Valérie Verneaux
University of Franche-Comté
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Featured researches published by Valérie Verneaux.
Frontiers in Ecology and Evolution | 2015
Marie-Elodie Perga; Victor Frossard; Jean-Philippe Jenny; Benjamin Alric; Fabien Arnaud; Vincent Berthon; Jessica Black; Isabelle Domaizon; Charline Giguet-Covex; Amy Kirkham; Michel Magny; Marina Manca; Aldo Marchetto; Laurent Millet; Christine Paillès; Cécile Pignol; Jérôme Poulenard; Jean-Louis Reyss; Frédéric Rimet; Olga Savichtcheva; Pierre Sabatier; Florence Sylvestre; Valérie Verneaux
Varved lake sediments provide opportunities for high-resolution paleolimnological investigations that may extend monitoring surveys in order to target priority management actions under climate warming. This paper provides the synthesis of an international research program relying on >150 years-long, varved records for three managed perialpine lakes in Europe (Lakes Geneva, Annecy and Bourget). The dynamics of the dominant, local human pressures, as well as the ecological responses in the pelagic, benthic and littoral habitats were reconstructed using classical and newly developed paleo-proxies. Statistical modelling achieved the hierarchization of the drivers of their ecological trajectories. All three lakes underwent different levels of eutrophication in the first half of the XXth century, followed by re-oligotrophication. Climate warming came along with a 2°C increase in air temperature over the last century, to which lakes were unequally thermally vulnerable. Unsurprisingly, phosphorous concentration has been the dominant ecological driver over the last century. Yet, other human-influenced, local environmental drivers (fisheries management practices, river regulations) have also significantly inflected ecological trajectories. Climate change has been impacting all habitats at rates that, in some cases, exceeded those of local factors. The amplitude and ecological responses to similar climate change varied between lakes, but, at least for pelagic habitats, rather depended on the intensity of local human pressures than on the thermal effect of climate change. Deep habitats yet showed higher sensitivity to climate change but substantial influence of river flows. As a consequence, adapted local management strategies, fully integrating nutrient inputs, fisheries management and hydrological regulations, may enable mitigating the deleterious consequences of ongoing climate change on these ecosystems.
Hydrobiologia | 2003
Jean Verneaux; Aimé Schmitt; Valérie Verneaux; C. Prouteau
Using the distribution patterns of benthic insects (198 species) and fishes ( 29 species) from 11 tributaries and the main channel of the Doubs River drainage basin (French Jura), the authors have tried to establish whether there is an organization of species into discrete, identifiable communities. Principal Component Analysis (PCA) was used to identify whether a continuum existed, and also used to select 50 least-disturbed sites, which were used to define a theoretical watercourse. The density classes of each species were projected on this longitudinal gradient and each species response was characterised by two typological traits: its typological preferendum (tp) and its typological amplitude (ta),thus creating a synthesis of ecological characteristics. In the typological index given in the appendix, the 210 species which form a biological templet are listed in alphabetical order with their tp and ta values. These typological species traits are useful contributions to a database for running waters biomonitoring.
Archiv Fur Hydrobiologie | 2003
Laurent Millet; Valérie Verneaux; Michel Magny
Chironomid assemblages were studied in Lake Lautrey (Jura, France) along a 2.50 m long core spanning the whole Lateglacial period. A stratigraphical constraint cluster analysis showed 7 biozones and 13 sub-biozones within the chironomid biostratigraphy. Characteristic taxa were allocated to each of the 7 biozones by simple analysis of the relative abundance diagram whereas several Correspondence Analyses (C.A.) were needed for the remaining 13 sub-biozones. Characteristic taxon compositions were interpreted using available quantitative inference models for total phosphorus concentration ([T.P.]), chlorophyll-a concentration ([Ch1-a]), hypolimnetic oxygen conditions, and water temperature. Optimum ranks of the characteristic taxa against the environmental factors provided by these inference models were used to deduce an evaluation of environmental conditions. Paleoenvironmental interpretations of chironomid assemblage changes showed the Lateglacial climatic event succession (Oldest Dryas, Bolling/Allerod Interstadial, and Younger Dryas) commonly recognized in the area. Moreover, a bipartition of the Oldest Dryas, the occurrence of two minor oscillations during the Bolling/Allerod Interstadial and a trend in environmental changes (climatic improvement) during the Younger Dryas were also found.
