brittany Hanrahan
PhD Student
Summer 2012 - Present
Research Interests:
Current Projects:
1. Quantifying the water quality benefits of implementing large-scale land cover change in an agricultural watershed
Problem: Excess fertilizer nutrients enter agricultural streams where they are transported downriver causing numerous environmental problems including harmful algal blooms and subsequent hypoxic dead zones.
Objective: Implement a best management practice at the watershed-scale that will reduce nutrient loss from agricultural fields and improve water quality.
2. Quantifying the influence of substrate size and heterogeneity on nutrient uptake
Problem: As agricultural land use continues to impact stream ecosystems, maximizing the potential of headwater streams to process nutrients prior to downstream export is critical for maintaining healthy freshwater resources.
Objective: Determine the influence of substrate on nutrient uptake by conducting short-term nutrient additions in four experimental streams with varying substrate at the University of Notre Dame's Linked Experimental Ecosystem Facility (ND-LEEF)
Summer 2012 - Present
Research Interests:
- Land use impacts on stream nutrient cycling,
- Agricultural land conservation practices and water quality
- Terrestrial-aquatic linkages
- Microbial nutrient processing
Current Projects:
1. Quantifying the water quality benefits of implementing large-scale land cover change in an agricultural watershed
Problem: Excess fertilizer nutrients enter agricultural streams where they are transported downriver causing numerous environmental problems including harmful algal blooms and subsequent hypoxic dead zones.
Objective: Implement a best management practice at the watershed-scale that will reduce nutrient loss from agricultural fields and improve water quality.
- Cover crops, like ryegrass, are planted after corn/soybean harvest and grow during Winter and Spring when fields would normally be bare.
- During their growing season, cover crops take up excess fertilizer nutrients reducing nutrient runoff from agricultural fields.
- Implementing cover crops at the watershed-scale has the potential to significantly reduce nutrient export from agricultural watershed and improve water quality downstream.
2. Quantifying the influence of substrate size and heterogeneity on nutrient uptake
Problem: As agricultural land use continues to impact stream ecosystems, maximizing the potential of headwater streams to process nutrients prior to downstream export is critical for maintaining healthy freshwater resources.
Objective: Determine the influence of substrate on nutrient uptake by conducting short-term nutrient additions in four experimental streams with varying substrate at the University of Notre Dame's Linked Experimental Ecosystem Facility (ND-LEEF)
- Headwater streams are biogeochemical "hotspots" within watersheds where nutrients from the adjacent terrestrial landscape undergo efficient biological retention and transformation, thereby delaying downstream transport.
- Small-scale variation in substrate heterogeneity and substrate-specific biofilms may play an important role in controlling nutrient processing; however, the influence of substrate is difficult to isolate in the field.
- ND-LEEF's unique facility allowed us to manipulate and control the substrate in 4 streams in order to investigate the influence of substrate on nutrient uptake and transient storage (Dr. Antoine Aubeneau, Dr. Diogo Bolster).
3. Validating a novel method to quantify the influence of heterotrophic microbial biofilms on stream ecosystem function
Problem: Heterotrophic assemblages (i.e., bacteria and fungi) are major components of stream biofilms (in addition to algae) and are critical to stream ecosystem function, yet their role in biogeochemical cycling is often difficult to partition and hence biofilm activity is often treated as a "black box".
Objective: Use new research techniques that specifically target heterotrophic microbial assemblages to "open the black box" of biofilm function and quantify the influence of microbial assemblages on stream ecosystem function.
Contact Information:
[email protected]
Twitter:
@brhanrahan
Problem: Heterotrophic assemblages (i.e., bacteria and fungi) are major components of stream biofilms (in addition to algae) and are critical to stream ecosystem function, yet their role in biogeochemical cycling is often difficult to partition and hence biofilm activity is often treated as a "black box".
Objective: Use new research techniques that specifically target heterotrophic microbial assemblages to "open the black box" of biofilm function and quantify the influence of microbial assemblages on stream ecosystem function.
- Heterotrophic assemblages in stream biofilms are extremely important for stream ecosystem functions like nutrient uptake. However, previous research investigating the role of factors, like sediment grain size, algal growth, and sediment organic matter, in controlling heterotrophic activity have reported mixed results.
- Several novel research techniques, including the raz-rru method (Haggerty et al. 2009), allow us to target the heterotrophic assemblages in biofilms and determine the influence of substrate variation and substrate-specific biofilms.
Contact Information:
[email protected]
Twitter:
@brhanrahan