Long-term monitoring of benthic invertebrate communities in a highly invaded ecosystem, the Mosel River

International audienceExotic species, once established in the recipient ecosystem, can established and, in some cases, become invasive. However, long-term monitoring of invaded ecosystems remains quite rare, while it’s the unique method to describe and understand how local communities adapt -or not- to the continuous fluxes of new exotic invasive species, and how these exotic species manage to persist within these local communities. Some species’ proliferations can indeed be only transitory, with sometimes their disappearance, either naturally or through the interaction with a newcomer. The Mosel River, located in North-eastern France, is studied since 1994 with the same protocol to investigate benthic macroinvertebrates communities. It is one of the main corridors for aquatic invasions in France, with near to 20 exotic invertebrate species, mainly molluscans and crustaceans, established within its biocenosis. Benthic communities were investigated 13 times between 1994 and 2021, by dredge-sampling from a boat at four stations in spring and/or autumn. Our results evidenced strong modifications of community composition over years, while structure index showed a come-back of 2021 structure to that identified in 1996, that is however not a pre-invasion state. We also evidenced that the species richness did not increase with the increasing number of exotic species, suggesting that newcomers took the place of species already there, and did not colonize a vacant niche. The investigation of trophic groups showed communities strongly dominated by parasites and predators in 1994, filter-feeder and detritivore from 1996 to 2001, and a stabilization of the relative abundance of the different groups in recent years. Such observation strategies need to be developed in other systems for a better description of exotic species dynamic, especially now that global change is potentially accelerating migration of species

Evidence for a hornbeam woodland from charcoal kilns in Meuse lowlands (northeastern France): past management record or local anomaly?

International audienceAn anthracological study is being conducted in Meuse (northeastern France) to assess past forest resources exploitation to produce charcoal for local industries. The study area comprises 57 km 2 of mainly broadleaved-mixed forests in a lowland region with former royal (now state-owned), municipal and private forests. The analysis of airborne LiDAR images allowed to infer that there are around 2600 potential charcoal kilns in the area. The sampling campaigns yielded the validation of 285 platforms and 48 of them were sampled for charcoal remains in an area of 3.5km 2. Results from charcoal analysis provided the identification of 12 taxa being Carpinus betulus (hornbeam) the dominant taxon with over 66% of total diversity, followed by Fagus sylvatica (c. 12%) and Corylus avellana (c. 7%), Quercus sp. (3%) and the remaining taxa are residually represented.These results, especially the dominance of hornbeam relegating to a second plan the presence of Fagus and Quercus, appear to be in contradiction to the so far admitted forest trajectory in the area. Indeed, today lowland temperate forests in northeastern France are largely dominate by oak and beech woodlands. This was also the case in the past since, at least, the antiquity and, at least at regional scale.Several questions arise from this disparity between the dominance of oak and beech in the woodlands and their relative subrepresentation in the charcoal assemblage. Are they a consequence of a prioritization of understorey vegetation for charcoal production instead of oak and beech? or the display of former management practices (e.g. coppicing), while standing trees, possibly oak or beech, were reserved for other purposes?To develop these hypotheses, this study will be enriched with data from written sources since the 17th century onwards, allowing a better clarification of former woodland exploitation in the region, according local industrial development

From the forest to the forge: charcoal production in northeastern France lowlands (XVII-XX centuries)

International audienceWood was an essential source of energy in pre-industrial times for several activities ranging from domestic needs (e.g. cooking or heating) to production of goods such as glass or metal products. The exploitation of forest resources to produce charcoal, essential for high-temperature demands for metal smelting were widespread in forest areas all over Europe, leaving traces behind that can be studied today. These traces – charcoal kilns or charcoal production sites – contain the remnants of the use of wood for charcoal production and they can be analyzed to understand in which way the resources were used in the past. An interdisciplinary study is being conducted in Northeastern France lowlands in order to assess the extent of former charcoal production activities in the forest and the legacies left in the environment and in the landscape. The main goals of this study are: (1) quantification of the number of kilns in the area and their distribution, (2) taxonomic identification and dendrological evaluation of the taxa present in the charcoal assemblage, (3) pointing to a chronology of charcoal production, (4) propose a former structure and composition of the forest and (5) assess the legacies on the soil and forest massif resulting from the former resources’ exploitation.A forest area covering around 57km2 in Meuse (Grand Est, France) was investigated and more than 2600 kilns were detected through the analysis of LiDAR (Light Detection and Ranging) images. Along with the detection, more than 400 kilns were field-validated aiming to prove their correct detection in the images and, additionally, contribute to a robust dataset for automatic detection of charcoal kilns (Oliveira et al., submitted). Concerning the diversity of taxa used for charcoal production, a set of 48 kilns was analyzed. Small caliber Carpinus betulus (hornbeam) was the most frequent taxa observed, along with Fagus sylvatica (beech) and Corylus avellana (hazelnut tree). A set of radiocarbon dating was already performed and the results point to a large diachrony of charcoal production of over 300 years. The legacies on soils and forest structure and composition and vegetation dynamics connected to the presence of charcoal kilns are still being investigated where the impacts of these components within and outside of the charcoal kilns are being compared.The completion of the goals proposed for this study will allow a better understanding of the dynamics, changes and evolution of the resources’ exploitation, landscape and the legacies of charcoal production over space and time putting into perspective the sustainable use of wood in the era of energy transition

