Phytoplankton biomass, as chlorophyll a was quantified along 6 bights used for mussel culture in the coastal area of Santa Catarina State. Chlorophyll a, determined by high performance liquid chromatography (HPLC), showed similar mean values among the sites, ranging from 1,63 to 3,36 µg.l-1, with a maximum for 10.57 µg.l-1 found in Praia Alegre, Penha, SC. The results indicates that all bight show a similar biomass and a moderate trophic grade.