Re-evaluation of the physiological ecology of coccolithophores

Abstract

Recent data on coccolithophore abundance and calcification from the Atlantic, Pacific and Indian Oceans is interpreted within the traditional physiological ecology paradigm known as the "Margalef Mandala" (Margalef 1978). As predicted by Margalef, coccolithophores should be most abundant in conditions of moderate turbulence and nutrient concentrations. However, blooms of coccolithophores (and other algal groups, too) show day length preferences, suggesting that the Margalef Mandala might be expanded to include day length as a third dimension. Variability in calcification per cell makes it difficult to extrapolate coccolithophore abundance (in the Margalef Mandala) to carbon fixation and vertical carbon fluxes. Because of this, there is a discrepancy between biologists and geologists concerning when coccolithophores should be most abundant. Biologists contend that coccolithophores are found in stratified, mesotrophic, environments while geologists contend that they are most abundant in highly productive environments. A conceptual model is presented which attempts to bridge the two schools based on a) variable calcification per cell, and b) grazing differences between mesotrophic and eutrophic environments that will alter the vertical flux of the coccolithophores to the sediments.