Biology subjects

Turgeon, K.

Publications and source records attributed to Turgeon, K..

9 recordsLinked to original sources

bioRxiv2026

Inverted trophic pyramids and transient fish community reorganization in large reservoirs

The rapid global expansion of dams has significantly reshaped freshwater ecosystems, yet long-term trophic dynamics and food-web stability within reservoirs remain underexplored. This study examines the reorganization of fish communities induced by the trophic surge following dam construction and river impoundment. We used the predator-to-consumer mass ratio (PCMR) as a proxy for trophic pyramid structure to track changes in fish biomass distribution across three large boreal reservoirs in Quebec, Canada, over 20 years, using data from before and after impoundment. We found transient top-heaviness events (i.e., PCMR values > 1; predator accumulation), characterized by a hump-shaped trajectory of the PCMR values in two reservoirs (Opinaca and Robert Bourassa). The third reservoir (Caniapiscau) showed a gradual increase in top-heaviness but did not exhibit a clear transient pattern. The magnitude and duration of top-heaviness varied across reservoirs, potentially due to differences in the system's capacity to receive and accumulate nutrients, which are driven by water residence time and reservoir size. This research provides a conceptual framework for understanding the long-term trophic dynamics of reservoirs, which can help inform the development of more effective management strategies to preserve ecological health in these ecosystems.

ecology↗

bioRxiv2026

A Reproducible Methodology for High-Resolution 3D and Orthomosaic Mapping in Forested Streams

1 - Frequent, fine-scale assessments of forested stream morphology are essential for understanding habitat conditions and guiding management, yet dense canopy and budget constraints often limit airborne LiDAR and conventional surveys. 2 - We present a reproducible, ground-based photogrammetry workflow using a chest-mounted action camera (GoPro) and the Agisoft Metashape software to generate scaled, georeferenced 3D models and orthomosaics of stream reaches. The workflow details image acquisition under variable lighting and flow conditions, image alignment, dense cloud/mesh generation, and export of GIS-ready products. 3 - Applied in Mont-Tremblant National Park and Kenauk Nature (Quebec, Canada) across 56 forest-stream reaches in a single summer field season, the workflow produced scaled, GIS-ready orthomosaics with nominal pixel sizes as low as [~]1.36 mm/pixel. These products captured fine-scale channel morphology, enabling consistent reach-scale habitat mapping and temporal comparisons for restoration monitoring. 4 - By reducing equipment costs and simplifying logistics relative to airborne or terrestrial LiDAR, this practical tool enables frequent, high-resolution surveys in dense-canopy streams. Future extensions (e.g., automated substrate classification via machine learning) can further standardize habitat assessment and support long-term ecological monitoring.

ecology↗

bioRxiv2026

Fish presence alters amphibian and zooplankton communities in kettle lakes, but not hydrological connectivity

Fishless lakes, critical drivers of biodiversity across freshwater landscapes, are becoming increasingly rare due to fish introductions. Although the impacts of fish introduction are well understood in high-elevation fishless lakes, their effects on fishless kettle lakes remain poorly understood. Many kettle lakes are disconnected from the surface water network and are therefore fishless. In this study, we examined how amphibian and zooplankton communities differ between fishless and fish-bearing kettle lakes by comparing 36 lakes in Quebec, Canada. Some kettle lakes are hydrologically connected to surrounding aquatic ecosystems, allowing natural colonization by fish. We therefore also evaluated how amphibian and zooplankton communities differ between connected and disconnected kettle lakes. Fish presence was associated with differences at each stage of the amphibian life cycle. Reproductive calls of adult amphibians were detected regardless of fish presence, indicating that reproduction occurred in all lake types. However, the presence of fish was associated with fewer amphibian egg masses and lower larval abundance, and the absence of salamanders at the larval stage. Small-bodied zooplankton were more abundant in fish-bearing lakes, while overall species richness was lower. In particular, Chaoborus americanus, a large top-predatory zooplankton species, was found exclusively in fishless lakes. In contrast to fish presence, hydrological connectivity had no significant effect on most communities, except for adult American toads, adult wood frogs, and mink frogs larvae, which responded positively to the interaction between fish presence and connectivity. Based on our results, we recommend avoiding fish stocking of kettle lakes to preserve essential reproductive habitats for amphibians, maintain refuges for sensitive zooplankton species, and safeguard the spatial heterogeneity that underpins landscape-scale biodiversity.

