Diatoms (Bacillariophyta) from different benthic habitats within seven upland lakes in the Laguna San Rafael National Park, Chile

Abstract

Diatom assemblages from 18 samples from 7 lakes along an altitudinal gradient in the Laguna San Rafael National Park, on the eastern side o f the Patagonian ice cap, were analysed. Over 190 taxa from 38 genera were found and identified to species or variety wherever possible. Some taxa could not be allocated to known species. The diatom floras o f the lakes differed considerably, with the lake environment showing a stronger effect on the assemblage than did the habitat type in two lakes (Alpha and Hielo Azul). However, the highest similiarities were found between epiphytic samples from four lakes. Oxbow lake, Lagos Leones, Alpha and Quito. A few cosmopolitan species were found in almost all the lakes, but many taxa were restricted to one o r two lakes. Assemblage data from all samples was subjected to TWINSPAN revealing three major groups o f assemblages, discriminated primarily by two cosmopolitan species and several acidophilic taxa. Fuller water chemistry was available for four lakes allowing the relationships between diatoms and water chemistry to be analysed using CANOCO. None o f the environmental gradients were large, but DCCA discriminated clearly between the lakes, placing Buena Vista and Cachorro far apart, as they have no taxa in common. Alpha and Quito fell in between, but separate^ from each other because they share only a few, uncommon, taxa.