Across our research projects, we seek to understand how environmental change alters biogeochemical cycling in fluvial landscapes (streams, rivers, wetlands, floodplains). Our research projects are topically (and disciplinarily) diverse, melding concepts from the ecological and hydrologic sciences and integrating lab, field, data science, and modeling approaches.
Ongoing research projects seek to answer three broad overarching questions:
Hydrologic connectivity and stream ecosystem dynamics-
How do streams reflect, integrate, and alter signals from the landscape?
Biogeochemical and hydrologic regime shifts in coastal landscapes -
How do interactions among management activities, land development, and climate change affect wetland ecosystem functions?
Biogeochemical cycling from stream reaches to networks -
What are the roles of stream networks in carbon and nutrient cycling in changing landscapes?
Ongoing research projects seek to answer three broad overarching questions:
Hydrologic connectivity and stream ecosystem dynamics-
How do streams reflect, integrate, and alter signals from the landscape?
Biogeochemical and hydrologic regime shifts in coastal landscapes -
How do interactions among management activities, land development, and climate change affect wetland ecosystem functions?
Biogeochemical cycling from stream reaches to networks -
What are the roles of stream networks in carbon and nutrient cycling in changing landscapes?
(1) Hydrologic connectivity and stream ecosystem dynamics
Humans alter the chemical and hydrologic landscape, water transports elements around the landscape, and aquatic ecosystems are both affected by and affect the fate of elements added to the land surface. Our overarching research goal is to understand how stream and river ecosystems reflect, integrate, and alter hydrologic, thermal, and chemical signals from the landscape. I am particularly interested in disentangling how connectivity between the land surface, groundwater, and streams over space and time affects contemporary (and future) stream ecosystem dynamics.
Here are examples of recent projects under this topic:
Humans alter the chemical and hydrologic landscape, water transports elements around the landscape, and aquatic ecosystems are both affected by and affect the fate of elements added to the land surface. Our overarching research goal is to understand how stream and river ecosystems reflect, integrate, and alter hydrologic, thermal, and chemical signals from the landscape. I am particularly interested in disentangling how connectivity between the land surface, groundwater, and streams over space and time affects contemporary (and future) stream ecosystem dynamics.
Here are examples of recent projects under this topic:
Groundwater discharge of nitrogen at the scale of river networks
Reactive nitrogen (N) applied to land surfaces infiltrates with precipitation and accumulates in aquifers, creating a source of legacy N that is later discharged from groundwater to surface waters. Groundwater transport times can be months, decades, or even centuries longer than surface water transport times, which causes substantial lags between when N is applied to land surfaces and when it actually enters surface waters. These focused groundwater discharges can obstruct water quality management strategies that are based on reducing present-day N applications. Yet, not all N that enters the groundwater system is delivered to surface waters. Some fraction of N is removed by microbial processes during transport along regional groundwater flow paths. At the end of long groundwater flow paths, streambank and streambed (i.e., stream interface) sediments can remove N at relatively high rates, further reducing N delivery to surface waters. This project, funded by NSF-Hydrologic Sciences with co-PIs Dr. Marty Briggs and Dr. Jeff Starn (USGS), integrates extensive field measurements across a river network with groundwater models to 1) characterize the spatial patterns of focused groundwater discharge at the river network scale, 2) quantify patterns and drivers of legacy N transport through and removal within stream interface sediments, 3) scale legacy N cycling to the river channel network. PhD student Eric Moore and MS students Kevin Jackson, Adam Haynes, and Alaina Bisson lead our research efforts on this project. You can see an overview and update of this project as part of the CLEAR webinar series, recorded here.
