Low field-relevant tebufenozide concentrations affect reproduction in Chironomus riparius (Diptera: Chironomidae) in a long-term toxicity test

A few studies reporting the effects of tebufenozide, a non-steroidal ecdysone agonist that mimics natural moulting hormones in chironomids exist in the literature. However, nothing is known about its chronic or multigenerational effects on the reproduction of aquatic insects, although tebufenozide is present in aquatic ecosystems. Here, we investigated the chronic toxicity of tebufenozide in two successive generations of Chironomus riparius using nominal concentrations that ranged from 4 to 26.2 μg/L. We started the test from the first instar larvae in the parental (P) generation, quantifying life cycle parameters (emergence, sex ratio, development rate, fecundity and fertility) until the emergence in the subsequent F1 generation. Results showed a reduction in reproduction and a significant decrease in male developmental rate of midges for all treatments, in the F1 generation compared with the P generation (paired t?test; p?<?0.001). Two-way analysis of variance revealed a significant exposure?×?generation effect on male fraction with male fraction increasing (P generation) or decreasing (F1 generation) with increasing exposure. These effects on C. riparius underline the importance of conducting long-term studies with environmentally relevant concentrations to investigate population-level endpoints for endocrine disrupting chemicals.     

More European heritage awards

News and Comments

More European heritage awards     

Grazing,forest density,and carbon storage: towards a more sustainable land use in Caatinga dry forests of Brazil

Grazing is the main land use in semi-arid regions of the world, and sustainable management practices are urgently needed to prevent their degradation. However, how different grazing intensities affect forest density and ecosystem functions is often not sufficiently understood to allow for management adaptations that safeguard the ecosystems and their functions in the long run. We assessed the aboveground carbon stocks and plant densities along a grazing gradient in the semi-arid seasonally dry tropical forest of north-eastern Brazil (Caatinga). On 45 study plots, we analysed the aboveground carbon stocks of the vegetation and determined forest density and recruitment as well as the population structure of the most abundant tree species. Grazing intensity was accounted for based on the weight of livestock droppings and classified as low, intermediate, or high. Mean aboveground carbon stock was 15.74?±?1.92 Mg ha^?1 with trees and shrubs accounting for 89% of the total amount. Grazing at high intensities significantly reduced aboveground carbon stocks of herbs but not of other plant functional types. Instead, aboveground carbon stocks of trees and shrubs were negatively related to altitude above sea level, which is a proxy for reduced water availability along with lower anthropogenic impact. The population structure of the most common tree species was characterised by abundant recruitment, irrespective of grazing, whereas the recruitment of less frequent woody species was negatively affected by grazing. Overall, our data imply that grazing and forage management need to be adapted, including the reduction of free-roaming livestock and storage of fodder, to maintain carbon storage and forest density.     

Probabilistic risk assessment of insecticide concentrations in agricultural surface waters: a critical appraisal

Due to the specific modes of action and application patterns of agricultural insecticides, the insecticide exposure of agricultural surface waters is characterized by infrequent and short-term insecticide concentration peaks of high ecotoxicological relevance with implications for both monitoring and risk assessment. Here, we apply several fixed-interval strategies and an event-based sampling strategy to two generalized and two realistic insecticide exposure patterns for typical agricultural streams derived from FOCUS exposure modeling using Monte Carlo simulations. Sampling based on regular intervals was found to be inadequate for the detection of transient insecticide concentrations, whereas event-triggered sampling successfully detected all exposure incidences at substantially lower analytical costs. Our study proves that probabilistic risk assessment (PRA) concepts in their present forms are not appropriate for a thorough evaluation of insecticide exposure. Despite claims that the PRA approach uses all available data to assess exposure and enhances risk assessment realism, we demonstrate that this concept is severely biased by the amount of insecticide concentrations below detection limits and therefore by the sampling designs. Moreover, actual insecticide exposure is of almost no relevance for PRA threshold level exceedance frequencies and consequential risk assessment outcomes. Therefore, we propose a concept that features a field-relevant ecological risk analysis of agricultural insecticide surface water exposure. Our study quantifies for the first time the environmental and economic consequences of inappropriate monitoring and risk assessment concepts used for the evaluation of short-term peak surface water pollutants such as insecticides.     

The Development of a Sampling System for Determining Odor Emission Rates from Areal Surfaces: Part I. Aerodynamic Performance

Abstract

An improved portable odor sampling system (OSS) of the wind tunnel type was designed to determine odor emissions from areal sources. The aerodynamics of the odor emission hood was observed using a number of smoke tests and dry ice tests. The velocity profiles were also measured horizontally and vertically in the hood by an anemometer. Modifications in the form of an extension inlet duct, flat vanes, and a baffle were necessary to achieve repeatable, uniform, and steady velocity profiles inside the hood. The optimum velocity for use of the OSS was found to be 0.33 m/s, based upon the aerodynamic performance of the OSS and the sensitivity of the anemometer at a lower velocity.