Paleolimnologic records consist of the layers of sediment which accumulate at the bottom of lakes over time.  These layers can be dated and provide a kind of environmental ‘time machine’.  Sediment washed into lakes from the surrounding landscape, or formed within the lake itself, includes chemical compounds, the remains of algae and aquatic plants, remains of pollen and plants from the surrounding landscape, minerals produced within the lake and other signatures of what the lake chemistry, the lake’s inhabitants, and the environment around the lake were like at the time of each layer’s formation.  The study of the sequence of layers can provide detailed information on how the lake, its biota, and its local environment have changed over time.  Using these records, we can unravel how changes in climate, land use, and other factors affect watersheds and aquatic organisms.  Understanding interactions between climate, land-use, watershed response, and aquatic ecology can facilitate present-day conservation strategies.

I focus on examining the changes in diatom (microscopic algae) and other biological communities in the cores to infer how lakes have changed over time.  Among my main research interests are using paleolimnologic records to understand the history of drought and how climate changes affect water availability and water quality in different regions.  I also investigate how human-induced changes to the landscape interact with natural cycles in climate to affect lake ecosystems.  The main tool I employ in this research are changes in the abundance, diversity, and composition of communities of diatoms – microscopic, single-celled, siliceous algae.  Diatoms are abundant and highly sensitive to physical and chemical changes in lakes.  By combining records of changing diatom communities in core records with sediment and chemical changes, a broad picture emerges of how lakes and the environments that surround them have evolved over time, and how they are linked to the local, regional, and global environment.