Productivity in Rivers
The ability to measure and model gross primary productivity (GPP), or the total amount of photosynthesis, in rivers has rapidly expanded following advances in sensor and modeling technology. So much so, that we can use time-series of GPP across many rivers to quantify variability in GPP and better understand the drivers of that variability. Light availability and hydrologic disturbance are likely candidates (Bernhardt et al. 2022) and my research aims to identify to what extent that is true, and what other drivers influence year-to-year and within-year variability.
River GPP also serves as an important basal resource in food webs for consumers, from bacteria to manatees. If there is large year-to-year variation in GPP, how do these organisms and their food webs respond to deficits or surplus? Do food webs become more or less complex? Does total biomass of consumers change? Rivers are highly regulated and are subject to a huge number of stressors that affect the metabolic foundation: we are now asking how to combine information about productivity with food webs to determine if stresses to rivers has played a role in reducing river biodiversity and ecosystem function.
Tropical Stream Ecology and Biogeochemistry
My dissertation research built on an established research program in stream ecology at the La Selva Biological Station (LSBS), Costa Rica.
Streams at LSBS receive or do not receive geothermally modified groundwater (GMW) that is high in solutes (P, DIC, Ca, Mg, et al.). Several of these solutes are biologically relevant and influence the decomposition, production, metabolism, and function. Additionally, GMW inputs to streams increase the buffering capacity against episodic reductions in pH, which are tied to precipitation reductions during extreme El Niño Southern Oscillation events. Our current research investigates the effects on adding buffering capacity (HCO3) to streams and buffer these streams against future pH reductions.
Another research interest involves long-term increases in NO3- into streams, irrespective of GMW inputs. The increase in NO3 is consistent with nutrient pollution across the globe, but the rise at LSBS is likely due to different sources. We will explore possible sources of N, including atmospheric deposition, local groundwater, GMW, and surface runoff. Land cover at LSBS is dominated by N-fixing Pentaclethra macroloba, which may be a source of N to the forest as a whole, including to streams.
Much more to come here!
Collaborators: Marcelo Ardón (NCSU), Alonso Ramírez (NCSU), Carissa Ganong (Missouri Western St. Univ), Chip Small (Univ of St. Thomas), David Genereux (NCSU), Cathy Pringle (UGA)
Reservoir ecology and influence of invasive species
This work stems from my MS and work following. Lake Seminole, the most downstream reservoir in the ACF basin of, has been invaded (likely since its impoundment in the 1950s) by a variety of species from many taxa groups, and are abundant enough to significantly drive biogeochemical processes and lake function. These processes are crucial in the watershed, which is the focus of on-going Supreme Court cases regarding water use in Florida and Georgia. Our group has shown that the variability in precipitation drives submerged aquatic vegetation (SAV) in the lake, which then drives N and P sequestration in plant biomass and in lake sediments. The Asian clam, Corbicula fluminea, is found throughout the lake sediments and rapid filtration rates are a sink of nutrients to the sediments. More recent introductions of herbivorous P. maculata raise interesting questions on the consumption of SAV by snails and loss of function provided by SAV to the system.
Collaborators: Steve Golladay (JERC), Alan Covich, Susan Wilde (UGA), Stephen Shivers (UGA, JERC), Matt Waters (Auburn Univ), Carla Atkinson (Univ of Alabama), Chelsea Smith (JERC), Chase Patrick (Waters Lab), Phillip Ashford (UGA, JERC)
The ability to measure and model gross primary productivity (GPP), or the total amount of photosynthesis, in rivers has rapidly expanded following advances in sensor and modeling technology. So much so, that we can use time-series of GPP across many rivers to quantify variability in GPP and better understand the drivers of that variability. Light availability and hydrologic disturbance are likely candidates (Bernhardt et al. 2022) and my research aims to identify to what extent that is true, and what other drivers influence year-to-year and within-year variability.
River GPP also serves as an important basal resource in food webs for consumers, from bacteria to manatees. If there is large year-to-year variation in GPP, how do these organisms and their food webs respond to deficits or surplus? Do food webs become more or less complex? Does total biomass of consumers change? Rivers are highly regulated and are subject to a huge number of stressors that affect the metabolic foundation: we are now asking how to combine information about productivity with food webs to determine if stresses to rivers has played a role in reducing river biodiversity and ecosystem function.
Tropical Stream Ecology and Biogeochemistry
My dissertation research built on an established research program in stream ecology at the La Selva Biological Station (LSBS), Costa Rica.
Streams at LSBS receive or do not receive geothermally modified groundwater (GMW) that is high in solutes (P, DIC, Ca, Mg, et al.). Several of these solutes are biologically relevant and influence the decomposition, production, metabolism, and function. Additionally, GMW inputs to streams increase the buffering capacity against episodic reductions in pH, which are tied to precipitation reductions during extreme El Niño Southern Oscillation events. Our current research investigates the effects on adding buffering capacity (HCO3) to streams and buffer these streams against future pH reductions.
Another research interest involves long-term increases in NO3- into streams, irrespective of GMW inputs. The increase in NO3 is consistent with nutrient pollution across the globe, but the rise at LSBS is likely due to different sources. We will explore possible sources of N, including atmospheric deposition, local groundwater, GMW, and surface runoff. Land cover at LSBS is dominated by N-fixing Pentaclethra macroloba, which may be a source of N to the forest as a whole, including to streams.
Much more to come here!
Collaborators: Marcelo Ardón (NCSU), Alonso Ramírez (NCSU), Carissa Ganong (Missouri Western St. Univ), Chip Small (Univ of St. Thomas), David Genereux (NCSU), Cathy Pringle (UGA)
Reservoir ecology and influence of invasive species
This work stems from my MS and work following. Lake Seminole, the most downstream reservoir in the ACF basin of, has been invaded (likely since its impoundment in the 1950s) by a variety of species from many taxa groups, and are abundant enough to significantly drive biogeochemical processes and lake function. These processes are crucial in the watershed, which is the focus of on-going Supreme Court cases regarding water use in Florida and Georgia. Our group has shown that the variability in precipitation drives submerged aquatic vegetation (SAV) in the lake, which then drives N and P sequestration in plant biomass and in lake sediments. The Asian clam, Corbicula fluminea, is found throughout the lake sediments and rapid filtration rates are a sink of nutrients to the sediments. More recent introductions of herbivorous P. maculata raise interesting questions on the consumption of SAV by snails and loss of function provided by SAV to the system.
Collaborators: Steve Golladay (JERC), Alan Covich, Susan Wilde (UGA), Stephen Shivers (UGA, JERC), Matt Waters (Auburn Univ), Carla Atkinson (Univ of Alabama), Chelsea Smith (JERC), Chase Patrick (Waters Lab), Phillip Ashford (UGA, JERC)