Évaluation des effets cumulatifs des changements globaux sur les écosystèmes : le cas de l'estuaire et du golfe du Saint-Laurent

RÉSUMÉ: Les écosystèmes sont de plus en plus soumis aux effets cumulatifs d'une variété de stresseurs environnementaux en réponse à la demande croissante en ressources naturelles et à l'intensification des changements climatiques. Ces observations stimulent une demande croissante pour les approches de gestion écosystémique et les évaluations régionales des effets cumulatifs. Pourtant, une gestion environnementale par silos centrée sur les évaluations par espèces et stresseurs individuels demeure la norme. Cette absence d'approches holistiques est particulièrement inquiétante pour la gestion d'espèces exploitées ou en péril puisque leur dynamique, comme celle de toutes espèces, est régie par le réseau d'interactions liant les espèces entre elles au sein d'une communauté écologique et à travers lequel les effets des stresseurs peuvent se propager indirectement. Cette disparité entre les besoin d'approches holistiques et la pratique est partiellement expliquée par un manque généralisé de connaissances théoriques des effets de multiples stresseurs sur les communautés écologiques et par des contraintes logistiques et méthodologiques. Dans ce contexte, l'objectif général de ma thèse est d'évaluer les effets cumulatifs des changements climatiques et des activités humaines sur les communautés écologiques du Système du Saint-Laurent au Canada. Les hypothèses générales de la thèse sont que les interactions influencent la propagation indirecte et non-additive des effets de multiples stressors à travers les communautés et que, en tant que tel, les interactions et les stresseurs devraient être considérés conjointement au sein d'analyse d'effets cumulatifs communauté-centrée.La thèse est divisée en trois parties. Dans la première partie (chapitre 1), je conceptualise la propagation des stresseurs environnementaux à travers les réseaux trophiques et j'explore théoriquement comment des stresseurs simulés affectent des motifs à trois espèces et des communautés du Système du Saint-Laurent. Nous trouvons que négliger les interactions écologiques sous-estime systématiquement les effets des stresseurs et que les effets synergiques et antagonistes sont fréquents à travers les interactions. À l'échelle des réseaux, nous trouvons que les prédateurs apicaux sont négativement affectés, alors que les méso-prédateurs bénéficient des effets des stresseurs dans le Système du Saint-Laurent. Par contre, la sensibilité des espèces dépend de la structure des réseaux trophiques. Le travail théorique proposé au chapitre 1 permet de valider les hypothèses générale de la thèse et offre un cadre accessible et appuyé par la théorie écologique pour inclure les interactions écologiques à l'évaluation des effets cumulatifs.La deuxième partie de ma thèse aborde des défis logistiques et méthodologiques pour l'évaluation des effets cumulatifs des changements climatiques et des activités humaines sur les communautés du Système du Saint-Laurent. Au chapitre 2, j'aborde le défi de caractériser les interactions écologiques au sein de systèmes où peu de données sont disponibles. Je présente une nouvelle méthode d'apprentissage non supervisée pour prédire les interactions binaires à partir de la proximité taxonomique entre espèces et d'une collection d'interactions empiriques connues entre espèces marines. Les résultats suggèrent que les interactions écologiques peuvent être prédites avec précision, ce qui pourrait promouvoir leur utilisation pour la gestion environnementale. Au chapitre 3, j'identifie des enjeux environnementaux et suggère des priorités de recherche et de gestion pour promouvoir les évaluations d'effets cumulatifs et la gestion écosystémique dans le Système du Saint-Laurent. Au chapitre 4, je caractérise la distribution et l'intensité de stresseurs environnementaux issus des activités humaines et des changements climatiques dans le Système du Saint-Laurent. À partir de collaborations, d'initiatives environnementales existantes et de portails de données ouvertes, 22 stresseurs d'origine côtière, du climat, de la pêche et du trafic maritime ont été car ctérisés. Les résultats du chapitre 4 démontrent que les stresseurs sont répandus partout dans le Système du Saint-Laurent et que l'estuaire, la gyre d'Anticosti, et les milieux côtiers sont particulièrement exposés aux stresseurs.Dans la troisième partie de la thèse (chapitre 5), je présente une évaluation des effets cumulatifs sur 193 espèces du Système du Saint-Laurent à partir d'une nouvelle approche communauté-centrée qui considère les interactions écologiques et les effets indirects. L'approche proposée s'appuie sur le cadre théorique présenté au chapitre 1 et utilise les résultats et méthodes des chapitres 2, 3 et 4. Je compare cette approche à une approche conventionnelle espèce-centrée pour exposer des propriétés émergentes provenant des interactions écologiques et des effets sur des espèces qui seraient normalement ignorés. Pour certaines espèces, considérer les interactions écologiques pourraient être l'unique moyen d'évaluer les effets des stresseurs environnementaux. Les poissons et les mammifères marins sont particulièrement susceptibles aux effets indirects de tous les types de stresseurs considérés; ceci est un contraste marqué avec le nombre limité de stresseurs qui les affectent directement.En alliant théorie, gestion environnementale et bio-informatique, ma thèse montre que les interactions écologiques sont un élément clé à considérer pour l'évaluation des effets de multiple stresseurs et propose une approche accessible pour les intégrer aux évaluations d'effets cumulatifs. Mes résultats sont particulièrement pertinents pour la gestion d'espèces exploitées et en péril, pour qui nous ignorons potentiellement des risques importants en négligeant les effets indirects