Acidification des eaux de surface sous l'influence des précipitations acides : rôle de la végétation et du substratum, conséquences pour les populations de truites. Le cas des ruisseaux des Vosges

L'étendue de l'acidification des ruisseaux des Vosges a été étudié. L'influence des précipitations atmosphériques acides, accentuée par la présence de résineux et de roches mères pauvres en minéraux altérables, a provoqué l'acidification de certains ruisseaux. L'acidité (pH 200 ppb) constituent des facteurs limitants à la présence de truites dans ces ruisseaux

Water quality assessment by means of HFNI valvometry and high-frequency data modeling

International audienceThe high-frequency measurements of valve activity in bivalves (e.g., valvometry) over a long period of time and in various environmental conditions allow a very accurate study of their behaviors as well as a global analysis of possible perturbations due to the environment. Valvom- etry uses the bivalve's ability to close its shell when exposed to a contaminant or other abnormal environmental conditions as an alarm to indicate possible perturbations in the environment. The modeling of such high-frequency serial valvom- etry data is statistically challenging, and here, a nonparametric approach based on kernel estima- tion is proposed. This method has the advantage of summarizing complex data into a simple den- sity profile obtained from each animal at every 24-h period to ultimately make inference about time effect and external conditions on this profile. The statistical properties of the estimator are pre- sented. Through an application to a sample of 16 oysters living in the Bay of Arcachon (France), we demonstrate that this method can be used to first estimate the normal biological rhythms of permanently immersed oysters and second to de- tect perturbations of these rhythms due to changes in their environment. We anticipate that this ap- proach could have an important contribution to the survey of aquatic systems

In the darkness of the polar night, scallops keep on a steady rhythm

Published version. Source at http://doi.org/10.1038/srep32435. License CC BY 4.0.Although the prevailing paradigm has held that the polar night is a period of biological quiescence, recent studies have detected noticeable activity levels in marine organisms. In this study, we investigated the circadian rhythm of the scallop Chlamys islandica by continuously recording the animal’s behaviour over 3 years in the Arctic (Svalbard). Our results showed that a circadian rhythm persists throughout the polar night and lasts for at least 4 months. Based on observations across three polar nights, we showed that the robustness and synchronicity of the rhythm depends on the angle of the sun below the horizon. The weakest rhythm occurred at the onset of the polar night during the nautical twilight. Surprisingly, the circadian behaviour began to recover during the darkest part of the polar night. Because active rhythms optimize the fitness of an organism, our study brings out that the scallops C. islandica remain active even during the polar night

Monitoring biological rhythms through the dynamic model identification of an oyster population

International audienceThe measurements of valve activity in a population of bivalves under natural environmental conditions (16 oysters in the Bay of Arcachon, France) are used for a physiological model identification. A nonlinear auto-regressive exogenous (NARX) model is designed and tested. The method to design the model has two parts. 1) Structure of the model: The model takes into account the influence of environmental conditions using measurements of the sunlight intensity, the moonlight, tide levels, precipitation and water salinity levels. A possible influence of the internal circadian/circatidal clocks is also analyzed. 2) Least square calculation of the model parameters. Through this study, it is demonstrated that the developed dynamical model of the oyster valve movement can be used for estimating normal physiological rhythms of permanently immersed oysters and can be considered for detecting perturbations of these rhythms due to changes in the water quality, i.e. for ecological monitoring

A Fault Detection Method for Automatic Detection of Spawning in Oysters

Using measurements of valve activity (i.e., the distance between the two valves) in populations of bivalves under natural environmental conditions (16 oysters in the Bay of Arcachon, France, in 2007, 2013, and 2014), an algorithm for an automatic detection of the spawning period of oysters is proposed in this brief. Spawning observations are important in aquaculture and biological studies, and until now, such a detection is done through visual analysis by an expert. The algorithm is based on the fault detection approach and it works through the estimation of velocity of valve movement activity, which can be obtained by calculating the time derivative of the valve distance. A summarized description of the methods used for the derivative estimation is provided, followed by the associated signal processing and decision-making algorithm to determine spawning from the velocity signal. A protection from false spawning detection is also considered by analyzing the simultaneity in spawning. Through this study, it is shown that spawning in a population of oysters living in their natural habitat (i.e., in the sea) can be automatically detected without any human expertise, saving time and resources. The fault detection method presented in this brief can also be used to detect complex oscillatory behavior which is of interest to control engineering community.<br/

