Stéphane Campeau | Université du Québec à Trois-Rivières (original) (raw)

Papers by Stéphane Campeau

Research paper thumbnail of Intégrité biologique des cours d’eau du Parc de la Gatineau: application de l’Indice diatomées de l’est du Canada (IDEC)

Research paper thumbnail of Development of a diatom index for river bioassessment for use in Ontario

Research paper thumbnail of Natural and human-induced variability in the stoichiometry of benthic organisms in rivers

Research paper thumbnail of Evidence of food quality limitation in benthic river insects

Research paper thumbnail of Analysis of the Impacts of Changes in Streamflow and of Restoration on the Morphological Evolution of the Matambin River Channel in the St. Lawrence Lowlands (Quebec, Canada)

InTech eBooks, Oct 18, 2017

Although many plots of land that were once farmed have been reforested in the St Lawrence Lowland... more Although many plots of land that were once farmed have been reforested in the St Lawrence Lowlands of Quebec since the 1950s, no study has yet looked at the morphological impacts of this land-use change. To address this, we analyzed the evolution of the Matambin River (99 km 2) channel width and sinuosity using diachronic analysis of air photographs taken between 1935 and 2008. Results of this analysis show a roughly 21% decrease in mean channel bankfull width from 1935 to 1964. This time interval was characterized by a low frequency of strong flood flows in the region and a roughly 32% increase in the forested land area, the reforestation having started in the 1950s. After 1964, a trend of increasing mean channel bankfull width is observed. This increase is associated with the increase in frequency of strong flood flows in the region and a decrease in the amount of suspended sediments produced by soil erosion following the increase in forest cover in the watershed. In contrast, channel sinuosity did not change much over the period from 1935 to 2008.

Research paper thumbnail of Landscape diversity and forest edge density regulate stream water quality in agricultural catchments

Ecological Indicators, 2017

Abstract It is well known that the composition of land cover within a watershed plays a large rol... more Abstract It is well known that the composition of land cover within a watershed plays a large role in regulating stream water quality. However, there remains significant uncertainty regarding the effect of spatial configuration of different types of land cover on water quality. Using periphytic algae (diatoms) as indicators of stream trophic state, we investigated the relationship between landscape configuration and water quality in a large number of watersheds (590) at varying catchment scales in Eastern Canada. Variation partitioning analysis showed that landscape configuration explained 48% of the variation in water quality. However, since the physiographic setting constrains most agricultural activities, most of the variation was attributed to the shared influence of surficial deposits, land cover and landscape configuration (34%). The results from regression models showed that the geomorphological setting of watersheds (surficial deposits and slopes) and the proportion of different land cover types (mainly forests, wetlands, crops and urban areas) have a major impact on stream water quality. Nevertheless, a few configuration metrics emerged as important factors. Landscape diversity appeared to have a negative impact on water quality, whereas forest and wetland edge densities had a positive impact. Moreover, the influence of these lanscape metrics seems to occur at certain thresholds. In areas of intensive farming, streams with a forest area that covers at least 47% of the watershed have a better water quality. Below this threshold, eutrophic and meso-eutrophic conditions are more frequent in streams and rivers. The shape and location of forested patches were also found to be relevant. Woodlands and wetlands with an edge density higher than 36 m/ha and located along streams and gullies have a positive impact on water quality. For the same proportion of forest, complex patches will be more efficient filters than large regular patches. Forest edge density seems to control the extent of the interface with the agricultural sources and thus promotes the “sink” effect of forests on nutrients.

Research paper thumbnail of Monitoring Water Turbidity in a Temperate Floodplain Using UAV: Potential and Challenges

Canadian Journal of Remote Sensing

Research paper thumbnail of Typology and prediction of diatom assemblages in rivers: building of database and first predictive model

Research paper thumbnail of Diatoms from the Beaufort Sea coast, southern Arctic Ocean (Canada) : Modern analogues for reconstructing Late Quaternary environments and relative sea levels

Research paper thumbnail of Guide d’identification des diatomées des rivières de l’Est du Canada

Les diatomées sont des algues microscopiques qui vivent en suspension dans l'eau ou ... more Les diatomées sont des algues microscopiques qui vivent en suspension dans l'eau ou attachées au fond des rivières, des lacs et des océans. La plupart des diatomées fixent le carbone par photosynthèse. Elles sont des producteurs primaires qui jouent un rôle ...

