Nutrient Input and the Summer Nanoplankton Bloom in the Northern Adriatic Sea

Abstract. A four-year oceanographic data set from the Northern Adriatic Sea identified the factors favoring development of the nanoplankton or microplankton components of the phytoplankton crop. Latitudinally atypical summer nanoplankton blooms, perhaps of recent origin, develop under vertically stratified conditions in the presence of high nutrient concentrations (including silicates). Including the summer blooms, the nanoplankton were responsible for more than half the total phytoplankton production about 90% of the time. No single mechanism governed phytoplankton cell size or size succession, but rather a number of mechanisms which were not mutually exclusive.