Varia？？o nictemeral da clorofila α, produ？？o primária do fitoplancton e fatores ambientais da regi？o de Ubatuba (Lat. 23o30'S Long. 45o06'W)

a series of experiments with natural phytoplankton populations was carried out to study the diel variation of chlrophyll a, primary production and some environmental factors. samples were collected from surface over a period of 24 hours and always from one fixed station located in flamengo inlet, ubatuba region, southern brazil the experiments were performed in situ and simulated conditions to verify the patterns of diel cycles of both biotic and abiotic factors. the results obtained showed that diel variations were markedly pronounced mainly in relation to primary production and chlorophyll a. diel variations of biological factors seems to be due to exogenous and endogenous phenomena.