Charlotte Roehm | McGill University (original) (raw)

Papers by Charlotte Roehm

Research paper thumbnail of Quantifying the relative importance of lake emissions in the carbon budget of a subarctic catchment

Journal of Geophysical Research, 2010

Research paper thumbnail of Insights on riverine metabolism from continuous measurements of CDOM fluorescence in Eastmain-1 Reservoir, Quebec

Internationale Vereinigung für theoretische und angewandte Limnologie: Verhandlungen, 2010

Rivers are notorious1y variab1e. In contrast to 1akes where factors influencing the metabolic ba1... more Rivers are notorious1y variab1e. In contrast to 1akes where factors influencing the metabolic ba1ance of the ecosystem are fairly well constrained, rivers are typically more difficu1t to predict and genera1ize. In 1acustrine systems, the interp1ay between externa1 organic carbon 1oads and in-1ake metabo1ic processes (primary production, sediment accumu1ation, pe1agic and benthic respiration) is key to determining the net status of these systems, and simp1e ru1es app1y generally. For examp1e, in temperate and borea1 1akes, an upper thresho1d va1ue of5-6 mg L-1 DOC often constitutes the average concentration for net heterotrophic 1akes (HANSON et al. 2003). Surprising1y, this thresho1d is not very sensitive to the trophic status oflakes (PRAIRIE 2008). This dominance of respiration over primary production 1eads to co2 supersaturation and thus evasion to the atmosphere, a phenomenon observed in the majority of aquatic systems (COLE et al. 1994, DuARTE & PRAIRIE 2005).

Research paper thumbnail of Synthesis

Environmental Science and Engineering, 2005

The objectives of this chapter are to present a comprehensive review of the current state of know... more The objectives of this chapter are to present a comprehensive review of the current state of knowledge and to identify the gaps in the greenhouse gas issues in hydroelectric reservoirs and natural ecosystems. It has become essential to integrate our knowledge of the carbon cycle at the larger temporal and spatial scales in order to properly assess the magnitude of GHG fluxes from reservoirs1 and natural ecosystems. The information available comes from small scale and short term (1 to 10 years) studies mostly from boreal regions but also from semi-arid and tropical regions. Natural variability of GHG fluxes due to regional climatic variations and their impacts on whole biological production are far more important than the techniques available to measure them. Therefore, one must keep in mind that the uncertainties in the GHG fluxes are related to natural spatial and temporal variations of fluxes and not necessarily from the measurement techniques themselves. This synthesis is based on the findings of over ten years of studies reported by research teams from many universities, governmental agencies and power utilities.

Research paper thumbnail of ThepCO2dynamics in lakes in the boreal region of northern Québec, Canada

Global Biogeochemical Cycles, 2009

In this study, we examine the magnitude and temporal variability of surface water pCO 2 in a set ... more In this study, we examine the magnitude and temporal variability of surface water pCO 2 in a set of lakes in boreal Québec, and explore the links between lake and catchment properties. The study lakes were consistently supersaturated in CO 2 , with the mean lake pCO 2 ranging from 400 to over 1800 matm. There was significant interannual variability in pCO 2 , apparently driven by regional patterns in precipitation. The best multivariate model of average pCO 2 included dissolved organic carbon (DOC), lake area and chlorophyll as independent variables, suggesting that external carbon (C) loading to lakes plays a central role in lake CO 2 dynamics and that lake trophic status may modulate the influence of external C loading. We show that even if the key drivers of lake pCO 2 are similar, they interact differently among regions and the resulting models may be dramatically different. In particular, we show that although pCO 2 is invariably correlated to DOC, the shape of this relationship varies greatly among regions, suggesting large-scale regional differences in C delivery, quality, and in-lake processing. As a consequence, current models cannot be extrapolated across regions unless we apply region-specific variables.

