hydrological seasons (dry and rainy). The study was developed in a completely randomized factorial scheme 35 × 3 x 3 (35 fish farms, 3 ponds and 3 repetitions per ponds). Microplastic sampling was performed following a modified method based on National Oceanic and Atmospheric Administration (NOAA). Samples of 250 mL freshwater collected, which were deionized and pre-filtered through 6.0 mm mesh granulometric sieves. The average abundances of the different hydrological seasons were compared by Student's t-test, with differences statistically significant at p < 0.05. The microplastics were morphological categorized into fibers and colors blue, red or transparent. Microplastic contamination was confirmed in freshwater of 9 fish farming, with greater abundance of blue fibers and greater quantification in the rainy season. Fish farms P3, P4 and P6 had the highest quantifications of blue fiber in the two seasons (6 and 43, 19 and 56, 11 and 88 items mL-1, respectively). Almost all fish farms had a higher abundance of microplastics in the rainy season. It is important to highlight the prominence of microplastics in the blue fiber rainy season (286 items mL-1) compared to the dry season (58 items mL-1). Fish farms P3, P4 and P6 showed a strong positive correlation between the factors distance from the nearest urban area (r = 0.94, 0.79 and 0.97, respectively) and seasonality (r = 0.98, 0.77 and 0.96, respectively). Rainfall variations influenced the abundance of microplastics, especially of blue fibers. Fish farms are supplied with fresh water by rivers or streams, so it is possible that microplastics originate outside the fish farm, perhaps they were introduced due to high soil occupation, although surface runoff (of water contaminated by sewage) caused by heavy rains the most important factor. Therefore, one factor must be considered, surface runoff and groundwater contaminated by urban, agricultural and urban effluents may have contaminated rivers and streams and then contaminated the water in the fish farm ponds.

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BACKGROUND: Geographic distribution of essential metals on earth is largely uneven. Therefore, regional specific approaches to assess metal contents in freshwater ecosystems are mandatory. Cd, Cu, Cr, Pb, Ni, Mn and Zn concentrations were measured in water, sediments and fish tocharacterize the partitioning of these essential and non-essential metals in three river ecosystems of the Pampean Plain==. METHODS: Water, sediment and eight fish species were collected at three rivers from the Pampean Plain. After sample-specific pretreatments, Cd, Cr, Cu, Mn, Ni, Pb and Zn concentrations in water, sediment and muscle were determined in triplicate by Inductively Coupled Plasma Optical Emission Spectrometer (ICP-OES). Contamination (Hakanson´s index) and bioconcentration factors were calculated to assess the degree of contamination and the relationship between the matrices, while the target hazard quotient was estimated to explore the risk to human health from fish consumption. RESULTS: Water metal concentration was below detection limit in all sampled rivers. Sediments were mostly enriched by Mn (186-474 mg kg-1) followed by Zn (36.8-40.3 mg kg-1), whereas in fish, the situation was the opposite, suggesting different biogeochemical pathways and uneven bioaccumulation of these elements. The largest concentrations for all explored metals were invariably recorded in fish from the Sauce Grande River, although only Cd, Cu and Ni in sediments were highest at this site. Indeed, the bioconcentration factor showed that Cd and Zn are actively accumulated by almost all species in all sampled rivers. The Targeted Hazard Quotient based on the muscle metal concentration tissue of the edible fish species (Odontesthes bonariensis) was less than 1. CONCLUSION: None metal seemed to pose a significant risk for humans. In some sites biota-sediment concentration factors of Cd and Zn and muscle Cd, Cr, Ni, Zn and Pb levels were highest in the silurid Pimelodella laticeps, suggesting that it may be used as a sentinel species for biomonitoring programs in Neotropical fish assemblages.

