Phytoplankton in Sardinian reservoirs

Abstract

A picture of the studies carried out in the past 20 years on phytoplankton from the 36 reservoirs and one natural lake in Sardinia is presented. Processing of the 1994 seasonal data shows that the dominant or subdominant algal species in the 36 reservoirs in terms of density belong to only 8 genera, with species of the genus Microcystis in 17 reservoirs, Chlorella in 15, Cyclotella in 12, Ankistrodesmus and Anabaena in 9, Aphanizomenon in 8, Melosira in 7 and Oocystis in 6. Processing of the data from the 16 reservoirs in which annual or plurennial surveys were carried out, shows that on the basis of the biomass the most likely floristic pattern is Microcystis aeruginosa Kg., Microcystis flos-aquae (Wittr.) Kichn., Anabaena flos-aquae (Lyngb.) Bréb., Anabaena planctonica Brunnth., Aphanizomenon flos-aquae (L.) Ralfs., Melosira granulata (E.) Ralfs and Closterium aciculare T. West. In general terms this means that most of these reservoirs are eutrophic. In fact the species are capable of describing an increasing trophic gradient in agreement with the one described using other variables. Specific cases of reservoirs where plurennial surveys have been carried out are considered. From these surveys a great quali-quantitative variability of the phytoplankton is inferred.