The structure and species composition of the diatom communities in tropical volcanic lakes of eastern Mexico

Abstract

Six nutrient-rich tropical volcanic lakes in eastern Mexico were investigated to document their characteristic diatom floras. Plankton and sedimentary diatom communities were compared to verify the representativity of the sediment assemblage by identifying the plankton species present in the sediment. Relationships between surface sediment diatom communities and 20 physico-chemical variables were evaluated using multivariate analysis. High phosphorus concentrations were measured in all the lakes sampled and chlorophyll a concentrations were found to be useful in describing lake trophic status which ranged from meso- to hypereutrophic. The results showed that the species composition and distribution of the diatom community in these lakes was most influenced by nutrient availability (P) and ionic composition. Canonical correspondence analysis showed that cation dominance explained a significant amount of the variation in the diatom community composition. It allowed the identification of three lake types: (1) Na⁺-dominated lakes where diatom communities had>50% Achnanthidium minutissimum (Grunow) Czarnecki; (2) Mg²⁺-dominated lakes, where the characteristic species were A. minutissimum (<30%) and Cymbella microcephala Grunow (<50%); and (3) one Ca²⁺-dominated lake, where Navicula arvensis Hustedt and Discostella pseudostelligera (Hustedt) Houk & Klee were the most abundant diatoms (>20%). The results suggest that some epiphytic diatoms (e.g., A. minutissimum, C. microcephala) can use other plankton algae as substrate; this is a strategy that allows them to remain within the euphotic zone in deep, eutrophic, turbid lakes. The lakes with the lowest nutrient levels had the best preserved terrestrial vegetation cover on the crater walls. This suggests that deforestation has been a factor that has accelerated the process of lake eutrophication during recent decades in this region.

Keywords:

• diatoms
• ions
• nutrients
• crater lakes
• CCA
• Tuxtlas
• Mexico

Acknowledgements

We thank Javier Tolome for fieldwork support, Ariadna Martínez for laboratory analyses and Tiburcio Laez for assistance with the scanning electron microscope observations. Keith MacMillan revised the English version of the manuscript. We thank two anonymous reviewers for their comments and constructive suggestions. This work was supported by Instituto de Ecología, A.C. and the Universidad Nacional Autónoma de México (Grant DGAPA IN 107902).