Evoluzione recente della qualità delle acque dei laghi profondi sudalpini (Maggiore, Lugano, Como, Iseo e Garda) in risposta alle pressioni antropiche e alle variazioni climatiche

This paper presents a synthesis of the most important studies performed on the deep insubrian lakes (Maggiore, Lugano, Como, Iseo and Garda). Samples taken continuously over the last decades form the basis for a description of the trophic evolution of the lakes, inferred from concentrations of algal nutrients and dissolved oxygen. The results show an improvement in the condition of Lake Maggiore, currently approaching oligotrophy, and in that of lakes Como and Lugano, which are still nevertheless in an unacceptable eutrophic state. Lake Garda has been affected by an increase in mean P concentration since the 1970s, but it has stabilised in recent years. Also in Lake Iseo P concentration has not changed in the last twenty years, but the lake still remains in an eutrophic condition. It is noteworthy that the consequences of eutrophication are accentuated by the incomplete circulation of most of these lakes. This situation has particularly affected lake Iseo, causing permanent anoxic conditions in the water below a depth of 150 m.