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Alfonso, S., Sadoul, B., Cousin, X., & Begout, M. - L. (2020). Spatial distribution and activity patterns as welfare indicators in response to water quality changes in European sea bass, Dicentrarchus labrax. Appl. Anim. Behav. Sci., 226, Unsp-104974.
Résumé: In aquaculture, fish are exposed to unavoidable stressors that can be detrimental for their health and welfare. However, welfare in farmed fish can be difficult to assess, and, so far, no standardized test has been universally accepted as a welfare indicator. This work contributes to the establishment of behavioural welfare indicators in a marine teleost in response to different water quality acute stressors. Groups of ten fish were exposed to high Total Ammonia Nitrogen concentration (High TAN, 18 mg.L-1), Hyperoxia (200 % O-2 saturation), Hypoxia (20 % O-2 saturation), or control water quality (100% O-2 saturation and TAN < 2.5 mg.L-1) over 1 hour. Fish were then transferred in a novel environment for a group behaviour test under the same water quality conditions over 2 hours. Videos were recorded to assess thigmotaxis, activity and group cohesion. After this challenge, plasma cortisol concentration was measured in a subsample, while individual behavioural response was measured in the other fish using novel tank diving test. Prior to this study, the novel tank diving test was validated as a behavioural challenge indicative of anxiety state, by using nicotine as anxiolytic drug. Overall, all stress conditions induced a decrease in activity and thigmotaxis and changes in group cohesion while only fish exposed to Hypoxia and High TAN conditions displayed elevated plasma cortisol concentrations. In post-stress condition, activity was still affected but normal behaviour was recovered within the 25 minutes of the test duration. Our work suggests that the activity, thigmotaxis and group cohesion are good behavioural indicators of exposure to degraded water quality, and could be used as standardized measures to assess fish welfare.
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Cozzoli, F., da Conceicao, T. G., Van Dalen, J., Fang, X., Gjoni, V., Herman, P. M. J., et al. (2020). Biological and physical drivers of bio-mediated sediment resuspension: A flume study on Cerastoderma edule. Estuar. Coast. Shelf Sci., 241, 106824.
Résumé: Predictive models accounting for the effect of bioturbation on sediment resuspension must be based on ecological theory as well as on empirical parametrization. The scaling trend of individual metabolic and activity rates with body mass may be a key to the mechanistic understanding of the observed patterns. With this study we tested if general size scaling rules in bio-mediated sediment resuspension may apply to a broad range of physical contexts for the endobenthic bivalve Cerastoderma edule. The effect on sediment resuspension of populations of C. edule differing by individual size was measured across physical gradients of current velocity and sediment composition in terms of fraction of fine particles. C. edule were able to enhance the resuspension of sediment containing silt, while they had scarce effect on the resuspension of coarse sediment. The effect of bioturbation was maximal at intermediate current velocity, when the hydrodynamic forcing is not strong enough to overcome the abiotic sediment resistance but it is able to suspend the bioturbated sediment. Although differences in sediment silt content and intensities of hydrodynamic stress have a relevant influence in determining the bioturbators individual contribution to sediment resuspension, the observed mass scaling trend is consistent across all treatments and close to theoretical expectation for size scaling of individual metabolic rates. This observation supports the hypothesis that the contribution of individual bioturbators to sediment resuspension is directly related to their energy use. Therefore, the proposed approach allows the formulation of expectations of biotic contribution to sediment resuspension based on the general size scaling laws of individual energy use.
Mots-Clés: Allometry; benthic macroinvertebrates; Bioturbation; bivalves scrobicularia-plana; Body size; Cerastoderma edule; cohesive sediment; Cohesiveness; cross-community approach; current-velocity; ecosystem engineers; metabolic theory; mortality responses; noncohesive sediments; nutrient fluxes; Sediment resuspension
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de Oliveira, J., Chadili, E., Turies, C., Brion, F., Cousin, X., & Hinfray, N. (2021). A comparison of behavioral and reproductive parameters between wild-type, transgenic and mutant zebrafish: Could they all be considered the same “zebrafish” for reglementary assays on endocrine disruption? Comp. Biochem. Physiol. C-Toxicol. Pharmacol., 239, 108879.
Résumé: Transgenic zebrafish models are efficiently used to study the effects of endocrine disrupting chemicals (EDC); thereby informing on their mechanisms of action. However, given the reported differences between zebrafish strains at the genetical, physiological and behavioral levels; care should be taken before using these transgenic models for EDC testing. In the present study, we undertook a set of experiments in different transgenic and/or mutant zebrafish strains of interest for EDC testing: casper, cyp19a1a-eGFP, cyp19a1a-eGFP-casper, cyp11c1-eGFP, cypncl-eGFP-casper. Some behavioral traits, and some biochemical and reproductive physiological endpoints commonly used in EDC testing were assessed and compared to those obtained in WT AB zebrafish to ensure that transgene insertion and/or mutations do not negatively modify basal reproductive physiology or behavior of the fish. Behavioral traits considered as anxiety and sociality have been monitored. Sociality was evaluated by monitoring the time spent near congeners in a shuttle box while anxiety was evaluated using the Novel tank diving test. No critical difference was observed between strains for either sociality or anxiety level. Concerning reproduction, no significant difference in the number of eggs laid per female, in the viability of eggs or in the female circulating VTG concentrations was noted between the 5 transgenic/mutants and the WT AB zebrafish studied. In summary, the transgene insertion and the mutations had no influence on the endpoints measured in basal conditions. These results were a prerequisite to the use of these transgenic/mutant models for EDC testing. Next step will be to determine the sensitivity of these biological models to chemical exposure to accurately validate their use in existing fish assays for EDC testing.
