Lago di Como - Italy

Lake Como is the deepest italian lake (425metres) and is part of the group of deep lakes located south of the Alps in one of the most densely populated and highly idustrialized area of Italy.Owing to its shape, resembling an upside-down “Y”, Lake Como may be subdivided in three sub-basins, i.e. the Western, the Eastern and the Northern basins with different bathymetric , hydrological characteristics. Lake Como, originally oligotrophic, has undergone a process of eutrophication since the 60's that culminate in the '80s when the concentration of total phosphorus at Como was detected in 80 μg l-1. In this phase, the composition of the phytoplankton population has undergone considerable variations with the gradual growth in the importance of some species such as Planktothrix rubescens, Stephanodiscus hantzschii, Fragilaria crotonensis and M. aeruginosa thata gave rise an extensive bloom in 1983 in Como. The data relating to zooplanktonic community showed an increase of cladocerans especially Eubosmina sp. The subsequent reduction of loads, that caused the decrease of total phosphorus concentration in the lake up to 46 and 40 μgP l-1, respectively in the west basin and along the north-eastern axis , led to the decline of the biomass. Even the zooplankton community has recorded a decrease of the density of cladocerans (Daphnia hyalina and Eubosmina sp.) and an increase in that of Diaptoms (Eudiaptomus padanus). The decrease of the concentration of total phosphorus concentration is continued up to reach 35 μgP l-1 in 1999 without determining significant variations nor the specific composition of the phytoplankton communities , in this period occasionaly dominated by P. rubescens (up to 50,000 cell ml-1 at Como), either in its abundance expressed as total biovolume.In Lake Como, only few studies were carried out irregularly by various Institutions up to the end of the 1990s. Since the beginning of the 2000, with the establish of the Envinromental Protection Agency of Lombardia (ARPA Lombardia), continuous monthly samplings and measurements were carried out by our envinromental agency.The data collected at monthly frequency since 2000 includes water temperature and oxygen. Phytoplankton and chemistry data were collected since 1997, while zooplankton were collected from 2004 to 2006 and since 2010. In 2008 and 2009 were characterized the communities of the macrophytes and benthic macroinvertebrates (sublittoral and profundal zone) of the entire lake.