Our view of marine phytoplankton has radically changed
in the past two decades with the discovery of picoplankton
and the realization that nitrogen is not the universal
limiting nutrient. Many research challenges still lie ahead,
in particular concerning how phytoplankton controls key
elemental cycles and how it will respond to the forecasted
global environmental changes. Novel approaches, in
particular those originating from molecular biology, will
certainly be critical to address these questions.