RESUMO
Wetlands play a crucial role in providing valuable ecosystem services, including the removal of various pollutants. In agricultural basins, wetlands are exposed to agrochemical loads. This study aims to assess the attenuation effect of the ubiquitous macrophyte Azolla spp. on the toxicity of lambda-cyhalothrin to sensitive aquatic organisms. An indoor mesocosm experiment was conducted to compare the concentration of lambda-cyhalothrin at different time points after pesticide application in vegetated and unvegetated treatments, including a control without pesticide addition. Toxicity tests were performed throughout the experiment on three organisms: a fish (Cnesterodon decemmaculatus), a macroinvertebrate (Hyalella curvispina), and an amphibian (Boana pulchella). The results demonstrated that lambda-cyhalothrin concentration and toxicity in water were significantly lower in the Azolla spp. treatment. Furthermore, the half-life of lambda-cyhalothrin decreased from 1.2 days in the unvegetated treatment to 0.4 days in the vegetated treatment. The vegetated treatment also resulted in a significantly lower mortality rate for both H. curvispina and C. decemmaculatus. However, no mortality was observed in B. pulchella for any of the treatments. Sublethal effects were observed in this organism, such as lateral bending of the tail and impairment of the ability to swim, which were attenuated in the vegetated treatment. We conclude that Azolla spp. can effectively reduce the concentration and toxicity of lambda-cyhalothrin, suggesting its potential use in farm-scale best management practices to mitigate the effects of pesticide loads from adjacent crops.
Assuntos
Organismos Aquáticos , Nitrilas , Piretrinas , Poluentes Químicos da Água , Piretrinas/toxicidade , Nitrilas/toxicidade , Animais , Poluentes Químicos da Água/toxicidade , Organismos Aquáticos/efeitos dos fármacos , Áreas Alagadas , Inseticidas/toxicidade , Peixes/fisiologia , Anfípodes/efeitos dos fármacos , Anfípodes/fisiologiaRESUMO
In recent decades agriculture has intensified in the Argentine Pampa, and pesticide application has also increased. Livestock fields, although being progressively replaced by crops, are still commonly interspersed with crop fields. The objective of the present work is to assess the effects of land use on the benthic invertebrate assemblages of streams in the main Argentine agricultural region. Two areas were sampled during the 2011/12 growing season (November-March): Arrecifes, a homogeneous intensively cultivated area, and La Plata, a heterogeneous area of mixed livestock pasture, cropland and biological reserve. Nutrient concentrations in water were significantly higher in the streams surrounded by cropland. Measured pesticides in stream sediments were those most commonly used in crop production: chlorpyrifos, cypermethrin, lambda-cyhalothrin, endosulfan and its degradation product endosulfan sulfate. Detection frequency and pesticide concentrations were generally higher in streams surrounded by cropland than in streams surrounded by pasture or reserve. Macroinvertebrate assemblages were significantly different in streams with different land uses. Palaemonidae (Decapoda) and Caenidae (Ephemeroptera) were the taxa best represented in the reserve. Hyalellidae (Amphipoda) and Hirudinea were dominant at the streams surrounded by livestock fields. Within the streams surrounded by croplands, Oligochaeta and Hirudinea were best represented in La Plata while Chironomidae, Gastropoda and Oligochaeta were dominant at Arrecifes. Present evidence suggests that agrochemical applications contribute, in combination with other environmental variables, to the observed differences in macroinvertebrate assemblages in streams of different land use.
Assuntos
Monitoramento Ambiental , Praguicidas , Agricultura , Animais , Argentina , Ecossistema , Invertebrados , Praguicidas/análiseRESUMO
The present study reported the effect of natural and anthropic environmental variables on the fish assemblages in the pampean streams, in the coastal strip along the Río de la Plata, Buenos Aires province, Argentina. Five streams were sampled at 12 sites surrounded by land devoted to different uses. A correspondence analysis sorted the streams into two groups: a less impacted group formed by sites surrounded by livestock- raising pastures and a more impacted one passing through urban sites and including a stream adjacent to a modest rural urbanization with a dairy in the stream's basin. The nutrient concentrations were significantly higher in the more impacted group; with species richness, diversity, abundance, and biomass being significantly lower. A canonical-correspondence analysis linked the more impacted sites to high concentrations of soluble reactive phosphorus and impoverished fish assemblages, composed of species tolerant to environmental pollution. On the other hand, sites with higher oxygen concentrations and pH were related to richer assemblages pointing to good environmental conditions at the sites surrounded by livestock-raising pastures. The downstream sites on the less impacted streams contained fish assemblages in which the juvenile stages of species corresponding to the Río de la Plata were dominant.
