Individual sensitivity distribution evaluation from survival data using a mechanistic model: implications for ecotoxicological risk assessment

Two main alternatives are typically used to model mechanistically dose-survival relationship in ecotoxicity tests. Effects are related to a concentration of concern, for instance body concentration, and, to account for their differences relative to time-to-death, individuals have either different concentration thresholds for death (“individual tolerance approach”), or equal probability to die, with death occurring randomly (“stochastic death approach”). A general framework to unify both approaches has recently been proposed. We derived a model from this framework to analyse five datasets (daphnids exposed to selenium, guppies exposed to dieldrin and second, third and fourth instars chironomids exposed to copper), by extending the standard stochastic death approach. We showed the possibility to estimate properly the toxicity parameters together with inter-organisms differences of sensitivity for at least one of these parameters (here the threshold for effect). For the daphnids, there was no improvement of using the extended model, which confirms the expected low variability among genetically identical individuals. For all the other datasets, our model outperformed the standard approach without accounting for differences of sensitivity. We estimated coefficients of variations in the distribution of the logarithm of the threshold from 44% to 4% and showed, for chironomids, a decrease of inter-individual differences of sensitivity with the age of the larvae. All standard threshold estimates were close but above the medium value of the distribution in the new approach, which means that a concentration equal to the standard threshold would ultimately result in the death of more than half of the exposed organisms. A more relevant parameter, such as the concentration protecting 95% of the population, would be 2-4 times inferior to the standard threshold.     

Does anthracene affect microbial activities and organic matter decomposition? A comparative study in Pinus halepensis litters from Mediterranean coastal and inland areas

The widespread concern about pollution caused by Polycyclic Aromatic Hydrocarbons (PAHs) raises the question of how they affect soil microbial communities which are potentially involved in the transformation of these pollutants. Using microcosms, we describe the effect of anthracene, a model PAH, on microbial communities inhabiting a Pinus halepensis litter from both coastal (COS) and inland (INL) Mediterranean sites. The microcosms were incubated over 3 months (25 °C, 60% WHC) and the effects of anthracene on microbial activities of both litters were monitored. Different enzyme activities (laccase, cellulase, β-glucosidase and acid phosphatase) and microbial respiration were measured and variations in litter chemical composition over incubation were determined using ¹³C Nuclear Magnetic Resonance (NMR) from both sites. Our results show that lignocellulolytic enzymes increased markedly after a 3-month incubation in COS microcosms, especially in the presence of anthracene, whereas INL microcosms were not similarly affected. These results show that anthracene not only has no toxic effect on the microbial activities tested but actually enhances the lignocellulolytic activities of the fungal communities from coastal litters, demonstrating the detoxification potential and resistance of stressed Mediterranean coastal ecosystems.     

Fifty Shades of Green? Political differences between elites,members and supporters of Europe Ecologie Les Verts

In recent years, many political parties have created new forms of affiliation and have justified the blurring of membership boundaries with claims that sympathisers would be more representative of the electorate and less radical. Such claims are based on ‘popular wisdom’ inspired by John May’s ‘special law of curvilinearity’, which states that activists hold more extreme views than voters and elites. When this expectation has been tested, results have been at best inconclusive; but testing has so far never used a single survey to compare different groups. Using an online survey of Europe Ecologie Les Verts party members and their extended networks (affiliated supporters, lapsed members, sympathisers), relationships between ideological differences and degree of investment in party activities and decision-making are analysed. The results, contradicting May’s special law along all ideological dimensions other than intra-party democracy, can be explained if May’s narrowly instrumental assumptions about preference formation are rejected.     

Seasonal variation and diversity of rotifers in Ehoma lake, Nigeria

The zooplankton and physicochemistry of Ehoma lake were studied from March 2005 to August 2006 in order to evaluate seasonal trend in species composition and abundance in relation to water quality. Forty two (42) species of rotifers dominated by Keratella tropica tropica were encountered. Species richness declined by nearly 50% from dry season values during the rainy season. Species richness was higher in the littoral zone during the dry season, the reverse was the case during the rainy season. Species abundance followed similar trend as species richness. Abundance was closely associated with dissolved oxygen, biological oxygen demand and width of the lake and these in turn varied significantly between seasons. Shannon-Weaver diversity varied from 2.2 to 3.8 bit ind(-1) and significantly between seasons (p<0.05). Anuraeopsis navicula navicula and Euchlanis dilatata dilatata Ehrenbreg were the only species gained during the flood periods.     

