Importance of grey mullets on coastal food webs in a context of omega-3 deficiency: from sub-individual level to trophic dynamics

International audienc

A toolbox to evaluate data reliability for whole-ecosystem models: Application on the Bay of Biscay continental shelf food-web model

Ecosystem models are always simplifications of reality and as such their application for ecosystem-based management requires standard validation. Here, the “DataReli” toolbox is proposed to evaluate the quality of the data used during the construction of ecosystem models, their coherence across trophic levels, and whether data limitations prevent the model long-term applications. This toolbox is the combination of three operational and complementary analyses: (i) the pedigree index to determine to what extent a model was calibrated on data of local origin; (ii) the graphical analysis known as PREBAL to assess whether a model respects some basic ecological and fisheries principles; and (iii) a sensitivity analysis to evaluate the robustness of model predictions to small variations in input data. The toolbox is delivered to potential users with main generic recommendations on how interpreting results conjointly and on which decisions to make about parameters’ revisions or model uses’ restrictions. (i) Corrections of parameters should be preferentially envisaged when modelling data-rich environments. (ii) For those models with an overall pedigree index above 0.4, a closer look at the pedigree routine, i.e. values by parameters and compartments, and the PREBAL analysis would help to prioritize parameters needing improvement. (ii)’ For Ecopath models of no overall acceptable quality (overall pedigree index <0.4), we recommend stopping the DataReli procedure at this point. (iii) In terms of sensitivity analysis, marked responses of model predictions to small variations in the input values must preferentially lead to restrictions in the model applications compared to corrections of parameter estimates. A concrete application of the “DataReli” toolbox to the pre-existing Ecopath model of the Bay of Biscay continental shelf food web is presented. For the present case study, the general level of input data reliability is considered as satisfying with regard to the model applications

An ecosystem-wide approach for assessing the spatialized cumulative effects of local and global changes on coastal ecosystem functioning

Coastal ecosystems are subjected to an increasing number of anthropogenic drivers, including marine renewable energies and climate change (CC). These drivers can interact in complex ways, which may lead to cumulative effects (CEs) whose potential consequences on the ecosystems need to be addressed. We used a holistic approach—ecological network analysis (ENA)—coupled with a two-dimensional food web model—Ecospace—to conduct an ecosystem study of the CEs of CC plus the operation of an offshore wind farm on ecosystem functioning in the extended Bay of Seine (English Channel). Mapped ENA indices showed that CEs were not restricted to the wind farm area, i.e. where anthropogenic drivers are concomitant. CEs varied both in space and among ecosystem properties, displaying that ENA indices can distinguish between different cumulative pathways that modify ecosystem functioning in multiple ways. Moreover, the effects seemed to be tied to the structuring role of CC, and differed under the 2050 and 2100 conditions. Such changes resulted in stronger loss of ecosystem resilience under the 2100 conditions despite the benefits of the reef and reserve effects of the wind farm

Modelling species distribution, ecosystem structure and function and climate change

In recent decades, oceans have been increasingly stressed by human activities that induced significant changes in its abiotic properties. Temperature increase, acidification, deoxygenation, deregulation of ocean currents are some examples of the anthropogenic impact on our oceans. In addition, pollution and overexploitation of marine resources will lead to severe and possibly irreversible changes for marine life. As environmental conditions directly affect the physiology of species, changes in species distribution and trophic interactions have already been observed and are expected to increase in the near future. Predicting future oceans is currently a great challenge for scientists that work to maintain, as best as possible, the goods and services they provide. In this context, ecologists have developed several modeling approaches able to simulate changes in both species distribution (Ecological Niche Models – ENMs) and interactions (static and dynamic food-web models). This chapter explains these two approaches in detail as well as the ways by which these two families of models can be coupled. In each part, the main existing algorithms will be reviewed, with their advantages and limitations, and some key examples retrieved from recent scientific literature will be presented. Finally, we will discuss the current issues of these methods and their potential improvement

