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Nyanza Project Faculty



Catherine O'Reilly

Department of Biology
Bard College
Annandale-on-Hudson, NY

Watershed/lake interactions at Lake Tanganyika, stable isotopes and food web interpretation, ecology of influent streams

Research Interests

I am interested in how ecosystem changes (both natural regimes and human impacts) can affect the structure and function of lakes and streams. I am also interested in the spatial and temporal extent of ecosystem processes, such as linkages between terrestrial and aquatic environments, and the role of seasonal or other periodic events in structuring ecosystems.

One of my research areas is the effect of land use change on streams. I have been doing both dry and wet season sampling of ten streams that flow through protected watersheds in Gombe Stream National Park or through villages in the watersheds to the north and south of the park. We have been examining stream nutrient concentrations, algal nutrient limitation, algal species composition, leaf decomposition, and benthic invertebrate community composition. We are finding strong, consistent differences in stream function between the forested and deforested sites, as well as seasonal differences in the relative effect of land use change on nutrient concentrations and food web structure.

Potential research projects for this coming year are as follows. How does deforestation affect nutrient dynamics? How do benthic invertebrate communities vary among substrate types and between land use patterns? Are crabs the dominant shredders in these streams (providing allochthonous resources) and do they have food preferences? We have evidence that there are large changes in hydrologic flow associated with deforestation; how does this affect substrate distribution, movement, and patterns of erosion?

Another area of interest is nutrient and food web dynamics in the pelagic zone of the lake. During the dry season, there are periodic upwelling events that introduce deep nutrient-rich water to the surface. This causes changes in phytoplankton biomass, which subsequently affects higher trophic levels. I am interested in how these nutrient additions affect food quality as well as quantity. Since the lake is very nutrient-poor, yet maintains a productive fishery, I am also interested in studying nutrient demand and recycling by the pelagic community. How do upwelling events affect phytoplankton and zooplankton biomass and composition? What role do fish play in nutrient recycling?

I encourage you to read past Nyanza student abstracts about the work we have done on the lake, to think creatively about research you might be interested in, and to contact me to discuss your ideas.


At Vassar College, I have taught Global Change, Environmental Science, Biogeochemical Cycles, and Ecology. I also teach the Environmental Science Seminar with topics that included Stable Isotope Ecology. Hands-on experience with all aspects of doing research teaches you much better and faster than any classroom lecture. I encourage students to take on small research projects independently or in collaboration with organizations such as The Nature Conservancy, or to work with other scientists at places like the Institute for Ecosystem Studies. Many of my past Nyanza students have continued their projects on the side or as senior theses, and they have presented their findings at national science conferences.


I have a BA from Carleton College and a PhD from the University of Arizona.

Contact Information

Dr. Catherine O'Reilly
Department of Biology
Bard College
Annandale-on-Hudson, NY 12504-5000


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