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Here we evaluated the potential for trace metal accumulation of two parasitic species, Hysterothylacium sp. (Nematoda) and Phyllodistomum sp. (Digenea), found parasitizing Hoplias malabaricus, a characiform fish also known as trahira, collected from two neotropical rivers, Jacaré-Pepira and Jacaré-Guaçú, in southeastern Brazil. Fish were collected between July 2017 and July 2019, totaling 90 fish specimens analyzed, 45 from each river. From fish, we take samples of three different tissues: muscle, intestine and liver. Along with the parasite samples taken from fish hosts, tissue samples were analyzed by an Inductively Coupled Plasma Mass Spectrometer (ICP-MS) for obtaining the trace metal (Al, Cr, Mn, Fe, Ni, Cu, As, Cd e Pb) concentrations. All elements were found in statistically higher concentrations in the parasites, both nematodes and digeneans, than in the host tissues, but in comparison, was observed that Hysterothylacium sp. had higher concentrations than those obtained in Phyllodistomum sp. We also found that uninfected fish had statistically higher concentrations of metals than infected ones. And in those who are infected, the size of the parasitic infrapopulations correlated negatively with the concentrations of trace metals obtained in the hosts tissues, that is, the concentrations in fish showed a tendency to decrease as the parasitic infrapopulations increased, or vice versa. In addition, our results show that the influence of the parasitic infrapopulations on metal concentrations in the fish host is not affected in cases of mono-infection or co-infection.

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Effects of the pyrethroid lambda-cyhalothrin (LCH) were investigated in matrinxa Brycon amazonicus, a non-target freshwater teleost. The fish were submitted to a single-pulse exposure (10% of LC50; 96 h, 0.65 µg L-1), followed by 7 days of recovery in clean water. Hematologic parameters indicated impairments in oxygen transport, which were not recovered. Plasma [Na+], [Cl-], and protein were diminished, and only [Na+] remained low after recovery. Gill Na+/K+ATPase activity was increased and recovered to basal values. Brain acetylcholinesterase activity was not responsive to LCH. Liver ascorbic acid concentration was not altered, and reduced glutathione levels remained augmented even after recovery. LCH inhibited hepatic superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx) activities, while glutathione-S-transferase (GST) and glucose-6-phosphate dehydrogenase (G6PDH) activities were steady. After recovery, SOD remained low, and GPx was augmented. Liver depicted lipid peroxidation, which was not observed after recovery. Hepatic morphology was affected by LCH and was not completely recovered. These responses, combined with the persistence of changes even after recovery span, clearly show the feasibility of these biomarkers in evaluating LCH toxic potential to non-target organisms, highlighting the importance of pyrethroids' responsible use.

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The aims of this study were: (i) to assess if carbamate pesticides and ammonium, widely detected in European freshwater bodies, can be considered ecologically relevant endocrine-disrupting chemicals (EDCs) for benthic and interstitial freshwater copepods; and (ii) to evaluate the potential of copepods as sentinels for monitoring ecosystem health. In order to achieve these objectives, four species belonging to the harpacticoid copepod genus Bryocamptus, namely B. (E.) echinatus, B. (R.) zschokkei, B. (R.) pygmaeus and B. (B.) minutus, were subjected to chronic exposures to Aldicarb and ammonium. A significant deviation from the developmental time of unexposed control cultures was observed for all the species in test cultures. Aldicarb caused an increase in generation time over 80% in both B. minutus and B. zschokkei, but less than 35% in B. pygmaeus and B. echinatus. Ammonium increased generation time over 33% in B. minutus, and 14, 12 and 3.5% for B. pygmaeus, B. zschokkei and B. echinatus, respectively. On the basis of these results it can be concluded that chronic exposure to carbamate pesticides and ammonium alters the post-naupliar development of the test-species and propose their potential role as EDCs, leaving open the basis to search what are the mechanism underlying. A prolonged developmental time would probably produce a detrimental effect on population attributes, such as age structure and population size. These deviations from a pristine population condition may be considered suitable biological indicators of ecosystem stress, particularly useful to compare polluted to unpolluted reference sites. Due to their dominance in both benthic and interstitial habitats, and their sensitivity as test organisms, freshwater benthic and hyporheic copepods can fully be used as sentinel species for assessing health condition of aquatic ecosystems as required by world-wide water legislation.

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