provenant des interactions entre espèces. Développer ces capacités holistiques est essentiel en vue d'opérationnaliser un mode de gestion environnementale écosystémique. -- Mot(s) clé(s) en français : effets cumulatifs, stresseurs environnementaux, effets indirects, interactions biotiques, effets non-additifs, communautés écologiques, réseaux trophiques, Système du Saint-Laurent, activités humaines, changements climatiques. -- ABSTRACT: With demands for natural resources increasing alongside populations, and the effects of climate change intensifying, ecosystems worldwide are increasingly burdened with the cumulative effects of a vast array of environmental stressors. These observations stimulate a growing demand for ecosystem-based approaches and regional cumulative effects assessments. Yet environmental management still overwhelmingly operates in silos, focusing instead on single-stressor and single-species assessments. This is particularly concerning for exploited and endangered species whose dynamics, like that of all species, is driven by the network of interactions structuring ecological communities and through which the effects of stressors can propagate indirectly. A general lack of theoretical understanding of the effects of multiple stressors on ecological communities, and methodological and logistical constraints explain part of this discrepancy. In this context, the general objective of this thesis is to evaluate the cumulative effects of climate change and human activities on the ecological communities of the St. Lawrence System in eastern Canada. The general hypotheses guiding the thesis are that species interactions influence the indirect and non-additive spread of the effects of multiple stressors through communities and that, as such, species interactions and stressors should be considered together in network-scale cumulative effects assessments.The thesis is divided in three parts. In the first part (chapter 1), I conceptualize how stressors propagate through food webs and explore theoretically how they affect simulated 3-species motifs and food webs of the Canadian St. Lawrence System. We find that overlooking species interactions invariably underestimates the effects of stressors, and that synergistic and antagonistic effects through species interactions are prevalent. At the scale of food webs, we find that apex predators are generally negatively affected and mesopredators benefit from the effects of stressors in the St. Lawrence System, but that species sensitivity is dependent on food web structure. The theoretical simulations proposed in chapter 1 validate the general hypotheses of the thesis and provide an accessible and theory-grounded framework for the inclusion of species interactions in cumulative effects assessments.The second part of the thesis addresses logistical and methodological challenges for the cumulative effects assessment of climate change and human activities on communities of the St. Lawrence System. In chapter 2, I address the challenge of characterizing ecological interactions in data-deficient ecosystems. I present a new unsupervised machine learning method to predict interactions between any given set of species, given pairwise taxonomic proximity and a collection of known empirical interactions between marine species. Results from chapter 2 suggest that ecological interactions can be predicted with high accuracy, which could promote their use for environmental management. In chapter 3, I identify environmental issues and suggest research and management priorities to promote cumulative effects assessment and ecosystem-based management in the St. Lawrence System. In chapter 4, I characterize the distribution and intensity of environmental stressors arising from human activities and climate change in the St. Lawrence System. Through collaborations, existing environmental initiatives and open data portals, data-based indicators for 22 coastal, climate, fisheries, and marine traffic stressors were developed. Results from chapter 4 show that stressors are widespread and that coastal areas and the Estuary, Anticosti Gyre, and coastal areas are particularly exposed to cumulative exposure and cumulative hotspots.In the third part of the thesis (chapter 5), I present a cumulative effects assessment on 193 species of the St. Lawrence System using a novel network-scale approach that explicitly considers ecological interactions and indirect effects. The approach is built on the framework presented in chapte 1 and uses results and methods from chapters 2, 3 and 4. I compare our approach to a conventional species-scale assessment to expose transgressive properties arising from species interactions and uncover cumulative effects to species that would otherwise be overlooked. Fishes and marine mammals appear particularly prone to indirect effects from all types of stressors; this contrasts considerably with the limited number of stressors affecting them directly. For certain species, considering interactions may even be the only means of assessing the effects of stressors.In pairing theory, environmental management and computational capabilities, my thesis shows that ecological interactions are key to assess the effects of multiple stressors on species and proposes an accessible approach to integrate interactions to cumulative effects assessments. This is particularly relevant to the management of exploited and endangered species for which we may currently ignore significant threats by overlooking the less obvious yet no less significant effects arising from species interactions. Developing these holistic capabilities is essential to operationalize ecosystem-based management. -- Mot(s) clé(s) en anglais : cumulative effects, environmental stressors, indirect effects, biotic interactions, non-additive effects, ecological network, food web, St. Lawrence System, human activities, climate change

