Research

CURRENT RESEARCH

We study element cycling in ecosystems, and we are most interested in studying how the form, magnitude and timing of carbon, nutrient and contaminant imports and exports are shifting in response to rapid environmental change. Our tools work anywhere, and currently we apply them in rivers, wetlands and watersheds stretching from New Hampshire to the Peruvian Amazon. We also love data synthesis and collaborations which allow for upscaling and for expanding our scope of inference beyond the bounds of any individual study. Below we describe current research in the lab.

Measuring the Pulse of Global Rivers (NSF Macrosystems, USGS Powell Center)

New Hope Creek in the Duke Forest. Photo by ES Bernhardt

Learn more about the StreamPULSE project, explore or make use of all of our data, and view all of our protocols at data.streampulse.org

Bernhardt is lead PI of this five year, multi-institution effort to measure the productivity and net ecosystem carbon balance of rivers throughout North America and to facilitate data collection and modeling by stream ecologists around the world. Mike Vlah is our project's data scientist. Brooke Hassett and Alexander Miele manage our local field measurements of metabolism in Piedmont rivers.

Alice Carter and Audrey Thellman are conducting their PhD research as part of this larger project. Alice is examining how ecosystem energetics change along a river continuum in New Hope Creek (pictured on the left) and the importance of hypoxia and anaerobic metabolism in Piedmont rivers. Audrey is interested in how climate change induced shifts in forest phenology and river hydrology together influence the productivity regimes of small forested streams.

Lab alumni Phil Savoy and Aaron Berdanier conducted their research as part of the StreamPULSE project. Former PhD students Elizabeth Sudduth and Joanna Blaszczak and former postdoc Tim Covino each invested much of their time in the lab studying stream ecosystem energetics.

Macrosheds: Enabling macroscale watershed science (NSF Macrosystems)

Bernhardt and Matt Ross (CSU) are coPIs of this five year grant aimed at collating and analyzing watershed ecosystem study data from every long-term watershed study in the United States. Our goal is to massively increase access, use and analysis of watershed ecosystem data by building high powered data infrastructure and visualization tools and training the next generation of watershed scientists through our macroscale watersheds training camps. Mike Vlah is the lead data scientist for this project and we are collaborating closely with the aquatic science experts at the National Ecological Observatory Network.

Stay tuned for live data platforms by the start of 2020.

Measuring the environmental impact of mountaintop removal coal mining (NSF Hydrology)

Expansion of surface coal mining across Central Appalachia 1985-2015 (source)

Check out this and other data visualization apps that document the impacts of MTMVF by visiting our DataViz page

Bernhardt and Brian McGlynn were coPIs of this four year NSF Hydrology grant to study the topographic, hydrologic, biogeochemical and biodiversity impacts of mountaintop removal coal mining. Over the course of four years we mapped the total extent of MTMVF mines (Pericak et al 2018), estimated the extent of topographic flattening and the volume of 1544 valley fills (Ross et al. 2016) and used paired catchment studies to document dramatic shifts in stream hydrographs (Nippgen et al 2017) and rates of rock weathering derived solute exports (Ross et al. 2018) from mined watersheds. We are currently finalizing papers reporting the results of a large scale eDNA survey across a gradient of mining activity; documenting the concentrations and bioaccumulation of selenium and mercury in the food webs of mined streams; documenting the transfer of substantial quantities of selenium pollution from streams into riparian food webs via emergent aquatic insects; and reporting the long-term accumulation of mining derived contaminants using reservoir sediment cores.

Currently, Jackie Gerson is conducting part of her dissertation research on this topic. Lab alumni Matt Ross, Andrew Pericak, Alex Brooks, Kris Voss, Raven Bier and Brian Lutz all conducted some portion of their graduate research on this topic.

Tracking mercury pollution from small scale gold mines into Amazonian forests (Bass Connections)

Gold Mine on the Madre de Dios, sampling transport, tree core collection - photos by ES Bernhardt

Visit our project website, peruviangold.weebly.com, to learn more about the human health, economic and environmental costs of artisinal gold mining

Within the last decade small scale gold mining (often referred to as artisanal gold mining) has become the dominant source of global atmospheric mercury pollution. Most of this activity is illegal but poorly regulated and is taking place throughout developing nations of the southern hemisphere. Jackie Gerson began studying the fate, transport and methylation of mercury because of her experiences as a Peace Corps volunteer in Senegal where she encountered miners with mercury poisoning. Jackie is now leading field studies of the biogeochemical cycling of mercury in the Madre de Dios region of Peru, an incredible biodiversity hotspot that also happens to support one of the most rapidly accelerating rates of mining associated deforestation and mercury pollution in the tropics. Jasmine Parham is planning to conduct her PhD research on birds in the Madre de Dios, and is specifically interested in understanding how the feeding strategies of birds affects their risk of Hg exposure, and whether the answers to this question can help us better understand where Hg is entering forest food webs.

Coastal Ecosystem Impacts of Saltwater intrusion and Sea Level Rise (NSF Coastal SEES, NASA, Seagrant)

Ghost Forest, Marcelo Ardon checks SETS, Emily Ury measures salinity. Coastal NC 2019. Photos by ES Bernhardt

Learn more about our coastal work at our Coastal SEES project website

Bernhardt is collaborating with Duke's Justin Wright , NCSU's Marcelo Ardon and Ryan King, and UNC's Todd BenDor in a five year project to estimate the extent of saltwater intrusion and saltwater intrusion vulnerabilities for North Carolina's coastal forested wetlands. In addtion to quantifying the rate of forested wetland loss and the formation of ghost forests, we are interested in understanding how soil carbon stocks and greenhouse gas emissions are affected during these rapid ecosystem transitions.

