What we do

In our lab we study phytoplankton ecology and biogeochemistry. We are specifically interested in how different phytoplankton groups respond to environmental perturbations such as changes in CO₂, light intensity and nutrient availability. My students and I aim to not only characterize the responses of phytoplankton to a multitude of environmental factors, but also to understand the underlying processes of the measured responses, such as photosynthetic pathways, carbon acquisition processes and protein regulation. In collaboration with my colleagues at FSU, within the US and around the globe, we investigate these ecophysiological responses on different levels (from gene expression to ecosystem function) and in many ecosystems (Gulf of Mexico, tropical oligotrophic regions, Southern Ocean and coastal upwelling regions). We hope that our work will inform many different groups of researchers. For example:

• Our work on nitrogen isotopes in the Southern Ocean aims to inform the interpretation of paleo proxies on the strength of the biological carbon pump during glacial and interglacial cycles.
• Our work on N₂ fixing organisms will inform biogeochemical modelers on current and projected future productivity of our oceans
• The work on marine productivity will inform ecologists, physiologists and numerical modelers on processes affecting the base of the marine food web.
• We further hope that our work on the toxic dinoflaggelate Karenia brevis, a Gulf of Mexico red tide organism, will inform decision makers and ecosystem managers to better understand and predict the socio-economic impact of this organism in the current and future ocean.

Despite their microscopic size, phytoplankton are responsible for about half of the global primary production. This diverse group of organisms is an integral component of the global biosphere, driving biogeochemical cycles of important elements while exporting large amounts of carbon to deep waters and sediments. In coastal regions, these organisms also have a socioeconomical significance as they affect water quality and fisheries. Consequently, understanding the current distribution and productivity of phytoplankton in ecological important ocean basins, and assessing how and why the phytoplankton community may respond to perturbations driven by environmental change, constitutes a major challenge in aquatic research. We aim to understand community composition and productivity of phytoplankton in the World’s oceans. For this, we study phytoplankton communities and monoclonal cultures under different environmental scenarios such as changes in temperature, light intensit, CO₂ concentrations and/or availability of iron. A suite of in vivo assays based on standard and cutting-edge techniques provide a mechanistic understanding of the observed responses. Processes such as productivity, cellular composition, photosynthetic efficiency, the modes of carbon and nutrient acquisition and isotope fractionation are investigated on multiple cellular levels. Laboratory studies with isolated monoclonal cultures and research cruises increase our process understanding of how and why phytoplankton, found in the different regions of the World’s oceans, respond to environmental stressors.