Deep behavioral impairment in the pearl oyster Pinctada radiata exposed to anthropogenic noise and light stress

The pearl oyster Pinctada radiata is an iconic species in the Arabian Gulf, which is one of the ecosystems most at risk in the world because of the multiple sources of pollution it faces. Alongside chemical pollution, the Gulf is ranked first with regard to noise and light pollution, and pearl oyster populations are at risk. The impact of these latter types of pollution on marine invertebrates is still poorly known. We used the difference in noise and brightness that can exist between a very quiet room without artificial lighting and a standard laboratory room equipped with a standard aquarium as a testbed to explore the possible impact of noise and light pollution on the behavioral and biological traits of Pinctada radiata without added chemical exposure. During an experiment that lasted 2.5 months, we analyzed their grouping behavior, valve activity, biological rhythm, growth rate and spawning activity. In the standard aquarium kept in the laboratory room, the oysters dispersed instead of regrouping as in their natural environment, regrouping which was observed in the quiet room. They stayed closed longer, the opening amplitude of their valves was systematically lower, and in the closed position, they squeezed their valves more tightly when subjected to noise and light pollution. Their daily opening rhythm was strongly structured by switching the electric light on and off, and females showed significantly less egg-laying behavior. In conclusion, seemingly innocuous human activities can lead to very significant alterations in pearl oyster behavior. We propose that it could have significant effects on populations and ecosystems

Model-based adaptive filtering of harmonic perturbations applied to high-frequency noninvasive valvometry

International audienceIn this paper, a model-based adaptive filter is used to suppress electrical noise in a high-frequency noninvasive valvometry device, which is part of an autonomous biosensor system using bivalve mollusks valve-activity measurements for ecological monitoring purposes. The proposed model-based adaptive filter uses the dynamic regressor extension and mixing method to allow a decoupled estimation of the parameters. Once the desired regression form of the output model is obtained, a fixed-time estimation approach is used to identify its parameters. By applying these two techniques, a flexible filter structure is obtained with the property of retaining the major relevant components of interest of the original valve-activity signals, even in the case when the unwanted signal frequency components are in the same frequency range as the useful variables

Oxygen as a Driver of Early Arthropod Micro-Benthos Evolution

BACKGROUND: We examine the physiological and lifestyle adaptations which facilitated the emergence of ostracods as the numerically dominant Phanerozoic bivalve arthropod micro-benthos. METHODOLOGY/PRINCIPAL FINDINGS: The PO(2) of modern normoxic seawater is 21 kPa (air-equilibrated water), a level that would cause cellular damage if found in the tissues of ostracods and much other marine fauna. The PO(2) of most aquatic breathers at the cellular level is much lower, between 1 and 3 kPa. Ostracods avoid oxygen toxicity by migrating to waters which are hypoxic, or by developing metabolisms which generate high consumption of O(2). Interrogation of the Cambrian record of bivalve arthropod micro-benthos suggests a strong control on ecosystem evolution exerted by changing seawater O(2) levels. The PO(2) of air-equilibrated Cambrian-seawater is predicted to have varied between 10 and 30 kPa. Three groups of marine shelf-dwelling bivalve arthropods adopted different responses to Cambrian seawater O(2). Bradoriida evolved cardiovascular systems that favoured colonization of oxygenated marine waters. Their biodiversity declined during intervals associated with black shale deposition and marine shelf anoxia and their diversity may also have been curtailed by elevated late Cambrian (Furongian) oxygen-levels that increased the PO(2) gradient between seawater and bradoriid tissues. Phosphatocopida responded to Cambrian anoxia differently, reaching their peak during widespread seabed dysoxia of the SPICE event. They lacked a cardiovascular system and appear to have been adapted to seawater hypoxia. As latest Cambrian marine shelf waters became well oxygenated, phosphatocopids went extinct. Changing seawater oxygen-levels and the demise of much of the seabed bradoriid micro-benthos favoured a third group of arthropod micro-benthos, the ostracods. These animals adopted lifestyles that made them tolerant of changes in seawater O(2). Ostracods became the numerically dominant arthropod micro-benthos of the Phanerozoic. CONCLUSIONS/SIGNIFICANCE: Our work has implications from an evolutionary context for understanding how oxygen-level in marine ecosystems drives behaviour