Research paper thumbnail of Carbon Cycling in a Northern Peatland

Research paper thumbnail of Seasonal contribution of CO2fluxes in the annual C budget of a northern bog

Global Biogeochemical Cycles, 2003

Research paper thumbnail of Carbon Cycling in Alpine and Arctic watersheds affected by permafrost degradation: An insight from Sweden

Linking the processes and dynamics acting within and between terrestrial and aquatic ecosystems i... more Linking the processes and dynamics acting within and between terrestrial and aquatic ecosystems is crucial in order to understand the impacts of environmental change on the re-distribution and transformation of energy within watersheds. Nearly 1300 Pg of carbon are stored in permafrost soils in boreal and arctic ecosystems. Permafrost degradation can result in the loss of significant amounts of terrestrial carbon, both through the release to the atmosphere in the form of carbon dioxide and methane, or through export downstream to lakes and rivers. The fate and effects of this carbon in lake ecosystems is poorly understood. We investigated the capacity of lake bacteria to utilize carbon from different adjacent mire soils in a discontinuous permafrost region of northern Sweden. We, additionally, studied other lake ecosystems by using organic matter quality as a proxy for the state of permafrost degradation within the watershed. Finally, we propose simple predictive models for the bioa...

Research paper thumbnail of The Issue of Greenhouse Gases from Hydroelectric Reservoirs: From Boreal to Tropical Regions

The role of greenhouse gas emissions (GHG) from freshwater reservoirs and their contribution in i... more The role of greenhouse gas emissions (GHG) from freshwater reservoirs and their contribution in increasing atmospheric GHG concentrations is actually well discussed worldwide. The amount of GHGs emitted at the air-water interface of reservoirs varies over time. The maximum is attained within 3 to 5 years after impoundment. In reservoirs older>10 years in boreal and semi-arid regions, GHG emissions are similar than those of natural lakes. In tropical regions, the time to return to natural values may be longer depending on the water quality conditions. Hydropower is a very efficient way to produce electricity, showing emission factors between one and two orders of magnitude lower than the thermal alternatives. The major greenhouse gases are carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) (IPCC, 2001). These gases are emitted from both natural aquatic (lakes, rivers, estuaries, wetlands) and terrestrial ecosystems (forest,

Research paper thumbnail of Regulation of Decomposition and Methane Dynamics across Natural, Commercially Mined, and Restored

We examined aerobic and anaerobic microbial car-bon dioxide (CO2) and methane (CH4) exchange in p... more We examined aerobic and anaerobic microbial car-bon dioxide (CO2) and methane (CH4) exchange in peat samples representing different profiles at nat-ural, mined, mined-abandoned, and restored northern peatlands and characterized the nutrient and substrate chemistry and microbial biomass of these soils. Mining and abandonment led to reduced nutrient and substrate availability and occasionally drier conditions in surface peat resulting in a drastic reduction in CO2 and CH4 production, in agreement with previous studies. Owing mainly to wetter conditions, CH4 production and oxidation were faster in restored block-cut than natural sites, whereas in one restored site, increased substrate and

Research paper thumbnail of Iron, sulfur, and dissolved carbon dynamics in a northern peatland

Fundamental and Applied Limnology

Research paper thumbnail of Carbon dynamics in northern peatlands, Canada /

Research paper thumbnail of Using preliminary NEON data to test aquatic organismal sample timing strategies

Research paper thumbnail of NEON: A New Platform for Large River Ecology

Research paper thumbnail of NEON aquatic macroinvertebrate sampling strategies over the continental scale

Research paper thumbnail of Novel approach to define the morphology of shallow lakes

Background/Question/Methods The National Ecological Observatory Network (NEON) will detect and en... more Background/Question/Methods The National Ecological Observatory Network (NEON) will detect and enable forecasting of ecological change from regional to continental scales over multiple decades, through the collection of data on the impacts of climate change, land use change and invasive species on natural resources and biodiversity. In order to enable comparative data analysis across the US at multiple temporal and spatial scales, the NEON infrastructure will be standardized both at the sensor and the field sampling level. Following stringent quality-control checks the data will be posted on the open-access NEON web portal. This poster presents technological capabilities to quantify lake bathymetry and morphology. Over the next year, NEON will census potential users of these data (e.g. lake ecologists, hydrologists) to determine the utility of various data products. Lake bathymetry and morphology are crucial data products used to drive both biological and chemical sampling strategie...