Impacts of environmentally realistic silver nanoparticle exposure on Gammarus roeseli (Crustacea Amphipoda) from individual to functional levels

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Cross-effects of nickel contamination and parasitism on zebra mussel physiology

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Benthic indicators of sediment quality associated with run-of-river reservoirs

International audienceFreshwater ecosystems have been fragmented by the construction of large numbers of dams. In addition to disruption of ecological continuity and physical disturbance downstream, accumulation of large amounts of sediment within run-of-river reservoirs constitutes a latent ecotoxic risk to aquatic communities. To date, run-of-river reservoirs and ecotoxic risks associated with contaminated sediment to the biodiversity and functioning of such systems are little studied. Therefore, the main objective of this study was to describe macroinvertebrate assemblages, and the functioning of these systems, and to propose indicators of sediment contamination to integrate in in-situ risk assessment methodology. To identify specific assemblages of run-of-river reservoirs, we first compared macroinvertebrate assemblages and their biotrait profiles (i.e. from a database of biological and ecological traits) in reservoirs (n = 6) and associated river sites (upstream and downstream of dams). Then, we compared responses of assemblages and biotrait profiles to sediment contamination of the banks and channels of reservoirs to select the most useful spatial scale to identify sediment contamination. Nineteen indicator taxa were observed to be specifically associated with channel habitats of reservoirs. Among these, the abundance of three taxa (Tanypodinae (Diptera), Ephemerella (Ephemeroptera) and Atherix (Diptera)) revealed the effect of metal sediment contamination. "Between-reservoirs" differences in their biotrait profile were found along the contamination gradient, with a shift of communities' composition and functionality, and an increase in functional similarity. Many traits (response traits), for example "maximum size", "transverse distribution", "substrate preferences", "saprobity", "temperature", "resistance forms", and "locomotion", were specifically linked to contamination of sediments by metals. This study indicates how sediment contamination can change the structural and functional composition of run-of-river reservoir assemblages. Indicator taxa and response traits identified in this study could improve current risk assessment methodology and potentially enable prediction of the risks of contaminated sediments stored in reservoirs in downstream ecosystems

Organic-matter decomposition as a bioassessment tool of stream functioning: A comparison of eight decomposition-based indicators exposed to different environmental changes

International audienceOrganic-matter decomposition has long been proposed as a tool to assess stream functional integrity, but this indicator largely depends on organic-matter selection. We assessed eight decomposition-based indicators along two well-known environmental gradients, a nutrient-enrichment gradient (0.2-1.4 mg DIN/L) in central Portugal and an acidification gradient (pH: 4.69-7.33) in north-eastern France to identify the most effective organicmatter indicator for assessing stream functional integrity. Functional indicators included natural leaf litter (alder and oak) in 10-mm and 0.5-mm mesh bags, commercial tea (Lipton green and rooibos teas in 0.25-mm mesh bags), wood sticks (wood tongue depressors) and cotton strips. Biotic indices based on benthic macroinvertebrates (IPtIN for Portugal and IBGN for France) were calculated to compare the effectiveness of structural and functional indicators in detecting stream impairment and to assess the relationship between both types of indicators. The effectiveness of organic-matter decomposition rates as a functional indicator depended on the stressor considered and the substrate used. Decomposition rates generally identified nutrient enrichment and acidification in the most acidic streams. Decomposition rates of alder and oak leaves in coarse-mesh bags, green and rooibos teas and wood sticks were positively related with pH. Only decomposition rates of rooibos tea and wood sticks were related with DIN concentration; decomposition rates along the nutrient-enrichment gradient were confounded by differences in shredder abundance and temperature among streams. Stream structural integrity was good to excellent across streams; the IPtI N index was unrelated to DIN concentration, while the IBGN index was positively related with pH. The relationships between decomposition rates and biotic indices were loose in most cases, and only decomposition rates of alder leaves in coarse-mesh bags and green tea were positively related with the IBGN. Commercial substrates may be a good alternative to leaf litter to assess stream functional integrity, especially in the case of nutrient enrichment

Assessing the effects of silver nanoparticles on the ecophysiology and ecology of Gammarus roeseli

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Modèle mixte hiérarchisé pour analyser la composition de communautés

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Development of a mixed hierarchical multinomial regression model to analyze community composition

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