Behavioural indicators of welfare in farmed fish

Behaviour represents a reaction to the environment as fish perceive it and is therefore a key element of fish welfare. This review summarises the main findings on how behavioural changes have been used to assess welfare in farmed fish, using both functional and feeling-based approaches. Changes in foraging behaviour, ventilatory activity, aggression, individual and group swimming behaviour, stereotypic and abnormal behaviour have been linked with acute and chronic stressors in aquaculture and can therefore be regarded as likely indicators of poor welfare. On the contrary, measurements of exploratory behaviour, feed anticipatory activity and reward-related operant behaviour are beginning to be considered as indicators of positive emotions and welfare in fish. Despite the lack of scientific agreement about the existence of sentience in fish, the possibility that they are capable of both positive and negative emotions may contribute to the development of new strategies (e. g. environmental enrichment) to promote good welfare. Numerous studies that use behavioural indicators of welfare show that behavioural changes can be interpreted as either good or poor welfare depending on the fish species. It is therefore essential to understand the species-specific biology before drawing any conclusions in relation to welfare. In addition, different individuals within the same species may exhibit divergent coping strategies towards stressors, and what is tolerated by some individuals may be detrimental to others. Therefore, the assessment of welfare in a few individuals may not represent the average welfare of a group and vice versa. This underlines the need to develop on-farm, operational behavioural welfare indicators that can be easily used to assess not only the individual welfare but also the welfare of the whole group (e. g. spatial distribution). With the ongoing development of video technology and image processing, the on-farm surveillance of behaviour may in the near future represent a low-cost, noninvasive tool to assess the welfare of farmed fish.Fundação para a Ciência e Tecnologia, Portugal [SFRH/BPD/42015/2007]info:eu-repo/semantics/publishedVersio

Les capacités d'adaptation du silure glane en hypoxie : un cas exemplaire d'homéostasie du milieu intérieur

Nous étudions les principes généraux qui expliquent comment les animaux aquatiques assurent leurs échanges gazeux (O2 et CO2) en fonction d'une part, de leurs besoins physiologiques et d'autre part, des changements des caractéristiques physico-chimiques du milieu. Cette synthèse, basée sur le cas exemplaire du silure glane, résume nos observations sur les mécanismes qui permettent à des animaux aquatiques physiologiquement très différents de s'adapter aux variations d'oxygénation du milieu ambiant. Le but de la stratégie d'adaptation est de maintenir constant l'état d'oxygénation du sang, à une faible valeur de pression partielle d'O2 (Po2) dans le sang artériel, indépendamment des variations de Po2 dans l'eau. Chez le silure, la valeur la plus couramment mesurée de Po2 dans le sang artériel est 2 kPa (15 mm Hg) pour des variations de Po2 dans l'eau comprises entre 3 et 40 kPa (1,5 à 20 mg.1−1 à 13 °C). Ce qui est aussi particulier chez cet animal est que toute l'adaptation est réalisée par la ventilation : il n'y a aucun changement de débit cardiaque, ni de modification de l'affinité de l'hémoglobine pour l'oxygène via le pH sanguin. La valeur de Po2 inspirée jusqu'à laquelle la consomation d'O2 peut être assurée pendant au moins 24 h à 13 °C est 2 à 3 kPa. Nous pensons que chez le silure cette valeur de Po2 est largement indépendante de la température car chez des animaux aussi divers que la carpe, la truite ou l'écrevisse (adaptés au laboratoire à différentes températures comprises entre 10 et 23 °C) la valeur de Po2 critique est aussi égale à 2-3 kPa indépendamment de la température. Toutes les mesures que nous citons ont été faites chez des animaux à jeun au laboratoire mais le principe du « fonctionnement » de très nombreux animaux aquatiques avec de faibles valeurs de Po2 artériel, indépendamment de la température, a été vérifié dans le milieu naturel. Nous n'avons actuellement aucune idée sur les capacités du silure dans un élevage intensif, en particulier lorsque des pathologies s'y développent. Néanmoins, il est clair que les capacités maximales d'adaptation du silure face à l'hypoxie sont très grandes