I strive to design research that advances both our fundamental understanding of inland waters and our stewardship of these ecosystems. My dissertation research focuses on the mechanisms that produce spatiotemporal variation in the biogeochemical cycles of lakes and reservoirs. I use field studies, laboratory experiments, numerical modeling, and literature synthesis to address my questions. Keep reading to learn more about my current projects!
how do aquatic plants affect lake hydrodynamics?
Aquatic plants, or macrophytes, have always fascinated me. Macrophyte beds are like miniature, underwater forests. Just as trees provide habitat for other organisms and change the forest environment through their physical structure, so too do macrophytes. From roots to canopy, these ecosystem engineers structure their watery environment, influencing whole-lake productivity and biogeochemical cycling. And yet, there is still much that we don’t know about how macrophyte beds regulate water flow and gas and solute transport in shallow waterbodies. To begin addressing this knowledge gap, I designed a study to quantify how mixed beds of native macrophytes influence thermal stratification and dissolved oxygen transport in shallow ponds. I measured horizontal and vertical variation in temperature and dissolved oxygen using combination of high frequency, in situ sensors and intensive manual measurements. I used these data to characterize the three-dimensional physical and dissolved oxygen environment of the study ponds and analyze spatiotemporal relationships between macrophytes, stratification, and dissolved oxygen. My research compliments experimental work on ecosystem resilience by Tyler Butts and nutrient limitation by Quin Shingai (Principal Investigator Dr. Grace Wilkinson) as well as greenhouse gas production in productive ponds by Robert Johnson (Principal Investigators Drs. Steven Hall and Grace Wilkinson).
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what are the causes and consequences of variation over space and time in aquatic nutrient cycles?
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seasonal and spatial variation in reservoir phosphorus cycling
Bottom sediments are an integral component of aquatic ecosystems. The sediments are a complex system that mediates whole-lake biogeochemical cycles through both diagenetic processes and material exchange across the sediment-water interface. I am especially interested in how the nutrient phosphorus is cycled between sediments and the water column. Phosphorus held in lakebed sediments can be mobilized and released into the overlying water due to disturbance, microbial activity, or changes in chemical conditions. Sediment P sources are especially influential in shallow lakes and reservoirs. In these systems, substantial sediment P loads often fuel algal blooms and delay eutrophication recovery. Despite the importance of sediment P sources, few studies have quantified both spatial and temporal heterogeneity in sediment P fluxes as well as the underlying mechanisms. Lacking a mechanistic understanding of spatiotemporal variation in P fluxes limits our ability to scale measurements, predict fluxes, and ultimately manage sediment P sources. To begin addressing this knowledge gap, I designed a field and laboratory study to measure how sediment P fluxes varied across seasons and along the longitudinal gradient of a temperate reservoir. I also measured sediment phosphorus chemistry, reservoir thermal structure, and water column chemistry to identify environmental conditions associated with high phosphorus flux rates. My research compliments work on consumer-mediated nutrient cycling in the reservoir, led by Tyler Butts, as well as intensive monitoring by the Iowa Department of Natural Resources Lake Restoration Program. This work was done in collaboration with Dr. Grace Wilkinson, with funding from the NSF Graduate Research Fellowship Program and the Iowa Water Center.
Bottom sediments are an integral component of aquatic ecosystems. The sediments are a complex system that mediates whole-lake biogeochemical cycles through both diagenetic processes and material exchange across the sediment-water interface. I am especially interested in how the nutrient phosphorus is cycled between sediments and the water column. Phosphorus held in lakebed sediments can be mobilized and released into the overlying water due to disturbance, microbial activity, or changes in chemical conditions. Sediment P sources are especially influential in shallow lakes and reservoirs. In these systems, substantial sediment P loads often fuel algal blooms and delay eutrophication recovery. Despite the importance of sediment P sources, few studies have quantified both spatial and temporal heterogeneity in sediment P fluxes as well as the underlying mechanisms. Lacking a mechanistic understanding of spatiotemporal variation in P fluxes limits our ability to scale measurements, predict fluxes, and ultimately manage sediment P sources. To begin addressing this knowledge gap, I designed a field and laboratory study to measure how sediment P fluxes varied across seasons and along the longitudinal gradient of a temperate reservoir. I also measured sediment phosphorus chemistry, reservoir thermal structure, and water column chemistry to identify environmental conditions associated with high phosphorus flux rates. My research compliments work on consumer-mediated nutrient cycling in the reservoir, led by Tyler Butts, as well as intensive monitoring by the Iowa Department of Natural Resources Lake Restoration Program. This work was done in collaboration with Dr. Grace Wilkinson, with funding from the NSF Graduate Research Fellowship Program and the Iowa Water Center.
