Impacts des sons anthropiques sur la faune marine

International audienceLoin du monde du silence, le milieu marin doit se concevoir comme un environnement sonore. L’océan est porteur de bruits d’origine physique (vagues, pluie, glace, séismes) et biologiques (chant des baleines, clics des dauphins, claquements de crevettes ou d’oursins). Ce paysage acoustique est essentiel pour la faune marine. Il participe, entre autres, à l’orientation des larves, à la communication des animaux entre eux, à la détection de prédateurs. Toutefois, depuis un peu plus d’un siècle, les activités humaines modifient grandement ce paysage acoustique. Les bruits d’origine anthropique proviennent des navires, des installations posées en mer, des sonars et plus récemment de l’utilisation des énergies marines renouvelables. La faune marine perçoit-elle ces nouveaux sons ? La question de l’impact des sons anthropiques sur la faune marine se révèle un enjeu écologique et économique majeur pour les années à venir. Les auteurs montrent la diversitéde leurs effets sur la faune grâce à une approche multidisciplinaire associant la physique, la réglementation, la biologie et l’étude d’impact ; une place particulière est donnée aux premiers retours d’expérience de production d’énergies marines renouvelables (EMR) en Europe. Cet ouvrage se veut un premier état des lieux d’un champ de recherche qui ne fait que commencer

Insights into the behavioural responses of juvenile thornback ray Raja clavata to alternating and direct current magnetic fields

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Effects of anthropogenic magnetic fields on the behavior of a major predator of the intertidal and subtidal zones, the velvet crab Necora puber

With the progress of the offshore renewable energy sector and electrical interconnection projects, a substantial rise in the number of submarine power cables is expected soon. Such cables emit either alternating or direct current magnetic fields whose impact on marine invertebrates is currently unknown and hardly studied. In this context, this study aimed to assess potential short-term exposure (30 min) effects of both alternating and direct magnetic fields of increasing intensity (72-304 & mu;T) on the behavior of the high-ecological value velvet crab (Necora puber). Three experiments were designed to evaluate whether the strongest magnetic field intensities induce crabs' attraction or repulsion responses, and whether foraging and sheltering behaviors may be modified. We extracted from video analyses several variables as the time budgets crabs spent immobile, moving, feeding, or sheltering as well as total and maximal distance reached in the magnetic field (MF) gradient. The crabs exposed to artificial MF did not exhibit significant behavioral changes compared with those exposed to the "natural" MF. Overall, our results suggest that, at such intensities, artificial magnetic fields do not significantly alter behaviors of N. puber. Nevertheless, future studies should be conducted to examine the effects of longer exposure periods and to detect potential habituation or resilience processes

A current synthesis on the effects of electric and magnetic fields emitted by submarine power cables on invertebrates

International audienceThe goal of clean renewable energy production has promoted the large-scale deployment of marine renewable energy devices, and their associated submarine cable network. Power cables produce both electric and magnetic fields that raise environmental concerns as many marine organisms have magneto and electroreception abilities used for vital purposes. Magnetic and electric fields’ intensities decrease with distance away from the cable. Accordingly, the benthic and the sedimentary compartments are exposed to the highest field values. Although marine invertebrate species are the major fauna of these potentially exposed areas, they have so far received little attention. We provide extensive background knowledge on natural and anthropogenic marine sources of magnetic and electric fields. We then compile evidence for magneto- and electro-sensitivity in marine invertebrates and further highlight what is currently known about their interactions with artificial sources of magnetic and electric fields. Finally we discuss the main gaps and future challenges that require further investigation

Signal processing and valvometry : from instrumentation to description of a biological state

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Signal processing and valvometry : from instrumentation to description of a biological state

International audienceIn order to obtain descriptors of the ocean state this internship focused on characterizingking scallops, Pecten maximus, behaviour. This works presents the development of tools toanalyse automatically accelerometry and valvometry signals acquired from new sensorsfixed on scallops. These tools are developed on data acquired during a two weeks experimentaiming at studying scallops in a stable environment. First the conditions of this experimentare presented. A calibration process to obtain valve distance signal (millimeter) from theoriginal valvometry data (millivolt) is explained and validated. Cycle analysis using PowerSpectral Density is preformed in order to see if light variations have an in influence onscallops behaviour. To describe the behaviour more precisely a movement detectionalgorithm based on the scalogram of the valve distance signal is developed. Then themovements are analysed. Jumps are identified thanks to a k-means clustering on specificfeatures of the movements. All this information is used to compute behaviour descriptors.These descriptors are of two types : number of movements descriptors and base openingdescriptors. Further development should focus on the combination of valvometry distanceand accelerometry signals and on movement classification