Pseudo-Nitzschia, Brasiliana (Bacillariophyceae), an opportunistic diatom on the coast of the state of Rio de Janeiro, Brazil

Abstract

The occurrence of Pseudo-nitzschia brasiliana Lundholm, Hasle & Fryxell, a recently described marine diatom, is reported for two distinct environments on the coast of the state of Rio de Janeiro, Brazil, during the El Niño-ENSO summer of 1998. These occurrences took place almost simultaneously, as a bloom event, which is defined here not only through high cell abundance, but also in terms of high relative contribution to total cell numbers. The booms occurred at times when each one of these environments was under a specific stress, suggesting an opportunistic behavior for this diatom. In Sepetiba Bay, P. brasiliana was the first species to dominate (2.8 x 106 cells l-1; 85% of the microphytoplankton fraction) after a bloom of the raphidophyte Chattonella sp. was subsiding in early February. In Imboassica Lagoon, a oligohaline coastal system ca. 150km north of Sepetiba Bay, P. brasiliana was the dominant species (1.3 - 3.6 x 107 cells l-1; 90% of total phytoplankton) after the lagoon-sea connection was forced opened in mid-February, which allowed the contribution of more saline waters into the lagoon, that probably carried out a seed-stock of P. brasiliana present along the coast during this period.