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| Distribution of cumulative exposure in the St. Lawrence System.

| Distribution of cumulative exposure in the St. Lawrence System.

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Article
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The St. Lawrence is a vast and complex socio-ecological system providing a wealth of services that sustain numerous economic sectors. This ecosystem is subject to significant human pressures that overlap and potentially interact with climate-driven environmental changes. Our objective in this paper was to systematically characterize the distributio...

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Context 1
... now focus on the integrative exposure indicators. Apart from the northeastern Gulf, cumulative exposure is ubiquitous in the St. Lawrence (Figure 3). Cumulative exposure is generally highest along coasts (Figure 3), with hotspots located in the vicinity of coastal cities (Figure 4). ...
Context 2
... from the northeastern Gulf, cumulative exposure is ubiquitous in the St. Lawrence (Figure 3). Cumulative exposure is generally highest along coasts (Figure 3), with hotspots located in the vicinity of coastal cities (Figure 4). In general, offshore areas are less exposed to cumulative drivers, with the Estuary and the Anticosti Gyre being notable exceptions (Figures 3, 4). ...
Context 3
... exposure is generally highest along coasts (Figure 3), with hotspots located in the vicinity of coastal cities (Figure 4). In general, offshore areas are less exposed to cumulative drivers, with the Estuary and the Anticosti Gyre being notable exceptions (Figures 3, 4). This is not to say that offshore areas are free from exposure, as most of the St. Lawrence is exposed to multiple overlapping drivers (Figures 3, 4). ...
Context 4
... general, offshore areas are less exposed to cumulative drivers, with the Estuary and the Anticosti Gyre being notable exceptions (Figures 3, 4). This is not to say that offshore areas are free from exposure, as most of the St. Lawrence is exposed to multiple overlapping drivers (Figures 3, 4). For example, the heads of the Anticosti and Esquiman channels are highly exposed to cumulative drivers (Figure 3). ...
Context 5
... is not to say that offshore areas are free from exposure, as most of the St. Lawrence is exposed to multiple overlapping drivers (Figures 3, 4). For example, the heads of the Anticosti and Esquiman channels are highly exposed to cumulative drivers (Figure 3). ...
Context 6
... informative, the hypoxia-fisheries example focuses on a single pair of drivers and falls short of the number of drivers typically overlapping at high intensities throughout the St. Lawrence (Figure 4). The number of drivers overlapping in the St. Lawrence increases with cumulative exposure ( Figure S3). Areas with high exposure such as the Estuary, the Anticosti Gyre, and the southwestern Gulf coastline (Figures 3, 4) are thus areas where driver interactions are most likely and where they can arise between a host of different drivers. ...
Context 7
... number of drivers overlapping in the St. Lawrence increases with cumulative exposure ( Figure S3). Areas with high exposure such as the Estuary, the Anticosti Gyre, and the southwestern Gulf coastline (Figures 3, 4) are thus areas where driver interactions are most likely and where they can arise between a host of different drivers. Identifying areas with similar cumulative exposure profiles provides a crucial tool to simplify the multi-dimensional complexity of overlapping drivers (Bowler et al., 2019). ...

Citations

... Finally, terrestrial and aquatic ecosystems are interlinked and while drivers may emerge from one ecosystem, they may affect adjacent ones. Therefore, terrestrial and coastal environments (freshwater or marine) must be incorporated since coastlines are not impermeable barriers (Beauchesne et al. 2020). To do so, we can investigate the effect of landbased drivers on freshwater ecosystems and vice versa (e.g., terrestrial nutrient input to freshwater or marine coastal waters). ...