Reactive nitrogen (N) applied to land surfaces infiltrates with precipitation and accumulates in aquifers, creating a source of legacy N that is later discharged from groundwater to surface waters. Groundwater transport times can be months, decades, or even centuries longer than surface water transport times, which causes substantial lags between when N is applied to land surfaces and when it actually enters surface waters. These focused groundwater discharges can obstruct water quality management strategies that are based on reducing present-day N applications. Yet, not all N that enters the groundwater system is delivered to surface waters. Some fraction of N is removed by microbial processes during transport along regional groundwater flow paths. At the end of long groundwater flow paths, streambank and streambed (i.e., stream interface) sediments can remove N at relatively high rates, further reducing N delivery to surface waters. This project, funded by NSF-Hydrologic Sciences with co-PIs Dr. Marty Briggs and Dr. Jeff Starn (USGS), integrates extensive field measurements across a river network with groundwater models to 1) characterize the spatial patterns of focused groundwater discharge at the river network scale, 2) quantify patterns and drivers of legacy N transport through and removal within stream interface sediments, 3) scale legacy N cycling to the river channel network. PhD student Eric Moore and MS students Kevin Jackson, Adam Haynes, and Alaina Bisson lead our research efforts on this project. You can see an overview and update of this project as part of the CLEAR webinar series, recorded here.
1934 Aerial Image of farmland that is now forested and urban along the Connecticut River
Can watershed land use legacies inform nitrogen management?
Past land use activities (or land use “legacies”) can be strong indicators of contemporary water quality; yet, watershed management strategies often neglect the lag times associated with land change. Therefore, the goal of our project is to understand how land use history and intensity influence water quality (with a focus on nitrogen) in streams and rivers of the Long Island Sound (LIS) watershed. To do this we will develop maps of potential land use legacies based on historic aerial imagery (dating back to the 1930s for CT) and satellite-derived land use land cover (dating back to the 1990s). We plan to use patterns of agricultural land use, deforestation and afforestation, and developed land use over time to identify watersheds where land use history may have a disproportionate effect on current water quality. Next, we will pair our legacy maps with existing datasets of water quality, water quality indicators (stream macroinvertebrates and diatoms), and targeted stream chemistry sampling to quantify the relationships between land use legacies and water quality. We intend to share maps and water quality relationships produced from this project broadly (including through an online platform) so they may help inform land conservation and watershed management goals and expectations.
This project is funded by the EPA Long Island Sound Study. Project partners include: University of Connecticut (Helton, lead PI), UConn Center for Land Use Education and Research (CLEAR, Emily Wilson, Chet Arnold, and Qian Lei-Parent), University of New Hampshire (Wil Wollheim), CT Department of Energy and Environmental Protection (Chris Bellucci and Mary Becker), Footprints in the Water, LLC (Paul Stacey), and the USGS New England Water Climate Science Center (Janet Barclay). MS student Ariana Dionisio and PhD student Eric Moore lead our research efforts on this project.
You can see an overview and update of this project as part of the CLEAR webinar series, recorded here.
Past land use activities (or land use “legacies”) can be strong indicators of contemporary water quality; yet, watershed management strategies often neglect the lag times associated with land change. Therefore, the goal of our project is to understand how land use history and intensity influence water quality (with a focus on nitrogen) in streams and rivers of the Long Island Sound (LIS) watershed. To do this we will develop maps of potential land use legacies based on historic aerial imagery (dating back to the 1930s for CT) and satellite-derived land use land cover (dating back to the 1990s). We plan to use patterns of agricultural land use, deforestation and afforestation, and developed land use over time to identify watersheds where land use history may have a disproportionate effect on current water quality. Next, we will pair our legacy maps with existing datasets of water quality, water quality indicators (stream macroinvertebrates and diatoms), and targeted stream chemistry sampling to quantify the relationships between land use legacies and water quality. We intend to share maps and water quality relationships produced from this project broadly (including through an online platform) so they may help inform land conservation and watershed management goals and expectations.
This project is funded by the EPA Long Island Sound Study. Project partners include: University of Connecticut (Helton, lead PI), UConn Center for Land Use Education and Research (CLEAR, Emily Wilson, Chet Arnold, and Qian Lei-Parent), University of New Hampshire (Wil Wollheim), CT Department of Energy and Environmental Protection (Chris Bellucci and Mary Becker), Footprints in the Water, LLC (Paul Stacey), and the USGS New England Water Climate Science Center (Janet Barclay). MS student Ariana Dionisio and PhD student Eric Moore lead our research efforts on this project.
You can see an overview and update of this project as part of the CLEAR webinar series, recorded here.