Research paper thumbnail of The Eastern Canadian Diatom Index (IDEC) Version 2.0: Including Meaningful Ecological Classes and an Expanded Coverage Area that Encompasses Additional Geological Characteristics

Water Quality Research Journal, 2010

In 2006, the Eastern Canadian Diatom Index (IDEC: Indice Diatomées de l'Est du Canada) was de... more In 2006, the Eastern Canadian Diatom Index (IDEC: Indice Diatomées de l'Est du Canada) was developed to monitor the biological integrity of streams and rivers in Eastern Canada. The first version of the IDEC has been successfully used to evaluate the biological status of numerous sites. A new version of the index (IDEC 2.0) was recently developed to cover a larger geographic area that encompasses additional geological characteristics. IDEC 2.0 is now applicable for the biological assessment of streams in Quebec, Ontario, New Brunswick, Nova Scotia, and Prince Edward Island. Moreover, the approach used to define the biological interpretation of the index values was revised. IDEC 2.0 presents ecologically meaningful differences among biological communities (ecological thresholds or class boundaries) based on diatom biotypes, providing a more relevant interpretation of the diatom community changes along the alteration gradient.

Research paper thumbnail of Local and regional drivers of taxonomic homogenization in stream communities along a land use gradient

Global Ecology and Biogeography, 2019

AimThe interaction of land use with local versus regional processes driving biological homogeniza... more AimThe interaction of land use with local versus regional processes driving biological homogenization (β‐diversity loss) is poorly understood. We explored: (a) stream β‐diversity responses to land cover (forest versus agriculture) in terms of physicochemistry and physicochemical heterogeneity; (b) whether these responses were constrained by the regional species pool, i.e. γ‐diversity, or local assembly processes through local (α) diversity; (c) whether local assembly operated through the regional species abundance distribution (SAD) or intraspecific spatial aggregation; and (d) the dependence on body size, dispersal capacity and trophic level (producer versus consumer).LocationUSA, Canada and France.Time period1993–2012.Major taxa studiedStream diatoms, insects and fish.MethodsWe analysed six datasets totalling 1,225 stream samples. We compared diversity responses to eutrophication and physicochemical heterogeneity in forested versus agricultural streams with regression methods. Nul...

Research paper thumbnail of Algae-based Biomonitoring: Predicting Diatom Reference Communities in Unpolluted Streams using Classification Trees, Random Forests, and Artificial Neural Networks

Water Quality Research Journal, 2010

The Eastern Canadian Diatom Index (IDEC) was developed to evaluate the ecological integrity of st... more The Eastern Canadian Diatom Index (IDEC) was developed to evaluate the ecological integrity of streams along a pollution gradient, as a function of the dissimilarity between current diatom communities and suitable reference communities. Distinguishing natural variations in community structure from those induced by human activities is essential for proper assessment of dissimilarity. To account for the effect of the natural variation in pH on this assessment, two IDEC subindices were used: one for sites with diatom reference communities typical of naturally alkaline water pH, and another for sites with communities typical of naturally circumneutral water pH. This study used three statistical models, namely classification trees (CT), random forests (RF), and artificial neural networks (ANN) to: (i) identify the environmental variables discriminating between alkaline and neutral reference communities (“biotypes”), and (ii) compare their predictive capacities. Models identified clay roc...

Research paper thumbnail of Gomphonema caperatum sp. nov., G. obstipum sp. nov. and similar taxa from rivers of North America

Diatom Research, 2017

Two new species of Gomphonema with linear-lanceolate valves, narrow cells (width ≤ 6 μm), wide ax... more Two new species of Gomphonema with linear-lanceolate valves, narrow cells (width ≤ 6 μm), wide axial areas, short uniseriate striae, and one stigmoid per valve are described. Gomphonema caperatum sp. nov. has narrow, almost linear valves with short marginal striae, apically elongated slit-like areolae, and transapically oriented linear markings on the external valve surface, which are only observable under scanning electron microscopy. This is a common and often abundant species in rivers across Eastern North America, especially in the Appalachian region, but is also found on the West Coast. Gomphonema obstipum sp. nov. has lanceolate valves with bent apices, variously shaped apically elongated areolae, and shallow circular depressions on the external valve surface. This species has only been found in two Virginian rivers. We compare the new taxa with several species of Gomphonema from North American rivers that are morphologically similar, such as Gomphonema amerhombicum Reichardt, Gomphonema stoermeri Kociolek & Kingston, and other species with linear-lanceolate valves and wide axial areas. In addition, we report here for the first time the occurrence of Gomphonema incognitum in North America. This study underscores the insufficiency of our knowledge of diatom diversity in North America and the need for more detailed taxonomic investigations.

