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International audience; AbstractForaging honey bees (Apis mellifera) seem to use the presence of conspecific foragers as cues for flower quality. However, there is disagreement regarding how a conspecific cue is perceived by other foragers (enhancement or inhibition). Most studies manipulate the total number of bees foraging in an arena or the presence or absence of a bee on a flower and then observe the behavior of one forager in response to a single conspecific, which does not reflect natural foraging. We tested how a range of conspecifics on flowers affected on which flowers foraging honey bees landed. We trained students from a biology class for non-STEM majors to collect data and tested whether the number of conspecifics on flowers influences on which flower foragers land. We found that foragers land more frequently on flowers occupied by more conspecifics, which supports the hypothesis that conspecifics are cues for local enhancement. Our results increase our understanding of how honey bees forage once at a flower patch.

International audience; As we move towards shipboard-underway and automated systems for monitoring water quality and assessing ecological status, there is a need to evaluate how effective the existing monitoring systems are, and how we could improve them. Considering the existing limitations for processing numerous and complex data series generated from automated systems, and because of processes involved in phytoplankton blooms, this paper proposes a data-driven evaluation of an unsupervised classifier to optimize the way we track phytoplankton, including harmful algal blooms (HABs), and to identify the main associated hydrological conditions. We used in situ data from a portable flow-through automatic measuring system coupled with a multi-fixed-wavelength fluorometer implemented in the eastern English Channel during a bloom of Phaeocystis globosa (high biomass, non-toxic HAB species). This combination of technologies allowed high resolution online hydrographical and biological measurements, including spectral fluorescence as a means of quantifying phytoplankton biomass and simplifying the phytoplankton community structure inference. An unsupervised spectral clustering method was applied to this multi-parameter high-resolution time series, which allowed discrimination under near real-time of 6 to 33 contrasting water masses based on their abiotic and biotic characteristics. In addition, areas subject to extreme events such as HABs could be precisely identified, so controlling factors or their direct and indirect effects could be hierarchized. Considering the benefits and limitations of such a strategy, future applications of such methods will be important in the context of implementing the Marine Strategy Framework Directive.

In numerical models for marine biogeochemistry, bio-optical data, such as measurements of the light field, may be important descriptors of the dynamics of primary producers and ultimately of oceanic carbon fluxes. However, the paucity of field observations has limited the integration of bio-optical data in such models so far. New autonomous robotic platforms for observing the ocean, i.e., Biogeochemical-Argo floats, have drastically increased the number of vertical profiles of irradiance, photosynthetically available radiation (PAR) and algal chlorophyll concentrations around the globe independently of the season. Such data may be therefore a fruitful resource to improve performances of numerical models for marine biogeochemistry. Here we present a work that integrates into a 1-dimensional model 1314 vertical profiles of PAR acquired by 31 BGC-Argo floats operated in the Mediterranean Sea between 2012 and 2016 to simulate the vertical and temporal variability of algal chlorophyll concentrations. In addition to PAR as input, alternative light and vertical mixing models were considered. We evaluated the models’ skill to reproduce the spatial and temporal variability of deep chlorophyll maxima as observed by BGC-Argo floats. The assumptions used to set up the 1-D model are validated by the high number of co-located in-situ measurements. Our results illustrate the key role of PAR and vertical mixing in shaping the vertical dynamics of primary produces in the Mediterranean Sea. Moreover, we demonstrate the importance of modeling the diel cycle to simulate chlorophyll concentrations in stratified waters at the surface.

