A light-limited continuous culture study of Emiliania huxleyi: determination of coccolith detachment and its relevance to cell sinking

The coccolithophore Emiliania huxleyi (Lohm.) Hay and Mohler is one of the most abundant calcite producing organisms on earth, producing calcium carbonate plates known as coccoliths. Consequently, these coccoliths represent a major carbon sink in the world ocean. This study addresses the rate of detachment of coccoliths from coccolithophores under controlled growth conditions using light-limited continuous cultures. Cells were grown at six different growth rates between 0.24 day −1 and 1.00 day −1. Other cell properties including chlorophyll, particulate inorganic carbon, and total particulate carbon, were also investigated with regard to growth rate of the cells. The coccolith detachment rate increased linearly with cellular growth rate at a ratio not significantly different from 1.00. This change in detachment with growth could affect several processes such as sinking rates of cells and the appearance of blooms in remotely-sensed imagery. The importance of sinking to coccolithophores is discussed.