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Estudos sobre a variação sazonal do fitoplâncton e clorofila-a foram desenvolvidos na região de Ubatuba, extremo norte do Estado de São Paulo (Lat. 23º30'S, Long. 45º07'W), através de coletas mensais, durante o período de junho de 1974 a setembro de 1975. Foram também avaliados a temperatura da água, salinidade, oxigênio dissolvido e transparência. Paralelamente, foram obtidos dados pluviométricos da região, referentes ao período considerado. As amostras destinadas aos referidos estudos foram coletadas verticalmente, em três níveis de profundidade: superfície, profundidade de extinção do disco de Secchi e 60 centímetros acima do fundo. Qualitativamente, as diatomáceas apresentaram-se como o grupo mais diversificado e, em segundo lugar, os dinoflagelados. Quantitativamente, a população fitoplanctônica apresentou-se constituída fundamentalmente por fitoflagelados, seguidos por diatomáceas e dinoflagelados. Cianofíceas e silicoflagelados também estiveram presentes, porém em quantidades muito menores. Excluindo-se os fitoflagelados, as espécies mais representativas da população fitoplanctônica da região foram as diatomáceas Nitzchia closterium, Thalassionema nitzschioides, Navicula sp. e o dinoflagelado Gymnodinium sp. O número máximo de células observado, de um modo geral, ocorreu durante o verão, evidenciado tanto pelas contagens (máximo de 1.028.000 células/litro), como pelas determinações de clorofila-a (máximo de 6,86 µg/1); nesta época, houve um máximo de precipitação pluviométrica e modificação na estabilidade térmica da coluna d'água. Os estudos de fracionamento demonstraram que a fração menor que 20 µm (nanofitoplâncton) é a predominante no fitoplâncton total.Seasonal changes in phytoplankton populations in the chlorophyll-a concentration and on some environmental factors were studied monthly from June 1974 to September 1975 at Ubatuba, northern coast of São Paulo. Water temperatures ranged from 20ºC in August to 29.5ºC in March and salinities from 33.06 º/.. in March to 35.80 º/.. in January. The maximum salinity value observed in January near the bottom, associated with the thermal stratification found only during this month, seems to indicate an oceanic contribution to the enrichment of the local water mass. Pluviometric values ranged from 37.2 mm in August to 468.5 mm in January. Phytoplankton cell counts fluctuated from 64,000 to 1,028,000 cells/l and chlorophyll-a values varied from 0.52 to 6.86 µg/l. Maximum standing-stock was observed during summer, particularly in March, and it is probably associated with land drainage due to precipitation. A second bloom was observed in September 1975, and it is associated probably with the discontinuous impact of the wind. The phytoplankton populations were dominated by unidentified phytoflagellates, followed by diatoms and dinoflagellates. Nitzchia closterium and Thalassionema nitzschioides, along with Navicula sp., were the most representative species of diatoms. Among the dinoflagellates, Gymnodinium sp. was the most important. Blue-green algae and silicoflagellates were poorly represented. The diatoms Chaetoceros simplex, Chaetoceros spp, Nitzchia longissima, Nitzchia spp, Rhizosolenia delicatula and Rhizosolenia stolterfothi were found with high densities, only during bloom periods. The chlorophyll-a fractionation experiments demonstrated that organisms in size classe smaller than 20 µm represented, for all depths, between 54.93 and 98.15 º/.. of the total phytoplankton population.

ABSTRACT There is an increasing demand for bioprospection focusing on microalgae isolated from the northeastern region of Brazil with potential importance for food industries. To attend that need, we evaluated the characteristics of 12 regional species of microalgae grown under controlled cultivation conditions (temperature = 24 ± 1 ºC, illumination 150 µmol photons m-2 s-1, photoperiod of 12 h) in terms of their nutritional quality and lipid profiles. Significant differences in growth characteristics and chemical compositions were observed among the species investigated. High carbohydrate contents (> 25 g 100 g-1) were recorded in various strains of Chlorococcum and the marine microalga Amphidinium carterae; high protein contents (> 35 g 100 g-1) were observed in Scenedesmus acuminatus and Pediastrum tetras; and high lipid contents (> 25 g 100 g-1) in A. carterae and some strains of Chlorococcum sp. (cf. hypnosporum). Chlamydomonas sp. demonstrated the greatest production of carotenoids (64.92 mg g-1), chlorophyll-a (234.74 mg g-1), and chlorophyll-b (59.34 mg g-1). The lipid profiles of Chlorella cf. minutissima, four strains of Chlorococcum sp. (cf. hypnosporum), P. tetras, Planktothrix isothrix, and S. acuminatus indicated the presence of palmitic, oleic (ω-9), linoleic (ω-6) and α-linolenic (ω-3) acids, with more than 50% omegas in the total composition of their fatty acids. In terms of chemical nutrients, the microalgae cited were found to be potential sources of omegas, carotenoids, and chlorophylls that could be used in food industries.