The Regional Environmental Protection Agency of Friuli Venezia Giulia (ARPA-FVG) monitored the coastline of the Gulf of Trieste during summer 2009. At the end of September 2009 a bloom of O. ovata was revealed in a tidal pool of the coastline of the Gulf. During sampling hydrological parameters were recorded. The composition and abundance of the epiphytic community and nutrient concentrations were analyzed. During the bloom the dinoflagellate abundance reached 3.106 cells L- 1. The geomorphological characteristic of the tidal pool, its sheltered position from the wind and wave action, together with the good weather condition and nutrient concentrations, supported the development of O. ovata bloom.
