Le comunità fitoplanctoniche del Lago di Acquatina (Mar Adriatico meridionale)

Spatial distribution and taxonomy of the phytoplankton communities found in the Acquatina Pond (Southern Adriatic Sea) during an annual monitoring (2007-2008) are discussed in this paper. A monthly sampling was conducted at three stations which were representative of three different hydrological features. Water samples were taken at the surface using Niskin bottle, immediately fixed with a Lugol solution (1%) and examined with an inverted microscope (Labovert FS Leitz) at a magnification of 400x. Depending on phytoplankton concentrations, sub-samples varying from 25 to 50 ml were allowed to settle for 12-24 hours and counted by using the Utermöhl (1958) method. Results evidenced that trends in cell abundance were seasonal, with annual peaks occurring in spring and fall periods. Annual abundances ranged between 53,6 and 615,2 x 103 cells l-1. From a qualitative point of view, "others", mainly represented by undetermined phytoflagellates < 10?m dominated the phytoplankton community. Furthermore, the most representative species were the diatoms Navicula sp., Nitzschia sp., Chaetoceros spp., Cylindrotheca closterium and Thalassiosira sp. and the dinoflagellate Prorocentrum minimum. Among cyanobacteria, Oscillatoria spp. e Leptolyngbya spp. were the most abundant. In the considered ecosystem, the spatial distribution of the phytoplankton communities was associated both to seasonality and to the hydrodynamic regime of the Pond.