Lake Prespa, a European natural monument, endangered by irrigation and eutrophication?

Abstract

The most interesting (Hutchinson, 1957), and at the same time oldest graben lakes of Europe, are Lakes Ohrid and Prespa. According to geologists and geographers, both originated during the Pliocene. They show karstic features and differ by volume, much less by area. At the occasion of an excursion to Lake Prespa in September 1994, an absence of oxygen in the hypolimnion between 17 m and the maximum lake depth, 48 m, was observed, for the first time since Stankovic' (1926) record. Moreover, a continuous decrease in lake level since the 1960s, the lowest transparency ever recorded from Megali Prespa, and high nutrient values, though only observed during a short part of the late stagnation period, are alarming signals, all suggesting eutrophication.