Research paper thumbnail of The NEON fish sampling design

Background/Question/Methods The National Ecological Observatory Network (NEON) will collect data ... more Background/Question/Methods The National Ecological Observatory Network (NEON) will collect data on aquatic organisms over 30 years, thereby enabling the research community to assess ecological response to climate change and land use change at regional and continental scales. To allow data integrations over multiple spatial and temporal scales, the Observatory requires standardized, consistent methodologies for field data collection. Here, we define the strategy and details of the fish sampling plans at wadeable streams and shallow lakes. One consideration is whether reach-scale or macrohabitat-scale sampling is the most useful sampling design for NEON. NEON’s main objective is to provide data to assess changes in fish diversity over space and time. Fish sampling will be conducted annually using standardized procedures. NEON-generated fish data will allow the research community to assess changes in biodiversity over spatial and temporal scales within a physical-chemical-foodweb cont...

Research paper thumbnail of NEON's higher education program: providing undergraduate experiences in observatory building and continental scale ecology

Background / Purpose: NEON’s higher education program is designed to provide faculty with state-o... more Background / Purpose: NEON’s higher education program is designed to provide faculty with state-of-the-art resources and tools to facilitate integration of large datasets into university classrooms. It also provides students with real-world experiences (internship, REU) in helping build an ecological observatory and using big data to better understand ecological change over large regions. Main conclusion: NEON's undergraduate internship program expanded to seven students in 2014. NEON's higher education program also initiated a collaborative University-focused online education portal with content that includes 1) interactive, online multi-media that explain key big data concepts, and 2) packaged “lab” activities featuring NEON data and code.

Research paper thumbnail of The NEON Aquatic Network: Standardizing deployment of aquatic instrument systems across continental ccosystems

Background/Question/Methods The National Ecological Observatory Network (NEON) is a national-scal... more Background/Question/Methods The National Ecological Observatory Network (NEON) is a national-scale research platform for assessing the impacts of climate change, land-use change, and invasive species on ecosystem structure and function. NEON will collect data for 30 years to facilitate spatial-temporal analysis of environmental responses and rivers of ecosystem change, ranging from local through continental scales. Using standardized methods and designs, the data collected can be compared across a wide variety of ecosystems at multiple scales. Standardized quality assurance and quality control allow data to be processed efficiently and disseminated to users through an online data portal. Currently, the network is in construction phase. This poster will present the design of the aquatic instrumentation systems within the NEON network and discuss the challenges and opportunities for water monitoring across the observatory using NEON data. Results/Conclusions The aquatic instrument sys...

Research paper thumbnail of NEON aquatic instrument deployment design

Come one, come all, to hear about NEON’s aquatic instrument systems (AIS). Does curiosity of aqua... more Come one, come all, to hear about NEON’s aquatic instrument systems (AIS). Does curiosity of aquatic measurements made by a variety of instruments ail you? NEON’s AIS will provide information to please many a curious mind. Do streams, rivers, and lakes occupy your every waking moment? NEON’s AIS will provide enjoyable challenges and opportunities. Do the words “standardized methods” and “ecosystems” pluck the strings of your passion? NEON’s AIS will conduct an orchestra within you. Come learn more about the deployment of NEON AIS. (Caution: product is meant to inform, and does not claim to affect the health of attendees.)

Research paper thumbnail of NEON Aquatic Program: Tools for large river ecology

Background/Question/Methods The National Ecological Observatory Network (NEON) is a national-scal... more Background/Question/Methods The National Ecological Observatory Network (NEON) is a national-scale research platform designed to assess the impacts of climate change, land-use change, and invasive species on ecosystem structure and function. The NEON Aquatic program will produce over 200 data products at each of its 36 sites for 30 years to facilitate spatiotemporal analysis of the drivers of ecosystem change using a combination of continuous in situ measurements and observational sampling. While the majority of aquatic sites are wadeable streams and lakes, four river sites will also be constructed. Two large river sites in Alabama were chosen to address the question of an eco-hydrologic gradient spanning the watershed from headwater stream to navigable river. Continuous measurements includes surface water physical, chemical and biological parameters (PAR, level, temperature, conductivity, pH, DO, nitrate, turbidity, Chl a, cDOM), groundwater level, temperature and conductivity and ...

