Ecology and evolution of marine diatoms and parmales

Abstract

Diatoms and Parmales are microscopic, photosynthetic algal groups that both have siliceous cell walls. It is probable that they shared a common ancestor, but each has evolved along a quite distinct path. Diatoms have undergone extensive adaptive radiation and colonized a wide range of freshwater, terrestrial and marine habitats. They are particularly important in the ecology of the oceans, where it has been estimated that they are responsible for 40 % of global marine production. In contrast, Parmalean algae have remained restricted to more specific niches, mainly in marine coastal areas at high latitudes. They are small (from 2 to 5 μm) and single celled. Until recently, their ecology was largely unknown, but new research has begun to reveal their biology for the first time. In this review, we concentrate on the roles and adaptations of both groups in the marine plankton, highlighting areas for future research.