This collaborative project aims to improve undergraduate understanding of data science in biology, computer science, engineering, and environmental science. We will develop, implement, and assess new learning modules based on high-frequency, real-time data from water and traffic monitoring systems. Collaborators: KX Pérez Rivera, K Xia, V Lohani,  & L Marston (Virginia Tech); G Biswas, A Dubey, & C.Vanags (Vanderbilt); MK Jha, N Aryal, & EH Park  (North Carolina Agricultural & Technical State University). "Collaborative Research: An Interdisciplinary Approach to Prepare Undergraduates for Data Science Using Real-World Data from High Frequency Monitoring Systems" - funded by NSF DUE. Funding period: 2019-2023.

We tested the effects of temperature on organic matter breakdown at the stream reach and stream network scales. We used data from temperature manipulations at multiple spatial and temporal scales at Coweeta Hydrologic Laboratory, NC to (1) inform ecological theory that uses basic principles to understand how the effects of temperature scale from individual organisms to entire ecosystems, and (2) build a model that simulates the effects of temperature on organic matter processing at the stream network scale. PIs: JP Benstead (University of Alabama), V Gulis (Coastal Carolina University), AM Helton (University of Connecticut), AD Rosemond (University of Georgia), ER Hotchkiss (Virginia Tech). "Collaborative Research - Headwater stream networks in a warming world: Predicting heterotrophic ecosystem function using theory, multi-scale temperature manipulations and modeling" - funded by NSF DEB. Funding period: 2017-2022.

What processes drive organic carbon removal in streams? How does dissolved organic carbon removal regulate the degree to which running waters are biological reactors versus exporters of carbon? This project addressed these unresolved questions by (1) integrating carbon spiraling metrics with more common stream carbon cycling measurements and (2) developing a proof-of-concept approach to test the degree to which non-additive effects of mixed organic matter sources (i.e., priming) control organic carbon removal in streams. PIs: MA Baker (Utah State), RO Hall (Montana), ER Hotchkiss (Virginia Tech). "Collaborative Research - Rivers and the carbon cycle: A mechanistic basis for dissolved organic carbon removal" - funded by NSF DEB. Funding period: 2018-2022.

Stream ecosystem processes respond rapidly to physical changes in channels and corridors; quantifying process rates requires good estimates of time- and space-varying physical parameters such as inundated surface area and turbulence at the air-water interface. Uncertainties in channel morphology and gas exchange at time scales compatible with water quality sensor data currently limit our ability to produce high-quality estimates of ecosystem processes (e.g., ecosystem metabolism). Our collaborations used novel applications of remote sensing and acoustic tools to enhance real-time monitoring of stream corridor health. Collaborators from different projects include: WC Hession (Virginia Tech), M Klaus (Umeå University).

This project tested (1) how rates of ecosystem metabolism in Swedish rivers are shaped by regional climatic and anthropogenic gradients from hemi-boreal to the arctic, (2) the extent to which streams in the Swedish landscape degrade terrestrial organic carbon and contribute to greenhouse gas evasion, and (3) the use of metabolism as a tool for environmental monitoring programs. PIs: R Sponseller, J Karlsson (Umeå University), ER Hotchkiss (Virginia Tech), H Laudon (Swedish University of Agricultural Sciences). "Taking the pulse of Swedish rivers: Using metabolism to monitor ecosystem responses to environmental change" - funded by Swedish Research Council Formas. Funding period: 2017-2019.

We measured the sources, transformations, and fluxes of dissolved organic matter, greenhouse gases, and microbial assemblages in a large boreal river network, from soils to the sea. The Romaine River was dammed for hydropower, so we also had the opportunity to identify distinct contributions of river/reservoir sections at varying stages of pre- and post-dam to network- and landscape-scale biogeochemistry. With P del Giorgio, M Gérardin (Université du Québec à Montréal), et al.

The proportions of carbon dioxide (CO2) emitted from streams and rivers that come from terrestrially-derived CO2 or from CO2 produced within freshwaters through aquatic metabolism are not well quantified. We compared stream and river metabolism, groundwater-streamwater exchange, fluvial organic C export, and freshwater CO2 emissions to place in-stream biological processes in the context of network-scale C budgets.

We explored interactions between nutrient and carbon availability, metabolism, and microbial assemblages in boreal streams with varying water chemistry and landscape characteristics. 

Large subsidies of terrestrial organic matter support heterotrophic carbon (C) and nutrient demands in boreal streams, but the degree to which in-stream photosynthesis contributes to food web dynamics is not well known. We used stable isotopes to measure the contributions of terrestrial and aquatic C to invertebrate consumers. We also linked diet sources with ecosystem C pools and fluxes, including rates of whole-stream metabolism. 

