Life-history strategies constrain invertebrate community tolerance to multiple stressors: A case study in the Ebro basin

AbstractContextMultiple stressors constitute a serious threat to aquatic ecosystems, particularly in the Mediterranean region where water scarcity is likely to interact with other anthropogenic stressors. Biological traits potentially allow the unravelling of the effects of multiple stressors. However, thus far, trait-based approaches have failed to fully deliver on their promise and still lack strong predictive power when multiple stressors are present.GoalWe aimed to quantify specific community tolerances against six anthropogenic stressors and investigate the responses of the underlying macroinvertebrate biological traits and their combinations.MethodsWe built and calibrated boosted regression tree models to predict community tolerances using multiple biological traits with a priori hypotheses regarding their individual responses to specific stressors. We analysed the combinations of traits underlying community tolerance and the effect of trait association on this tolerance.ResultsOur results validated the following three hypotheses: (i) the community tolerance models efficiently and robustly related trait combinations to stressor intensities and, to a lesser extent, to stressors related to the presence of dams and insecticides; (ii) the effects of traits on community tolerance not only depended on trait identity but also on the trait associations emerging at the community level from the co-occurrence of different traits in species; and (iii) the community tolerances and the underlying trait combinations were specific to the different stressors.ConclusionThis study takes a further step towards predictive tools in community ecology that consider combinations and associations of traits as the basis of stressor tolerance. Additionally, the community tolerance concept has potential application to help stream managers in the decision process regarding management options

Using conditional tree forests and life history traits to assess specific risks of stream degradation under multiple pressure scenario

International audienceThe full accomplishment of the European Water Framework Directive objectives has required from EU members three successive steps: (i) the evaluation of their water body ecological status, (ii) the risk assessment of different anthropogenic pressure categories and (iii) the implementation of appropriate management and restoration programs.We aimed at designing an innovative retrospective ecological risk assessment (ERA) tool working for most of the French wadeable rivers in a context of multiple anthropogenic pressures (step ii). This tool, including conditional tree forest (CTF) models, was built on combinations of benthic macroinvertebrate trait-based metrics for each of sixteen anthropogenic pressure categories.For eleven pressure categories, CTF models have given good impairment risk assessment (i.e. AUC >= 0.70), even at moderate risk level and in a multi-pressure context. The four other models have provided poorer but promising results (AUC = 0.67 +/- 0.02).Identifying the potential weight of individual anthropogenic pressures that lead to biotic assemblage impairment in streams under multiple pressure scenario, is a key step for managers to implement appropriate stream restoration programs. Simultaneously considering the whole complexity of bio-ecological adaptations within biotic assemblages subjected to human pressures provides a functional diagnostic tool both (i) ecologically relevant and (ii) efficient for ERA

Une nouvelle génération d’indicateurs : l’exemple de l’indice invertébrés multimétrique I2M2.

International audiencePour répondre aux nouvelles règles d’évaluation fixées par la directive cadre européenne sur l’eau, les méthodes de bioindication basées sur l’observation des invertébrés ont été renouvelées et améliorées. Grâce à la combinaison de plusieurs métriques taxonomiques et fonctionnelles, le nouvel indice multimétrique I2M2 permet aujourd’hui de mieux évaluer l’état écologique d’un cours d’eau et d’améliorer la détection de certaines pressions liées aux activités humaines, comme par exemple la présence de micropolluants

Stoichiometric traits predict the composition of macroinvertebrate communities: Extending the Growth Rate Hypothesis to species development

International audienc

Linking Micropollutants to Trait Syndromes across Freshwater Diatom, Macroinvertebrate, and Fish Assemblages

The ecological quality of freshwater ecosystems is endangered by various micropollutants released into the environment by human activities. The cumulative effects of these micropollutants can affect the fitness of organisms and populations and the functional diversity of stream ecosystems. In this study, we investigated the relationships between the joint toxicity of micropollutants and trait syndromes. A trait syndrome corresponds to a combination of traits that could occur together in communities due to the trait selection driven by exposure to these micropollutants. Our objectives were to (i) identify trait syndromes specific to diatom, macroinvertebrate, and fish assemblages and their responses to exposure, taking into account four micropollutant types (mineral micropollutants, pesticides, PAHs, and other organic micropollutants) and nine modes of action (only for pesticides), (ii) explore how these syndromes vary within and among the three biological compartments, (iii) investigate the trait categories driving the responses of syndromes to micropollutant exposure, and (iv) identify specific taxa, so-called paragons, which are highly representative of these syndromes. To achieve these objectives, we analyzed a dataset including the biological and physico-chemical results of 2007 sampling events from a large-scale monitoring survey routinely performed in French wadeable streams. We have identified five (diatoms), eight (macroinvertebrates), and eight (fishes) trait syndromes, either positively or negatively related to an increasing toxicity gradient of different clusters of micropollutant types or modes of action. Our analyses identified several key trait categories and sets of paragons, exhibiting good potential for highlighting exposure by specific micropollutant types and modes of action. Overall, trait syndromes might represent a novel and integrative bioassessment tool, driven by the diversity of trait-based responses to increasing gradients of micropollutant toxic cocktail

Intérêt de la biodiversité de quelques bioagresseurs de la vigne

National audienc

Long-term trends in trait structure of riverine communities facing predation risk increase and trophic resource decline

Many large European rivers have undergone multiple pressures which have strongly impaired ecosystem functioning at different spatial and temporal scales. Global warming and other environmental changes have favoured the success of invasive species, deeply modifying the structure of aquatic communities in large rivers. Some exogenous species could alter trophic interactions within assemblages by increasing the predation risk for potential prey species (top-down effect) and limiting the dynamics of others via resource availability limitation (bottom-up effect). Furthermore, large transboundary rivers are complex aquatic ecosystems which have often been poorly investigated so that data for assessing long-term ecological trends are missing. In this study, we propose an original approach for investigating long-term combined effects of global warming, trophic resource decrease, predation risk and water quality variations on the trait-based structure of macroinvertebrate and fish assemblages over 26 years (1985-2011) and 427-km stretch of the river Meuse (France and Belgium). The study of temporal variations in biological, physiological and ecological traits of macroinvertebrate and fish allowed identifying community trends and distinguishing impacts of environmental perturbations from those induced by biological alterations. We provide evidence, for this large European river, of an increase in water temperature (close to 1°C) and a decrease in phytoplankton biomass (- 85%), as well as independent effects of these changes on both invertebrate and fish communities. The reduction of trophic resources in the water column by invasive molluscs has dramatically affected the density of omnivorous fish in favour of invertebrate-feeders, while scrapers became the major feeding guild among invertebrates. Macroinvertebrate and fish communities have shifted from large-sized organisms with low fecundity to prolific, small-sized organisms, with early maturity, as a response to increased predation pressure

Bioindication : des outils pour évaluer l'état écologique des milieux aquatiques - Perspectives en vue du 2e cycle DCE - Eaux de surface continentales

[Departement_IRSTEA]Eaux [TR1_IRSTEA]QUASARE [TR2_IRSTEA]BELCAAprès une présentation des besoins en matière d'évaluation de la qualité des milieux aquatiques continentaux, ce document présente l'état de l'art sur le développement des bioindicateurs tels qu'il a été présenté lors du séminaire organisé par l'Onema les 19 et 20 avril 2011 à Paris. Il s'agit donc d'une synthèse des journées "DCE et bioindication