Climate implication for the poleward migration of marine calcifiers

Coccolithophores are one of the most abundant eukaryotic phytoplankton in the oceans and are distinguished by their ability to build calcitic platelets (coccoliths). Of the numerous species, Emiliania huxleyi is considered one of the major calcifiers in the pelagic ocean. There is growing concern that increasing levels of CO2 in the atmosphere and the subsequent acidification of the ocean may disrupt the production of coccoliths. Any change in the global distribution and abundance of E. huxleyi relative to non-calcifying groups of phytoplankton (e.g. diatoms) will have important effects on the biogeochemical cycling of carbon and climatic feedbacks. There is now a large body of evidence that E. huxleyi is increasingly expanding its range into the polar oceans. These observations contribute to the debate on the climatic effects on natural coccolithophore populations. We postulate that E. huxleyi may be more sensitive to recent environmental changes such as increasing sea surface temperature and salinity than to changing ocean carbonate chemistry. Any potentially important climatic feedbacks of coccolithophores need a better knowledge of the mechanisms and rates of adaptation by natural populations. Here we use modeling work such as the recently developed global ECCO-Darwin and satellite observation to estimate the contribution of the poleward expansion to biogeochemical processes.