sediment phosphorus chemistry within and among shallow lakes
I love studying shallow lakes because they are full of surprises. Many of the simplifying assumptions that we try to make about them just don't hold up in the real world. For example, many researchers assume that shallow waterbodies are well-mixed throughout the open water season, with little justification. High frequency monitoring with aquatic sensors has revealed complex, daily cycles of water column mixing and thermal stratification in shallow, vegetated waterbodies, demonstrating that these ecosystems are anything but homogeneous. As we begin to better understand heterogeneity in the water column of shallow lakes, I wanted to go deeper and investigate the degree of spatial heterogeneity in the bottom sediments of shallow lakes, in the context of phosphorus cycling. A key mechanism that controls internal phosphorus loading is the sediment phosphorus pool, including how much phosphorus is present and in which chemical forms. There are many different forms of sediment phosphorus, and some are more "mobile" than others, meaning they are more likely to be released into the overlying water. Sediment phosphorus chemistry varies among different waterbodies due to differences in watershed soils and land cover. Sediment phosphorus is also expected to be heterogeneous within individual waterbodies as a result of sediment transport processes, sediment disturbance, and the location of aquatic plants. However, spatial heterogeneity in sediment phosphorus within shallow lakes as well as the underlying mechanisms remain poorly described and quantified. In order to quantify spatial heterogeneity in sediment phosphorus in shallow lakes, I measured sediment phosphorus chemistry across seven shallow, glacial lakes. I evaluated how watershed soils and land cover related to differences in sediment phosphorus chemistry among the study lakes. I also explored relationships between lake basin morphometry and within-lake spatial variation in sediment phosphorus in order to make practical recommendations regarding sediment sampling procedures. My research asserts that shallow waterbodies are spatially complex systems and that this heterogeneity affects ecosystem function. This work was done in collaboration with Dr. Grace Wilkinson, Quin Shingai, and Rachel Fleck, with funding from the Iowa Department of Natural Resources Lake Restoration Program.
I love studying shallow lakes because they are full of surprises. Many of the simplifying assumptions that we try to make about them just don't hold up in the real world. For example, many researchers assume that shallow waterbodies are well-mixed throughout the open water season, with little justification. High frequency monitoring with aquatic sensors has revealed complex, daily cycles of water column mixing and thermal stratification in shallow, vegetated waterbodies, demonstrating that these ecosystems are anything but homogeneous. As we begin to better understand heterogeneity in the water column of shallow lakes, I wanted to go deeper and investigate the degree of spatial heterogeneity in the bottom sediments of shallow lakes, in the context of phosphorus cycling. A key mechanism that controls internal phosphorus loading is the sediment phosphorus pool, including how much phosphorus is present and in which chemical forms. There are many different forms of sediment phosphorus, and some are more "mobile" than others, meaning they are more likely to be released into the overlying water. Sediment phosphorus chemistry varies among different waterbodies due to differences in watershed soils and land cover. Sediment phosphorus is also expected to be heterogeneous within individual waterbodies as a result of sediment transport processes, sediment disturbance, and the location of aquatic plants. However, spatial heterogeneity in sediment phosphorus within shallow lakes as well as the underlying mechanisms remain poorly described and quantified. In order to quantify spatial heterogeneity in sediment phosphorus in shallow lakes, I measured sediment phosphorus chemistry across seven shallow, glacial lakes. I evaluated how watershed soils and land cover related to differences in sediment phosphorus chemistry among the study lakes. I also explored relationships between lake basin morphometry and within-lake spatial variation in sediment phosphorus in order to make practical recommendations regarding sediment sampling procedures. My research asserts that shallow waterbodies are spatially complex systems and that this heterogeneity affects ecosystem function. This work was done in collaboration with Dr. Grace Wilkinson, Quin Shingai, and Rachel Fleck, with funding from the Iowa Department of Natural Resources Lake Restoration Program.
