Geographic and seasonal patterns and limits on the adaptive response to temperature of European Mytilus spp. and Macoma balthica populations

Seasonal variations in seawater temperature require extensive metabolic acclimatization in cold-blooded organisms inhabiting the coastal waters of Europe. Given the energetic costs of acclimatization, differences in adaptive capacity to climatic conditions are to be expected among distinct populations of species that are distributed over a wide geographic range. We studied seasonal variations in the metabolic adjustments of two very common bivalve taxa at European scale. To this end we sampled 16 populations of Mytilus spp. and 10 Macoma balthica populations distributed from 39° to 69°N. The results from this large-scale comprehensive comparison demonstrated seasonal cycles in metabolic rates which were maximized during winter and springtime, and often reduced in the summer and autumn. Studying the sensitivity of metabolic rates to thermal variations, we found that a broad range of Q10 values occurred under relatively cold conditions. As habitat temperatures increased the range of Q10 narrowed, reaching a bottleneck in southern marginal populations during summer. For Mytilus spp., genetic-group-specific clines and limits on Q10 values were observed at temperatures corresponding to the maximum climatic conditions these geographic populations presently experience. Such specific limitations indicate differential thermal adaptation among these divergent groups. They may explain currently observed migrations in mussel distributions and invasions. Our results provide a practical framework for the thermal ecophysiology of bivalves, the assessment of environmental changes due to climate change and its impact on (and consequences for) aquaculture

Dynamique spatiale de la remise en suspension du microphytobenthos dans un écosystème estuarien

La remise en suspension du microphytobenthos est contrôlée par un certain nombre de facteurs physiques tels que l'hydrodynamisme et biologiques comme la bioturbation. Afin de mieux caractériser ce phénomène, un écosystème estuarien a été étudié, à marée basse pour la zone intertidale et au jusant pour la colonne d'eau. Les premiers résultats suggèrent un effet important des facteurs/processus impliqué

Participatory Qualitative Modeling to Assess the Sustainability of a Coastal Socio-Ecological System

International audienceAssessing the sustainability of socio-ecological systems requires understanding the interactions between numerous ecological, economic and social components. Models are often used to investigate how interactions shape system feedbacks and drive the complex dynamics at play in such systems. However, building these models is a non-trivial exercise, which often neglects stakeholder knowledge and perceptions. We adopted a participatory approach that relies on conducting workshops to engage stakeholders into the development of qualitative models of system feedback. This type of participatory qualitative modeling is well suited to address the complexity of socio-ecological systems in a holistic manner, identify key stakes and feedbacks, and predict responses to perturbations. We use this approach to investigate the factors that condition sustainability of the socio-ecological system associated with shellfish aquaculture in the Normand-Breton Gulf in France. Six region-specific workshops were organized with shellfish producers, managers and other stakeholders to identify and describe key components, interactions and pressures that contribute to overall socio-ecological dynamics. Differences and commonalities in system perceptions were identified across the different regions and focus groups. We reconciled stakeholder-specific discrepancies in model structure into a synthetic representation that conciliates alternative views of the system. Next, we predicted how the system might respond to alternative scenarios of change. Overall, our participatory qualitative modeling exercise identified key drivers of the system under study that constitute effective management levers to maintain system sustainability. For instance, low social acceptability of the aquaculture industry generally appears to be a major constraint on the sustainability of shellfish aquaculture in the Normand-Breton Gulf, while reducing rearing density appears to be a key driver of sustainability

Connectivities with shellfish farms and channel rivers are associated with mortality risk in oysters