Article
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Natural ecosystems are experiencing unprecedented rates of change due to anthropogenic activities and global change, leading to either gradual changes in a given response or tipping points. While the tipping point concept has been tested in an array of habitats since the 1960s, the spatiotemporal superposition of multiple drivers in different ecosystems needs to be considered when investigating the response of species, communities, populations, and ecosystems along environmental gradients. Here, we (1) develop a historical and current perspective of tipping point studies in terrestrial, freshwater, and marine ecological systems; (2) portray the research effort in different freshwater and marine habitats; and (3) explore the results of experimental studies focusing on tipping points measured at the individual, communities, ecosystem level, as well as ecosystem functions and services in a context of single and multiple stressors. The number of studies mentioning the concept of tipping points increases every year, but very few studies have specific objective to identify them. Even fewer studies consider how the addition of another stressor into an ecosystem may alter a tipping point. In addition, many studies investigated multiple responses, but only one‐fourth (7 out of 28) of them concentrate their effort on multiple biological or ecological levels of complexity. This review allowed us to identify shortcomings in this research field and propose ways to make this ecological concept anew.
... We focused on the shallow subtidal zone between 5 and 15 m and within the limits of the Sept-Îles Port Authority (Fig. 1) where several potentially impacting activities are concentrated, including commercial and recreational fisheries, boating, shipping, contaminant spills/runoff, and waste-water outflow (Beauchesne et al., 2020;Carrière, 2018). Within this area, we identified three broad sectors: BSI (hereafter "the bay"), the Archipel des Sept-Îles (hereafter "the archipelago"), and Baie de St. Marguerite (Fig. 1). ...
... Salinity and freshwater input descriptors were obtained from Dutil et al. (2012). Site exposure to potential anthropogenic drivers included: the 25th percentile distance from sources of human disturbance (i.e., stormwater drainage and wastewater outfalls, dumping areas for dredged sediments, ship anchoring and trans-shipment areas, piers and shipping lanes; data from Carrière (2018) and OpenStreetMap) and the intensity of four types of commercial fisheries (traps, bottom dredging, bottom trawling and nets; data from Beauchesne et al., 2020). Details on sediment analysis and driver quantification are provided as supplementary material. ...
Article
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The assessment of natural ecosystem status is a fundamental premise to enable environmental management at local scales to maintain ecosystem functioning, services and resilience. Ecologists have developed many biological and environmental indices to inform and support environmental management and policies. To promote efficient use of resources, existing indices would ideally be informative for the widest geographic extent to avoid the development of new but redundant indices. The Ecosystem-Based Quality Index (EBQI), developed for the Mediterranean Sea, may be adaptable to other ecosystems due to its functional approach being closer to a methodological framework than a specialized index. We investigated the adaptability of EBQI beyond its original geographical setting and its applicability to a predefined location rather than a predefined ecosystem. We propose a workflow to apply EBQI to areas without a priori well-defined ecosystems: the shallow subtidal coastal areas of Baie des Sept Îles (Gulf of St. Lawrence, Canada), a major industrial port where the seafloor ranges from soft to mixed substrata (i.e., boulders and gravel in a soft-bottom matrix), creating ecosystem heterogeneity where species typical of different habitats often co-occur. We then tested the index for the assessment of this ecosystem with an explicit consideration of the ecosystem heterogeneity in shallow areas, typically unaccounted for by other indices. Using field sampling and a literature review, we showed that the EBQI can be implemented in areas where little prior information about a given ecosystem is available. Our EBQI implementation, shGSL-EBQI (shallow heterogeneous Gulf of St. Lawrence-EBQI), provided ecosystem status classifications that were robust and consistent with available environmental assessments in the area. We then showed that shGSL-EBQI relates to multiple environmental and anthropogenic drivers and suggest approaches to limit the effect of confounding environmental gradients. Finally, we discuss the potential applicability of shGSL-EBQI to other regions of the Gulf of St. Lawrence and provide advice on how a coastal monitoring initiative could facilitate widespread adoption of EBQI in Canada. As efforts to base future development on sustainability through ecosystem-based management increase both in Canada and internationally, we demonstrate that EBQI is well suited to the Canadian context and thus likely more generally in other jurisdictions.
... For each motif in a species motif census, we evaluate which pathway of effect-if any-is affecting the motif. We consider the most prevalent sources of offshore human-and climate-induced stress in the St. Lawrence System to identify pathways of effect; these are shipping, trawl, trap and pelagic fisheries, ocean acidification, hypoxia and bottom-and surface-water temperature anomalies (Beauchesne et al., 2020). As modelling or observing each pathway of effect on empirical three-species interactions is not realistic, we used the results from the simulations on theoretical motifs to infer-rather than a modelling approach-a species sensitivity to stressors as a function of its position in a food web. ...
