Atelomixis as a possible driving force in the phytoplankton composition of Zirahuén, a warm-monomictic tropical lake

Abstract

The present work reviews our current understanding of the limnology of Lake Zirahuen and extends this knowledge through an analysis of the phytoplankton, illustrating phenomena that typify monomictic tropical lakes. The analysis reinforces the postulate that atelomixis determines the variation in phytoplankton composition of deep tropical lakes with a monomictic mixing regime. Similarly, it is proposed that an incomplete or partial atelomixis, generating a highly dynamic mixing layer, is a force that possibly drives the selection of algal groups, like the Desmidiaceae, with a high surface area to volume ratio. These organisms, characteristic of tropical lakes, though found in the deep epilimnetic layer, receive sufficient irradiance to support their high photosynthetic rate; their high population density survive thanks to a constant supply of nutrients. Lake Zirahuen is a particularly relevant case for Mexico, since the low calcium concentration and the trophic level of the lake provide an explanation for the otherwise uncommon presence of desmids in other Mexican lakes, even in lakes that exhibit atelomictic phenomena.