Spatialized ecological network analysis for ecosystem-based management: effects of climate change, marine renewable energy, and fishing on ecosystem functioning in the Bay of Seine

International audienceIntegrative and spatialized tools for studying the effects of a wide variety of ecosystem drivers are needed to implement ecosystem-based management and marine spatial planning. We developed a tool for analyzing the direct and indirect effects of anthropic activities on the structure and functioning of coastal and marine ecosystems. Using innovative modelling techniques, we ran a spatially explicit model to carry out an ecological network analysis (ENA) of the effects of climate change (CC), of an offshore wind farm (OWF) and of multiple fishing scenarios on the Bay of Seine (eastern part of the English Channel) ecosystem. ENA indices described the effects of those different drivers in a holistic and spatial way. The spatial analysis of ecosystem properties revealed local and global patterns of modifications attributed to CC, while the OWF resulted in localized changes in the ecosystem. This ability of ENA indicators to detect human-induced changes in ecosystem functioning at various spatial scales allows for a more integrative view of the effects of human activities on ecosystems. ENA indices could be used to link both local and global ecosystem changes, for a more cross-scale approach to ecosystem management

Spatialized ecological network analysis for ecosystem-based management: effects of climate change, marine renewable energy, and fishing on ecosystem functioning in the Bay of Seine

Integrative and spatialized tools for studying the effects of a wide variety of ecosystem drivers are needed to implement ecosystem-based management and marine spatial planning. We developed a tool for analyzing the direct and indirect effects of anthropic activities on the structure and functioning of coastal and marine ecosystems. Using innovative modelling techniques, we ran a spatially explicit model to carry out an ecological network analysis (ENA) of the effects of climate change (CC), of an offshore wind farm (OWF) and of multiple fishing scenarios on the Bay of Seine (eastern part of the English Channel) ecosystem. ENA indices described the effects of those different drivers in a holistic and spatial way. The spatial analysis of ecosystem properties revealed local and global patterns of modifications attributed to CC, while the OWF resulted in localized changes in the ecosystem. This ability of ENA indicators to detect human-induced changes in ecosystem functioning at various spatial scales allows for a more integrative view of the effects of human activities on ecosystems. ENA indices could be used to link both local and global ecosystem changes, for a more cross-scale approach to ecosystem management

Impacts of climate change on the Bay of Seine ecosystem: Forcing a spatio‐temporal trophic model with predictions from an ecological niche model

Climate change is already known to cause irreversible impacts on ecosystems that are difficult to accurately predict due to the multiple scales at which it will interact. Predictions at the community level are mainly focused on the future distribution of marine species biomass using ecological niche modelling, which requires extensive efforts concerning the effects that trophic interactions could have on the realized species dynamics. In this study, a set of species distribution models predictions were used to force the spatially‐explicit trophic model Ecospace in order to evaluate the potentials impacts that two 2,100 climate scenarios, RCP2.6 and RCP8.5, could have on a highly exploited ecosystem, the Bay of Seine (France). Simulations demonstrated that both scenarios would influence the community of the Bay of Seine ecosystem: as expected, more intense changes were predicted with the extreme scenario RCP8.5 than with the RCP2.6 scenario. Under both scenarios, a majority of species underwent a decrease of biomass, although some increased. However, in both cases the stability of the majority of species dynamics was lowered, the sustainability of the fishery. Differences between niche modelling predictions and those obtained through the forcing in Ecospace highlighted the paramount importance of considering trophic interactions in climate change simulations. These results illustrate the requirement of multiplying novel approaches for efficiently forecasting potential impacts of climate change

Importance des mugilidés sur les réseaux trophiques côtiers dans un contexte de carence en oméga-3 : du niveau sub-individuel à la dynamique trophique