In collaboration with UVA's Xi Yang, Bernhardt is leading a two year "Coastal Margins" working group aimed at bringing research groups together from throughout the US coastal plain (Cape Cod to the Gulf coast of Texas) to synthesize our current understanding, begin mapping and assessing the cumulative loss of freshwater wetlands and create a strategic plan for future, coordinated research efforts on this important topic.

Currently, PhD student Emily Ury is measuring the impacts of coastal salinization on the ground in large-scale salt addition experiments, in the air using drone based imagery and from space using satellite remote sensing. Lab alumni Jen Morse, Marcelo Ardon, Hayes Neely, Ben Riegel and Ashley Helton all conducted part of their research on NC coastal wetlands and global change.

Long-term change in watershed ecosystems of the northeast (NSF LTER, NSF LTREB)

Hubbard Brook and Upper Paradise Brook, New Hampshire. Photos by ES Bernhardt

Learn about the sixty years of ecological research conducted in this northeastern forest by visiting the Hubbard Brook Ecosystem study website

Play with the long-term record of stream and precipitation chemistry through our data visualization app http://hbwater.org/

Bernhardt and Emma Rosi (Cary IES) are together in charge of maintaining the world's longest continuos streamwater and precipitation chemistry monitoring program. Since 1963, stream and precipitation samples have been collected every week from multiple streams and rain gauges in this beautiful valley within the White Mountains National Forest of NH. In the past, these data were used to document the existence of acid rain and the efficacy of the Clean Air Act and Clean Air Act Amendment and were used to make the first watershed ecosystem estimates of mineral weathering and to document the impact of deforestation on nutrient losses from forest soils. In the coming decade of NSF LTREB funding we will be exploring how highly variable winter snowpack, shifting forest phenology and the legacy of acid rain are interacting to drive changes in the timing, magnitude and form of water and solute exports from these watersheds. Rosi and Bernhardt are also affiliated with the Hubbard Brook LTER program and, in 2017, initiated new data collection programs which will allow us to document long-term change in the productivity, carbon cycling and aquatic insect communities of these northeastern streams in response to climate change, disturbance and the legacy impacts of prior experiments and acid rain.

PhD student Audrey Thellman is reconstructing the long-term history of stream climate at HBEF using remote sensing data and is testing the constraints on stream productivity across the Hubbard Brook valley. Lab alumni Richard Marinos conducted his PhD research at HBEF. Bernhardt conducted her PhD research with Gene Likens in these streams.

Microbial Community Structure & Function in response to stressors

Learn more about the Microbiome Stress Project by visiting the web page or by reading this paper. The MSB was begun by lab postdocs Jenny Rocca and Marie Simonin and the leadership team now includes lab alumni Joanna Blaszczak and Raven Bier.

You cannot study biogeochemistry without gaining a great appreciation for the amazing capacities of microbes. In recent years the work of our lab has been considerably enriched through the use of gene and metagenome sequencing to study how microbial communities change along environmental gradients and how they respond to experimental manipulations. We are most interested in making the elusive connection between changes in community membership and shifts in the relative importance or efficiency of microbially mediated processes. Currently, postdoc Jenny Rocca has been conducting a series of novel experimental tests to measure the changes in community membership when previously separate microbial communities are brought together under intermediate chemical conditions. Jenny's experiments have allowed us to test microbial responses to gradients we are already studying in other research efforts, as she has pitted microbes from mining impacted streams against their counterparts from unmined watersheds; coastal ocean microbes against the microbes found in freshwater coastal wetlands; and groundwater fed spring microbes against the communities in blackwater rivers. We are excited about the opportunity to identify key indicator taxa within environmental communities. Ultimately, the incredible diversity of microbes may offer new approaches for estimating the complex chemical mixtures found in natural environments.

Lab alumni Raven Bier, Marie Simonin and Joanna Blaszczak were engaged in these questions while in the lab.

Synthetic chemicals as agents of global change

The Duke Forest wetland mesocosm facility where we have conducted numerous chemical exposure experiments. Photo by Steve Anderson.

An ever increasing diversity of synthetic chemicals are being added to the Earth's land surface at an exponentially increasing rate (Bernhardt et al. 2017). While harder to detect with the naked eye than land use change, the consequences of toxic substances and contaminant mixtures can have significant negative consequences for organisms and ecosystem processes. A variety of prior and current projects fall under this umbrella. For the last decade, Bernhardt has been the Ecosystem Research Theme leader for the Center for the Environmental Implications of Nanotechnology. In work led first by Ben Colman (now at U Montana) and then Dr. Marie Simonin (now at INRA in Angers, France) we conducted a series of field mesocosm experiments to document significant consequences of nanomaterial exposure as a result of realistic, low-level, chronic release of several widely used nanoparticles. We have also had a longstanding interest in the chemical stressor mixtures in urban streams with lab alumni Joanna Blaszczak and Ethan Baruch focused on this topic.

New work in the lab will focus on identifying the contaminant signatures of cities, and in asking whether ubiquitous (wastewater, stormwater) and disparate (industry, infrastructure) pollution sources interact to produce common or distinct contaminant mixtures across cities with divergent histories and economies. PhD student Jonny Behrens will be leading this effort in collaboration with Bernhardt and coadvisor Martin Doyle.