Archiv Fur Hydrobiologie | 2004
Valérie Verneaux; Jean Verneaux; Aimé Schmitt; Jean-Claude Lambert
Previous papers have underlined the major role played by dissolved oxygen and organic matter in macrobenthos distribution in lakes, especially in the bathymetric decrease in faunal richness. The present study deals with relationships between these two factors and a biotic index based on endobenthos taxon richness and density. Biological and environmental data refer to 40 sites plotted at 4 different relative depths in 10 lakes of the French Jura (9 lakes) and Pre-Alps (Lake Annecy). From 735 samples of soft sediment and 640 values of dissolved oxygen, the observed relationships of total organic carbon (TOC % dw) and dissolved oxygen (DO % sat) with a biodiversity gradient are presented in three figures. Despite the complexity in determining any biodiversity, the limiting effect of minimum DO values and maximum TOC values on the biotic potential are underlined. DO proved to be limiting below 90 % saturation and very limiting below 65 %. For TOC, a preferendum appeared around 3 % dw. From samples selected in non-limiting conditions of oxygen or organic carbon contents, each of these two factors was connected with the biodiversity index by a regression. In lake typology a 10 % sediment organic matter content indicates the onset of dysbiotic features for macroconsumers. The proposed results might be used as guidelines for lake monitoring and functional studies.
Hydrobiologia | 1998
Valérie Verneaux; Lotfi Aleya
A survey of the spatial and temporal distribution of the chironomid community was conducted in Lake Abbaye (France). Samples were taken monthly (from May to November) at five depths (−1 m to − 20 m) using artificial substrates. The results showed that both depth and season contributed to variations in the chironomid community. However, correspondence analysis clearly showed that most of the variation was due to bathymetric gradients. These results indicate that information on the depth distribution of the chironomid species may be useful in lake classification. However, this classification requires multiple-season sampling, so as to include the different lifecycle patterns of species.
Archiv Fur Hydrobiologie | 2005
A. L. Borderelle; Valérie Verneaux; D. Gerdeaux
The Lake Biotic Index (VERNEAUX et al. 2004 a), a new lake biological quality assessment method based on the bathymetric distribution of macroinvertebrate assemblages, was applied to three reference French lakes having different geomorphological characteristics (altitude, size, geology, maximum depth). The Lake Biotic Index (LBI) is interpreted through its two sub-indices; one is a littoral quantitative index (littoral biotic index: Bl which considers the littoral taxon richness and the littoral density per m 2 ) related to lake trophic potential, the second (taxon deficit index: Df) is a qualitative index reflecting the relative loss of taxon richness between littoral and deep zones in relation to the lakes ability to transfer available matter up to consumers (trophic functioning). The results show a great impact of the geomorphological characteristics of the lakes on the reference LBI values (from 12/20 to 18.5/20) due only to different littoral macroinvertebrate biodiversities. Lake Annecy, a great lake situated 457 m a. s. on calcareous substratum, showed a much higher Bl value (62.6) than the two other lakes (Lake Crop Bl: 26.2, Lake Grand-Domenon Bl: 26.4) which are small lakes located at high altitudes on siliceous substratum. Concerning the qualitative index Df, no differences were observed between the three lakes which obtained high Df values (Lake Annecy Df: 0.9/1, Lakes Crop and Grand-Domenon Df: 1/1). It can therefore be concluded that the geomorphological factors considered did not affect the efficiency of lake trophic functioning.
The Holocene | 2009
Laurent Millet; Fabien Arnaud; Oliver Heiri; Michel Magny; Valérie Verneaux; Marc Desmet
Journal of Paleolimnology | 2010
Laurent Millet; Charline Giguet-Covex; Valérie Verneaux; Jean-Claude. Druart; Thierry Adatte; Fabien Arnaud
Journal of Paleolimnology | 2014
Simon Belle; Claire Parent; Victor Frossard; Valérie Verneaux; Laurent Millet; Panagiota-Myrsini Chronopoulou; Pierre Sabatier; Michel Magny
Journal of Paleolimnology | 2013
Victor Frossard; Simon Belle; Valérie Verneaux; Laurent Millet; Michel Magny