Phytoplancton de la lagune de Venise. II-Bassin Central (Avril 1989-Mars 1990).

To continue the research on the lagoonal phytoplanktonic communities, we carried out monthly samplings (from April 1989 to March 1990) on four sampling stations, located in the central basin (Malamocco basin) of the Venice lagoon, during the flood and the ebb tide. The same methods were used during the present work and the previous research to compare the results. Environmental parameters showed the influence of the sea water also in the inner areas. Phytoplankton was influenced by the environment: there were many eupelagic species; the freshwater species, instead, were not abundant. Phytoplankton was constituted by 258 taxa, 75% of them were diatoms. During the summer the phytoplanktonic densities were often higher than 5x105 cells/ml; during the cold season, we registered high density values only in March, due to a bloom of Skeletonema costatum. This diatom was very abundant during the same period also in the Northern and in the Southern basins of the lagoon. Diatoms were present during all the year with fluctuations different among the stations. Microflagellates sometimes were more abundant than diatoms; the other groups, included Dinoflagellates and Euglenophyceans did not show significant density values.