International audienceIl est aujourd'hui reconnu qu'à son rythme actuel le changement global va entraîner une réduction de laproduction d’acides gras oméga-3 à longue chaîne à la base du réseau trophique marin, en conséquence del'altération des assemblages de microalgues et de leur physiologie. Ces oméga-3 ont un rôle vital dans lemaintien des fonctions physiologiques des organismes supérieurs et une baisse de leur production à la basedu réseau trophique marin devrait mécaniquement avoir des répercussions sur la disponibilité de cesnutriments pour les consommateurs primaires et secondaires, tels que les poissons marins, presqueincapables de les synthétiser. Les mugilidés sont des poissons opportunistes qui occupent une diversité d’habitats et tolèrent une large gamme de conditions environnementales. Ils occupent généralement une position intermédiaire dans les réseaux trophiques côtiers : ils broutent le biofilm microalgal, et sont consommés par d’autres espèces de poissons exploités. Ils jouent donc un rôle central dans le couplage entre les compartiments trophiques de fond et ceux de la colonne d’eau, et contribuent ainsi au transfert des oméga-3 vers l’Homme.De récents résultats expérimentaux sur le mulet doré ont démontré que certaines de ses performancesphysiologiques et comportementales s’altèrent en réponse à une carence trophique en oméga-3, mais lesconséquences de ces changements aux niveaux d’intégration supérieurs et notamment du réseautrophique restent méconnues. Le but de la présente étude est de proposer une approche de modélisationpermettant d’intégrer des données écophysiologiques dans une suite de modèles afin d'estimer l'impactde ces changements sur les réseaux trophiques côtiers. Des modèles DEB (Dynamic Energy Budget) ont été développés pour les deux espèces de mugilidés présentes en baie de Marennes-Oléron afin de forcer un modèle trophique multi-spécifique dynamique et non-déterministe, et simuler les évolutions possibles des caractéristiques de ce réseau trophique sous contraintes de diminution trophique des oméga-3

Importance des mugilidés sur les réseaux trophiques côtiers dans un contexte de carence en oméga-3 : du niveau sub-individuel à la dynamique trophique

International audienceIl est aujourd'hui reconnu qu'à son rythme actuel le changement global va entraîner une réduction de laproduction d’acides gras oméga-3 à longue chaîne à la base du réseau trophique marin, en conséquence del'altération des assemblages de microalgues et de leur physiologie. Ces oméga-3 ont un rôle vital dans lemaintien des fonctions physiologiques des organismes supérieurs et une baisse de leur production à la basedu réseau trophique marin devrait mécaniquement avoir des répercussions sur la disponibilité de cesnutriments pour les consommateurs primaires et secondaires, tels que les poissons marins, presqueincapables de les synthétiser. Les mugilidés sont des poissons opportunistes qui occupent une diversité d’habitats et tolèrent une large gamme de conditions environnementales. Ils occupent généralement une position intermédiaire dans les réseaux trophiques côtiers : ils broutent le biofilm microalgal, et sont consommés par d’autres espèces de poissons exploités. Ils jouent donc un rôle central dans le couplage entre les compartiments trophiques de fond et ceux de la colonne d’eau, et contribuent ainsi au transfert des oméga-3 vers l’Homme.De récents résultats expérimentaux sur le mulet doré ont démontré que certaines de ses performancesphysiologiques et comportementales s’altèrent en réponse à une carence trophique en oméga-3, mais lesconséquences de ces changements aux niveaux d’intégration supérieurs et notamment du réseautrophique restent méconnues. Le but de la présente étude est de proposer une approche de modélisationpermettant d’intégrer des données écophysiologiques dans une suite de modèles afin d'estimer l'impactde ces changements sur les réseaux trophiques côtiers. Des modèles DEB (Dynamic Energy Budget) ont été développés pour les deux espèces de mugilidés présentes en baie de Marennes-Oléron afin de forcer un modèle trophique multi-spécifique dynamique et non-déterministe, et simuler les évolutions possibles des caractéristiques de ce réseau trophique sous contraintes de diminution trophique des oméga-3