Growth performance and feeding activities of brown trout selected for growth (S) and control lines (C) maintained without a selection pressure were compared. Groups of 500 fish of each line with the same initial weight (4 g) were constituted and fed for 115 days ad libitum using self-feeders or automatic feeders (2 lines×2 feeding methods×3 replicates). After 35 days of food deprivation, all groups were re-fed by self-feeders for 46 days. The feeding demands of groups fed by self-feeders were recorded continuously. Growth, feed intake and uneaten feed were measured at regular intervals. In both lines, growth rates were higher in self-fed than in automatically fed fish (P 0.36), the better growth of S was caused by higher feed intake. Self-fed brown trout ate 16–20% of their daily intake at dawn and on average 5% per h thereafter. This feeding activity profile was more discernible for S, which ate more than C at dawn (P<0.01). At the end of the starving period the loss of weight was slightly higher for S than for C (P<0.06). It was compensated during the re-feeding period for both lines by hyperphagia and higher feed efficiency. The mean final BW was approximately 90% higher for S than for C. Both lines restored rapidly their own feeding profiles. How this selection process may determine the features of the correlated responses is discussed.

Abstract It is shown in the present paper how the addition of a moderate amount of carbon black filler to a polychloroprene gum modifies the local strain state and alters the ability of the polymer to strain-crystallize. The study combines mechanical and X-ray diffraction performed during classical mechanical cycling and tensile impact tests. It highlights the fact that the strain modification induced by the filler addition is highly inhomogeneous: the crystallization behavior and the local draw ratio state are affected differently. The partial relaxation of the amorphous fraction by the strain-induced crystallization evidenced in the pure gum is still present and should play a protective role. The effect of temperature on the crystallization correlates with the evolution of stress-strain curves. In particular the role of crystallization in stress-hardening is apparently amplified by the presence of the filler. Preliminary tensile tests reveal a drastic decrease of the induction time necessary for crystallization to develop. This implies a strain amplification effect higher than predicted from mechanical cycling analysis. It is proposed that carbon black particles have no time to relax during the fast stretching period. All these observations point to a synergistic effect between filler addition and strain-induced crystallization.

Plastic pollution in the environment is increasing at global scale. Microplastics (MP) are derived from degradation of larger plastic items or directly produced in microparticles form (<5 mm). Plastics, widely used in structures and equipments of pearl farming, are a source of pollution to the detriment of the lagoon ecosystem. In order to evaluate the impact of MP on the physiology of Pinctada margaritifera, a species of ecological and commercial interests, adult oysters were exposed to polystyrene microbeads (micro-PS of 6 and 10 μm) for 2 months. Three concentrations were tested: 0.25, 2.5, 25 μg L-1 and a control. Ingestion and respiration rate and assimilation efficiency were monitored on a metabolic measurement system to determine the individual energy balance (Scope For Growth, SFG). Effects on reproduction were also assessed. The assimilation efficiency decreased significantly according to micro-PS concentration. The SFG was significantly impacted by a dose-dependent decrease from 0.25 μg L-1 (p < 0.0001). A negative SFG was measured in oysters exposed to 25 μg L-1. Gonads may have provided the missing energy to maintain animals’ metabolism through the production of metabolites derived from germ cells phagocytosis. This study shows that micro-PS significantly impact the assimilation efficiency and more broadly the energy balance of P. margaritifera, with negative repercussions on reproduction.

Ecological intensification is a new concept in agriculture that addresses the double challenge of maintaining a level of production sufficient to support needs of human populations and respecting the environment in order to conserve the natural world and human quality of life. This article adapts this concept to fish farming using agroecological principles and the ecosystem services framework. The method was developed from the study of published literature and applications at four study sites chosen for their differences in production intensity: polyculture ponds in France, integrated pig and pond polyculture in Brazil, the culture of striped catfish in Indonesia and a recirculating salmon aquaculture system in France. The study of stakeholders' perceptions of ecosystem services combined with environmental assessment through Life Cycle Assessment and Emergy accounting allowed development of an assessment tool that was used as a basis for co-building evolution scenarios. From this experience, ecological intensifica-tion of aquaculture was defined as the use of ecological processes and functions to increase productivity, strengthen ecosystem services and decrease disservices. It is based on aquaecosystem and biodiversity management and the use of local and traditional knowledge. Expected consequences for farming systems consist of greater autonomy, efficiency and better integration into their surrounding territories. Ecological intensification requires territorial governance and helps improve it from a sustainable development perspective. International audience