ecology↗

bioRxiv2025

Social Perspectives on Larvicide-Based Mosquito Control in Urban Quebec

The spreading of Bacillus thuringiensis israelensis (Bti) in urban waterways, as a biological larvicide to control biting insect populations and mitigate disease transmission, has been subject to scientific scrutiny due to its potential environmental impacts. Public and political discussions have revealed recurring opinions that reflect broader social perspectives. While scientific research on Bti progresses, knowledge of public understanding and perspectives, which are important for decision-making, remains limited. The main objective of this research was to identify and compare the social perspectives of Quebec citizens, primarily in the city of Gatineau, regarding the use of Bti for mosquito and black fly control in aquatic environments. We used Q methodology, a mixed approach combining both quantitative and qualitative methods to identify social perspectives related to the use of Bti. Our analysis revealed three social perspectives, which account for 51% of the explained variance. They reflect the broader range of opinion within citizens, and are described as "The critical environmentalist", "The diligent mosquito hunter", and "The Bti enthusiast". Each accounting for 29%, 12% and 10% of the explained variance, respectively. The common thread across all three perspectives is the minimal public awareness and understanding of Bti and its environmental implications. Providing a first characterization of social perspectives in North America regarding larvicides, this research contributes to a more comprehensive understanding of public opinion and informs the development of inclusive and transparent policies.

scientific communication and education↗

bioRxiv2021

The impacts of hydropower on freshwater macroinvertebrate richness: A global meta-analysis

Hydroelectric dams and their reservoirs have been suggested to affect freshwater biodiversity. However, studies investigating the consequences of hydroelectric dams and reservoirs on macroinvertebrate richness have reached opposite conclusions. We carried out a meta-analysis devised to elucidate the effects of hydropower dams and their reservoirs on macroinvertebrates richness while accounting for the potential role played by moderators such as biomes, impact types, study designs, sampling seasons and gears. We used a random and mixed effect model, combined with robust variance estimation, to conduct the meta-analysis on 72 pairs of observations (i.e., impacted versus reference) extracted from 17 studies (more than one observation per study). We observed a large range of effect sizes, from very negative to very positive impacts of hydropower. However, according to this meta-analysis, hydropower dams and their reservoirs did not have an overall clear, directional and statistically significant effect on macroinvertebrate richness. We tried to account for the large variability in effect sizes using moderators, but none of the moderators included in the meta-analysis had statistically significant effect. This suggests that some other moderators, which were unavailable for the 17 studies included in this meta-analysis, might be important (e.g., temperature, granulometry, wave disturbance and macrophytes) and that macroinvertebrate richness may be driven by local, smaller scale processes. As new studies become available, it would be interesting to keep enriching this meta-analysis, as well as collecting local habitat variables, to see if we could finally draw statistically significant conclusions about the impacts of hydropower on macroinvertebrate richness.

ecology↗

bioRxiv2019

Changes in freshwater macroinvertebrate richness due to river impoundment in the United States

Whether it is for water supply, flood control or hydropower uses, the transformation of a river into a reservoir can impact freshwater ecosystems and their biodiversity. Using the National Lake Assessment (NLA; 148 reservoirs) and the National Rivers and Streams Assessment (NRSA; 2121 rivers and streams) of the United States Environmental Protection Agency (USEPA), we evaluated the impacts of river impoundment on macroinvertebrate biodiversity at three spatial scales (i.e., reservoir, ecoregion and country scale). We used a space-for-time substitution approach to model the impact of impoundment (i.e., we used rivers and streams as the before-impoundment conditions, and reservoirs as the after-impoundment conditions). We expressed the impact on biodiversity in terms of potentially disappeared fraction of species (PDF) to be used in the life cycle assessment (LCA) framework. To understand the role of regionalization, and some potentially influential variables, on changes in macroinvertebrate richness following impoundment in the United States, we used analyses of variance (ANOVAs) as well as variation partitioning, and developed empirical predictive models. Overall, 26% of macroinvertebrate taxa disappeared following impoundment in the United States, and PDFs followed a longitudinal gradient across ecoregions (i.e., higher PDFs in the western part of the country, lower PDFs in the eastern part). We also observed that large and oligotrophic reservoirs, located in high elevation had high PDFs. This study provides the first empirical PDF values for macroinvertebrates to be used as characterization factors (CFs) by LCA practitioners. We also provide strong support for regionalization and a simple predictive model to be used by LCA modellers.

ecology↗

bioRxiv2019

Empirical characterization factors assessing the effects of hydroelectricity on fish richness across three large biomes

