Growth dependence of coccolith detachment, carbon fixation and other associated processes by the coccolithophore Emiliania huxleyi

Date of Award




Degree Name

Doctor of Philosophy (Ph.D.)

First Committee Member

William M. Balch - Committee Chair


This series of experiments was designed to examine a variety of carbon-related processes in the cosmopolitan coccolithophore species Emiliania huxleyi, including photosynthesis, calcification, coccolith biomass, size, integrity, production, and detachment rates. Separate experiments were conducted in different environmental growth conditions including increasing turbulence levels, light limitation and nitrate limitation.With respect to turbulence, cell growth in exponential growth phase was reduced up to 38% at high kinetic energy dissipation rates, above 3.3 cm$\sp2$ s$\sp{-3},$ while photosynthesis and calcification were enhanced at 3.3 cm$\sp2$ s$\sp{-3}.$ During stationary phase, organic and inorganic carbon fixation were severely reduced due to turbulence, whereas coccolith detachment increased significantly.Light- and nitrate-limited continuous cultures focused examination to specific cellular growth rates. Photosynthesis and calcification increased with growth rate under nitrate limitation. In contrast, calcification and coccolith production did not co-vary with growth, as determined by changing coccolith carbon content. For nitrate-limited cells, coccoliths contained more carbon at low growth rates than at higher growth rates. Different types of growth limitation revealed a trend of increasing coccolith carbon contents from nitrate to light to carbon limitation.With respect to coccolith detachment, intrinsic rates of increase of detached coccoliths (d$\sp{-1})$ equaled cellular growth rates (d$\sp{-1})$ for both light- and nitrate-limited cells, and thus, could be used as a species-specific estimator of growth rate. Both coccolith detachment rates and intrinsic rates of increase of detached coccoliths were determined in the Gulf of Maine and during the monsoon and intermonsoon periods in the Arabian Sea under non-blooming conditions to test this hypothesis. Average coccolith detachment rates for those regions were 5, 5.5, and 4.2 coccoliths cell$\sp{-1}$ d$\sp{-1},$ respectively. Intrinsic rates of increase of detached coccoliths predicted regional growth rates of 0.2, 0.42, and 0.3 d$\sp{-1},$ respectively, all of which are reasonable estimates of growth rate in this coccolithophore.


Biology, Oceanography

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