Research paper thumbnail of Quantifying the relative importance of lake emissions in the carbon budget of a subarctic catchment

Journal of Geophysical Research, 2010

Research paper thumbnail of Insights on riverine metabolism from continuous measurements of CDOM fluorescence in Eastmain-1 Reservoir, Quebec

Internationale Vereinigung für theoretische und angewandte Limnologie: Verhandlungen, 2010

Rivers are notorious1y variab1e. In contrast to 1akes where factors influencing the metabolic ba1... more Rivers are notorious1y variab1e. In contrast to 1akes where factors influencing the metabolic ba1ance of the ecosystem are fairly well constrained, rivers are typically more difficu1t to predict and genera1ize. In 1acustrine systems, the interp1ay between externa1 organic carbon 1oads and in-1ake metabo1ic processes (primary production, sediment accumu1ation, pe1agic and benthic respiration) is key to determining the net status of these systems, and simp1e ru1es app1y generally. For examp1e, in temperate and borea1 1akes, an upper thresho1d va1ue of5-6 mg L-1 DOC often constitutes the average concentration for net heterotrophic 1akes (HANSON et al. 2003). Surprising1y, this thresho1d is not very sensitive to the trophic status oflakes (PRAIRIE 2008). This dominance of respiration over primary production 1eads to co2 supersaturation and thus evasion to the atmosphere, a phenomenon observed in the majority of aquatic systems (COLE et al. 1994, DuARTE & PRAIRIE 2005).

Research paper thumbnail of Synthesis

Environmental Science and Engineering, 2005

The objectives of this chapter are to present a comprehensive review of the current state of know... more The objectives of this chapter are to present a comprehensive review of the current state of knowledge and to identify the gaps in the greenhouse gas issues in hydroelectric reservoirs and natural ecosystems. It has become essential to integrate our knowledge of the carbon cycle at the larger temporal and spatial scales in order to properly assess the magnitude of GHG fluxes from reservoirs1 and natural ecosystems. The information available comes from small scale and short term (1 to 10 years) studies mostly from boreal regions but also from semi-arid and tropical regions. Natural variability of GHG fluxes due to regional climatic variations and their impacts on whole biological production are far more important than the techniques available to measure them. Therefore, one must keep in mind that the uncertainties in the GHG fluxes are related to natural spatial and temporal variations of fluxes and not necessarily from the measurement techniques themselves. This synthesis is based on the findings of over ten years of studies reported by research teams from many universities, governmental agencies and power utilities.

Research paper thumbnail of ThepCO2dynamics in lakes in the boreal region of northern Québec, Canada

Global Biogeochemical Cycles, 2009

In this study, we examine the magnitude and temporal variability of surface water pCO 2 in a set ... more In this study, we examine the magnitude and temporal variability of surface water pCO 2 in a set of lakes in boreal Québec, and explore the links between lake and catchment properties. The study lakes were consistently supersaturated in CO 2 , with the mean lake pCO 2 ranging from 400 to over 1800 matm. There was significant interannual variability in pCO 2 , apparently driven by regional patterns in precipitation. The best multivariate model of average pCO 2 included dissolved organic carbon (DOC), lake area and chlorophyll as independent variables, suggesting that external carbon (C) loading to lakes plays a central role in lake CO 2 dynamics and that lake trophic status may modulate the influence of external C loading. We show that even if the key drivers of lake pCO 2 are similar, they interact differently among regions and the resulting models may be dramatically different. In particular, we show that although pCO 2 is invariably correlated to DOC, the shape of this relationship varies greatly among regions, suggesting large-scale regional differences in C delivery, quality, and in-lake processing. As a consequence, current models cannot be extrapolated across regions unless we apply region-specific variables.

