Absorption and accumulation of bioavailable cyanobacterial metabolites (including cyanotoxins) are likely in fish after senescence and the rupturing of cells during bloom episodes. We determined the toxicity of cyanopeptides identified from two strains of Microcystis (M. panniformis MIRS-04 and M. aeruginosa NPDC-01) in a freshwater tropical fish, Astyanax altiparanae (yellowtail tetra, lambari). Aqueous extracts of both Microcystis strains were prepared in order to simulate realistic fish exposure to these substances in a freshwater environment. Both strains were selected because previous assays evidenced the presence of microcystins (MCs) in MIRS-04 and lack of cyanotoxins in NPDC-01. Identification of cyanobacterial secondary metabolites was performed by LC-HR-QTOF-MS and quantification of the MC-LR was carried out by LC-QqQ-MS/MS. MIRS-04 produces the MCs MC-LR, MC-LY and MC-HilR as well as micropeptins B, 973, 959 and k139. NPCD-01 biosynthetizes microginins FR1, FR2/FR4 and SD-755, but does not produce MCs. Larval fish survival and changes in morphology were assessed for 96 h exposure to aqueous extracts of both strains at environmentally relevant concentrations from 0.1 to 0.5 mg (dry weight)/mL, corresponding to 0.15 to 0.74 μg/mL of MC-LR (considering dried amounts of MIRS-04 for comparison). Fish mortality increased with concentration and time of exposure for both strains of Microcystis. The frequencies of morphological abnormalities increased with concentration in both strains, and included abdominal and pericardial oedema, and spinal curvature. Results demonstrate that toxicity was not solely caused by MCs, other classes of cyanobacterial secondary metabolites contributed to the observed toxicity.
Several pharmaceutical compounds have been detected in natural aqueous systems and ibuprofen (IBF), one of the most consumed medicament, has been detected in many countries. The degradation efficiency of IBF under TiO2/UV radiation was evaluated. Optimum degradation results were observed using 20 mg•L −1 of TiO2, pH 7.8 and 5 mg•L −1 of IBF. Under these experimental conditions total IBF removal was achieved in less than 60 min of irradiation. Although total IBF concentration was observed, the total mineralization of the compound was not achieved. The by-products generated during TiO2/UV reaction showed to be more toxic against Daphnia similis than the initial IBF present in aqueous solution.
A great amount of heavy metals enter Pampulha Reservoir via it's main tributaries (Sarandi and Ressaca). Although no water quality classification has been carried out for these tributaries, the reservoir is expected to be in class 2 of the CONAMA-86 system. As part of a monitoring scheme of the Pampulha Watershed, heavy metals (Zn, Pb, Cd, Ni, Cu, Cr, Mn and Fe) were investigated in the water at a control site (considered free from direct human influence) and at potential sites of toxicity and contamination during August A relatively high concentration of cadmium was also detected at the confluence of the two streams. During the second sampling period, there was an increase in the concentrations of zinc at all sampling sites except the control, with values varying from 0.71 mg.L -1 (the Sarandi Stream) to 2.50 mg.L -1 (the Ressaca Stream). Lead, cadmium, nickel and chromium concentrations were also higher in the Ressaca Stream, but not detected at the other sampling sites. Copper values were higher than in the first period: 0.10 mg.L -1 at the control up to 0.38 mg.L -1 at the confluence of the streams. Similar results were found for manganese and iron, with values reaching up to 19.30 and 125 mg.L -1 , respectively. Moreover, all values recorded in the second sampling period were much higher than recommended for class 2 waters. These results emphasize the need for such monitoring in relation to better water quality management of this reservoir. Key words: heavy metals, monitoring, Pampulha Watershed, water quality. RESUMO Metais pesados em tributários da represa da Pampulha, Minas GeraisOs efluentes lançados nos principais tributários da represa da Pampulha (Sarandi e Ressaca) estão em grande parte representados por metais pesados. Embora não haja enquadramento para a qualidade da água destes tributários, por apresentarem trechos canalizados, os limites recomendados para o reservatório o classificam como classe 2. Dentre os aspectos ecotoxicológicos considerados no monitoramento da Bacia da Pampulha, foram investigados teores de metais pesados (Zn, Pb, Cd, Ni, Cu, Cr, Fe e Mn) na água, em locais com potencial de toxicidade e contaminação, durante agosto (estação seca) e novembro/98 (estação chuvosa). Os primeiros resultados mostraram concentrações relativamente elevadas de zinco (0,22 mg.L -1 ) na porção inicial do reservatório. No início do Córrego Sarandi, foram encontrados os maiores teores de níquel e cromo (0,19 e 0,89 mg.L -1 , respectivamente), enquanto as maiores concentrações de chumbo (0,05 mg.L -1 ), cádmio (0,014 mg. L -1 ), manganês (0,43 mg.L -1 ) e ferro (15,25 mg.L -1 ) foram encontradas no Córrego Ressaca, onde está situado o aterro sanitário de Belo Horizonte. Uma concentração relativamente elevada de cádmio também foi verificada Braz. J. Biol., 61(3)
This study proposes assays with a freshwater chironomid, Chironomus xanthus, distributed over South America, based on subindividual (acetylcholinesterase activity) and individual (survival and postexposure feeding) level endpoints. Sediment and aquatic-rooted floating macrophyte assays were developed, due to the importance of both substrates for toxicant exposure in subtropical/tropical environments. Assays were evaluated under realistic exposure scenarios by simulating a runoff over an agricultural field dosed with deltamethrin. In situ assays were performed within microcosms to discriminate the effects of deltamethrin from those of additional potential stress factors (organism handling and caging, microcosms, use of aquatic roots, and runoff per se). A laboratory sediment assay based on feeding was conducted with samples from the microcosms. In all assays, both sublethal endpoints were responsive to deltamethrin and more sensitive than survival. Survival and feeding were more sensitive in situ than in the laboratory. In the in situ sediment assays, both sublethal endpoints were within a similar range of sensitivity; they were significantly inhibited as of the lowest Decis dose, from approximately 20 to 70%. In situ feeding was more sensitive in the sediment than in the macrophyte assay, where it was inhibited significantly only at the two highest Decis doses (up to approximately 60%). Larval performance was not influenced significantly by any of the other potential stress factors.
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