(2) Biogeochemical regime shifts in coastal wetland landscapes
Sea level rise along with changing drought and storm frequency and severity are increasing the susceptibility of the coast worldwide to flooding, saltwater intrusion, or both. At the same time, coastal areas are some of the most densely inhabited spaces on the planet with built infrastructure that limits the spatial extent of natural coastlines and delivers large loads of nutrients and other contaminants to coastal ecosystems, including wetlands. These seaward and landward pressures generate hydro-chemical fronts, creating complex biogeochemical regimes in wetlands that affect ecosystem functions (e.g., greenhouse gas fluxes, Helton et al. 2014; C export, Ardon et al. 2016). Wetland restoration and management add additional complexity – often altering upstream or downstream hydrologic connectivity and vegetation communities, either directly through planting or indirectly through species shifts caused by changes in salinity and hydrologic regimes. My research goal is to understand how the interactions of these hydro-chemical fronts, and the role of management activities in exacerbating or ameliorating their interactions, drive patterns of ecosystem function in coastal wetland landscapes.
Here are examples of current and recent projects under this topic:
Evaluating thin layer placement in Long Island Sound marshes using a multi-scale approach
Rising seas and limits to marsh migration pose serious threats to remaining Long Island Sound tidal marshes and the services they provide, with up to 97% of high elevation salt marsh projected to be lost by 2100. Implementing restoration techniques that build elevation capital and promote coastal resilience, such as thin layer placement (TLP, in which a layer of sediment is applied to marsh surfaces) is key to tidal marsh maintenance and a high priority for regional managers. Our primary objectives are 1) to test how sediment texture and tidal amplitude alter the effectiveness of thin layer placement, 2) to evaluate whether small-scale thin layer placement experiments are representative of management-scale applications, and 3) to promote understanding of sea level rise, coastal wetlands, and thin layer placement restoration to diverse stakeholders. Funded by the Long Island Sound Study, Helton is a co-PI with Beth Lawrence (PI, UConn NRE), Chris Elphick (co-PI, UConn EEB), and Min Huang (co-PI, CT DEEP). PhD student Madeline Kollegger leads the Helton lab efforts on this project in which we are also examining how incorporating soil amendments in TLP may improve its effectiveness.
How will sea level-rise driven shifts in wetland vegetation alter ecosystem services?
The overarching objective of this project is to quantify how shifts in vegetation may alter carbon and nitrogen cycling in Long Island Sound tidal wetlands and predict how those services change under sea-level rise scenarios. This project includes extensive field surveys of plant communities and soils, in situ "marsh organ" experiments, and spatiotemporal scaling of wetland ecosystem services in southern New England. Funded by the Long Island Sound Study, Helton is a co-PI with Beth Lawrence (PI, UConn NRE) and Chris Elphick (co-PI, UConn, EEB). In Helton's lab, former students Sean Ooi (MS 2019) and Kayleigh Granville (undergraduate Honor's 2019) collaborated on this project to quantify spatial and temporal patterns of salt marsh denitrification.
Here are examples of current and recent projects under this topic:
Evaluating thin layer placement in Long Island Sound marshes using a multi-scale approach
Rising seas and limits to marsh migration pose serious threats to remaining Long Island Sound tidal marshes and the services they provide, with up to 97% of high elevation salt marsh projected to be lost by 2100. Implementing restoration techniques that build elevation capital and promote coastal resilience, such as thin layer placement (TLP, in which a layer of sediment is applied to marsh surfaces) is key to tidal marsh maintenance and a high priority for regional managers. Our primary objectives are 1) to test how sediment texture and tidal amplitude alter the effectiveness of thin layer placement, 2) to evaluate whether small-scale thin layer placement experiments are representative of management-scale applications, and 3) to promote understanding of sea level rise, coastal wetlands, and thin layer placement restoration to diverse stakeholders. Funded by the Long Island Sound Study, Helton is a co-PI with Beth Lawrence (PI, UConn NRE), Chris Elphick (co-PI, UConn EEB), and Min Huang (co-PI, CT DEEP). PhD student Madeline Kollegger leads the Helton lab efforts on this project in which we are also examining how incorporating soil amendments in TLP may improve its effectiveness.
How will sea level-rise driven shifts in wetland vegetation alter ecosystem services?
