Coccolithophores are unicellular algae and an important component of marine plankton. Through photosynthesis and calcification, they fundamentally affect the chemistry of seawater and are one of the most important drivers of the ocean's carbon cycle and ultimately the Earth's climate. One feature that has a major impact on the calcite production of coccolithophores, and perhaps on their global success, has received little attention: their unique life cycle. They have a haplo-diplontic life cycle, in which diploid and haploid phases reproduce independently by mitosis. These two life cycle phases differ in their morphology, carbon content, and ecology, but there is little information about their haploid phase. Without a clear understanding of the role of the coccolithophore life cycle in the oceanic carbon cycle, we risk underestimating the impacts of global climate change. We will transform our understanding of the life cycle of coccolithophores and facilitate clarification of their impact on the oceanic carbon cycle. More broadly, we will make bioenergetics, calcification, and related genomic and transcriptomic data available to the public, providing the basis for future ecological, physiological, and biogeographic studies, as well as a more accurate assessment of the global carbon budget.