Dr. Monika Poxleitner

Research Interests

Experimental plankton ecology: micro-and mesocosms

Phytoplankton, zooplankton: species composition, stoichiometry, biodiversity, interactions

Evolutionary ecology: Daphnia life history, population structures, genetic analyses

Project

Resource use efficiency of different nitrogen compounds in natural and artificial phytoplankton communities under phosphorous limitation

Scholarship: Cusanuswerk

Project funding: Deutsche Forschungsgemeinschaft (DFG)

Human activities cause the production and release of different reactive nitrogen compounds. From those compounds, especially ammonium and nitrate can potentially be used for primary production; however with varying efficiency. Their use efficiency was so far mainly analyzed in nitrogen limited systems but must also have consequences in phosphorous limited systems. As most of our lakes are phosphorous limited, I investigate the nitrate and ammonium uptake of phytoplankton under phosphorous limitation. In the lab, I investigate artificial algae communities, which are exposed to different proportions of ammonium to nitrate. In field mesocosm experiments, natural plankton communities are exposed to a nitrogen gradient and to different proportions of ammonium to nitrate. Parameters that are analyzed are: species community composition and diversity, biomass parameters, parameters of photosynthesis and the chemical composition of phytoplankton.

This study contributes to the understanding of possible changes of species compositions in lakes with increasing anthropogenic nitrogen pollution.