Détermination des substrats lacustres par hydroacoustique : application au suivit de qualité morphologique

La diversité des écosystèmes lacustres s’explique en partie par la variété hydromorphologique des lacs ; la nature et la répartition du substrat qui tapisse leur fond sont des composantes de ce paramètre. C’est pour cela que la Directive Cadre sur l’Eau impose une description de la nature des sédiments des plans d’eau. Plus généralement, la répartition des substrats peut être considérée comme un facteur de structuration des espèces biologiques qu’abrite un lac. Des outils traditionnels comme l’utilisation d’une benne à sédiment ou d’une caméra subaquatique permettent de déterminer la nature des substrats de manière très ponctuelle mais ces techniques atteignent leurs limites lorsque tout un plan d’eau doit être caractérisé. Depuis les années 1980 des méthodes de caractérisation des sédiments utilisant des outils acoustiques qui permettent d’obtenir des informations en continu le long de parcours réalisés par un navire ont été développées et commercialisées. Pour l’application aux écosystèmes lacustres, de part leur mise en oeuvre, les systèmes utilisant les échosondeurs mono‐faisceau paraissent les plus appropriés. Ces appareils permettent de réaliser des cartes de la répartition des substrats à l’échelle du lac. Les informations pertinentes qui permettent de décrire un état biologique potentiel ou de définir un état initial peuvent être ainsi intégrer dans la mise en place des réseaux de suivi de la qualité des milieux. / The lake ecosystem diversity is explained, in part, by the hydromorphological diversity of lakes; nature and repartition of the substrata give information about this parameter. That is the reason why the European Water Framework imposes a substrata nature description of lakes. The substrata repartition could be considered as a factor of the biological structuring presents in lakes. Traditional tools like grab samplers or video cameras enable to determine the substrata nature but they are not appropriate for getting a high resolution description for an entire lake. From the beginning of the 80’s, acoustic devices specialized in seabed classification have been developed and commercialized. For lakebed surveys, systems using single beam sounders seem to be more appropriate; they enable to obtain maps of the lakebed at the whole lake scale. Information which describes a potential biological state can be used for the establishment of a quality monitoring

Adaptive device for disease awareness and treatment adherence of asthma in children

International audienceAsthma is the first chronic disease in children: that concerns 10% of them. This is a real public health issue, because its frequency and gravity increase since 2000’s in this population. The major identified problem in asthma kids is the low rate of treatment adherence (50%). To increase adherence rate, there is some strategies as therapeutic education programs and numerical technologies as serious games or mobile applications but those learning systems are the same for all children, and it is proved that personalized program is more efficient than generic learning. In first step, we created a web responsive application composed by several interactive contents linked to asthma (based on criteria learnt in asthma therapeutic education) and displayed to different forms: learning activities with quiz, short games and videos. In a participatory design approach, the interfaces are tailored to children : they had been designed with iterative and user-centered methods. Moreover, asthma experts validated all the proposed content in the application and it was tested by asthma kids. In a preliminary study, we experimented usability, motivation and knowledge of few contents on 40 control children in choice/no-choice conditions. Observations showed KidBreath was easy to use, children were more motivated using it and acquire more knowledge in the choice condition rather no-choice. Later, to personalize learning activities linked to asthma, we have the objective to integrate learning optimization algorithm as an intelligent tutoring system in KidBreath

Amélioration des techniques de reconstitution en espèces feuillues de la forêt méditerranéenne

Le reboisement est une des techniques de reconstitution possible de la forêt méditerranéenne, notamment après incendie. Si les techniques d'installation des résineux sont aujourd'hui bien maîtrisées, celles concernant les feuillus sont moins connues. Cette étude, à partir de dispositifs expérimentaux mis en place au début des années 1990, permet de tirer les premiers enseignements sur l'installation des plants feuillus

Effects of fish predation on density and size spectra of prey fish communities in lakes

