Les diatomées dans l'upwelling de Cabo Frio (Brésil): liste d'espèces et étude écologique

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Abstract
The diatoms in the Cabo Frio (Brazil) upwelling: check list and ecological study. A qualitative and quantitative study on the diatoms from the Cabo Frio area was made and a check list produced. Sampling was carried out over one year at an anchorage station in the upwelling zone. Data were analysed by means of a multivariate statistical method, in order to show the main synecological aspects of the diatom populations. Diatoms dominate in most samples, except in the Brazil current water where dinoflagellates are dominant, and where there is a poor population of thermophilic diatoms. Recently upwelled water has a poor phytoplankton composed of epiphytic and benthic species; these are substituted by intense blooms of neritic and opportunist diatoms when the temperature rises. The annual distribution of the diatoms accompanies the occurrence of upwelling. The vertical thermal gradient or water stability is the most important factor affecting the specific composition and distribution of the diatom communities.