Research paper thumbnail of Determination of Diatom Reference Communities and Restauration Goals for Streams in Quebec

Agu Spring Meeting Abstracts, May 1, 2005

Research paper thumbnail of Classification des diatomées par les descripteurs de Fourier du contour

Nous présentons dans cet article un système automatique de classification des diatomées fondée su... more Nous présentons dans cet article un système automatique de classification des diatomées fondée sur une extraction des angles normaux d'un contour 8-connecté antihoraire. Pour cela, nous avons utilisé un modèle paramétrique qui consiste à caractériser le contour des diatomées suivant un vecteur des descripteurs de Fourier. Sur une base de données d'images de diatomées de 450 images, nous avons obtenu un taux de bonne classification de 97%.

Research paper thumbnail of Diatom typology of low-impacted conditions at a multi-regional scale: combined results of multivariate analyses and SOM

Modelling Community Structure in Freshwater Ecosystems

Page 1. 5 Diatom and other algal assemblages 317 5.6 Diatom typology of low-impacted conditions a... more Page 1. 5 Diatom and other algal assemblages 317 5.6 Diatom typology of low-impacted conditions at a multi-regional scale: combined results of multivariate analyses and SOM* Gosselain V†, Campeau S, Gevrey M, Coste ...

Research paper thumbnail of Biosuivi de l’intégrité écologique de ruisseaux et de lacs du Parc de la Gatineau à l’aide des diatomées et des autres groupes d’algues

Research paper thumbnail of Using diatoms to monitor stream biological integrity in Eastern Canada: An overview of 10 years of index development and ongoing challenges

Science of The Total Environment, 2014

An improved version of the Eastern Canadian Diatom Index (IDEC: Indice Diatomées de l&amp... more An improved version of the Eastern Canadian Diatom Index (IDEC: Indice Diatomées de l'Est du Canada) was developed, incorporating modifications to optimize diatom-based monitoring in Eastern Canada. The most significant improvement with this version of the IDEC is the extended coverage area including additional reference sites. This new version of the IDEC also incorporated a simplified list of diatom taxa to reduce the variability among analysts as it gains in popularity. Rare taxa (<2%) were excluded and various morphotypes were grouped. The index was created based on three sub-indices that were adapted to cover the range of natural pH and conductivity values allowing us to partial out the strong influence of natural pH and conductivity from the general pollution gradient. The index was created using 648 diatom assemblages including those from nearly 150 reference (or least-disturbed) sites. The reference sites covered a large range of natural characteristics. The diatom assemblages collected in these environments constitute "biotype class A" in each sub-index and represent a realistic goal for restoration. Associated total phosphorus and total nitrogen showed that class A generally reflects conditions that are considered oligotrophic (<0.025 mg L(-1)) or oligo-mesotrophic, while class D at the opposite end of the pollution gradient reflects eutrophic or hyper-eutrophic environments. There is a good correspondence between IDEC values and nutrient criteria, water quality indices based on physico-chemistry measurements, the presence of agricultural activities, and urban areas. The IDEC has a great potential to assist water quality monitoring, particularly when the objective is to assess the trophic status of a watercourse.

Research paper thumbnail of Buttes cryogènes saisonnières de plages arctiques, péninsule de Tuktoyaktuk, Territoires du Nord-Ouest

Géographie physique et Quaternaire, 1995

Des buttes cryogènes saisonnières en système fermé ont été observées de 1991 à 1993 sur les flèch... more Des buttes cryogènes saisonnières en système fermé ont été observées de 1991 à 1993 sur les flèches sableuses de la péninsule de Tuktoyaktuk, dans les Territoires du Nord-Ouest. Les buttes ont une forme circulaire et convexe. Leur diamètre varie entre 5 et 15 m et leur hauteur, entre 15 et 25 cm. Le coeur des buttes est constitué d'une lentille de glace intrusive de même diamètre que les buttes. La lentille a une forme convexe et sa base est horizontale. L'épaisseur de la lentille est égale à l'élévation des buttes, soit entre 15 et 25 cm. Les buttes se forment dans une pseudo-dépression située entre la berme de tempête et la berme du rivage de la lagune. À la fin de l'été, les débordements de tempête saturent en eau de mer le sable des flèches. L'engel provoque un accroissement de la pression hydrostatique à l'intérieur de la dépression. Les lentilles de glace intrusive se développent ainsi en système fermé. Les buttes se forment au cours de l'hiver pour...