... Knowledge on the distribution and intensity of stressors (e.g. Halpern et al., 2015;Beauchesne et al., 2020), species occurrences (e.g. GBIF, 2020; OBIS 2020), interactions (e.g. ...
Article
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Evaluating the effects of multiple stressors on ecosystems is becoming increasingly vital with global changes. The role of species interactions in propagating the effects of stressors, although widely acknowledged, has yet to be formally explored. Here, we conceptualise how stressors propagate through food webs and explore how they affect simulated three‐species motifs and food webs of the Canadian St. Lawrence System. We find that overlooking species interactions invariably underestimate the effects of stressors, and that synergistic and antagonistic effects through food webs are prevalent. We also find that interaction type influences a species’ susceptibility to stressors; species in omnivory and tri‐trophic food chain interactions in particular are sensitive and prone to synergistic and antagonistic effects. Finally, we find that apex predators were negatively affected and mesopredators benefited from the effects of stressors due to their trophic position in the St. Lawrence System, but that species sensitivity is dependent on food web structure. In conceptualising the effects of multiple stressors on food webs, we bring theory closer to practice and show that considering the intricacies of ecological communities is key to assess the net effects of stressors on species. The role of species interactions in propagating the effects of stressors, although widely acknowledged, has yet to be formally explored. Here, we conceptualise how stressors propagate through food webs and we find that overlooking species interactions invariably underestimate the effects of stressors. In conceptualising the effects of multiple stressors on food webs, we bring theory closer to practice and show that considering the intricacies of ecological communities is key to assess the net effects of stressors on species.
... Combined with global changes, this intense human use has concomitantly exposed this ecosystem to multiple environmental changes. Like many inland seas, the EGSL has internal dynamics that restrict flushing and are subject to a convergence of pressures from land-based and marine disturbances as well as climatic changes (MacCraken et al., 2008;Beauchesne et al., 2020). Deep waters of the EGSL are warming, reaching new temperature records in 2019 due to altered ocean circulation dynamics (Claret et al., 2018;Galbraith et al., 2020). ...
... Data on environmental predictors were obtained from two datasets: the fisheries multidisciplinary research survey and eDrivers, an open-knowledge data platform (Beauchesne et al., 2020). For the fisheries survey data, an SBE19plusTM CTD mounted on the outside of the top of the trawl recorded temperature, salinity, and oxygen concentration on the bottom during the trawling at each site (Bourdages et al., 2018). ...
... Depth was also recorded at the beginning and end of each trawl to provide a mean for each site. The second set of predictors was extracted from the eDrivers platform for EGSL environmental data (Beauchesne et al., 2020). Selected drivers were aragonite (indicating acidification) and positive temperature anomalies (posAnom), as described in Galbraith et al. (2019). ...
Article
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The estuary and the Gulf of St. Lawrence (EGSL), eastern Canada form a vast inland sea that is subjected to numerous anthropogenic pressures. Management tools are needed to detect and quantify their effect on benthic communities. The aims of this study are to analyze the spatial distribution of epibenthic communities in the EGSL and quantify the impact of important pressures on them to identify indicator taxa. Epibenthic communities were sampled at 1314 EGSL sites between 2011 and 2018 by bottom trawling. Cluster analyses revealed the presence of six distinct epibenthic communities that seem to be strongly influenced by oxygen concentration. Threshold analyses confirm that oxygen is an important predictor of epibenthic community composition and distribution. A major oxygen threshold is observed around 50–100 μmol O2 L–1, resulting in a shift of community type. At these concentrations and below, opportunistic taxa dominate the community while sensitive taxa are absent or present at very low abundance. Biomass of the latter only starts to increase when oxygen concentrations reach 150 μmol O2 L–1. The species Actinostola callosa, Actinauge cristata, Ctenodiscus crispatus, and Brisaster fragilis were identified as good indicators for detecting this impact threshold forepibenthic communities. This study provides threshold-based indicator species that help to establish and monitor the ecological state of epibenthic communities in a marine ecosystem exposed to multiple pressures.
