CONICET | Buscador de Institutos y Recursos Humanos

The existence of potentially harmful phytoplanktonic species in Bahía Anegada shores capable of modifying quality and characteristics of water showed the necessity of analyzing their populations dynamics in response to abiotic parameters, in order to provide information for the oyster reef managements developed in this bay. The studied species were: diatoms Asterionellopsis glacialis, Ceratoneis closterium, Leptocylindrus minimus, Rhizosolenia setigera and Pseudo-nitzschia spp.; dinoflagellates Alexandrium sp., Dinophysis sp., Gymnodinium sp., Prorocentrum sp. and Protoperidinium sp. and cyanophytes Synechocystis sp., Agmenellum quadruplicatum and Anacystis montana. In the three sites (SB1, SB2 and LP) diatoms accounted for the most part to the total monthly phytoplanktonic abundance. They were low frequent and scarce in summer, increased in autumn until a winter maximum. Cyanophytes caused autumn and winter blooms only in SB1. Dinoflagellates were low frequent, increased their abundance in spring but never were dominant. Cylindrotheca closterium was the most frequent species with high abundance almost the whole year. Asterionellopsis glacialis reached its higher abundances from March to August and was absent in summer. Leptocylindrus minimus was abundant in September like has been recorded on another coasts of the world. The group Pseudo-nitzschia spp. showed high annual occurrence but without alarming densities. Rhizosolenia setigera was occasional, appearing in low abundance just in winter. Spermatozopsis sp. blooms in June and August 2006 caused a reduction of nitrogen availability, with an important increase of the latter when these blooms finished. Gymnodinium sp. reached high densities also in June 2006 in SB1.