Research paper thumbnail of Intégrité biologique des cours d’eau du Parc de la Gatineau: application de l’Indice diatomées de l’est du Canada (IDEC)

Research paper thumbnail of Development of a diatom index for river bioassessment for use in Ontario

Research paper thumbnail of Natural and human-induced variability in the stoichiometry of benthic organisms in rivers

Research paper thumbnail of Evidence of food quality limitation in benthic river insects

Research paper thumbnail of Analysis of the Impacts of Changes in Streamflow and of Restoration on the Morphological Evolution of the Matambin River Channel in the St. Lawrence Lowlands (Quebec, Canada)

InTech eBooks, Oct 18, 2017

Although many plots of land that were once farmed have been reforested in the St Lawrence Lowland... more Although many plots of land that were once farmed have been reforested in the St Lawrence Lowlands of Quebec since the 1950s, no study has yet looked at the morphological impacts of this land-use change. To address this, we analyzed the evolution of the Matambin River (99 km 2) channel width and sinuosity using diachronic analysis of air photographs taken between 1935 and 2008. Results of this analysis show a roughly 21% decrease in mean channel bankfull width from 1935 to 1964. This time interval was characterized by a low frequency of strong flood flows in the region and a roughly 32% increase in the forested land area, the reforestation having started in the 1950s. After 1964, a trend of increasing mean channel bankfull width is observed. This increase is associated with the increase in frequency of strong flood flows in the region and a decrease in the amount of suspended sediments produced by soil erosion following the increase in forest cover in the watershed. In contrast, channel sinuosity did not change much over the period from 1935 to 2008.

Research paper thumbnail of Landscape diversity and forest edge density regulate stream water quality in agricultural catchments

Ecological Indicators, 2017

Abstract It is well known that the composition of land cover within a watershed plays a large rol... more Abstract It is well known that the composition of land cover within a watershed plays a large role in regulating stream water quality. However, there remains significant uncertainty regarding the effect of spatial configuration of different types of land cover on water quality. Using periphytic algae (diatoms) as indicators of stream trophic state, we investigated the relationship between landscape configuration and water quality in a large number of watersheds (590) at varying catchment scales in Eastern Canada. Variation partitioning analysis showed that landscape configuration explained 48% of the variation in water quality. However, since the physiographic setting constrains most agricultural activities, most of the variation was attributed to the shared influence of surficial deposits, land cover and landscape configuration (34%). The results from regression models showed that the geomorphological setting of watersheds (surficial deposits and slopes) and the proportion of different land cover types (mainly forests, wetlands, crops and urban areas) have a major impact on stream water quality. Nevertheless, a few configuration metrics emerged as important factors. Landscape diversity appeared to have a negative impact on water quality, whereas forest and wetland edge densities had a positive impact. Moreover, the influence of these lanscape metrics seems to occur at certain thresholds. In areas of intensive farming, streams with a forest area that covers at least 47% of the watershed have a better water quality. Below this threshold, eutrophic and meso-eutrophic conditions are more frequent in streams and rivers. The shape and location of forested patches were also found to be relevant. Woodlands and wetlands with an edge density higher than 36 m/ha and located along streams and gullies have a positive impact on water quality. For the same proportion of forest, complex patches will be more efficient filters than large regular patches. Forest edge density seems to control the extent of the interface with the agricultural sources and thus promotes the “sink” effect of forests on nutrients.

Research paper thumbnail of Monitoring Water Turbidity in a Temperate Floodplain Using UAV: Potential and Challenges

Canadian Journal of Remote Sensing

Research paper thumbnail of Typology and prediction of diatom assemblages in rivers: building of database and first predictive model

Research paper thumbnail of Diatoms from the Beaufort Sea coast, southern Arctic Ocean (Canada) : Modern analogues for reconstructing Late Quaternary environments and relative sea levels

Research paper thumbnail of Guide d’identification des diatomées des rivières de l’Est du Canada

Les diatomées sont des algues microscopiques qui vivent en suspension dans l'eau ou ... more Les diatomées sont des algues microscopiques qui vivent en suspension dans l'eau ou attachées au fond des rivières, des lacs et des océans. La plupart des diatomées fixent le carbone par photosynthèse. Elles sont des producteurs primaires qui jouent un rôle ...

