Benthic macroinvertebrate assemblages of a stream-lake network in the upper zone of the trans-Andean basin of the Valdivia River (Chile)

Abstract

ABSTRACT Stream-lake networks include multiple transition zones between lake-like and river-like conditions. This study analysed environmental features, macroinvertebrate assemblages (MIB) and functional feeding groups in outlet, inlet and tributary streams (i.e. streams other than the main stem) of a stream-lake network in Chilean Andean lakes, to verify if lake outlets reflect an ecotone condition. Permutational analysis of variance and canonical analysis of principal coordinates based on environmental features and MIB revealed a significant difference between stream types. Higher taxa richness was found in tributaries, whereas population densities, equitability and diversity indices varied between stream types. Eighty-five taxa were identified, with 7% of taxa found exclusively in outlets, 5% in inlets, and 22% in tributaries. Collector-gatherers were dominant in all stream types and there was no statistical differences among feeding groups and stream types. The distance-based linear model identified water temperature, % rock, % sand, and % FPOM coverage as having significant influence on richness and density of MIB in summer, while water temperature and %FPOM coverage were significant in spring. Our results suggest that lake outlets house MIB different than lake inlets and tributaries, as well as environmental variables, supporting the idea that Andean lake outlets reflect an ecotone condition.