Assuntos
Biodiversidade , Monitoramento Ambiental , Peixes/classificação , Animais , Argentina , Armazenamento de Alimentos , RiosRESUMO
Pyrethroids are among the most widely applied insecticides worldwide and cypermethrin is the pyrethroid most used in Argentina. Pesticides used in crops can reach adjacent watercourses through runoff and may lead to non-target fauna receiving toxic pulse exposures. The aim of this study was to determine the effects of cypermethrin pulse exposures on the widely distributed crustacean Simocephalus vetulus. The 48h-LC50 of cypermethrin for S. vetulus was determined at 0.18 ± 0.09 µg/L. To assess the effects of cypermethrin under environmentally realistic exposures, two experiments were performed. In the first one, specimens were exposed for 90 min to cypermethrin at 0.02 (T1), 0.2 (T2) and 1 µg/L (T3), transferred to clean water and monitored for 24 h as regards survival and feeding rates; specimens exposed to T2 and T3 concentrations showed significant lower feeding rates than those in the control group. In the second experiment, specimens were exposed for 90 min every 7 days and monitored over 25 days; S. vetulus showed lower cumulative fecundity and reproduction rates at all concentrations tested, and lower population growth at the highest concentration. All exposure concentrations lay within reported environmental concentrations and risk assessment indicated risk (RQ > 1), suggesting that sensitive species would be affected by such pulse exposures of cypermethrin. The present study thus suggests that ongoing agricultural practices affect the non-target invertebrates in streams adjacent to crops.
Assuntos
Cladocera/efeitos dos fármacos , Inseticidas/toxicidade , Piretrinas/toxicidade , Poluentes Químicos da Água/toxicidade , Animais , Argentina , RiosRESUMO
Agriculture intensification in Argentina has increased agrochemicals consumption in the last decades and might represent an environmental risk for adjacent water bodies. The objective of the present work was to assess the effect of land use on water quality and invertebrate assemblages in the Argentine Pampas streams. Eight streams were sampled on 4 occasions during the 2013/14 growing season. Three streams are located within a biosphere reserve, two drain basins with extensive livestock fields, and three run through intensively cultivated plots; one of them contained a 30m wide uncultivated grass-covered strip between the crop and the stream. Macroinvertebrates were sampled from emergent vegetation by means of a D-net with a 500µm pore size, and 30cm diameter. Higher nutrient concentrations were measured in the agricultural streams. Endosulfan was measured in sediments of the agricultural streams, concentrations being significantly lower in the stream with the buffer strip. Invertebrate assemblages in the cropped streams were significantly different from those in the livestock and reserve streams, those in the latter not being different from each other. Ampullaridae (Pomacea canaliculata) and Planorbidae (Biomophalaria peregrina) were the taxa best represented in the agricultural streams. Hyalellidae (Hyalella curvispina), Zygoptera and Planorbidae (B. peregrina) were the taxa best represented in the reserve and livestock streams. Present evidence suggests that the observed differences in the invertebrate composition in the agricultural streams were related with the impact of agrochemicals and that buffer strips represent a useful attenuation practice. Cattle breeding on natural pastures represented a land use with low impact on the invertebrate assemblages.
Assuntos
Monitoramento Ambiental/métodos , Inseticidas/toxicidade , Invertebrados/efeitos dos fármacos , Rios/química , Poluentes Químicos da Água/toxicidade , Agricultura , Animais , Argentina , Ecossistema , Gado , Estações do Ano , Qualidade da ÁguaRESUMO
Agriculture and livestock may contribute to water quality degradation in adjacent waterbodies and produce changes in the resident invertebrate composition. The objective of the present study was to assess land use effects on the stream invertebrate assemblages in rural areas of the Argentine Pampa. The four sampling events were performed at six sites in four streams of the Pampa plain; two streams were sampled inside a biosphere reserve, and another one was surrounded by extensive livestock fields. The fourth stream was sampled at three sites; the upstream site was adjacent to agricultural plots, the following site was adjacent to an intensive livestock plot and the downstream site was adjacent to extensive breeding cattle plots. Higher pesticide concentrations were found at the site adjacent to agricultural plots and higher nutrient concentrations at the sites adjacent to agricultural and intensive breeding cattle plots. The invertebrate fauna were also different at these sites. Multivariate analysis showed a relationship between nutrient concentrations and taxonomic composition. Amphipoda (Hyalella curvispina) was the dominant group in the reserve and extensive breeding cattle sites, but was not present in the agricultural site. Also, Chironomidae were absent from the agricultural site while present at other sites. Gasteropoda (Biomphalaria peregrina), Zygoptera, and Hirudinea were dominant at the most impacted agricultural and intensive breeding cattle sites.