The overarching objective of this project is to quantify how shifts in vegetation may alter carbon and nitrogen cycling in Long Island Sound tidal wetlands and predict how those services change under sea-level rise scenarios. This project includes extensive field surveys of plant communities and soils, in situ "marsh organ" experiments, and spatiotemporal scaling of wetland ecosystem services in southern New England. Funded by the Long Island Sound Study, Helton is a co-PI with Beth Lawrence (PI, UConn NRE) and Chris Elphick (co-PI, UConn, EEB). In Helton's lab, former students Sean Ooi (MS 2019) and Kayleigh Granville (undergraduate Honor's 2019) collaborated on this project to quantify spatial and temporal patterns of salt marsh denitrification.
(3) Biogeochemical cycles from stream reaches to river networks
River networks transport, transform, and retain carbon, nutrients, and other pollutants as water flows from terrestrial landscapes to lakes and oceans. Small stream reaches are the most intensely sampled flowing waters, and we work to understand how measurements made in small stream reaches can inform whole stream- and river- network function across landscapes. Here are examples of two recent projects under this topic:
StreamPULSE
How do stream ecosystems respond to land development and climate change? With this project, we are seeking to understand what drives patterns of stream metabolism within and across streams. This large, collaborative NSF Macrosystems Biology project includes nine PIs across six Universities (Emily Bernhardt (lead), Jim Heffernan, and Brian McGlynn, Duke University; Bill McDowell, University of New Hampshire; Bob Hall, University of Wyoming; Matt Cohen, University of Florida; Emily Stanley, University of Wisconsin; Nancy Grimm, Arizona State University) and intensive data collection in five biomes coupled with extensive existing datasets of stream ecosystem metabolism across the United States. At UConn, Postdoctoral Associate Lauren Koenig will continue developing and begin testing process-based models of stream metabolic responses to disturbance regimes at the site and watershed-scales. You can read more about StreamPULSE on the project's website.
Carbon Response to Experimental Warming in Streams (CREWS)
Our goal is to understand and predict the effects of warming and other anthropogenic stressors on stream carbon dynamics. This large project, funded by NSF, examines the effects of temperature on organic carbon processing in forest stream networks, using a multi-scale design that includes a paired-catchment whole-stream warming experiment, an array of warmed streamside channels, laboratory studies of aquatic microbes, and reach- and network-scale modeling. The fieldwork will take place at the Coweeta Hydrologic Laboratory in North Carolina. Collaborators include John Benstead (lead, University of Alabama), Amy Rosemond & Seth Wenger (University of Georgia), Erin Hotchkiss (Virginia Tech), and Vlad Gulis (Coastal Carolina). PhD student Danielle Hare leads UConn's efforts on this project.
StreamPULSE
How do stream ecosystems respond to land development and climate change? With this project, we are seeking to understand what drives patterns of stream metabolism within and across streams. This large, collaborative NSF Macrosystems Biology project includes nine PIs across six Universities (Emily Bernhardt (lead), Jim Heffernan, and Brian McGlynn, Duke University; Bill McDowell, University of New Hampshire; Bob Hall, University of Wyoming; Matt Cohen, University of Florida; Emily Stanley, University of Wisconsin; Nancy Grimm, Arizona State University) and intensive data collection in five biomes coupled with extensive existing datasets of stream ecosystem metabolism across the United States. At UConn, Postdoctoral Associate Lauren Koenig will continue developing and begin testing process-based models of stream metabolic responses to disturbance regimes at the site and watershed-scales. You can read more about StreamPULSE on the project's website.
Carbon Response to Experimental Warming in Streams (CREWS)
Our goal is to understand and predict the effects of warming and other anthropogenic stressors on stream carbon dynamics. This large project, funded by NSF, examines the effects of temperature on organic carbon processing in forest stream networks, using a multi-scale design that includes a paired-catchment whole-stream warming experiment, an array of warmed streamside channels, laboratory studies of aquatic microbes, and reach- and network-scale modeling. The fieldwork will take place at the Coweeta Hydrologic Laboratory in North Carolina. Collaborators include John Benstead (lead, University of Alabama), Amy Rosemond & Seth Wenger (University of Georgia), Erin Hotchkiss (Virginia Tech), and Vlad Gulis (Coastal Carolina). PhD student Danielle Hare leads UConn's efforts on this project.
