Abstract

The water bodies studied herein are located in the Huerquehue National Park, a mountain zone with Nothofagus alpina, N. pumilio, N. dombeyi, and Araucaria araucana forests, at 700-1500 m a. s. l. There are numerous oligotrophic lakes, with characteristics similar to the deep Araucanian lakes. Many of these small lakes are difficult to reach, because the only routes leading there are long mountain paths. The sites studied in the present paper are five lakes: the first is located at the basis of the mountains (700 m a.s.l.) and is fed by a river that reaches it from series of three other lakes higher in the mountains (1300 m a.s.l.), which are connected by small streams. These four lakes are inhabited by fish populations. The fifth site is a small, shallow, and fishless pond located at one of the highest sites in the park (1400 m a.s.l). Samples were collected for analysis of chlorophyll concentrations and for littoral, aquatic crustaceans. All sites are oligotrophic, and show low crustacean species richness. In the four lakes with fishes, the crustacean littoral fauna was composed of Hyalella araucana (Amphipoda) only. In the fifth lake, the crustaceans collected were H. araucana, copepods (Boeckella gracilis and Mesocyclops longisetus), and large cladocerans (Scapholeberis spinifera and Simocephalus serrulatus). A direct relationship between species richness and both chlorophyll a and humic acid concentrations was found at all sites studied. These results would agree with literature descriptions that indicate the role of ultraviolet radiation and trophic status as conditioning factors for aquatic communities in Patagonian fresh waters. © 2007 Brill Academic Publishers.