what are the mechanisms controlling sediment phosphorus fluxes in lakes and reservoirs?
food web manipulations and phosphorus dynamics in shallow lakes
I participated in a team science project evaluating the impacts of commercial harvest of common carp (Cyprinus carpio) and bigmouth buffalo (Ictiobus cyprinellus) on nutrient cycling, water clarity, and aquatic plant communities in shallow lakes in northwest Iowa, USA. I was especially interested in the impacts of reduced carp biomass. Common carp are benthivores, meaning that they primarily feed on organisms or detritus found in bottom sediments. While searching the lakebed for food, carp disturb the sediments, which can release phosphorus, reduce water clarity by suspending sediments, and uproot or otherwise damage aquatic plants. Over three years, I measured aquatic plant distribution and richness, water column nutrients, and sediment resuspension in reference lakes and lakes with commercial harvest of common carp and bigmouth buffalo. This work was done in collaboration with Tyler Butts, Marty Simpson, and Quin Shingai (Principal Investigators Drs. Grace Wilkinson and Michael Weber) with funding from the Iowa Department of Natural Resources Lake Restoration Program.
I participated in a team science project evaluating the impacts of commercial harvest of common carp (Cyprinus carpio) and bigmouth buffalo (Ictiobus cyprinellus) on nutrient cycling, water clarity, and aquatic plant communities in shallow lakes in northwest Iowa, USA. I was especially interested in the impacts of reduced carp biomass. Common carp are benthivores, meaning that they primarily feed on organisms or detritus found in bottom sediments. While searching the lakebed for food, carp disturb the sediments, which can release phosphorus, reduce water clarity by suspending sediments, and uproot or otherwise damage aquatic plants. Over three years, I measured aquatic plant distribution and richness, water column nutrients, and sediment resuspension in reference lakes and lakes with commercial harvest of common carp and bigmouth buffalo. This work was done in collaboration with Tyler Butts, Marty Simpson, and Quin Shingai (Principal Investigators Drs. Grace Wilkinson and Michael Weber) with funding from the Iowa Department of Natural Resources Lake Restoration Program.
drivers of sediment phosphorus release across a diverse population of lentic systems
Effective eutrophication management requires a quantitative understanding of the many, many mechanisms that may control the mobilization and release of phosphorus from lakebed sediments. We know a great deal about the different physical, chemical, and biological mechanisms that regulate sediment phosphorus fluxes. However, the shape of the relationship between sediment phosphorus release and these various mechanisms remains poorly-quantified. Our capacity to predict when and where internal phosphorus loading will occur is further limited as the interactive effects of these mechanisms are not well-understood. In order to address this gap, I am conducting a meta-analysis of the driving mechanisms of sediment P mobilization and release across a diverse population of lakes, reservoirs, and wetlands. I am systematically reviewing studies that report direct measurements of sediment P release and compiling a data set of phosphorus flux rates and associated chemical, physical, and biological conditions. I will then use these data to explore the response of sediment phosphorus fluxes across gradients of key explanatory variables. This analysis will also identify gaps in research on internal phosphorus loading including geographic location, waterbody features, and mechanisms measured.
Effective eutrophication management requires a quantitative understanding of the many, many mechanisms that may control the mobilization and release of phosphorus from lakebed sediments. We know a great deal about the different physical, chemical, and biological mechanisms that regulate sediment phosphorus fluxes. However, the shape of the relationship between sediment phosphorus release and these various mechanisms remains poorly-quantified. Our capacity to predict when and where internal phosphorus loading will occur is further limited as the interactive effects of these mechanisms are not well-understood. In order to address this gap, I am conducting a meta-analysis of the driving mechanisms of sediment P mobilization and release across a diverse population of lakes, reservoirs, and wetlands. I am systematically reviewing studies that report direct measurements of sediment P release and compiling a data set of phosphorus flux rates and associated chemical, physical, and biological conditions. I will then use these data to explore the response of sediment phosphorus fluxes across gradients of key explanatory variables. This analysis will also identify gaps in research on internal phosphorus loading including geographic location, waterbody features, and mechanisms measured.
