Water level reduction and plant associated invertebrates in the deep Lake Albano (Central Italy).

The volcanic Lake Albano is one of the deepest Italian lakes (max. depth: 175m), subjected from 1960 to considerable eco-morphological modifications taken to encourage recreational activities. Recent climate changes and increasing amount of water drawing from the cathment basin further deteriorated the littoral area, following the water level reduction of about 5 m, which bared wide parts of lake bottoms, today transformed in emerged sandy shores. The comparison of recent preliminary data with a previous study on littoral invertebrates (1986) displayed the almost total disappearance of the aquatic vegetation in the whole perimeter, including also several parts of common reed bed. In some stations plants were completely replaced by sand characterized by predominance of coarse fractions. The disappearance of plants produced a dramatic decrease of the fauna abundance at shallow depths (0-4 m depth range) and, excluding one station, the total disappearance of fauna at deeper littoral areas (4-8 m). This decrease of production was associated with a slight reduction of total phosphorus in the water and a transparency increase (mean: 7.4 m in 1986, 9.5 m in 2008). In spite of this serious deterioration, the same number of plant taxa (9 in 1986 and 8 in 2008) and faunal groups (18 in 1986 and 20 in 2008) was still observed. The preservation of a high number of faunal groups is a sign of the high homeostatic capability of the littoral community, which represents the most important source of lake biodiversity and the basis of any possible amelioration of the environmental conditions.