Analysis of photosynthetic picoeukaryote community structure along an extended Ellett Line transect in the northern North Atlantic reveals a dominance of novel prymnesiophyte and prasinophyte phylotypes

► Photosynthetic picoeukaryote (PPE) community structure was analysed along an extended Ellett Line transect. ► The PPE community was dominated by members of the Prymnesiophyceae, Prasinophyceae and Mamiellophyceae. ► Several novel phylotypes were recovered within lineages for which cultured counterparts are unknown.