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      • Macro-scale drivers of Coastal Wetland Extent
      • Self-organization of karst wetlands and landscapes: Big Cypress Preserve
      • Landscape Resilience in the Florida Everglades
      • Urban Homogenization
      • StreamPULSE: Continental Scale Analysis of River Metabolism
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      • River metabolism and nutrient cycling
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The Heffernan Lab at Duke University

Core research questions

Research in our lab spans a wide range of disciplines and includes diverse study systems.  At present, we have three main foci: 1) studies of interactions between major element cycles, with a particular emphasis on high-frequency observarions of these processes; 2) resilience and alternative stable states in wetlands; and 3) the structure and function of urban lakes, streams, and wetlands.

Coupling of biogeochemical cycles

Transformations of one element (for example, carbon from CO2 to organic matter) are linked to transformations of others (for example, nitrogen and phosphorus) by the chemical reactions that organisms use to fuel their metabolism and build biomass.  One major line of research in our lab focuses on how this coupling influences nutrient dynamics over very fine temporal scales (hours-days).  To do this, we use new in situ sensors that provide detailed information about the dynamics of nutrient concentrations and metabolism.  Learn more here.

Biogeomorphology and ecosystem resilience

The distribution of organisms is strongly influenced by landforms and the geomorphic processes that shape them, but organisms also alter those landforms by adding organic matter, trapping sediments, and altering the flow of water.  These feedbacks can create complex responses of aquatic ecosystems to environmental change.  In particular, biogeomorphic feedbacks are responsible for thresholds and alternative stable states in diverse types of streams and wetlands, and therefore have important implications for how we manage these systems.  Our work in Sonoran Desert streams, the Florida Everglades, and coastal wetlands all address these questions.  Learn more here.

Urbanization and hydroscapes

Urbanization dramatically alters many features of landscapes, including the abundance and types of vegetation, impervious surfaces, and the distribution of chemicals.  These changes to uplands influence the ecological characteristics of individual streams and other aquatic systems, but we know much less about how urbanization directly alters the distribution and abundance of water (hydrography) on the landscape.  Our research in urban ecosystems uses hydrographic change (and other ecological characteristics) in lawns and residential landscapes to test the hypothesis that urbanization creates similar landscapes across diverse ecological regions.  Learn more here.
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