The Laboratory Culture of Coccolithophores

Abstract

Coccolithophores have now been cultured for over 75 years. This period has witnessed progressive improvements in culturing techniques and a steady increase in the number of coccolithophores which have been brought into culture. In certain respects our knowledge of the biology of coccolithophores is as advanced as that in any other group of microalgae and this is due in large part to culture experiments which have focused on two easily cultured species, E. huxleyi and P. carterae. A continued emphasis on E. huxleyi in culture investigations linked to global change issues is to be expected. There is, however, a definite lack of comparative culture data for other coccolithophore species and hence our comprehension of the biodiversity within this group is currently rather limited. There is considerable potential for addressing this situation by further exploiting existing cultures of other coccolithophore species currently maintained in collections around the world. While coccolithophores do not appear to be intrinsically more difficult to culture than other microalgal groups, the fact remains that the majority of coccolithophores have not yet been successfully cultured. There is a strong habitat and phylogenetic bias in our present culture collections: to date, culture techniques have been quite successful in culturing the more r-selected species from eutrophic and intermediate habitats, but there are few cultures of K-selected species from oceanic oligotrophic habitats. This may be because no one has ever tried to culture these species, but is probably also related to limitations inherent with current culturing techniques and culture media. K medium is perhaps the best available option for successful culturing of oceanic coccolithophores, but further advances, including the reduction in concentration of macro- and micro-nutrients, and the possible use of organic nutrients, should also be considered.