chlorophyll-a and carbendazim

Water quality monitoring is used to determine the impact of human activities on the environment. We evaluated water quality in the Água Boa stream, located within the municipality of Dourados, State of Mato Grosso do Sul, Brazil, by analyzing physico-chemical, chemical, and microbiological parameters, as well as chlorophyll concentrations. Five sets of water samples were collected between December 2012 and November 2013 from three locations within the stream. The results showed the presence of Escherichia coli and antibiotic-resistant Pseudomonas spp. strains and high concentrations of organic matter (total dissolved solids), inorganic species (Mg, Ca, and Fe), and agrochemical residues (thiamethoxam). The main stream water contaminants are derived from urban, industrial, and agricultural activities within the watershed. Given the presence of contaminants, it is important that such findings are disseminated in order to highlight the risks that contact with this water may pose to human health. To preserve the environment and improve site conditions, people would need to participate by demanding that normative national and international standards be respected and that the situation be supervised by the competent governmental agencies; this would make it possible to reverse or minimize contamination problems within the Água Boa stream.

Topics: Agriculture; Benzimidazoles; Brazil; Carbamates; Chlorophyll; Chlorophyll A; Drug Resistance, Bacterial; Environmental Monitoring; Escherichia coli; Humans; Industrial Waste; Industry; Metals; Neonicotinoids; Nitro Compounds; Oxazines; Pseudomonas; Rivers; Thiamethoxam; Thiazoles; Water Microbiology; Water Pollutants, Chemical; Water Pollution; Water Quality

Direct and indirect effects of the fungicide carbendazim on ecosystem structure and functioning were studied < or =8 weeks after application (nominal concentrations: 0, 3.3, 33, 100, and 1000 microg/L) to outdoor microcosms in Thailand. Direct effects on macroinvertebrates are discussed in detail in a separate article. The present article presents the effects on other end points and discusses the hypothesized ecologic effect chain. Negative treatment effects on the zooplankton community were only recorded for the highest carbendazim treatment (NOEC(community) = 100 microg/L). The rotifer Keratella tropica, cladocerans (Moina micrura, Ceriodaphnia cornuta, and Diaphanosoma sp.), and cyclopoid copepods were decreased or even eliminated at this treatment level. The decrease in zooplankton and macroinvertebrate abundances was accompanied by an increase in numbers of several tolerant invertebrates, presumably caused by a release from competition and predation. The death of sensitive invertebrates probably also led to an overall decreased grazing pressure because increased levels of chlorophyll-a and bloom of the floating macrophyte Wolffia sp. were noted. The increase in primary producers is discussed to be the probable cause of changes in physicochemical water conditions, eventually resulting in an anoxic water layer during the last 3 weeks of the experiment. This is likely to have resulted in decreased invertebrate abundances noted in that period. Furthermore, the decreased decomposition of Musa (banana) leaves observed 8 weeks after application is considered to be the indirect effect of a decreased microbial activity resulting from these anoxic water conditions, rather than a direct toxic effect of carbendazim.

Topics: Animals; Benzimidazoles; Carbamates; Chlorophyll; Chlorophyll A; Copepoda; Ecosystem; Environmental Monitoring; Fresh Water; Fungicides, Industrial; Invertebrates; Longevity; Phytoplankton; Rotifera; Thailand; Tropical Climate; Water Pollutants, Chemical

To validate the use of small indoor microcosms for the risk assessment of pesticides, the fate and effects of chlorpyrifos, carbendazim, and linuron were studied in 8.5-liter indoor freshwater microcosms. Functional and structural responses to selected concentrations were evaluated and compared with responses observed in larger-scale model ecosystem studies. Overall, the microcosms adequately displayed the chain of effects resulting from the application, although they did not always predict the exact fate and responses that were observed in larger semifield studies. Because closed systems were used that did not contain sediment and macrophytes, pesticides were relatively persistent in the present study. Consequently, calculated toxicity values were generally more comparable with those reported in studies with long- than with short-term exposure. Carbendazim had a higher overall no-observed-effect concentration (NOEC) compared with experiments performed in larger systems because macroinvertebrate taxa, the most sensitive species group to this fungicide, were not abundant or diverse. Future refinements to the test system could include the addition of a sediment compartment and sensitive macroinvertebrate taxa. However, the simple design offers the potential to perform experiments under more controlled conditions than larger and, consequently, more complex model ecosystems, while maintaining relatively high ecologic realism compared with standard laboratory tests. Further implications for risk-assessment studies are discussed in an ecotoxicologic and methodologic context.

Topics: Animals; Benzimidazoles; Carbamates; Chlorophyll; Chlorophyll A; Chlorpyrifos; Ecology; Ecosystem; Fresh Water; Hydrogen-Ion Concentration; Invertebrates; Linuron; Nitrates; No-Observed-Adverse-Effect Level; Oxygen; Pesticides; Phosphates; Population Density; Quaternary Ammonium Compounds; Risk Assessment; Water Pollutants, Chemical

To understand the phytotoxic effects that certain bezimidazole fungicides exert on plant growth, the aim of the present study was to determine the effect of the fungicide carbendazim, on foliar biomass, pigment content, and nutrient levels in tobacco plants (Nicotiana tabacum L. cv. Tennessee 86). The fungicide applied was carbendazim with a purity of 100%, at three different rates: 1.3 mM (carb1), 2.6 mM (the recommended concentration, carb2), and 5.2 mM (carb3). The control treatment was without carbendazim. The application of dosages of this fungicide lower than recommended (1.3 mM) resulted, on the one hand, in greater dry weight and, on the other, higher carotenoid concentrations, as well as higher N and K concentrations with respect to control. On the contrary, the application of the carbendazim dosage higher than recommended (5.2 mM) caused a decrease in dry weight and in all of the foliar pigments, as well as all of the nutrients, with respect to the other dosages and control. These results appear to indicate that besides its direct antibiotic action against pathogens, the effects of this fungicide in plants could be dangerous, especially at higher dosages. Nevertheless, the negative effects of carbendazim can be avoided by reducing the amount applied in current agriculture.

Topics: Benzimidazoles; Biomass; Carbamates; Carotenoids; Chlorophyll; Dose-Response Relationship, Drug; Fungicides, Industrial; Nicotiana; Nitrogen; Plant Leaves; Potassium