Trajectory variability: Road geometry difficulty indicator

The analysis of the variability of vehicle trajectories can reveal important information about how situational constraints influence drivers’ behaviour (e.g., lateral position and/or speed). Variability in the lateral position using a driving simulator was examined. Forty-two participants had to drive on two road environments: a 3 km straight road with a crest vertical curve (CVC) with perceptual treatments and narrowed lane width with subsequent provision of a hard shoulder, by relocation of the road markings. The results showed that, on the one hand the lateral position variability was greater when driving on the test CVC, before meeting oncoming vehicle and on the narrowed lane width; and on the other hand it was limited according to the perceptual treatment used. The lateral position variability would be a difficulty indicator of road geometry which would inform road managers of the presence of a risk zone on their road network.     

International standardized procedures for in vivo evaluation of multi-walled carbon nanotube toxicity in water

The classical approach in ecotoxicological evaluation of chemical substances consists of conducting standardized bioassays on organism models. In this work, the potential impact of industrial multi-walled carbon nanotubes was investigated by ecotoxicological standardized procedures using aquatic organisms of different trophic levels, namely bacteria, green algae, invertebrates, fish, and amphibians. The results indicated (1) inhibition of growth in amphibians at 50 mg L^?1 and higher, and (2) no effects on daphnia and fish up to 100 mg L^?1. With the exception of algae (for which Fe deficiency is measured), it seems that the observed toxicity may be due to physiological effects in relation to the ingestion of carbon nanotubes not necessarily related to their intrinsic effects.     

Development and evaluation of a Macroinvertebrate Biotic Integrity Index (MBII) for regionally assessing Mid-Atlantic Highlands Streams

The Macroinvertebrate Biotic Integrity Index (MBII) was developed from data collected at 574 wadeable stream reaches in the Mid-Atlantic Highlands region (MAHR) by the U.S. Environmental Protection Agency's (USEPA) Environmental Monitoring and Assessment Program (EMAP). Over 100 candidate metrics were evaluated for range, precision, responsiveness to various disturbances, relationship to catchment area, and redundancy. Seven metrics were selected, representing taxa richness (Ephemeroptera richness, Plecoptera richness, Trichoptera richness), assemblage composition (percent non-insect individuals, percent 5 dominant taxa), pollution tolerance [Macroinvertebrate Tolerance Index (MTI)], and one functional feeding group (collector-filterer richness). We scored metrics and summed them, then ranked the resulting index through use of independently evaluated reference stream reaches. Although sites were classified into lowland and upland ecoregional groups, we did not need to develop separate scoring criteria for each ecoregional group. We were able to use the same metrics for pool and riffle composite samples, but we had to score them differently. Using the EMAP probability design, we inferred the results, with known confidence bounds, to the 167,797 kilometers of wadeable streams in the Mid-Atlantic Highlands. We classified 17% of the target stream length in the MAHR as good, 57% as fair, and 26% as poor. Pool-dominated reaches were relatively rare in the MAHR, and the usefulness of the MBII was more difficult to assess in these reaches. The process used for developing the MBII is widely applicable and resulted in an index effective in evaluating region-wide conditions and distinguishing good and impaired reaches among both upland and lowland streams dominated by riffle habitat.     

