The structure of the zooplankton assemblages from two neighboring tropical high mountain lakes

We studied the zooplankton of two tropical high mountain lakes - Lake El Sol and Lake La Luna - located inside a volcano in central Mexico. A total of 3 5 taxa was recorded (two copepods, four cladocerans and 29 rotifers). Species richness was higher than that reported in high mountain lakes in temperate regions and even from other tropical systems. Aspelta psitta., Hexarthra bulgarica canadensis, Cephalodella delicata, and Alonella pulchella were recorded for the first time in Mexico, Although there was a high coincidence in species composition, the lakes displayed large differences in dominant taxa, density, and biomass. Seasonal dynamics of zooplankton taxa in both systems were rather comparable to those reported for temperate high mountain lakes. This pattern likely reflected a cold-dry period when abiotic factors (mainly temperature and pH) regulated the assemblage and a warm-rainy period that was regulated by biotic factors. Our results suggest that most important biotic dissimilarities observed between these two neighboring lakes were due to abiotic environmental conditions (mainly pH); however, we suggest that the relatively recent introduction of fish in one of these lakes has magnified the differences between them.