LIMNOLOGICAL STUDIES OF LAKE-DEL-TORO (CHILE) MORPHOMETRY, PHYSICS, CHEMISTRY, AND PLANKTON

Lake del Toro (51-degrees-12'S; 72-degrees-45'W) is located at 26 m ab ove sea level, has a surface area of 196.4 km and is of glacial origin , belonging to type 28 b according to its glacier origin (HUTCHINSON 1 957). A bathymetric map was made revealing a maximum depth of 317 m an d volume of 30.2 km3. The lake lies in an area of cold steppe climate with strong winds. No thermal stratification was detected possibly due to the strong summer winds. The lake is transparent during autumn, wh en winds diminish, but during summer transparency is very low due to a n increase of glacier sediments. The euphotic layer varies between 17 m (January 1989) and 34 m (May 1989) of depth. Some chemical condition s are within the ranges of oligotrophic lakes. In phytoplankton, Chlor ophyceae - with the species Monoraphidium saxatile and Gomphosphaeria lacustris - are predominant. Chlorophyll a concentrations are low, but primary productivity is relatively high. According to the information s obtained during the present work, Lake del Toro can be considered as oligotrophic, temperate, deep and of glacier origin with influence of glacier sediment. Due to wind force it is a polymictic lake without s tratification.