Despite the longstanding appreciation that algal C can fuel stream food webs, we know little about how primary production contributes to C cycling in running waters (e.g., the capacity of primary producers to influence C dynamics; the time scales over which newly fixed C turns over in different stream C pools). Using a whole-stream 13CDIC (dissolved inorganic C) pulse-chase experiment, we applied a novel combination of an ecosystem-level tracer addition and modeling to trace 13CDIC assimilation by algae, short-term release as CO2 and dissolved organic C, and longer-term fate of newly fixed C. While biology governed short-term fluxes of algal C, hydrology likely controlled longer-term fates.

We measured nitrogen, phosphorus, and carbon uptake and spiraling in rivers of the western and midwestern United States. My project employed a two-compartment Bayesian model and experimental microbial dissolved organic C (DOC) consumption assays to identify a positive priming effect in increasing microbial consumption of more refractory C. Biologically available DOC likely stimulates (i.e., primes) the consumption of more stable DOC by heterotrophic microbes in rivers.

We used microbial assemblage data and measurements of microbial carbon consumption from different freshwater ecosystems to test how microbes may respond to changes in carbon and nutrient sources.

Four non-native fish species (convict cichlid, green swordtail, guppy, tadpole madtom) and one non-native snail species (red-rim melania) have established populations in Kelly Warm Springs, Grand Teton National Park, Wyoming. We used historical samples to compare densities and biomass of native invertebrate species before and after the red-rim melania invasion. To quantify how multiple species invasions may influence stream food webs, we also measured fish and invertebrate population densities and biomass as well as fish stomach contents along a natural temperature gradient. 

Most aquatic ecosystem metabolism calculations assume respiration is constant over 24-hours or that diel respiration can be estimated using changes in water temperature. These assumptions limit our knowledge of diel mechanisms governing freshwater ecosystem metabolism and C cycling, as biologically available organic C may also vary over 24-hours. We used diel δ18O2 and O2 data, coupled with a Bayesian process model, to estimate diel ecosystem metabolism in three Wyoming streams. We found that daytime respiration exceeded nighttime respiration and temperature-adjusted calculations of respiration did not account for the magnitude of diel respiration modeled with δ18O2.

We quantified the role of hydrology, geomorphology, and biology in governing water chemistry and nitrate uptake along three different reaches of Red Canyon Creek, Wyoming.

We measured rates of biomass and CO2 production during growth and calcification by the invasive freshwater snail, Melanoides tuberculata, in Kelly Warm Springs, Wyoming. We also compared Melanoides CO2 and secondary production with ecosystem metabolism and fluxes of CO2 from the stream to the atmosphere. While snail biomass and calcification rates were high, CO2 produced from calcification was small compared to net ecosystem CO2 production. High rates of primary production appears to buffer the impacts of high-density invasive snails on native invertebrates and stream C cycling.

The loss of fish species may alter stream nitrogen (N) budgets. Land use changes and increased sedimentation also alter benthic substrate and N availability, and both are important factors in denitrification. We quantified denitrification in Rio Las Marías, Venezuela and compared denitrification to other rates of ecosystem N loss and cycling.

Erin was a graduate research assistant for the last season of LINX2 research on nitrogen (N) transport and uptake in streams using 15N tracer additions in urban, agricultural, and reference streams in and around Grand Teton National Park, Wyoming.

Erin worked as a seasonal research technician at Southern Illinois University-Carbondale on a project studying the density, diversity and productivity of aquatic plants and macroinvertebrates in a restored wetland, and their impact on waterfowl feeding behavior in Two Rivers National Wildlife Refuge, Illinois. 

Erin's undergraduate research project at Emory University quantified changes in house finch feeding behavior and aggression when infected with Microplasma gallisepticum.

Erin studied the role of limiting nutrients on chironomid larvae growth rates at La Selva Research Station, Costa Rica as a summer REU (research experience for undergraduates) Fellow with the Pringle Lab, University of Georgia. Erin also helped with a project measuring nutrient limitation of in-stream microbial respiration.

Erin's independent project while working as a summer undergraduate research tech with the Tank Lab at the University of Notre Dame compared potential rates of nitrification and denitrification in streams surrounded by different land-use types (forested, urban, and agricultural). Erin also assisted with field and laboratory work for several projects studying the nitrogen dynamics in Michigan streams and a reservoir in Illinois. 

During a summer undergraduate research internship at the Oak Ridge National Laboratory, Erin quantified the genetic diversity of spatially isolated switchgrass populations from the eastern United States.