Title: Professor Emeritus
Degrees: B.A., University of Vermont; M.S., Ph.D., University of Waterloo
Office Location: Steffee Hall B.222
My research focuses on the question “To what extent do limitations of nutrients and/or energy determine the quantitative and qualitative characteristics of biological communities in aquatic habitats?”
In most aquatic communities, the demand for phosphorus exceeds the supply, making phosphorus the limiting element in the classical sense. Part of reason for the shortage of phosphorus is that it is not recycled very efficiently within communities. The phosphorus cycle is intimately tied to the biogeochemical cycles of both iron and sulfur, and changes in the solubility of iron (regulated by redox changes) and changes in the availability of sulfur (derived from acid precipitation) have significant effects on the phosphorus cycle. Most recently we have been attempting to develop a model to predict phosphorus recycling efficiency, and the rates of phosphorus flux across the sediment/lake water interface. Related to nutrient limitation in lakes we have been doing a bit of “forensic limnology” by using biological and chemical cues in the sedimentary stratigraphic record of lakes to reconstruct historical trophic status and the effects of various land use changes (settlement, agriculture, mining, deforestation) on the ontogeny of lake ecosystems.
A second area of interest is the effects of invasive species on the structure of aquatic communities. Two invasives in particular (Eurasian water milfoil, and the zebra mussel) are gaining ground in northwest Pennsylvania lakes, and the consequences of their range expansions are not clear. Both are strong competitors, and have been shown to completely displace some native species, altering community structure and function. What might the long-term effects of these invaders have on local aquatic communities?