Assuntos
Agricultura , Organismos Aquáticos , Invertebrados , Rios , Qualidade da Água , Anfípodes , Animais , Argentina , Bovinos , Monitoramento Ambiental , Gado , Praguicidas/análiseRESUMO
Toxicity persistence to the nontarget amphipod Hyalella curvispina in runoff events following chlorpyrifos applications to soy experimental plots was compared in conventional and no-till management. Two application scenarios were compared: an early-season application with the soil almost bare and a late-season application after the foliage had attained complete soil cover. H. curvispina was exposed to chlorpyrifos using two different test systems: a short-term (48 h) runoff water exposure and a long-term (10 days) soil exposure. Both commonly used crop management practices for soybean production resulted in runoff toxicity following pesticide applications and represent a toxicity risk for adjacent inland waters. Toxicity persistence was longer after the earlier than the late season application, likely because of higher volatilization and photodecomposition losses from the soy canopy than from the soil. For the early-season application, toxicity persisted longer in the no-till plots than in the conventional tillage plots. Suspended matter was higher in the conventional treatment. Chlorpyrifos sorption to suspended matter likely contributed to the shorter persistence. For the late-season application, toxicity persisted longer in the conventional treatment. The causes remain conjectural. The soil organic carbon content was higher in the no-till treatment. Sorption to organic matter might have contributed to the shorter chlorpyrifos toxicity persistence in no-till management. Late applications are more frequent and prevail longer throughout the soy growing season. Overall, the no-till management practice seems preferably because shorter toxicity persistence in runoff represents a lower environmental risk for the adjacent inland waters.
Assuntos
Agricultura/métodos , Clorpirifos/toxicidade , Monitoramento Ambiental , Poluentes Químicos da Água/toxicidade , Anfípodes , Animais , Clorpirifos/análise , Inseticidas/toxicidade , Glycine max , Poluentes Químicos da Água/análiseRESUMO
Chlorpyrifos is the most used insecticide in Argentina. Cnesterodon decemmaculatus is a widely distributed, endemic fish from Neotropical America. It attains high densities in the shallow water assemblages of Argentina and Brazil. The aim of this study was to assess the acute toxicity of chlorpyrifos to C. decemmaculatus. The mean 96-h LC50 of three independent determinations was 105.3 (± 3.1) µg/L. Sublethal effects were observed. Swimming behavioral changes at each chlorpyrifos exposure concentration were reported. C. decemmaculatus represents a good model for ecotoxicological risk assessment.
Assuntos
Clorpirifos/toxicidade , Ciprinodontiformes/metabolismo , Inseticidas/toxicidade , Poluentes Químicos da Água/toxicidade , Animais , Relação Dose-Resposta a Droga , Feminino , Dose Letal Mediana , Masculino , NataçãoRESUMO
The objective of this study was to assess the effect of land use on nutrient concentrations in a Pampasic stream. Soluble reactive phosphorus (SRP) concentrations in the stream were higher at a site surrounded by fertilized double-cropped wheat/soybeans than at unfertilized soybeans plots. Nitrate and SRP concentrations in the stream were lower at sites surrounded by soybeans than livestock. It is suggested that crop fertilization and cattle manure increased nutrients loads released to the stream. It is suggested that preservation and restoration of riparian habitats may benefit water quality by decreasing nutrient loads.
Assuntos
Monitoramento Ambiental , Nitrogênio/análise , Fósforo/análise , Rios/química , Poluentes Químicos da Água/análise , Agricultura , ArgentinaRESUMO
The acute toxicity of cypermethrin to the amphipod Hyalella curvispina was evaluated by means of a toxicity test under laboratory conditions. Cypermethrin is one of the most widely used insecticides in Argentina. H. curvispina is a widely distributed and commonly abundant component of the invertebrate assemblages in shallow waters of southern South America. The experiments were repeated three times. The mean 48-h LC(50) value for H. curvispina was estimated at 0.066µg/l. H. curvispina represents a good model for exotoxicological risk assessment.