Research Interests
I am interested in the biological, chemical, geological, physical, and social processes influencing the fate, transport, and ecological impact of energy (i.e., biota biomass) and chemical contaminant mixtures through human impacted watersheds and their waterways. By advancing our collective knowledge in this field of research, we can provide tools for water managers on the city, state, federal, and international level to protect water resources, which are critical for humans and wildlife.

My research interests and methods are informed by prior and current work with science policy researchers and officials, studies in the field and laboratory, empirical and process-based models, and collaboration with community stakeholders. Below is a short overview of my research projects.
Collaborators (current and future!) are encouraged to visit this page to locate all data, code, methods for my dissertation research.

Unpacking Heterogenous Watersheds: Watershed Dynamics and Evolution

Credit: J. Behrens/CC BY-NC
Funding: Environmental System Science Program in DOE Office of Science's Biological and Environmental Research Program

Methods: water & microbial field sampling, benchtop and flume mesocosms, analytical chemistry, modeling
Freshwater ecosystems are sensitive to disturbances caused by climate change (e.g., shifts in the timing and magnitude of storms) and alterations to land-use (e.g., development of impervious surfaces). In the Tennessee River Basin of the Southeastern US, freshwater systems have been heavily relied upon for drinking water and hydropower for millions; protected waterways in this region also provide habitat for some of the most biodiverse communities of fish, amphibians, and other wildlife found in the US.

As a Postdoctoral Research Associate on the WADE: Watershed Dynamics and Evolution Science Focus Area at the Oak Ridge National Laboratory, I am conducting field and laboratory analyses and supporting the development of new modeling approaches to understand stream corridor processes (e.g., rates of stream gross primary production and ecosystem respiration; microbial community dynamics) and network function (e.g., shifts in landuse) in the TN River Basin. 

ORNL and External Mentors: Scott Brooks, Marie Kurz, Natalie Griffiths, and Erin Hotchkiss

A City and Its River: Exploring Drivers of Water Quality

Credit: J. Behrens/CC BY-NC
Funding: Duke Science and Technology Seed Grant, North Carolina Water Resources Research Institute, and Duke Bass Connections

Methods: spatial GIS modeling, analytical chemistry (ICP-MS and HPLC-MS), zebrafish toxicity assays (Daniovision and Seahorse), stakeholder interviews

Urban watersheds are dynamic ecological systems shaped by social, chemical, physical, and ecological forces. In our 2021-22 and 2022-23 Duke Bass Research Project, we are merging the fields of environmental chemistry, urban ecology, ecotoxicology, and social sciences to better understand how the distribution of ecological benefits and risks overlap with the distribution of economic and social capital of the Ellerbe Creek watershed in Durham, NC.

We are exploring how the prevalence of nutrients, ions, trace metals, e.coli, PFAS ("forever chemicals"), and various indicative organic contaminant compounds vary throughout the dynamic urban watershed across seasons. On-going efforts seek to explore potential relationships between infrastructure (e.g., roads and storm-water pipes) and water quality challenges. We are also exploring the degree to which these chemical contaminants place stress on these ecosystems through various ecotoxicological assays. Check out our data here (beta site)!

Faculty Collaborators: Emily Bernhardt, Nishad Jayasundara, Dean Urban, Christopher Timmins, and Lee Ferguson

The Ecological Impact of Stressors: A Tale of Two Streams (Urban and Forested)

Credit: J. Behrens/CC BY-NC
Funding: Duke Biology Grants in Aid, research also leverages NSF-funded StreamPULSE and Macrosheds project (14424390) data

Methods: biological specimen collection (emergent insects & benthic macroinvertebrates), in-stream sensors, R modeling of primary (streamMetabolizer) and secondary production (secpRod)
Urban stream biota face a wide array of physical, biological, and chemical stressors in urban watersheds dominated by stormwater and treated wastewater effluent. These stressors alter the energetic regimes of aquatic ecosystems, altering the total amount of energy entering these ecosystems (in the form of light or carbon-rich matter), the efficiency at which it is converted into biomass, the functional diversity of the resulting community of organisms, and ultimately the transport of biomass out to terrestrial ecosystems.

In our work, we extensively sampled neighboring forested and urbanized watersheds, finding distinct differences in the annual and sub-annual metabolic regimes of the watersheds. While elevated energetic inputs at our urban sites were observed (primary production), the efficiency at which this was converted into biomass (secondary production) was significantly reduced in the urban watershed, likely due to stressors. This was observed to limit the full potential of aquatic insect emergence from the urbanized sites. Emergent aquatic insects will be further assessed for trace metals to explore the potential transport of heavy metals (negative subsidies).

Faculty Collaborators: Emily Bernhardt, Martin Doyle, and Dean Urban

Contaminant Transport Via Biota: Effluent Dominated Streams

(Credit: J. Behrens/CC BY-NC)
Funding: USGS funds, Duke Biology Grants in Aid

Methods: biological specimen collection, HPLC-MS
Building on work conducted by collaborators in the Iowa and Illinois, we are exploring the extent to which contaminants common in wastewater effluent (e.g., pharmaceuticals) and industrial effluent (e.g., PFAS compounds) accumulate in aquatic food webs.

In their larval stage, or "youth", aquatic insects develop in the stream bed and are exposed to a multitude of chemical contaminants. When they emerge as winged adults, they can transport contaminants ("negative subsidy"), to predators in the riparian and terrestrial environment.

Therefore, we are exploring the extent to which emerging contaminants of concern are accumulating in stream biota and the degree to which this is being transported through the food web and into the paired riparian/terrestrial ecosystem.

Collaborators: Dana Kolpin, Greg LeFevre, Alyssa Mianecki, David Walters, Christopher Kotalik, and Laura Hubbard

Microbial Activity Critical to P-Cycling in Open Ocean: Stable Isotope Analysis

Bacterial cells, suspended in lysing media
(Credit: A. Mine)
Bacteria play an important role in the cycling and remineralization of phosphorus in the open ocean, where the nutrient is significantly limited. A model bacterium, E. coli, was grown under phosphorus-deplete conditions in the excess of organic-bound phosphate. The subsequent activity of an enzyme selected for during growth, alkaline phosphatase, was identified through fluorescence spectroscopy. Methods were developed to measure the kinetic P-fractionation using stable oxygen isotopes prior to and after the lysis of cells, catalyzed by alkaline phosphatase. The fingerprint isotope signatures of these pathways will provide an important proxy to identify the biologically-mediated route for Pi remineralization in the ocean.

Research was presented and accepted as an undergraduate honors thesis. Collaborators: Aric Mine, Albert Colman, and Gerard Olack.

Fatty Acids as Biomarkers for Food Web Structure in the Eastern North Pacific Ocean

2D gas chromatography analysis of particulate organic matter
(Credit: J. Behrens/CC BY-NC)
A novel approach was tested and deployed to analyze the fatty acid composition of biological matter, a tracer for food web interactions in the ocean (e.g., microbial vs. phytoplankton dominated systems). 2-dimensional gas chromatography-mass spectrometry (GC-MS) was used to analyze suspended particulate organic matter (POM) and zooplankton (primarily copepods) collected approximately 9 miles from San Diego's coast.

Research was presented at the 2015 AGU Fall meeting and funded by an NSF REU at Scripps Institute of Oceanography. Collaborators: Lihini Aluwihare, Brandon Stephens, and Neal Arakawa.