... Many international organizations have recognized the importance of biologically diverse ecosystems for humanity and have established objectives and targets for their protection and sustainable use (United Nations, 1992; Secretariat of the CBD, 2010;SDG, 2015). The management of ecosystems requires an understanding of how habitats and communities respond to drivers of change, i.e., forces that affect environmental processes and modify ecosystem state from equilibrium (Boonstra et al., 2015;Beauchesne et al., 2020;Orr et al., 2020). In addition to natural drivers (e.g., temperature anomalies, freshwater inputs, hypoxic events), influences from human activities (e.g., fisheries, chemical pollution, species introductions) are also considered as ecosystem drivers. ...
Article
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With the widespread influence of human activities on marine ecosystems, evaluation of ecological status provides valuable information for conservation initiatives and sustainable development. To this end, many environmental indicators have been developed worldwide and there is a growing need to evaluate their performance by calculating ecological status in a wide range of ecosystems at multiple spatial and temporal scales. This study calculated and contrasted sixteen indicators of ecological status from three methodological categories: abundance measures, diversity parameters and characteristic species. This selection was applied to coastal benthic ecosystems at Sept-Îles (Québec, Canada), an important industrial harbor area in the Gulf of St. Lawrence, and related to habitat parameters (organic matter, grain size fractions, and heavy metal concentrations). Nearly all indicators highlighted a generally good ecological status in the study area, where communities presented an unperturbed profile with high taxa and functional diversities and without the dominance of opportunistic taxa. Some correlations with habitat parameters were detected, especially with heavy metals, and bootstrap analyses indicated quite robust results. This study provides valuable information on the application of environmental indicators in Canadian coastal ecosystems, along with insights on their use for environmental assessments.
... Une "perturbation", dans le sens de disturbance en anglais, est une force qui affecte des processus environnementaux et/ou modifie un écosystème hors d'une situation d'équilibre (Odum et al., 1979;Rykiel Jr., 1985;Boonstra et al., 2015;Beauchesne et al., 2020b;Orr et al., 2020). Nombre de synonymes existent pour cette définition, comme "stresseur" (stressor), "déterminant" (driver of change) ou "pression" (pressure), et le débat n'est pas clos quant à savoir quel terme privilégier (Crain et al., 2008;Darling et Côté, 2008;Judd et al., 2015;Côté et al., 2016). ...
... Le déploiement de technologies telles qu'une puissance de calcul informatique et une couverture satellitaire accrues permettent aujourd'hui de considérer l'empreinte humaine d'une façon plus holistique (Micheli et al., 2016;Dreujou et al., 2020a). En particulier, il est possible d'étudier les effets émergents dus aux interactions entre différentes activités humaines, dans le but de mieux comprendre et prédire l'évolution des écosystèmes (Crain et al., 2008;Darling et Côté, 2008;Halpern et Fujita, 2013;Brown et al., 2014;Piggott et al., 2015;Galic et al., 2018;Hodgson et al., 2019;Beauchesne et al., 2020b). (Hurlbert, 1984;Legendre et Legendre, 1998;Quinn et Keough, 2002;Underwood, 2002Underwood, , 2012. ...
... En l'état des connaissances, considérer la vulnérabilité de façon adéquate demande un large volume de données (par ex. sur les tolérances physiologiques des espèces, les interactions biotiques ou les modes d'action des perturbations) qui peuvent être spécifiques à des écosystèmes particuliers, ce qui augmente rapidement la complexité de ces évaluations Beauchesne et al., 2020b). (Belley et al., 2010;Daigle et al., 2017;Schloss et al., 2017 for two taxa size classes (organisms > 0.5 mm and > 1 mm) and linked to habitat parameters using regression models. ...
