摘要：1 - Transitional waters are characterized by specific ecological features and an intrinsic heterogeneity; because of their high vulnerability they need particular conservation and management measures, specifically based on the knowledge of their biological and taxonomic diversity. 2 - In particular, the study of phytoplankton communities is widely used as an important water quality indicator because of its high species richness and sensitivity to environmental factors. 3 - This study investigated the phytoplankton community of the Lesina lagoon, describing its taxonomic composition and abundance in order to provide a systematic list that could be useful to improve our knowledge of the Lesina lagoon biological features and, in general, of transitional water phytoplankton communities. 4 - In the whole sampling area we identified 62 taxa, belonging to 18 classes or groups; Dinophyceae were the taxonomic group with the highest percentage of overall phytoplankton cell density (16.2 %), following by Cryptophyceae (11.0%) and Bacillariophyceae (10.1%). No dominant taxa were found considering all studied area. 5 - Phytoplankton taxonomic structure in the Lesina lagoon was characterized by Dinophyeceae and Bacillariophycea and also by a large number of species of small dimensions (particularly Phytoflagellates and Cryptophyceae), that are typical of the environments, like transitional waters, characterized by high instability in the structural characteristics of the water mass and in resource availability.