Planktivorous and benthivorous fish have been documented to influence the density and size structure of their prey communities in lakes. We hypothesized that piscivorous fish modify their prey fish communities in the same way and sought to find evidence for such predation effects from a comparison across 356 lakes located in nine European ecoregions. We categorized individual fish as being either piscivore, non-piscivore or prey of piscivores, depending on species and individual size. We calculated piscivore, non-piscivore and piscivore prey densities, respectively, and fit linear abundance size spectra (SS) on lake-specific piscivore, non-piscivore and piscivore prey size distributions. Multiple linear regressions were calculated to quantify the effect of piscivore density and SS slopes on non-piscivore and piscivore prey densities and SS slopes, by accounting for potentially confounding factors arising from lake morphometry, productivity and local air temperature. Piscivore density correlated positively with piscivore prey density, but was uncorrelated to density of non-piscivores. Across a subset of 76 lakes for which SS slopes of piscivores were statistically significant, SS slopes of piscivores were uncorrelated with SS slopes of either non-piscivores or piscivore prey. However, densities of piscivores, non-piscivores or piscivore prey were a significant negative predictor of SS slopes of the respective groups. Our analyses suggest that direct predation effects by piscivorous fish on density and size structure of prey fish communities are weak in European lakes, likely caused by low predator-prey size ratios and the resulting size refuges for prey fish. In contrast, competition may substantially contribute to between-lake variability in fish density and size

Can size distributions of European lake fish communities be predicted by trophic positions of their fish species?

An organism's body size plays an important role in ecological interactions such as predator-prey relationships. As predators are typically larger than their prey, this often leads to a strong positive relationship between body size and trophic position in aquatic ecosystems. The distribution of body sizes in a community can thus be an indicator of the strengths of predator-prey interactions. The aim of this study was to gain more insight into the relationship between fish body size distribution and trophic position in a wide range of European lakes. We used quantile regression to examine the relationship between fish species' trophic position and their log-transformed maximum body mass for 48 fish species found in 235 European lakes. Subsequently, we examined whether the slopes of the continuous community size distributions, estimated by maximum likelihood, were predicted by trophic position, predator-prey mass ratio (PPMR), or abundance (number per unit effort) of fish communities in these lakes. We found a positive linear relationship between species' maximum body mass and average trophic position in fishes only for the 75% quantile, contrasting our expectation that species' trophic position systematically increases with maximum body mass for fish species in European lakes. Consequently, the size spectrum slope was not related to the average community trophic position, but there were negative effects of community PPMR and total fish abundance on the size spectrum slope. We conclude that predator-prey interactions likely do not contribute strongly to shaping community size distributions in these lakes

Density-dependent effects as key drivers of intraspecific size structure of six abundant fish species in lakes across Europe

Fish size structure has traditionally been used for elucidating trophic interactions and patterns of energy transfer through trophic levels(Trebilco et al.2013). We analysed the siz estructure of six common freshwater fish species in several hundred European lakes. We found little effect on the strength of the environmental gradients of size structure. The intraspecific density-dependent effect was the strongest and most consistent predictor

Fish in lake ecological assessment in Europe: Quo Vadis?

It is well established that fish are sensitive indicators of environmental degradation and offer the major advantage of integrating the direct and indirect effects of stress over large scales of space and time. Nevertheless, the use of fish communities as indicators of environmental quality is highly challenging, therefore fish community has been one of the most neglected aspect of lake ecological monitoring. This paper gives an overview on fish-based assessment methods in Europe. By now, 15 Member States have finalised fish-based lake assessment systems, five of these assessment systems have been recently intercalibrated in the Alpine and Northern region, while Intercalibration is still ongoing in the Central-Baltic region. In contrary, several countries of the Mediterranean region have currently renounced the use of fish in lake assessment (mainly due to a low species richness, dominance of invasive taxa, and high costs of sampling), this opinion being strongly debated within region. This paper seeks to answer questions: How lake fish ecological assessment systems are built and used across Europe? Which pressures are assessed and are the pressure-response relationships tested? What are the main lessons and challenges of the lake fish methods` development and harmonization process