Research paper thumbnail of Carbon Cycling in a Northern Peatland

Research paper thumbnail of Seasonal contribution of CO2fluxes in the annual C budget of a northern bog

Global Biogeochemical Cycles, 2003

Research paper thumbnail of Carbon Cycling in Alpine and Arctic watersheds affected by permafrost degradation: An insight from Sweden

Linking the processes and dynamics acting within and between terrestrial and aquatic ecosystems i... more Linking the processes and dynamics acting within and between terrestrial and aquatic ecosystems is crucial in order to understand the impacts of environmental change on the re-distribution and transformation of energy within watersheds. Nearly 1300 Pg of carbon are stored in permafrost soils in boreal and arctic ecosystems. Permafrost degradation can result in the loss of significant amounts of terrestrial carbon, both through the release to the atmosphere in the form of carbon dioxide and methane, or through export downstream to lakes and rivers. The fate and effects of this carbon in lake ecosystems is poorly understood. We investigated the capacity of lake bacteria to utilize carbon from different adjacent mire soils in a discontinuous permafrost region of northern Sweden. We, additionally, studied other lake ecosystems by using organic matter quality as a proxy for the state of permafrost degradation within the watershed. Finally, we propose simple predictive models for the bioa...

Research paper thumbnail of The Issue of Greenhouse Gases from Hydroelectric Reservoirs: From Boreal to Tropical Regions

The role of greenhouse gas emissions (GHG) from freshwater reservoirs and their contribution in i... more The role of greenhouse gas emissions (GHG) from freshwater reservoirs and their contribution in increasing atmospheric GHG concentrations is actually well discussed worldwide. The amount of GHGs emitted at the air-water interface of reservoirs varies over time. The maximum is attained within 3 to 5 years after impoundment. In reservoirs older>10 years in boreal and semi-arid regions, GHG emissions are similar than those of natural lakes. In tropical regions, the time to return to natural values may be longer depending on the water quality conditions. Hydropower is a very efficient way to produce electricity, showing emission factors between one and two orders of magnitude lower than the thermal alternatives. The major greenhouse gases are carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) (IPCC, 2001). These gases are emitted from both natural aquatic (lakes, rivers, estuaries, wetlands) and terrestrial ecosystems (forest,

Research paper thumbnail of Regulation of Decomposition and Methane Dynamics across Natural, Commercially Mined, and Restored

We examined aerobic and anaerobic microbial car-bon dioxide (CO2) and methane (CH4) exchange in p... more We examined aerobic and anaerobic microbial car-bon dioxide (CO2) and methane (CH4) exchange in peat samples representing different profiles at nat-ural, mined, mined-abandoned, and restored northern peatlands and characterized the nutrient and substrate chemistry and microbial biomass of these soils. Mining and abandonment led to reduced nutrient and substrate availability and occasionally drier conditions in surface peat resulting in a drastic reduction in CO2 and CH4 production, in agreement with previous studies. Owing mainly to wetter conditions, CH4 production and oxidation were faster in restored block-cut than natural sites, whereas in one restored site, increased substrate and

Research paper thumbnail of Iron, sulfur, and dissolved carbon dynamics in a northern peatland

Fundamental and Applied Limnology

Research paper thumbnail of Carbon dynamics in northern peatlands, Canada /

Research paper thumbnail of Using preliminary NEON data to test aquatic organismal sample timing strategies

Research paper thumbnail of NEON: A New Platform for Large River Ecology

Research paper thumbnail of NEON aquatic macroinvertebrate sampling strategies over the continental scale

Research paper thumbnail of Novel approach to define the morphology of shallow lakes

Background/Question/Methods The National Ecological Observatory Network (NEON) will detect and en... more Background/Question/Methods The National Ecological Observatory Network (NEON) will detect and enable forecasting of ecological change from regional to continental scales over multiple decades, through the collection of data on the impacts of climate change, land use change and invasive species on natural resources and biodiversity. In order to enable comparative data analysis across the US at multiple temporal and spatial scales, the NEON infrastructure will be standardized both at the sensor and the field sampling level. Following stringent quality-control checks the data will be posted on the open-access NEON web portal. This poster presents technological capabilities to quantify lake bathymetry and morphology. Over the next year, NEON will census potential users of these data (e.g. lake ecologists, hydrologists) to determine the utility of various data products. Lake bathymetry and morphology are crucial data products used to drive both biological and chemical sampling strategie...

