Current Research Projects

Resilience of Ecosystems

While most ecosystem changes are incremental, some shifts are extensive and can have large effects on society if critical resources are lost. Ecosystem dynamics including large changes are often linked with environmental trends and variability, thresholds of key drivers, and disturbances. These dimensions of ecosystem change taken together account for the persistence, or resilience, of relationships within an ecosystem and its interactions with neighboring systems. A general concern is that ecosystems are losing resilience due a variety of human-driven impacts including climate change. Our group is conducting research to measure disturbance and recovery of ecosystems and to develop quantitative analyses of resilience.

This research is conducted on lakes where we use whole lake manipulations to test ideas using high frequency spatial and temporal measures of ecosystem variables like dissolved oxygen and phytoplankton pigments. We also work in the Virginia Coastal Reserve to study how ecosystems like seagrass beds and intertidal mudflats are affected by disturbance.

 Algal Blooms and the Trajectory of Aquatic Ecosystems

Dramatic increases of algae result in high biomass, green waters that often have harmful impacts. We’ve analyzed whether these ‘blooms’ of algae are getting worse. Our synthesis indicates that algal blooms are not intensifying for U.S. lakes that have long-term data. Instead, lakes exhibit a variety of trajectories. This observation raises the question of how these trajectories arise under similar forcings such as increased nutrient inputs, warming climate, diminishing biodiversity. We are exploring this idea with time series data from lakes using both statistical methods and simulation models.

Dissolved Organic Matter: Impacts on Aquatic Ecosystem Processes

Dissolved organic matter is a ubiquitous component of water that lends a brown color when in high concentrations. DOM has numerous impacts diminishing light penetration and serving as a resource in terms of carbon and nutrients. We are studying how changes in DOM affect aquatic ecosystems and influence stability and resilience.

Freshwater Salinization

Major ion concentrations in freshwaters are increasing in many regions due to land use change, resource extraction, climate change, saltwater intrusion, and accelerated weathering. Working with collaborators we coined the term ‘Freshwater Salinization Syndrome (FSS)’ to describe the interconnected effects of salinization on inland water ecosystems. This research involves mainly synthesis of existing data to analyze the increasing salinity of freshwaters and to explore the consequences of these changes.