Postfledging Survival and Local Recruitment of a Riparian Songbird in Habitat Influenced By Reservoir Operations

The impact of anthropogenic activities on breeding bird populations are typically assessed using nest success despite the importance of the postfledging period and juvenile survival for the population dynamics of many birds. Using a combination of radio telemetry data collected between 2012 and 2014, and long-term monitoring data collected between 2005 and 2016, we evaluated whether postfledging survival of Yellow Warblers (Setophaga petechia) is affected when their riparian nesting habitat becomes inundated by the Upper Arrow Lakes Reservoir in the Columbia River Valley near Revelstoke, British Columbia, Canada. Thirty-eight percent of radiotagged fledglings (n = 26) survived for at least 21 days after leaving the nest. Radio-tagged birds that fledged from nests in territories that were inundated by water tended to be have lower survival than those that fledged from nests in territories that were not inundated by water. Local recruitment was low (6.4%, n = 438). Local recruitment was nevertheless positively affected by nestling condition prior to fledging. Fledglings from territories that were not inundated by water also tended to be more likely to recruit locally than those that fledged from territories that were inundated by water. In both cases, we estimated that reservoir operations that flooded habitat reduced postfledging survival or local recruitment by approximately 50%. Our study emphasizes the importance of considering the postfledging period when developing mitigation measures or management plans aimed at minimizing the impact of anthropogenic activities on bird populations

Precision modeling of JWST's first cluster lens SMACSJ0723.3-7327

Exploiting the fundamentally achromatic nature of gravitational lensing, we present a lens model for the massive galaxy cluster SMACSJ0723.3-7323 (SMACS J0723, z=0.388) that significantly improves upon earlier work. Building on strong-lensing constraints identified in prior Hubble Space Telescope (HST) observations, the mass model utilizes 21 multiple-image systems, 16 of which were newly discovered in Early Release Observation (ERO) data from the James Webb Space Telescope (JWST). The resulting lens model maps the cluster mass distribution to an RMS spatial precision of 1.08'' and is publicly available at https://www.dropbox.com/sh/3iatmz5k4hafzqf/AAAh0JvLgpBVoLp6qsxYZkFGa?dl=0 . Consistent with previous analyses, our study shows SMACSJ0723.3-7323 to be well described by a single large-scale component centered on the location of the brightest cluster galaxy, however JWST data point to the need for two additional diffuse components west of the cluster, which in turn accounts for all the currently identified multiply imaged systems. A comparison of the galaxy distribution, the mass distribution, and gas distribution in the core of SMACS0723 based on HST, JWST, and Chandra data reveals a fairly concentrated regular elliptical profile along with tell-tale signs of recent merger activity, possibly proceeding aligned closely to our line of sight. The exquisite sensitivity of JWST's NIRCAM reveals in spectacular fashion both the extended intra-cluster-light distribution and numerous star-forming clumps in magnified background galaxies. The high-precision lens model derived here for SMACSJ0723-7323 demonstrates impressively the power of combining HST and JWST data for unprecedented studies of structure formation and evolution in the distant Universe.Comment: Updated to match the version submitted to ApJ - analysis, results and conclusions are unchanged. Link to the lensing outputs: https://www.dropbox.com/sh/3iatmz5k4hafzqf/AAAh0JvLgpBVoLp6qsxYZkFGa?dl=

