My educational background is in civil engineering. As an undergraduate I focused on mechanical design and construction while my graduate work focused, broadly speaking, on applied mathematical modeling of transport processes and mass and energy flows. I earned my PhD degree in 1988 from the Technical University of Denmark. After that I worked at the Danish National Environmental Research Institute where I was responsible for long-term modeling of nitrogen leaching from agricultural land. In 1996, I relocated to the University of Virginia (UVA) and have since then focused my research on biogeochemical cycling in aquatic benthic environments.
A dominant approach in my work at UVA has been the use of applied mathematical modeling, which I have combined with the development of new measuring techniques and approaches. I see these two foci as highly complementary and powerful, and on a personal level I am very excited to apply them to address research questions focusing on the benthic environment.
From 2001 forward, I pioneered the aquatic eddy covariance technique for oxygen flux measurements in collaboration with the Max Planck Institute for Marine Microbiology, Germany. At first, this was a side project to my ongoing modeling activities, but given our first successes and the potential of the approach, it quickly became the main focus of my work. Today I work exclusively on the eddy covariance technique. As reflected in the publications from my lab group this work is focusing on further developing the technique, and also on applying it to benthic environments where traditional flux approaches are hard to use, and where our knowledge on benthic exchange is thus limited.
A link to my diagenetic modeling work, including download options for papers and the profile interpretation software, PROFILE, is given here.
My research focuses on the dynamic of major biogenic elements in coastal zones and on the interactions between macrophytes and biogeochemical cycles in these environments. During my master degree, I carried out an in situ study on biogeochemical dynamics of redox species (O2, Fe2+, HS-, Fe3+ et FeS(aq)) in permeable sediments on tidal scales using in situ voltammetry. My PhD project focused on the influence of seagrasses on the cycles of biogenic elements such as O2, C, N and P. One part of this work was about the spatio-temporal dynamic of seagrass meadow metabolism (measured by ex situ core incubations) in relation to changes in the distributions of macrophytes and macrofauna. I also studied the impact of seagrass regression on the nutrient biogeochemistry in sediments of a coastal lagoon.
During my Post Doc position, I will quantify seagrass metabolism and its dynamics on hourly to seasonal time scales using the eddy covariance technique. I will use these data on benthic fluxes to quantify the integrated annual carbon sequestration of seagrass meadows. A chronosequence of restored meadows of different ages (time since seeding) located along Virginia coastal bays will be studied to better estimate how seagrass habitat restoration can enhance carbon sequestration.
My research will focus primarily on the ecology of oyster reefs in the shallow lagoons of the VCR-LTER. I will use the eddy covariance technique to measure oyster metabolism in response to a variety of environmental and ecological factors. I hope to measure the success of current oyster restoration efforts as well as quantify important factors for future reef restoration.
My research focuses on the ecology of seagrass meadows in the shallow coastal bays of the VCR-LTER. I will be using the eddy covariance technique to quantify whole-system metabolism in a seagrass meadow during its recovery from a die-off event that occurred in summer 2015. I hope to quantify ecosystem metabolism response to changes in environmental and ecological variables, and compare my results to those obtained when the seagrass meadow was healthy. The die-off event in 2015 presents a unique opportunity to monitor the recovery of seagrass ecosystems, which has implications for future restoration efforts.
While the drivers of metabolism in aquatic ecosystems are well known and include nutrients, sunlight, temperature, organic matter inputs, and water flow or mixing, our ability to quantify the effects of these drivers on metabolism is limited. This limits our understanding of the impacts of these drivers on water quality and aquatic carbon transformation. My research focuses on a novel hydrodynamic technique, eddy covariance, which can be used to determine the flux of oxygen, heat, and salt in an aquatic ecosystem at a high temporal resolution and without a gas transfer velocity correction. The calculated fluxes which result can improve our predictions of an aquatic ecosystem’s response to environmental change.
An abundant source of nutrients to freshwater and shallow marine ecosystems is groundwater. Because over-enrichment of surface waters with nutrients leads to water quality degradation and habitat loss, I have also worked with seepage meters, radioisotopic tracers, thermal imagery, and salt and heat fluxes calculated with the eddy covariance technique to quantify sources of groundwater discharge to surface waters. The delivery of groundwater nutrients to surface water at some locations is controlled by microbial activity in sediments. By improving our understanding of these processes we can improve the application of our effort to preserving water quality and aquatic habitats.
Former Location: School of Freshwater Sciences, University of Wisconsin-Milwaukee.
Current Location: Max Planck Institute for Marine Microbiology, Bremen, Germany.
My research focuses on coastal biogeochemistry and how natural and anthropogenic processes influence benthic carbon and nutrient cycling. These topics are important because human activities are rapidly altering these processes and the long-term effects of these changes are largely unknown. Because a large portion of the human population lives adjacent to the coast, we are tightly linked to the productivity and stability of coastal systems, and their ability to mitigate anthropogenic changes.
I use the eddy covariance technique to investigate the ambient, in-situ factors that control carbon cycling such as: nutrients, irradiance, benthic communities, waves, and currents. My PhD work is primarily on tropical coral reefs and seagrass meadows in south Florida. These results reveal the complex interactions of hydrodynamics with productivity, the tight link to irradiance, and complex benthic communities that efficiently harvest light to create linear photosynthesis to irradiance curves. These results also show the importance of sampling in-situ over large spatial scales as these effects are not able to be observed with any other methodology. Further, these measurements show extremely high production rates on coral reefs and why these areas are hotspots of biodiversity while being a large source of production for the surrounding areas.
Current Location: Woods Hole Oceanographic Institution.
I am interested in carbon dynamics in shallow coastal systems and how carbon cycling changes with a large scale ecosystem state change. My research focuses on using oxygen as a proxy for carbon metabolism at different stages of seagrass colonization in the shallow lagoons of the VCR-LTER. I use the eddy covariance technique to measure real time ecosystem metabolism throughout the year to observe seasonal variability in the ecosystem response to light, temperature, and flow.
Current Location: Woods Hole Oceanographic Institution.
My graduate thesis research focused on biogeochemical cycling and hydrodynamics of recovering seagrass meadows on the Eastern Shore of Virginia. Specifically, Dr. Berg and I adapted the micrometeorological concept of eddy-covariance to measure fluctuations of dissolved oxygen in order to determine ecosystem metabolism dynamics of seagrasses. As a graduate research student for Dr. Berg, I was lucky to participate in multiple research cruises and field campaigns around the globe. After graduating from UVa, I accepted a research assistant position at the Scottish Association for Marine Science in Oban, Scotland where I set up an aquatic eddy-covariance lab. Upon moving back to the United States, I decided to apply my educational background to marine policy and conservation.
Current location: World Wildlife Fund (WWF).