Behavioural and Physiological Responses of Gammarus pulex Exposed to Cadmium and Arsenate at Three Temperatures: Individual and Combined Effects

This study aimed at investigating both the individual and combined effects of cadmium (Cd) and arsenate (AsV) on the physiology and behaviour of the Crustacean Gammarus pulex at three temperatures (5, 10 and15°C). G. pulex was exposed during 96 h to (i) two [Cd] alone, (ii) two [AsV] alone, and (iii) four combinations of [Cd] and [AsV] to obtain a complete factorial plane. After exposure, survival, [AsV] or [Cd] in body tissues, behavioural (ventilatory and locomotor activities) and physiological responses (iono-regulation of [Na+] and [Cl−] in haemolymph) were examined. The interactive effects (antagonistic, additive or synergistic) of binary mixtures were evaluated for each tested temperature using a predictive model for the theoretically expected interactive effect of chemicals. In single metal exposure, both the internal metal concentration in body tissues and the mortality rate increased along metallic gradient concentration. Cd alone significantly impaired both [Na+] and [Cl−] while AsV alone had a weak impact only on [Cl−]. The behavioural responses of G. pulex declined with increasing metal concentration suggesting a reallocation of energy from behavioural responses to maintenance functions. The interaction between AsV and Cd was considered as ‘additive’ for all the tested binary mixtures and temperatures (except for the lowest combination at 10°C considered as “antagonistic”). In binary mixtures, the decrease in both ventilatory and locomotor activities and the decline in haemolymphatic [Cl−] were amplified when respectively compared to those observed with the same concentrations of AsV or Cd alone. However, the presence of AsV decreased the haemolymphatic [Na+] loss when G. pulex was exposed to the lowest Cd concentration. Finally, the observed physiological and behavioural effects (except ventilation) in G. pulex exposed to AsV and/or Cd were exacerbated under the highest temperature. The discussion encompasses both the toxicity mechanisms of these metals and their interaction with rising temperature

Improving ecological impact assessment by statistical data synthesis using process-based models

Population dynamic modelling often entails parameterizing quite sophisticated biological and ecological mechanisms. For models of moderate mechanistic complexity, this has traditionally been done in an "ad hoc" manner, with different parameters being estimated independently. The point estimates so obtained are then used for model simulation, perhaps with some further "ad hoc" adjustment based on comparison with any available data on population dynamics. Quantitative assessments of model adequacy and prediction uncertainty are not easily made using this approach. As an alternative, the paper investigates the practical feasibility of fitting a moderately complex population dynamic model directly and simultaneously to all the data available for parameterization of the model, and to all available data on the population dynamics of the target animal. This alternative approach allows us to combine all available quantitative information on the target species, to assess the viability of the model, the mutual consistency of model and different sources of data and to estimate the uncertainties that are associated with model-based predictions. The target organism in this study is the freshwater amphipod "Gammarus pulex" ("L."), which we model using a stage-structured population dynamic model, implemented via a set of delay differential equations describing the basic demography of the population. Target data include population dynamic data from two sites, information on basic physiological relationships and environmental temperature data. Fitting is performed by using a non-linear least squares approach supplemented with a bootstrapping method for avoiding small scale local minima in the least squares objective function. Variance estimation is performed by further bootstrapping. Interest in "Gammarus pulex" population dynamics in this case is primarily related to likely population level responses to chemical stressors, and for this we examine predicted 'recovery times' following exposure to a known toxicant. Copyright 2006 Royal Statistical Society.

A comparison of the short-term toxicity of cadmium to indigenous and alien gammarid species

Amphipods play an important role in many aquatic ecosystems and are commonly used in ecotoxicology and ecosystem health assessment. Several alien gammarids have been introduced in many regions of the world during the last decades. In this study, we investigated if differences in cadmium sensitivity occurred between (1) different species belonging to the family Gammaridae and (2) different populations of the same species originating from a polluted or a non-polluted site. The acute cadmium toxicity to two indigenous (Gammarus pulex and Gammarus fossarum) and four alien (Dikerogammarus villosus, Echinogammarus berilloni, Gammarus roeseli and Gammarus tigrinus) gammarids occurring in Belgium was tested. Significant differences (P < 0.05) in median lethal concentrations (LC50) were found between the different species, with 72 h-LC50s ranging from 6.3 to 268 μg/l and 96 h-LC50s from 4.7 to 88.9 μg/l. No clear trend in Cd sensitivity was found when comparing indigenous and alien gammarids. D. villosus, an alien invasive species, was the most sensitive to Cd toxicity and E. berilloni, another alien species, the least sensitive. In addition, larger Gammarid species were more sensitive to Cd toxicity than smaller ones. No significant differences were found between populations of the same species originating from metal polluted sites or non-polluted sites. Overall, our results showed that considerable differences in Cd sensitivity exist between gammarid species, which should be taken into consideration in environmental risk assessment and water quality standard setting. Finally, our data suggest that alien gammarids would not have an advantage over indigenous gammarids in Cd contaminated environments

Pressurised metered dose inhaler-spacer technique in young children improves with video instruction

© 2016, Springer-Verlag Berlin Heidelberg. The importance of good device technique to maximise delivery of aerosolised medications is widely recognised. Pressurised metered dose inhaler (pMDI)-spacer technique was investigated in 122 children, aged 2–7 years, w ith asthma. Eight individual steps of device technique were evaluated before and after viewing an instructional video for correct device technique. Video measurements were repeated every three months for nine months. Device technique improved directly after video instruction at the baseline study visit (p &lt; 0.001) but had no immediate effect at subsequent visits. Additionally, pMDI-spacer technique improved with successive visits over one year for the group overall as evidenced by increases in the proportion of children scoring maximal (p = 0.02) and near-maximal (p = 0.04) scores. Conclusion: Repeated video instruction over time improves inhaler technique in young children.What is Known:• Correct device technique is considered essential for sufficient delivery of inhaled medication.• Poor inhaler use is common in young asthmatic children using pressurised metered dose inhalers and spacers.What is New:• Video instruction could be used as a strategy to improve device technique in young children