Control of oestrus with a progesterone intravaginal device (Prid®): comparison of 2 insertion durations

International audienc

Simulation method linking dense microalgal culture spectral properties on the [400-750 nm] range to the physiology of the cells

International audienc

Simulation method design to link the spectral properties of dense microalgal culture to cell physiology

International audienceIt is seen as a promising source of biomass for crucial applications such as energy production,1 source of highly valuable molecules. Optimizing the monitoring of the mass cultivation process is challenging2 as it requires high frequency biochemical and physical characterization of the microalgal cells throughout the cultivation process. Visible (VIS) and near infrared (NIR) spectroscopy have the potential to characterize dense microalgal cultures status. This measurements are fast and can be performed with minimum or no sample preparation. Applying spectroscopic methods to dense algal cultures can be troublesome due to multiple scattering effects resulting from high cell density (106− 109cells/mL). In this study, we attempt to model the optical properties of dense algal sample in which multi scattering occurs. Our work aims at providing a simulation method that can be used to interpret the spectral properties of a dense algal culture, and to provide information on the biochemical and physical characteristics of the algal cells during growth. For this purpose, we implemented a method based on Kerker's solution of the extended Mie theory3 coupled with the numerical resolution of the radiative transport theory4 was implemented. The algal cells are thus modeled as multilayered spheres composed of different organic materials and dissolved photopigments5. Two different monospecific batch cultures of Isochrisys galbana and Phaeodactylum tricornutum were tested. The biochemical compositionof cell, the number, mean size and mean dry weight and the total transmittance over the [400-750 nm] spectral range were measured at three different growth (beginning, exponential and stationary) stages of each of the two cultures. The measured transmittance spectra were used in the simulation method in order to predict cell mean size and density on the one hand, and the pigment quantity and composition on the other for the two species at each growth phase. Thus the mean equivalent spherical diameter was retrieved for both strains and at each sampling date with a relative error below 10%. Cell density was also successfully predicted for I. galbana for each growth phase studied, with a relative error below 7%, which suggest that cell dynamics could be successfully monitored during cell population growth. However, more discrepancies are observed for P. tricornutum, for which the cell density is predicted with a higher relative error, up to 27% at day 34. This higher relative error is due to the non-spherical shape of the P. tricornutum cells. Predictions of the relative proportions of each pigments are closely match HLPC measurements, with relative errors below 9%. Therefore changes in the carotenoids/Chl ratio may also be successfully predicted with low relative errors (3-7%). For P. tricornutum, the predicted values show generally more discrepancies with the measurements than for I. galbana. This is likely explained also by the shape effect of these microalgae

A new transportable floating mesocosm platform with autonomous sensors for real-time data acquisition and transmission for studying the pelagic food web functioning

International audienc

Simulation Method Linking Dense Microalgal Culture Spectral Properties in the 400–750 nm Range to the Physiology of the Cells

[Departement_IRSTEA]Ecotechnologies [TR1_IRSTEA]INSPIREInternational audienceThis work describes a method to model the optical properties over the (400-750 nm) spectral range of a dense microalgal culture using the chemical and physical properties of the algal cells. The method was based on a specific program called AlgaSim coupled with the adding-doubling method: at the individual cell scale, AlgaSim simulates the spectral properties of one model, three-layer spherical algal cell from its size and chemical composition. As a second step, the adding-doubling method makes it possible to retrieve the total transmittance of the algal medium from the optical properties of the individual algal cells. The method was tested by comparing the simulated total transmittance spectra for dense marine microalgal cultures of Isochrysis galbana (small flagellates) and Phaeodactylum tricornutum (diatoms) to spectra measured using an experimental spectrophotometric setup. Our study revealed that the total transmittance spectra simulated for the quasi-spherical cells of Isochrysis galbana were in good agreement with the measured spectra over the whole spectral range. For Phaeodactylum tricornutum, large differences between simulated and measured spectra were observed over the blue part of the transmittance spectra, probably due to non-spherical shape of the algal cells. Prediction of the algal cell density, mean size and pigment composition from the total transmittance spectra measured on algal samples was also investigated using the reversal of the method. Mean cell size was successfully predicted for both species. The cell density was also successfully predicted for spherical Isochrysis galbana, with a relative error below 7%, but not for elongated Phaeodactylum tricornutum with a relative error up to 26%. The pigments total quantity and composition, the carotenoids:chlorophyll ratio in particular, were also successfully predicted for Isochrysis galbana with a relative error below 8%. However, the pigment predictions and measurements for Phaeodactylum tricornutum showed large discrepancies, with a relative error up to 88%. These results give strong support for the development of a promising tool providing rapid and accurate estimations of biomass and physiological status of a dense microalgal culture based on only light transmittance properties

