Chemical and biological features of a high altitude lake in the southern Alps (Laghetto Inferiore, Switzerland)
Since 1980, surveys have been performed nearly every three years on approximately 50 small high altitude alpine lakes located in the Swiss part of the Lake Maggiore watershed. On the basis of this information, since 1996 Laghetto Inferiore has been included in the Mountain Lakes Research (MOLAR) project, an extensive European cooperative research project with 23 partners. Laghetto Inferiore is located at 2074 m a.s.l.; its watershed is mainly composed of crystalline silicic rocks; it has a maximum depth of 33 m, and a theoretical renewal time of 41 days. The pH of the water is approximately 5.6; the alkalinity of the surface water is approximately 30 μmol and that of the bottom water approximately 60 μmol. Chemical studies were performed on the inputs from atmospheric deposition and the main tributary streams, the lake concentration (on a monthly basis), and the outflow. The results show that the characteristics of summer deposition (rain) differ significantly from those of winter deposition (snow). By means of a budget model it was possible to distinguish between the contribution from atmospheric deposition and the contribution from weathering. Biological studies revealed a considerable variety of phytoplankton species and a scarcity of zooplankton species. The vertical distribution of the main algal species shows a marked vertical stratification, with biomass concentrations higher in the profundal. Along this profile, the species of the same taxonomic class tend to gather in a particular depth band, while the single classes tend to be distributed at different depths, according to their specific light requirements.
Document Type: Research Article
Affiliations: 1: Laboratorio Studi Ambientali – Sezione Protezione Aria e Acqua, Riva Paradiso 15, CH-6900 Lugano-Paradiso, Switzerland and 2: National Research Council Istituto Italiano di Idrobiologia, Verbania-Pallanza, Italy
Publication date: 2001-03-01