Patterns of free-living and particle-attached bacteria along environmental gradients in Lake Taihu

To elucidate the effects of environmental heterogeneity on diversity, composition, and degree of overlap between free-living (FL) and particle-attached (PA) bacteria, we sampled large, shallow, eutrophic Lake Taihu, China across gradients spanning riverine inflow, cyanobacterial blooms, and the open limnetic area. Using high-throughput sequencing of the 16S rRNA gene, we show that (i) bacterial communities near riverine inflow had high a-diversity and a high degree of overlap between FL and PA lifestyles, (ii) communities in cyanobacterial blooms have reduced a-diversity within the PA lifestyle, and (iii) communities from the limnetic area had the lowest bacterial a-diversity within the FL lifestyle and a medium degree of overlap between the FL and PA lifestyles. Redundancy analysis showed that the variation of the FL bacterial community was shaped by suspended solids and total phosphorous, while the variation of the PA bacterial community was shaped by suspended solids, dissolved oxygen, and the percentage of organic matter in suspended solids. This study highlights the importance of environmental heterogeneity, riverine input, cyanobacterial blooms, and nutrient status on the spatial distribution patterns of FL and PA bacterial communities in freshwater lakes.