Adaptation and niche breadth of phytoplankton species along a nutrient gradient in the ocean

In the phytoplankton of the western North Atlantic, speciesare considered adapted to impoverished nutrient availabilityif they respond best to such conditions, and are consideredunadapted only if they do not respond. The same holds for improvednutrient availability. Further, if species adapted to impoverishednutrient availability are broader niched, then narrower nichedspecies are adapted only to improved nutrient availability.Thus two kinds of species are described: (i) adapted-to-impoverished-nutrient,broader niched species; (ii) adapted-to-improved-nutrient, narrowerniched species.