Benthic macroinvertebrates of two tropical, high-mountain lakes at Nevado de Toluca Volcano at central region of Mexico

Background. The benthic macroinvertebrates play an important role in the organic matter recycling and are sensitive indicators of human perturbation. Goals. The aim of this study was to recognize the spatial and temporal variation in taxonomic richness and density of the benthic macroinvertebrates of high mountain Lakes El Sol and La Luna, and their relationship with the environmental variables. Methods. Three deep stations (El Sol = 2 and La Luna = 1) and two in the littoral zone of El Sol (with and without vegetation) were selected. Results. We found eight taxa in El Sol: four oligochaetes (Limnodrilus hoffmeisteri, Tubifex tubifex, Lumbriculus variegatus and Nais pardalis), one bivalve (Pisidium casertanum), one hydrozoan (Hydra vulgaris) and two chironomids (Pagastia sp. and Tanytarsus sp.). Differently in La Luna there were just L. hoffmeisteri y Pagastia sp. The average density of the benthic macroinvertebrates was similar in the deep zone of both lakes (El Sol 5,526 +/- 3,807 org m(-2) y La Luna 7,955 +/- 7,349 org m(-2)). The density in the shallow zone without vegetation was higher (38,249 +/- 33.077 org m(-2)) than in the vegetated shallow zone (25.247 +/- 18.997 org m(-2)). Conclusions. The temporal variation of macroinvertebrates density seems to be regulated by the temperature and pH, showing the lowest values when the temperature and pH are lower.