Species Specific Division Rates of Diatoms: Response to Changes in Dissolved Silicate Concentrations

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The determination of species specific growth rates in natural populations is one of the most sought after measurements in phytoplankton ecology. This research program will investigate the response of diatom growth rates to perturbations in dissolved silicate supplies using a fluorescent dye (Rhodamine 123). Diatoms incubated in Rhodamine 123 actively accumulate it into the silica deposition vesicle and Rhodamine 123 is co- deposited with silica. The resulting valves and girdle bands become fluorescent and provides a marker for cell division in diatoms; thus allowing for the estimation of species specific growth rates. Experiments will be performed to investigate the potential of low dissolved silicate concentrations to limit the uptake of dissolved silicate and to limit diatom growth rates, ultimately influencing species succession with changes in ambient dissolved silica supply rates. The ability to distinguish between the limitation of uptake and the limitation of growth rate is critical to our understanding of nutrient limitation in aquatic systems. In addition, experiments will be performed to investigate the response of diatom growth rate may be a key factor governing the phytoplankton production to new nutrient input.