Variação temporal do fitoplâncton em três praias urbanas do litoral sul do estado de Pernambuco, Nordeste do Brasil

This study aimed to make a comparative analysis of phytoplankton community structure, biomass variation and environmental data in the surf-zone of Brasilia Formosa (8o04'S; 34o52'W), Boa Viagem (8o07'S; 34o53'W) and Piedade (8o10'S; 34o54'W) sandy beaches, on the Pernambuco coast. Bottle and net samples were collected during the rainy season (May, June and July/2005) and the dry season (November, December/2005 and January/2006) with simultaneous environmental data collection (water temperature, salinity, suspended material, nitrite, nitrate, phosphate, silicate, rainfall, wind speed and direction). Among the 119 infrageneric taxa identified, diatoms were the most representative group regarding abundance and frequency, notably Asterionellopsis glacialis (Castracane) Round, Bellerochea malleus (Brightwell) Van Heurck, Dactyliosolen fragilissimus (Bergon) Hasle, Helicotheca tamesis (Shrubsole) Ricard and Licmophora abbreviata Agardh. A. glacialis was dominant in the rainy season while H. tamesis was more numerous in the dry one. Study results indicate that specific composition, chlorophyll a and total density evidenced the seasonal environmental conditions, with occasional blooms (2.3 x 106 cells.L-1) in the dry season. Morphology and hydrodynamics were unfavorable to the formation of microalgae patches.