Thesis
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Coastal and ocean environments are influenced by human activities worldwide, the impacts of which can significantly modify the structure and integrity of ecosystems. In order to adequately protect the natural environment and support sustainable anthropogenic development, specifically in regions where multiple human activities co-occur, it is necessary to understand how marine ecosystems are influenced. Benthic communities are a particularly interesting compartment for studying these issues, because many species have a limited mobility due to their predominantly sessile lifestyle as well as a long life span. While studies assessing anthropogenic impacts have been carried out on a wide range of ecosystems around the world, few have specifically considered sub-Arctic ecosystems, where human activity is expected to increase in connection with climate change. In this context, my thesis’s main objective is to understand how the benthic ecosystems of a sub-Arctic industrial harbour area are influenced by human activities. The study area herein considered is located in the Sept-Îles region (Quebec, Canada), an important economic hub for Quebec, located in the Gulf of St. Lawrence. To address these topics, this thesis is divided into three chapters. The first chapter aimed to characterize the structure of the considered coastal ecosystems. During field campaigns and laboratory analyses, a total of 289 taxa were sampled, the majority of which, present in the Gulf of St. Lawrence, are new records in this region. Various abiotic parameters of the sediment were assessed, such as the concentration of organic matter, heavy metals and the distribution of particle size fractions. Similarity analysis of invertebrate assemblages larger than 0.5 mm showed signs of disturbance in some areas, with an increased number of pollution-tolerant and opportunistic species. Regression models highlighted which habitat variables had the most impact on the structure of communities. The second chapter looked at the ecological status of ecosystems based on the composition of benthic communities. Sixteen indicators of ecological status were selected through a literature review, divided into three categories according to their methodology: measures of abundance, community diversity and indicator species. These indicators were applied using the species lists obtained in the previous chapter, and the majority of which identified diverse communities with no obvious sign of disturbance. In addition, several significant correlations were detected between indicators and habitat parameters, especially with heavy metal concentrations. Each category of indicator provided important information on the state of the ecosystem while presenting limitations, in particular about reference conditions used to define ecological status. The last chapter examined human activities influencing the ecosystem, in order to calculate a local anthropogenic footprint on communities according to exposure gradients. An exposure index for each activity considered (aquaculture, dredging, industrial influence, city influence, fisheries, sewage discharges, shipping) was developed using the distance from their sources and fishing events. Several links were discovered between the exposure indices obtained and the distribution of benthic invertebrates, using predictive models Hierarchical Modelling of Species Communities. The cumulative exposure index revealed areas of superposition of human activity. The profile of the communities present in these zones is not particularly disturbed, which corroborates the results of the previous chapters on the status of the ecosystems considered. This PhD thesis improves ecological knowledge in sub-Arctic coastal ecosystems, in particular by presenting the first benthic biodiversity census in the Sept-Îles region. Methods for assessing ecological status and anthropogenic exposure have been developed at the local scale (< 100 km), which constitute particularly interesting tools for stakeholders in order to define management targets and support conservation initiatives.
Article
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Until 2012, the St. Lawrence Estuary beluga population was considered stable with about 1100 individuals. An abnormally high number of calves reported dead that year triggered a population status reassessment. This review article summarizes the findings from this reassessment and various studies subsequent to it and provides an updated analysis of carcass recovery rates up to 2019. The 2013 review indicated a decreased incidence of cancer in adults, suggesting positive impacts from the regulation of toxic substances (e.g., PCBs and PAHs). However, the review also revealed that the population initiated a decline of ca. 1% per year in the early 2000s and had reached a size of ca. 900 individuals by 2012. This decline was accompanied by high inter-annual variability in calf survival and pregnancy rates and by more frequent peripartum complications among dead females. The change in population dynamics coincided with a shift in the St. Lawrence ecosystem structure and warmer environmental conditions, suggesting a link through effects on reproductive success and adult female body condition. This was supported by the continued high calf mortality after 2012 and a documented decline of fat reserves in beluga blubber from 1998 to 2016. Other factors, such as the exposure to chronic vessel noise, increasing whale-watching activities, high contaminant levels and episodic harmful algal blooms, may also be contributing to the long-term non-recovery and current decline of the population. The strong natal philopatry and complex social system of the beluga likely increase its vulnerability to extinction risk by limiting dispersal.