Sediment bacteria in Lugu Lake

Understanding biodiversity patterns and the role of biotic attributes in governing these patterns remains one of the most important challenges in ecology. Here, taking water depth in Lake Lugu as a typical geographical gradient, we studied how these different taxa, that is bacteria, diatoms and chironomids, respond to the same depth and environmental gradients using molecular and morphological methods. We further evaluated the relative importance of water depth, environmental variables and biotic attributes in explaining biological characteristics, such as biomass, species richness and community composition. The biomass of chironomids and the richness of bacteria and chironomids both showed a nonlinearly decreasing pattern associated with water depth, while biomass and species richness of diatoms showed U-shaped and hump-shaped patterns, respectively. The three taxonomic groups all showed increasing dissimilarity with water depth changes, and there was clear cross-taxon congruence among the variations in community composition. Abiotic variables were pivotal in structuring biological characteristics; however, the biotic attributes also explained a unique portion of their variations. This suggests that biotic interactions significantly influenced the patterns of biomass, species richness and community compositions along the water depth gradients for the three taxonomic groups studied. Our results provide new evidence that biotic attributes could help in predicting the biodiversity of aquatic communities along geographical gradients, such as water depth gradients.