International audienceOyster diseases have major consequences on fisheries and aquaculture. In France,young Pacific oysters Crassostrea gigasare severely hit by the ostreid herpesvirus, whereas adultssuffer mortalities presumably caused by pathogenic bacteria. Here we investigated the origin andspread of mortalities that affect both young and adult oysters, and we identified and comparedtheir risk factors. Mortality was monitored in 2 age classes of oysters deployed in early spring at39 sites spread over a 37 km2surface area inside and outside of shellfish farms. Environmentaldata obtained from numerical modelling were used to investigate risk factors. Mortality of youngoysters associated with ostreid herpesvirus occurred in the oyster farming area. Hydrodynamicconnectivity with oyster farms was associated with higher mortality risk, whereas chlorophyll aconcentration was associated with a lower risk. Adult oysters experienced 2 mortality events thatwere associated with different risk factors. The first event, which occurred after deployment andwas probably caused by endogenous pathogens, was mainly associated with connectivity to chan-nel rivers and salinity. The second mortality event observed at the end of the summer was mainlyassociated with connectivity to oyster farms, suggesting pathogen transmission. The risk factorsinvolved in young and adult oyster mortalities were partly different, reflecting distinct origins.Connectivity with oyster farms is a mortality risk factor for both young and adult oysters; thus, dis-ease management strategies that focus on oyster farming areas will impact overall disease risk

Global stakeholder vision for ecosystem-based marine aquaculture expansion from coastal to offshore areas

Marine aquaculture is the most promising industry for ensuring future provision of seafood. Yet, the worldwide growth and expansion of this industry have been slower than expected, calling for the identification of environmentally suitable sites while accounting for all factors that could constrain or benefit its establishment. Here, we determine the main obstacles and risks hindering the growth and expansion of marine aquaculture, as well as the needs and recommendations to overcome such constraints. Our analysis is based on results obtained from a consultation process held in 16 study sites located around the world with the participation of 614 stakeholders representing the research community, aquaculture industry, government, conservation groups, and education and fishermen associations. A high level of commonality exists in the main issues hindering aquaculture growth and expansion in coastal, off-the-coast and offshore aquaculture with most being attributed to interactions with other maritime activities, including conflicts with other users and administrative procedures, including licensing. Critical needs for improved management and expansion of the aquaculture industry are related to planning and management of developments and technological advances, with economic and market needs featuring to a lesser extent. Key procedures recommended to assist further aquaculture growth are the standardisation and simplification of regulatory frameworks, improvement of governance, and the adoption of participatory processes to facilitate meaningful and productive stakeholder engagement. We strongly recommend stakeholder participation to enhance insights on the full environmental and human dimensions of marine management and for implementation of ecosystem-based marine spatial planning

Évaluation de la contamination et des effets écotoxiques des microplastiques en estuaire de Seine ; les premiers enseignements du projet Plastic-Seine

International audienceLe bassin versant de la Seine peut être considéré comme représentatif des bassins hydrographiques fortement impactés par l'activité humaine et à ce titre présente une forte pression de pollution. La pollution chimique constitue une menace supplémentaire pour des écosystèmes aquatiques déjà trèsfragiles tels que les estuaires et les zones marines côtières. Peu d'études se sont concentrées sur la contamination et l'impact des microplastiques (MP, taille < 5 mm) dans les écosystèmes estuariens et aucune à ce jour en estuaire de Seine. Le projet Plastic-Seine (GIP Seine-Aval et CPIER Vallée de Seine) vise d’une part à quantifier la présence et le flux de MP dans l'estuaire de la Seine et d’autre part à évaluer leur devenir et leur impact sur différentes espèces du réseau trophique. Plusieurs campagnes de terrain ont été menées depuis mars 2017 sur le continuum eau douce-eau salée à différentes saisons pour échantillonner les eaux de surface, les sédiments et sept espèces du réseau trophique (poissons, crustacés, mollusques, annélides) représentatives de l'écosystème estuarienne de la Seine. Les premiers résultats indiquent une contamination modérée (1,8-5,1 fragments/m3) mais généralisée des différents compartiments abiotiques et biotiques par des MP comprenant principalement des fibres et des fragments. Des MP ont été identifiés dans toutes les espèces analysées, quel que soit le site ou la saison de prélèvement. Des expositions à des MP environnementaux en conditions contrôlées de laboratoire ont démontré l’ingestion mais aussi l’égestion très rapide de ces MP par les annélides et la sole commune (les analyses sont en cours sur les copépodes). Des premiers effets significatifs des MP sur la survie et la reproduction du copépode E. affinis et sur le comportement des soles ont été observés. Ce projet devrait fournir d’ici 2020 une première évaluation de la distributionet du flux de microplastiques dans l'estuaire de la Seine et de la faune aquatique associée