Research paper thumbnail of The Eastern Canadian Diatom Index (IDEC) Version 2.0: Including Meaningful Ecological Classes and an Expanded Coverage Area that Encompasses Additional Geological Characteristics

Water Quality Research Journal, 2010

In 2006, the Eastern Canadian Diatom Index (IDEC: Indice Diatomées de l'Est du Canada) was de... more In 2006, the Eastern Canadian Diatom Index (IDEC: Indice Diatomées de l'Est du Canada) was developed to monitor the biological integrity of streams and rivers in Eastern Canada. The first version of the IDEC has been successfully used to evaluate the biological status of numerous sites. A new version of the index (IDEC 2.0) was recently developed to cover a larger geographic area that encompasses additional geological characteristics. IDEC 2.0 is now applicable for the biological assessment of streams in Quebec, Ontario, New Brunswick, Nova Scotia, and Prince Edward Island. Moreover, the approach used to define the biological interpretation of the index values was revised. IDEC 2.0 presents ecologically meaningful differences among biological communities (ecological thresholds or class boundaries) based on diatom biotypes, providing a more relevant interpretation of the diatom community changes along the alteration gradient.

Research paper thumbnail of Local and regional drivers of taxonomic homogenization in stream communities along a land use gradient

Global Ecology and Biogeography, 2019

AimThe interaction of land use with local versus regional processes driving biological homogeniza... more AimThe interaction of land use with local versus regional processes driving biological homogenization (β‐diversity loss) is poorly understood. We explored: (a) stream β‐diversity responses to land cover (forest versus agriculture) in terms of physicochemistry and physicochemical heterogeneity; (b) whether these responses were constrained by the regional species pool, i.e. γ‐diversity, or local assembly processes through local (α) diversity; (c) whether local assembly operated through the regional species abundance distribution (SAD) or intraspecific spatial aggregation; and (d) the dependence on body size, dispersal capacity and trophic level (producer versus consumer).LocationUSA, Canada and France.Time period1993–2012.Major taxa studiedStream diatoms, insects and fish.MethodsWe analysed six datasets totalling 1,225 stream samples. We compared diversity responses to eutrophication and physicochemical heterogeneity in forested versus agricultural streams with regression methods. Nul...

Research paper thumbnail of Algae-based Biomonitoring: Predicting Diatom Reference Communities in Unpolluted Streams using Classification Trees, Random Forests, and Artificial Neural Networks

Water Quality Research Journal, 2010

The Eastern Canadian Diatom Index (IDEC) was developed to evaluate the ecological integrity of st... more The Eastern Canadian Diatom Index (IDEC) was developed to evaluate the ecological integrity of streams along a pollution gradient, as a function of the dissimilarity between current diatom communities and suitable reference communities. Distinguishing natural variations in community structure from those induced by human activities is essential for proper assessment of dissimilarity. To account for the effect of the natural variation in pH on this assessment, two IDEC subindices were used: one for sites with diatom reference communities typical of naturally alkaline water pH, and another for sites with communities typical of naturally circumneutral water pH. This study used three statistical models, namely classification trees (CT), random forests (RF), and artificial neural networks (ANN) to: (i) identify the environmental variables discriminating between alkaline and neutral reference communities (“biotypes”), and (ii) compare their predictive capacities. Models identified clay roc...

Research paper thumbnail of Gomphonema caperatum sp. nov., G. obstipum sp. nov. and similar taxa from rivers of North America

Diatom Research, 2017

Two new species of Gomphonema with linear-lanceolate valves, narrow cells (width ≤ 6 μm), wide ax... more Two new species of Gomphonema with linear-lanceolate valves, narrow cells (width ≤ 6 μm), wide axial areas, short uniseriate striae, and one stigmoid per valve are described. Gomphonema caperatum sp. nov. has narrow, almost linear valves with short marginal striae, apically elongated slit-like areolae, and transapically oriented linear markings on the external valve surface, which are only observable under scanning electron microscopy. This is a common and often abundant species in rivers across Eastern North America, especially in the Appalachian region, but is also found on the West Coast. Gomphonema obstipum sp. nov. has lanceolate valves with bent apices, variously shaped apically elongated areolae, and shallow circular depressions on the external valve surface. This species has only been found in two Virginian rivers. We compare the new taxa with several species of Gomphonema from North American rivers that are morphologically similar, such as Gomphonema amerhombicum Reichardt, Gomphonema stoermeri Kociolek & Kingston, and other species with linear-lanceolate valves and wide axial areas. In addition, we report here for the first time the occurrence of Gomphonema incognitum in North America. This study underscores the insufficiency of our knowledge of diatom diversity in North America and the need for more detailed taxonomic investigations.

