How do changes in hydrologic regime affect watershed nutrient processing and export?
The Floodpulse Project
Wetlands are control points for nutrient processing and retention, improving water quality in streams and rivers. By removing nitrogen (N), wetlands mitigate negative impacts such as eutrophication in downstream waters. Much of N processing in wetlands is carried out by microbes that live in the soil, whose activity is regulated in part by the availability and quality of organic matter (i.e., dead plant material) and oxygen. Flood disturbances affect both organic matter delivery and oxygen dynamics in wetlands, potentially altering N removal processes. However, we do not understand how hydrologic connectivity, that is, the mode through which wetlands receive and export water, affects organic matter delivery to floods or the subsequent effects on wetland N removal. The objective of this study is to investigate wetland hydro-biogeochemical responses (specifically, N processing) to flood disturbances and the subsequent impacts on watershed nutrient export. This work, which is conducted at the Tanglewood J. Nicholene Bishop Biological Station in Alabama, is a collaboration between the Biogeochemistry Lab and Jones Ecohydrology Lab at UA, and the Pacific Northwest National Lab. Funded by DOE Environmental System Science (DE-FOA-0002584) |
LINKING NUTRIENT REACTIVITY AND TRANSPORT IN SUBSURFACE FLOWPATHS ALONG A TERRESTRIAL-ESTUARINE CONTINUUM
Salt marshes play an important role in improving coastal water quality, retaining upwards of one-third of terrestrially derived nitrogen (N) loads. This removal is largely driven by sediment microbial activity, which is controlled by spatial and temporal variability in redox characteristics and substrate availability, impacting the pathways by which N is processed by microbes. Our study objective is to address a knowledge gap in our understanding of the hydrologic and environmental factors that drive solute fate and transport at the subsurface terrestrial-marine boundary at tidal watershed mouths. At the Elkhorn Slough National Estuarine Research Reserve, we will couple field- and lab-based studies with reactive transport models to quantify the co-variation of hydrological and biogeochemical subsurface processes in coastal watersheds, with a particular emphasis on identifying drivers on N retention and removal over different hydrologic regimes. Through this effort, we are extending the DOE Scientific Focus Area testbed approach to a novel and underrepresented coastal ecosystem. This work is part of the NItrate TRansport and Transformations in Elkhorn Slough (NITRATES) collaborative research effort. Funded by DOE Environmental System Science (SC-FOA-0002184) |
What are the drivers of biogeochemical response to anthropogenic disturbances?
Does vegetation type mediate salt marsh biogeochemical response to burning? (Stay tuned for results!)
I am currently working at Weeks Bay National Estuarine Research Reserve to investigate the impact of fire on nitrate reduction in salt marsh soils. I measured denitrification and dissimilatory nitrate reduction to ammonium (DNRA) rates in plots dominated by three salt marsh plant species: Juncus roemerianus (Black needlerush), Cladium mariscus (swamp sawgrass), and Spartina patens (saltmarsh hay) before and after a controlled burn that took place in April 2022.
The pictures in the slideshow below were all taken from an observation deck - the sawgrass was over my head before the burn!
I am currently working at Weeks Bay National Estuarine Research Reserve to investigate the impact of fire on nitrate reduction in salt marsh soils. I measured denitrification and dissimilatory nitrate reduction to ammonium (DNRA) rates in plots dominated by three salt marsh plant species: Juncus roemerianus (Black needlerush), Cladium mariscus (swamp sawgrass), and Spartina patens (saltmarsh hay) before and after a controlled burn that took place in April 2022.
The pictures in the slideshow below were all taken from an observation deck - the sawgrass was over my head before the burn!
INVESTIGATING THE LONG-TERM IMPACTS OF THE DEEPWATER HORIZON OIL SPILL ON SALT MARSH BIOGEOCHEMISTRY
The 2010 Deepwater Horizon disaster resulted in 11 deaths and discharged 210M U.S. gallons of crude oil into the Gulf of Mexico. We conducted a series of studies investigating the long-term impacts of this spill on salt marshes in the Chandeleur Islands, a chain of barrier islands of the coast of Louisiana subjected to a gradient of oiling during the spill. We found that:
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Can human created systems provide the same ecosystem services as natural eCOSYSTEMs?
DITCHING NUTRIENTS: THE NITROGEN REMOVAL POTENTIAL OF ROADSIDE DRAINAGE NETWORKS
Human created drainage networks, such as ditches and canals, are a ubiquitous part of the landscape, yet their biogeochemical capacity is not well understood. In 2018, I conducted a study investigating the nitrate reduction potential and microbial community structure of roadside ditches draining predominantly forested, urban, and agricultural areas. We found that ditches had the potential to remove nearly 90% of nitrate on average through denitrification, and that ditches in more human impacted areas were characterized by microbial taxa associated with nitrogen cycling. Our study is impactful because it demonstrated that roadside drainage networks are potentially important sinks for anthropogenic N. It also identified critical unknowns, including how existing storm water infrastructure can be managed to provide sustainable water quality improvement. The results of this study are in a 2021 JGR Biogeosciences paper or you can read about it in this EOS article! |
COLLABORATIVE RESEARCH IN MARSH SOILS, ORGANISMS, & NUTRIENTS
I conducted a field study to determine (1) the vertical recovery in ecosystem function in a 30-year old constructed marsh compared to a nearby natural marsh on the Fowl River (AL), and (2) the mechanisms driving the recovery (or loss) of ecosystem function at these sites. I found that both nitrate reduction rates declined with increasing depth in both marshes, with the highest rates occurring in the upper 10 cm, but that these rates were higher overall in the natural marsh than the constructed marsh. The results of this study are detailed in a 2021 Restoration Ecology article. The CRIMSON Project is a collaborative research effort between UA's Biogeochemistry and Wetland Ecology lab groups. |