Environmental stressors drive fungal community homogenization and diversity loss in plateau freshwater lakes.

BACKGROUND

Fungi play a crucial role in aquatic ecosystems by driving nutrient cycling, organic matter decomposition, and water purification. However, the diversity and community structure of aquatic fungi, particularly in plateau freshwater lakes, remain underexplored. This study used high-throughput sequencing to investigate fungal communities in three plateau lakes (Chenghai, Erhai, and Lugu) with varying water quality, focusing on how environmental factors shape community composition.

RESULTS

Significant differences in fungal α-diversity and community structure were observed across the lakes. Chenghai Lake, with the poorest water quality, exhibited the lowest fungal diversity and a more homogenized community structure. Reduced diversity was associated with elevated salinity, pH, total dissolved solids (TDS), potassium (K), and nitrate (NO₃⁻), while the fungal community structure was influenced by both geographic and physicochemical factors. Saprotrophic fungi were the most predominant functional guild across all lakes. Geographical factors, particularly altitude, positively influenced the richness and abundance of all fungal functional guilds, while most physicochemical factors showed negative associations, with exceptions like NH₃-N and DO. The fungal network in Erhai Lake, characterized by higher complexity and connectivity, showed features consistent with an enhanced capacity for buffering against environmental fluctuations. In contrast, the simpler network structures in Chenghai and Lugu Lakes suggested greater resistance, maintaining stability through reduced sensitivity to environmental change. All three lakes exhibited predominantly positive correlations among fungal species, with Lugu Lake showing the highest proportion, potentially reflecting enhanced cooperative interactions under nutrient-limited conditions.

CONCLUSIONS

These findings highlight the strong dependence of aquatic fungal communities on environmental conditions, suggesting their potential as bioindicators for water quality. Variations in fungal co-occurrence patterns imply different adaptive strategies across lakes. Further research is needed to validate these findings and explore the broader applicability of fungal networks in environmental health monitoring.