Mots-Clés: adult zebrafish; Behavior; Casper; danio-rerio; exposure; fish; genetic-variation; levonorgestrel; mutations; pigmentation; Reproduction; responses; sex-ratio; Transgenic; Zebrafish
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De Wit, R., Leruste, A., Le Fur, I., Sy, M. M., Bec, B., Ouisse, V., et al. (2020). A Multidisciplinary Approach for Restoration Ecology of Shallow Coastal Lagoons, a Case Study in South France. Front. Ecol. Evol., 8.
Résumé: By the end of the twentieth century, many of the coastal lagoons along the French Mediterranean coast showed insufficient water quality and degraded ecosystem states due to anthropogenic impacts. Among these, nutrient over-enrichment, resulting in eutrophication, has been a major concern. The Water Framework Directive of the E.U. (WFD) has initiated public action to improve their water quality and ecosystem state using an approach rooted in restoration ecology. Here we analyse how this has been applied for the coastal lagoons in South France, considering eutrophication as an example of ecosystem degradation and oligotrophication as the corresponding way for ecological restoration of the eutrophied coastal lagoons. Oligotrophication trajectories, initiated by the reduction of external nutrient loading, have resulted in a quick recovery (i.e. within 3 years) of integrative water column variables (Chlorophyll a, total N and P). The biomass of phytoplankton dropped very quickly showing concomitant changes in their community compositions. Starting from hypertrophic systems, the oligotrophication trajectory is described by a sequence of three ecosystem states dominated respectively by (i) phytoplankton with bare non-vegetated sediments, (ii) opportunistic macroalgae, (iii) angiosperm and perennial macroalgae, punctuated by regime shifts between these ecosystem states. Nevertheless, the latter regime shift has not been observed for the most degraded ecosystems after 10-years oligotrophication. The N and P accumulated in sediments during eutrophication may also retard the ecological restoration. In shallow freshwater lakes, the phytoplankton-dominated and the angiosperm-dominated states are also characteristic for highly-degraded and fully-restored ecosystems states, respectively. In contrast, opportunistic macroalgae do not bloom in these systems. Hence, the multiple stable state model, used successfully for these lakes, cannot be applied straightforwardly for coastal lagoons. To be successful, ecological restoration should consider societal questions as according the DPSIR framework it typically is a response of society. Local citizens and highly-involved stakeholders strongly value the coastal lagoons and attribute very high importance to their regulating ecosystem services (ESs). Different stakeholder profiles are related to different perceptions and appreciations of cultural ESs. Finally, more studies are needed to asses compatibility and incongruencies between the WFD and the Habitats directives, as both apply to coastal lagoons.
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Garcon, V., Karstensen, J., Palacz, A., Telszewski, M., Aparco Lara, T., Breitburg, D., et al. (2019). Multidisciplinary Observing in the World Ocean's Oxygen Minimum Zone Regions: From Climate to Fish – The VOICE Initiative. Front. Mar. Sci., 6, 722.
Résumé: Multidisciplinary ocean observing activities provide critical ocean information to satisfy ever-changing socioeconomic needs and require coordinated implementation. The upper oxycline (transition between high and low oxygen waters) is fundamentally important for the ecosystem structure and can be a useful proxy for multiple observing objectives connected to eastern boundary systems (EBSs) that neighbor oxygen minimum zones (OMZs). The variability of the oxycline and its impact on the ecosystem (VOICE) initiative demonstrates how societal benefits drive the need for integration and optimization of biological, biogeochemical, and physical components of regional ocean observing related to EBS. In liaison with the Global Ocean Oxygen Network, VOICE creates a roadmap toward observation-model syntheses for a comprehensive understanding of selected oxycline-dependent objectives. Local to global effects, such as habitat compression or deoxygenation trends, prompt for comprehensive observing of the oxycline on various space and time scales, and for an increased awareness of its impact on ecosystem services. Building on the Framework for Ocean Observing (FOO), we present a first readiness level assessment for ocean observing of the oxycline in EBS. This was to determine current ocean observing design and future needs in EBS regions (e.g., the California Current System, the Equatorial Eastern Pacific off Ecuador, the Peru-Chile Current system, the Northern Benguela off Namibia, etc.) building on the FOO strategy. We choose regional champions to assess the ocean observing design elements proposed in the FOO, namely, requirement processes, coordination of observational elements, and data management and information products and the related best practices. The readiness level for the FOO elements was derived for each EBS through a similar and very general ad hoc questionnaire. Despite some weaknesses in the questionnaire design and its completion, an assessment was achievable. We found that fisheries and ecosystem management are a societal requirement for all regions, but maturity levels of observational elements and data management and information products differ substantially. Identification of relevant stakeholders, developing strategies for readiness level improvements, and building and sustaining infrastructure capacity to implement these strategies are fundamental milestones for the VOICE initiative over the next 2-5 years and beyond.
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