Research paper thumbnail of The NEON fish sampling design

Background/Question/Methods The National Ecological Observatory Network (NEON) will collect data ... more Background/Question/Methods The National Ecological Observatory Network (NEON) will collect data on aquatic organisms over 30 years, thereby enabling the research community to assess ecological response to climate change and land use change at regional and continental scales. To allow data integrations over multiple spatial and temporal scales, the Observatory requires standardized, consistent methodologies for field data collection. Here, we define the strategy and details of the fish sampling plans at wadeable streams and shallow lakes. One consideration is whether reach-scale or macrohabitat-scale sampling is the most useful sampling design for NEON. NEON’s main objective is to provide data to assess changes in fish diversity over space and time. Fish sampling will be conducted annually using standardized procedures. NEON-generated fish data will allow the research community to assess changes in biodiversity over spatial and temporal scales within a physical-chemical-foodweb cont...

Research paper thumbnail of NEON's higher education program: providing undergraduate experiences in observatory building and continental scale ecology

Background / Purpose: NEON’s higher education program is designed to provide faculty with state-o... more Background / Purpose: NEON’s higher education program is designed to provide faculty with state-of-the-art resources and tools to facilitate integration of large datasets into university classrooms. It also provides students with real-world experiences (internship, REU) in helping build an ecological observatory and using big data to better understand ecological change over large regions. Main conclusion: NEON's undergraduate internship program expanded to seven students in 2014. NEON's higher education program also initiated a collaborative University-focused online education portal with content that includes 1) interactive, online multi-media that explain key big data concepts, and 2) packaged “lab” activities featuring NEON data and code.

Research paper thumbnail of The NEON Aquatic Network: Standardizing deployment of aquatic instrument systems across continental ccosystems

Background/Question/Methods The National Ecological Observatory Network (NEON) is a national-scal... more Background/Question/Methods The National Ecological Observatory Network (NEON) is a national-scale research platform for assessing the impacts of climate change, land-use change, and invasive species on ecosystem structure and function. NEON will collect data for 30 years to facilitate spatial-temporal analysis of environmental responses and rivers of ecosystem change, ranging from local through continental scales. Using standardized methods and designs, the data collected can be compared across a wide variety of ecosystems at multiple scales. Standardized quality assurance and quality control allow data to be processed efficiently and disseminated to users through an online data portal. Currently, the network is in construction phase. This poster will present the design of the aquatic instrumentation systems within the NEON network and discuss the challenges and opportunities for water monitoring across the observatory using NEON data. Results/Conclusions The aquatic instrument sys...

Research paper thumbnail of NEON aquatic instrument deployment design

Come one, come all, to hear about NEON’s aquatic instrument systems (AIS). Does curiosity of aqua... more Come one, come all, to hear about NEON’s aquatic instrument systems (AIS). Does curiosity of aquatic measurements made by a variety of instruments ail you? NEON’s AIS will provide information to please many a curious mind. Do streams, rivers, and lakes occupy your every waking moment? NEON’s AIS will provide enjoyable challenges and opportunities. Do the words “standardized methods” and “ecosystems” pluck the strings of your passion? NEON’s AIS will conduct an orchestra within you. Come learn more about the deployment of NEON AIS. (Caution: product is meant to inform, and does not claim to affect the health of attendees.)

Research paper thumbnail of NEON Aquatic Program: Tools for large river ecology

Background/Question/Methods The National Ecological Observatory Network (NEON) is a national-scal... more Background/Question/Methods The National Ecological Observatory Network (NEON) is a national-scale research platform designed to assess the impacts of climate change, land-use change, and invasive species on ecosystem structure and function. The NEON Aquatic program will produce over 200 data products at each of its 36 sites for 30 years to facilitate spatiotemporal analysis of the drivers of ecosystem change using a combination of continuous in situ measurements and observational sampling. While the majority of aquatic sites are wadeable streams and lakes, four river sites will also be constructed. Two large river sites in Alabama were chosen to address the question of an eco-hydrologic gradient spanning the watershed from headwater stream to navigable river. Continuous measurements includes surface water physical, chemical and biological parameters (PAR, level, temperature, conductivity, pH, DO, nitrate, turbidity, Chl a, cDOM), groundwater level, temperature and conductivity and ...