Physiology of Southern Ocean Diatoms: Light, Fe, C/N, and Si analysis (2016)

Undergraduates: Jacob Dixon, Carly Moreno

Faculty Advisor: Adrian Marchetti
Department: Chemistry

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Diatoms play an important role in oceanic environments, acting as the base of most marine food chains. Previous studies have identified Light and Iron as the two major limiting factors of diatoms in the Southern Ocean; this study evaluates their physiology under iron and light limitation. Cultures will be grown under a matrix of light and iron conditions at 4¿¿C to stimulate austral summer natural environment: standard light[90 ¿¿mol photons m-2 s-1], low light [10 ¿¿mol photons m-2 s-1], iron replete [pFe19], and low iron conditions [pFe21.7]. Growth rates will be evaluated using a Turner 10-A fluorometer to evaluate culture concentration. FvFm ratios will be evaluated using a FIRe fluorometer to evaluate iron dependency. After initial growth rate analysis, four specific cultures (two pennates and two centrics) will be further evaluated for critical comparison. C/N ratios, Si, Cell counts and RNA analysis will then be collected for a complete physiological analysis, using a 2L culture grown after a stable growth rate is established. Data will be collected using filtration and specific methods outlines in Paasche (1973). This research helps evaluate a diatom¿¿¿s vulnerability to climate change, as temperature instability affects upwelling conditions and indirectly affects a diatom¿¿¿s access to light and nutrients.