Abstract
Lakes El Sol and La Luna, inside the crater of the Nevado de Toluca volcano, Central Mexico, are the only two perennial high mountain lakes [HML] in the country. HML are considered among the most comparable ecosystems worldwide. These lakes are “extreme” environments with diluted, oligotrophic, and cold waters exposed to high UV radiation doses. In this paper, we document the phytoplankton species inhabiting these two extreme tropical ecosystems. The phytoplankton diversity of Lakes El Sol and La Luna is low compared to the global phytoplankton diversity from other Mexican inland waters. Nonetheless, the phytoplankton diversity turned out to be high compared to other HML worldwide, both temperate and tropical. The phytoplankton community in Lake El Sol was formed by 92 morphospecies and in Lake La Luna by 63; in both, the most diverse groups were Bacillariophyceae and Chlorophyceae. All species found in Lake La Luna were present in Lake El Sol, but 29 species present in Lake El Sol were absent in Lake La Luna. Nevertheless, 57% of the most frequent and abundant taxa in Lake El Sol were rare in La Luna, and 47% of the most frequent and abundant taxa in Lake La Luna were rare in Lake El Sol. Associated with their shallowness and polymictic thermal pattern, 87.5% of the Bacillariophyceae morphospecies are tychoplantonic, while the remaining 12.5% are truly planktonic. Dominant taxa were Chlorophyceae in Lake El Sol and Cyanobacteria in Lake La Luna. The most extreme conditions of Lake La Luna (ultraoligotrophy, very low pH, high ultraviolet radiation) most likely explained the differences in the dominant species composition and lower species richness compared to Lake El Sol. Herein, we provide for the first time a taxonomic list of the phytoplankton community of Lakes El Sol and La Luna. This information constitutes a baseline needed to use these HML as sentinels of global and climate change.
Highlights
Introduction published maps and institutional affilPhytoplankton biodiversity responds to multiple stressors
The phytoplankton species richness found in Lakes El Sol and La Luna included 92 taxa of which 47 were identified to species [51%] and 45 [49%] were identified as morphospecies
Phytoplankton diversity from Mexican inland waters is estimated to be close to 1025 to 1100 species [62,63]. Taking this value as a reference, the total phytoplankton diversity found in the Nevado de Toluca HML lakes represents around 10% of the global phytoplankton richness reported for Mexican inland waters
Summary
Introduction published maps and institutional affilPhytoplankton biodiversity responds to multiple stressors. The size of the lakes usually associated with habitat diversity correlates positively with phytoplankton species richness [1,2,3]. Phytoplankton species richness decreases as the trophic status increases [4,5,6], with higher doses of UV radiation [7,8], acidification [9,10], and fish introduction [11,12]. High mountain lakes [HML] have recently attracted scientific attention because they are extremely sensitive ecosystems to global changes [13,14]. The harsh conditions prevailing in HML [e.g., diluted, oligotrophic and cold waters, high UV radiation doses] classify these water bodies as extreme aquatic environments [15,16,17].
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