Within-lake spatio-temporal dynamics of cladoceran and diatom communities in a deep subtropical mountain lake (Lugu Lake) in southwest China

Within-lake spatio-temporal variability of remains of cladocerans and diatoms were examined, using trap and surficial sediment sampling approaches in Lugu Lake, one of the deep mountain lakes in the subtropical region of southwest China, to understand the response to recent environmental change. Seasonality played a strong role in the distribution patterns of both cladocerans and diatoms, but their responses to seasonal change varied. The rich resources of food supported a cladoceran population peak during summer, while increased mixing and higher nutrient triggered diatom blooms in spring. The summer also witnessed increased grazing effects of primary consumers on diatoms when the water column was nutrient-enriched. In particular, Ceriodaphnia intensified grazing on small diatoms (Cyclotella ocellata), consequently affecting community patterns during summer, while increased wind activity during spring induced turbulence, remixing, transportation and depositional processes of remains of littoral Alona guttata and benthic diatoms. The distribution pattern of cladocerans in surface sediments was similar to that of diatoms. Seasonal community patterns and trophic interactions between cladocerans and diatoms in trap and surface sediments of differential depth gradients provide evidence that high-resolution sampling of multi-proxy biological remains in deep mountain lakes of southwest China can help reduce biases in paleoenvironmental reconstructions