DISSERTATION RESEARCH: Effects of phytoplankton on bacterial community structure across varying temperature and light contexts

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Understanding the abundance, diversity, and distribution of organisms in the environment is a central goal of ecology with broad implications including ecosystem function and conservation. Ecologists have described many examples of how species interactions, such as competition and predation, or environmental conditions, such as temperature and salinity, influencing community composition. However, the strength and relative importance of these forces and how they interact to determine community composition remains poorly understood. This research project will experimentally elucidate how forces that structure communities act together to determine the abundance and composition of microbial assemblages in lakes. Aquatic microbial communities provide an ideal system for studying forces that influence community composition, because these communities exhibit seasonal patterns of community change, are influenced by a number of biotic and environmental factors, and are relatively easy to manipulate. Observational studies and experimental manipulations indicate that phytoplankton have a substantial influence on temporal patterns of bacterial community change. Environmental conditions including temperature and light have the potential to affect bacteria directly as well as indirectly through modifying bacterial interactions with phytoplankton. This study will explore how bacterial community structure is influenced by species interactions with phytoplankton under different temperature and light conditions by use of manipulative, mesocosm experiments. Bacterial response to all combinations of phytoplankton, temperature, and light will be used to assess the relative influence of biotic and environmental factors on bacterial community composition and how phytoplankton influence changes across varying light and temperature contexts.Results from this research will enhance the ability of scientists to forecast responses of freshwater microbial communities to environmental change. This project supports the doctoral research of a graduate student and will provide research experiences for several undergraduate students. The principal investigators will participate in outreach efforts aimed at introducing local K-12 students to ecology and environmental science. Hands-on activities will be conducted for students at the Campus Middle School for Girls, and the Don Moyer Boys and Girls Club, and presentations will be made at the Illinois Envirothon, a statewide environmental competition for high school students.