The marine fish food web is globally connected

The productivity of marine ecosystems and the services they provide to humans are largely dependent on complex interactions between prey and predators. These are embedded in a diverse network of trophic interactions, resulting in a cascade of events following perturbations such as species extinction. The sheer scale of oceans, however, precludes the characterization of marine feeding networks through de novo sampling. This effort ought instead to rely on a combination of extensive data and inference. Here we investigate how the distribution of trophic interactions at the global scale shapes the marine fish food web structure. We hypothesize that the heterogeneous distribution of species ranges in biogeographic regions should concentrate interactions in the warmest areas and within species groups. We find that the inferred global metaweb of marine fish—that is, all possible potential feeding links between co-occurring species—is highly connected geographically with a low degree of spatial modularity. Metrics of network structure correlate with sea surface temperature and tend to peak towards the tropics. In contrast to open-water communities, coastal food webs have greater interaction redundancy, which may confer robustness to species extinction. Our results suggest that marine ecosystems are connected yet display some resistance to perturbations because of high robustness at most locations.Using a global interaction dataset, the authors quantify the distribution of trophic interactions among marine fish, finding a high degree of geographic connectivity but low spatial modularity.C.A. was supported by a MELS-FQRNT Postdoctoral Fellowship and a Ressources Aquatique Québec (RAQ) fellowship during the conception and writing of this manuscript. T.P., D.G. and D.B.S. acknowledge financial support by the CIEE through their working group programme. M.B.A. is funded through FCT project No. PTDC/AAG-MAA/3764/2014. A.R.C. is funded by a Natural Sciences and Engineering Research Council of Canada (NSERC) PGS-D scholarship. D.G., T.P., M.-J.F., P.A. and S.J.L. are supported by NSERC Discovery Grants. T.P. also acknowledges a FRQNT New Investigator award and a Université de Montréal starting grant. D.B.S. acknowledges support from the Royal Society of New Zealand (via Marsden Fast-Start No. UOC-1101 and a Rutherford Discovery Fellowship)

Impacts potentiels cumulés des facteurs de stress liés aux activités humaines sur l’écosystème marin du Saint-Laurent

Les activités humaines modifient l’environnement naturel, perturbant par le fait même les organismes qui y habitent. Dans l’écosystème marin du golfe du Saint-Laurent, les diverses perturbations affectent les écosystèmes à différents degrés. Pour certains d’entre eux, les effets sont mal connus ou simplement inconnus. De plus, plusieurs perturbations peuvent affecter simultanément une composante de l’écosystème ou un système en entier. Les effets cumulés sont encore moins connus. Dans ce chapitre, nous synthétisons les connaissances actuelles sur les facteurs de stress liés aux activités humaines, puis essayons de déterminer leurs interactions et leurs effets cumulés sur l’écosystème du Saint-Laurent

Post Punk Art Now

"There are a number of aesthetic similarities between the punk movement and certain 20th-century artistic currents. With its rejection of established values, its strong sense of self-derision and iconoclasm, punk is closely related to Dadaism. Early on, many of its proponents were also influenced by Situationism. The manager of the Sex Pistols, Malcolm McLaren, frequently alluded to the emblematic texts of the movement and even declared, “It’s marvellous to use Situationism in rock.” In addition, the parodic appropriation of religious or political imagery on punk album jackets or posters is very much in keeping with the deviational spirit of Situationism." -- Publisher's website

Precision Modeling of JWST's First Cluster Lens SMACS J0723.3-7327

peer reviewe

A cluster randomized trial of a transition intervention for adolescents with congenital heart disease: rationale and design of the CHAPTER 2 study

BACKGROUND: The population of adolescents and young adults with congenital heart disease (CHD) is growing exponentially. These survivors are at risk of late cardiac complications and require lifelong cardiology care. However, there is a paucity of data on how to prepare adolescents to assume responsibility for their health and function within the adult health care system. Evidence-based transition strategies are required. METHODS: The Congenital Heart Adolescents Participating in Transition Evaluation Research (CHAPTER 2) Study is a two-site cluster randomized clinical trial designed to evaluate the efficacy of a nurse-led transition intervention for 16–17 year olds with moderate or complex CHD. The primary endpoint is excess time to adult CHD care, defined as the time interval between the final pediatric cardiology appointment and the first adult CHD appointment, minus the recommended time interval between these appointments. Secondary endpoints include the MyHeart score (CHD knowledge), Transition Readiness Assessment Questionnaire score, and need for catheter or surgical re-intervention. Participants are enrolled in clusters based on week of attendance in the pediatric cardiology clinic. The intervention consists of two one-hour individualized sessions between a cardiology nurse and study participant. Session One focuses on knowledge of the participant’s CHD, review of their cardiac anatomy and prior interventions, and potential late cardiac complications. Session Two focuses on self-management and communication skills through review and discussion of videos and role-play. The study will recruit 120 participants. DISCUSSION: Many adolescents and young adults experience a gap in care predisposing them to late cardiac complications. The CHAPTER 2 Study will investigate the impact of a nurse-led transition intervention among adolescents with CHD. Fidelity of the intervention is a major focus and priority. This study will build on our experience by (i) enrolling at two tertiary care programs, (ii) including a self-management intervention component, and (iii) evaluating the impact of the intervention on time to ACHD care, a clinically relevant outcome. The results of this study will inform pediatric cardiology programs, patients and policy makers in judging whether a structured intervention program provides clinically meaningful outcomes for adolescents and young adults living with CHD. TRIAL REGISTRATION: ClinicalTrials.gov ID NCT0172333