Les leçons de Ziphia : un cas d’étude pour mieux protéger les mammifères marins du bruit anthropique dans la zone économique exclusive française

On February 2nd 2021, a Cuvier’s beaked whale (Ziphius cavirostris) stranded on the île de Ré (Northeast Atlantic, France). Preliminary analyses revealed that the death of the animal was probably caused by anthropogenic noise. Produced in the direct vicinity of an area where military tests were carried out by a vessel, this accident occurred within a marine protected area. This event became the starting point of an investigation aiming to trace its origin, and served as a basis for a broader collaborative work as part of the interdisciplinary research program of Esprit de Velox, Destination Ocean. At the confluence of several disciplines, our reflection highlights, through the lens of human-induced noise impacts on cetaceans, the complexity of the relationships between oceanic life and anthropic activities. In order to better understand and protect the ocean, we advocate for changes in the practices of ocean-related knowledge production, improvement of the legal norms governing the use and protection of the marine environment, and a transformation of our own anthropological relationship to the ocean.Le 2 février 2021, une baleine à bec de Cuvier (Ziphius cavirostris) s’échoue sur l’île de Ré (Atlantique nord-est, France). Les analyses préliminaires révèlent que la mort de l’animal est vraisemblablement liée à des bruits anthropiques. Le lieu probable de la mort de l’animal se situe à proximité directe d’une zone où un navire militaire effectuait des essais au sein d’une aire marine protégée. Point de départ d’une enquête visant à en retracer l’origine, cet événement cristallise la complexité des relations entre vie océanique et activités anthropiques. Il sert de point d’appui à une réflexion collaborative plus large à la confluence de plusieurs disciplines, en vue de faire évoluer la production des savoirs océaniques, les normes juridiques qui encadrent les usages et la protection du milieu marin, et notre rapport anthropologique à l’océan

Marine ecological aquaculture: a successful Mediterranean integrated multi-trophic aquaculture case study of a fish, oyster and algae assemblage

International audienceInspired by agroecology, ecological aquaculture proposes an alternative model that uses ecology as a paradigm to develop innovative, more eco-friendly aquaculture with environmental, economic and social benefits. Integrated multi-trophic aquaculture (IMTA) is one application of this principle. Inspired by the natural trophic chain, it associates primary producers with primary or secondary consumers, providing a new source of biomass without requiring supplementary feed by recycling inorganic and organic wastes. Of these systems, land-based IMTAs demonstrate several advantages, especially easier control of nutrient flows, contaminants and/or predators. This study focused on a land-based marine IMTA, combining a recirculating aquaculture system for fish consecutively with a natural marine polyculture of microalgae and oyster cultivation. The objective was to assess the ability of the microalgal polyculture both to bioremediate fish nutrients and to sustain oyster growth. For the first time in a Mediterranean climate, we confirmed the feasibility of developing a microalgae community of interest for oysters maintained by fish effluent. Despite strong variability in microalgae production, this IMTA system resulted in significant oyster growth over the experimental period of one month, with growth results of the same order of magnitude as natural juvenile growth. In the conditions tested, this IMTA with reduced human intervention allowed a gain in recoverable biomass of 3.7 g of oyster produced per kg of fish feed distributed. By transforming waste into additional biomass, IMTAs offer a more promising, ecological avenue for aquaculture, based on a circular economy, which may in turn increase the social acceptability of fish farming