Scent of a nest: discrimination of own-nest odours in Antarctic prions,<Emphasis Type="Italic"> Pachyptila desolata</Emphasis>

Petrels and albatrosses evolved well-developed olfactory anatomical structures comparable to those of mammals. To date it has been demonstrated that petrels are attracted by food-related odours, and that some hypogean species have decreased homing performances if anosmic. The ability to distinguish between familiar and unfamiliar odours had not been demonstrated. Here we show that the Antarctic prion, Pachyptila desolata, is able to distinguish between its own nest and that of a conspecific, relying on olfactory cues only. When tested in a maze, only prions with an intact sense of smell made a choice and recognized their own burrow whereas anosmic birds did not. In the absence of leading odours in the maze prions behaved similarly to anosmic birds. These results suggest the mechanism used in the short-range homing process of this species as an olfactory beaconing and suggest the skill of recognising individually distinctive odours. Evolving an efficient identification system in the dark allowed these hypogean petrels to return to their colony at night and recognise their own burrow without singing. This behaviour protects them from predation by skuas, Catharacta skua lönnbergi, that hunt petrels by vision and hearing.     

Atmospheric pollution in an urban environment by tree bark biomonitoring - part II: Sr, Nd and Pb isotopic tracing

The harmful effect of manmade particles on natural processes and human health is documented by a large number of studies showing a positive correlation between particulate matter (PM) concentration and health effects. Diminution of this health risk necessitates among others the precise knowledge of the particle sources, their physical and chemical properties and their dissemination in the environment. Pb isotope ratios have been successfully used during the past decades as tracers of anthropogenic Pb disseminated in the biosphere. Here we show that tree bark biomonitoring with lead (Pb), strontium (Sr) and neodymium (Nd) isotope ratios as tracers allow a thorough analysis of the impacts of industrial and other anthropogenic emissions on the urban environment. This is the first comprehensive multi-isotope tracer study of atmospheric pollution in an urban environment allowing to identify and to integrate the different plume paths of emissions in a digital map system. This innovative approach might become an important tool for environmental management and policy-making processes dealing especially with risks and surveillance of air quality in the urban environment.     

Use patterns of natural resources supporting livelihoods of smallholder communities and implications for climate change adaptation in Zimbabwe

Declining crop and livestock production due to a degrading land resource base and changing climate among other biophysical and socio-economic constraints, is increasingly forcing rural households in Zimbabwe and other parts of Southern Africa to rely on common natural resource pools (CNRPs) to supplement their household food and income. Between 2011 and 2013, we combined farmer participatory research approaches, remote sensing and geographic information systems (GIS) to (1) understand the contribution of CNRPs to household food and income in Dendenyore and Ushe smallholder communities in Hwedza District, eastern Zimbabwe and (2) assess changes of the CNRPs in both space and time, and their implications on climate change adaptation. Across study sites, wetlands and woodlands were ranked as the most important CNRPs. Extraction and use patterns of products from the different pools differed among households of different resource endowment. Resource-constrained households (RG3) sold an average of 183 kg household^?1 year^?1 of wild loquats fruits (Uapaca kirkiana), realising about US$48, while resource-endowed farmers (RG1) had no need to sale any. The RG3 households also realised approximately US$70 household^?1 year^?1 from sale of crafts made from water reeds (Phragmites mauritianus). Empirical data closely supported communities’ perceptions that CNRPs had declined significantly in recent years compared with two to three decades ago. More than 60 % of the respondents perceived that the availability of natural resources drawn from wetlands and woodlands, often used for food, energy and crafts, has decreased markedly since the 1980s. Classification of land cover in a GIS environment indicated that CNRPs declined between 1972 and 2011, supporting farmers’ perceptions. Overall, woodlands declined by 37 % in both communities, while the total area under wetlands decreased by 29 % in Ushe, a drier area and 49 % in Dendenyore, a relatively humid area. The over-reliance in CNRPs by rural communities could be attributed to continued decline in crop yields linked to increased within-season rainfall variability, and the absence of alternative food and income sources. This suggests limited options for rural communities to adapt to the changing food production systems in the wake of climate change and variability and other challenges such as declining soil fertility. There is therefore a need to design adaptive farm management options that enhance both crop and livestock production in a changing climate as well as identifying other livelihood alternatives outside agriculture to reduce pressure on CNRPs. In addition, promotion of alternative sources of energy such as solar power and biogas among rural communities could reduce the cutting of trees for firewood from woodlands.