Hydroelectricity is often presented as a clean, reliable, and renewable energy source, but is also recognized for its potential impacts on aquatic ecosystem biodiversity. We used empirical data on change in fish species richness following impoundment to develop Characterisation Factors (CF) and Impact Scores (IS) for hydroelectricity production for use in Life Cycle Assessment (LCA). We used data collected on 89 sampling stations (63 upstream and 26 downstream of a dam) belonging to 27 reservoirs from three biomes (boreal, temperate and tropical). Overall, the impact of hydroelectricity production on fish species richness was significant in the tropics, of smaller amplitude in temperate and minimal in boreal biome, stressing for the need of regionalisation. The impact of hydroelectricity production was also quite consistent across scales (i.e., same directionality and statistical significance across sampling stations, reservoirs and biomes) but was sensitive to the duration of the study (i.e., the period over which data have been collected after impoundment), highlighting the need for a clear understanding of transient situations before reaching steady states. Our CFs and ISs contribute to fill a gap to assist decision makers using LCA to evaluate alternative technologies, such as hydropower, to decarbonize the worldwide economy.\n\nHighlightsO_LIThis paper is the first to develop global and empirically based characterization factors of the impact of hydroelectricity production on aquatic ecosystems biodiversity, to be used in LCA;\nC_LIO_LIThe impact of hydroelectricity production on fish species richness was significant in the tropics, of smaller amplitude in temperate and minimal in boreal biome;\nC_LIO_LIThe impact of hydroelectricity production on fish richness was consistent across scales - same directionality and statistical significance across sampling stations, reservoirs and biomes;\nC_LIO_LIThe impact of hydroelectricity production on fish richness was sensitive to the duration of the study, highlighting the need for a clear understanding of transient situations before reaching steady states in LCA.\nC_LI

ecology↗

bioRxiv2018

Dams have varying impacts on fish communities across latitudes: A quantitative synthesis

Dams are recognized to impact aquatic biodiversity and ecosystem functions, but the magnitude of effects vary across studies. By using a meta-analytical approach, we examined the effects of impoundment on fish community across three large biomes. The impacts of dams on richness and diversity differed across biomes, with significant declines in the tropics, lower amplitude but similar directional changes in temperate reservoirs, and no changes in boreal reservoirs. Our analysis also showed that non-native species increased significantly in tropical and temperate reservoirs, but not in boreal reservoirs. In contrast, temporal trajectories in fish assemblage metrics were common across regions, with all biomes showing an increase in mean trophic position and in the proportion of generalist species after impoundment. Such changes in fish assemblages may affect food web stability and merit closer study. Across the literature examined, predominant factors or mechanisms that render fish assemblages susceptible to impacts from dams were: 1) the transformation of the lotic environment into a lentic environment; 2) habitat fragmentation and 3) invasive or non-native species. Collectively our results highlight that an understanding of the regional context and a suite of metrics are needed to make robust predictions about how fish will respond to river impoundments.

ecology↗

bioRxiv2017

River impoundments cause little change in fish boreal diversity, but clear species assemblage shifts

O_LIHydroelectricity is often presented as a clean and renewable energy source, but river flow regulation and fragmentation caused by dams are recognized to impact aquatic biodiversity in temperate and tropical ecosystems. However, the effects of boreal river impoundment are not clear as the few studies that exist have not been able to separate the hydrological changes brought about by dams from other factors (e.g. fish stocking, and species introduction).\nC_LIO_LIWe adopted a multi-scale analysis to examine changes in nearshore fish communities over 20 years (spanning before and after impoundment) using a network of 24 sampling stations spread across from four reservoirs and two hydroelectricity complexes located in the boreal region (Northern Quebec, Canada). Given the remote location, confounding factors were minimal.\nC_LIO_LIWe found no strong temporal trends in alpha- and gamma-diversity in impacted stations (upstream and downstream of the dam) relative to reference sites across the three spatial scales. Using beta-diversity analyses, we also detected a high stability in fish composition over time and space at the complex and reservoir scales.\nC_LIO_LIAt the scale of the sampling stations, we observed higher rates of species turnover (beta-diversity) coincident with the time of reservoir filling and shortly after. Likewise, we detected species assemblage shifts that correlated with time since impoundment only at the sampling station scale. This pattern was masked at the complex and reservoir scales.\nC_LIO_LISynthesis and applications. Overall, the isolated effect of impoundment in these remote boreal ecosystems caused no loss of species and little change in fish diversity over 20 years, but resulted in substantial species assemblage shifts. Our work shows that examining community data at different scales is key to understand the anthropogenic impacts on fish biodiversity.\nC_LI

ecology↗