Research paper thumbnail of Determination of Diatom Reference Communities and Restauration Goals for Streams in Quebec

Agu Spring Meeting Abstracts, May 1, 2005

Research paper thumbnail of Classification des diatomées par les descripteurs de Fourier du contour

Nous présentons dans cet article un système automatique de classification des diatomées fondée su... more Nous présentons dans cet article un système automatique de classification des diatomées fondée sur une extraction des angles normaux d'un contour 8-connecté antihoraire. Pour cela, nous avons utilisé un modèle paramétrique qui consiste à caractériser le contour des diatomées suivant un vecteur des descripteurs de Fourier. Sur une base de données d'images de diatomées de 450 images, nous avons obtenu un taux de bonne classification de 97%.

Research paper thumbnail of Diatom typology of low-impacted conditions at a multi-regional scale: combined results of multivariate analyses and SOM

Modelling Community Structure in Freshwater Ecosystems

Page 1. 5 Diatom and other algal assemblages 317 5.6 Diatom typology of low-impacted conditions a... more Page 1. 5 Diatom and other algal assemblages 317 5.6 Diatom typology of low-impacted conditions at a multi-regional scale: combined results of multivariate analyses and SOM* Gosselain V†, Campeau S, Gevrey M, Coste ...

Research paper thumbnail of Biosuivi de l’intégrité écologique de ruisseaux et de lacs du Parc de la Gatineau à l’aide des diatomées et des autres groupes d’algues

Research paper thumbnail of Using diatoms to monitor stream biological integrity in Eastern Canada: An overview of 10 years of index development and ongoing challenges

Science of The Total Environment, 2014

An improved version of the Eastern Canadian Diatom Index (IDEC: Indice Diatomées de l&amp... more An improved version of the Eastern Canadian Diatom Index (IDEC: Indice Diatomées de l'Est du Canada) was developed, incorporating modifications to optimize diatom-based monitoring in Eastern Canada. The most significant improvement with this version of the IDEC is the extended coverage area including additional reference sites. This new version of the IDEC also incorporated a simplified list of diatom taxa to reduce the variability among analysts as it gains in popularity. Rare taxa (<2%) were excluded and various morphotypes were grouped. The index was created based on three sub-indices that were adapted to cover the range of natural pH and conductivity values allowing us to partial out the strong influence of natural pH and conductivity from the general pollution gradient. The index was created using 648 diatom assemblages including those from nearly 150 reference (or least-disturbed) sites. The reference sites covered a large range of natural characteristics. The diatom assemblages collected in these environments constitute "biotype class A" in each sub-index and represent a realistic goal for restoration. Associated total phosphorus and total nitrogen showed that class A generally reflects conditions that are considered oligotrophic (<0.025 mg L(-1)) or oligo-mesotrophic, while class D at the opposite end of the pollution gradient reflects eutrophic or hyper-eutrophic environments. There is a good correspondence between IDEC values and nutrient criteria, water quality indices based on physico-chemistry measurements, the presence of agricultural activities, and urban areas. The IDEC has a great potential to assist water quality monitoring, particularly when the objective is to assess the trophic status of a watercourse.

Research paper thumbnail of Buttes cryogènes saisonnières de plages arctiques, péninsule de Tuktoyaktuk, Territoires du Nord-Ouest

Géographie physique et Quaternaire, 1995

Des buttes cryogènes saisonnières en système fermé ont été observées de 1991 à 1993 sur les flèch... more Des buttes cryogènes saisonnières en système fermé ont été observées de 1991 à 1993 sur les flèches sableuses de la péninsule de Tuktoyaktuk, dans les Territoires du Nord-Ouest. Les buttes ont une forme circulaire et convexe. Leur diamètre varie entre 5 et 15 m et leur hauteur, entre 15 et 25 cm. Le coeur des buttes est constitué d'une lentille de glace intrusive de même diamètre que les buttes. La lentille a une forme convexe et sa base est horizontale. L'épaisseur de la lentille est égale à l'élévation des buttes, soit entre 15 et 25 cm. Les buttes se forment dans une pseudo-dépression située entre la berme de tempête et la berme du rivage de la lagune. À la fin de l'été, les débordements de tempête saturent en eau de mer le sable des flèches. L'engel provoque un accroissement de la pression hydrostatique à l'intérieur de la dépression. Les lentilles de glace intrusive se développent ainsi en système fermé. Les buttes se forment au cours de l'hiver pour...