Cyanobacterial blooms caused by water eutrophication have become a global environmental problem. Dredging, alternatively known as removal of sediment, has been reported as an effective approach for mitigating cyanobacterial blooms, and plays important roles in enhancing water quality of urban lakes. However, the research on the ecological mechanisms behind dredging is not deep enough. 

The CAS Key Laboratory of Aquatic Plants and Watershed Ecology, associate professor WAN Wenjie and professor YANG Yuyi of the Environmental Genomics Group of Wuhan Botanical Garden, collaborated with professor Hans-Peter Grossart of the Leibniz Institute of Freshwater Ecology and Inland Fisheries (IGB) in Germany.  

The researchers took Lake Nanhu (Wuhan, China) as the research object, and determined bacterioplankton community composition along with water and sediment physicochemical properties before and after dredging. Besides, the researchers evaluated environmental adaptation of rare and abundant bacterioplankton to dredging disturbance by using some statistical analysis methods.    

The results of this study show that the rare bacterioplankton presents broader environmental breadths and stronger phylogenetic signals than the abundant bacterioplankton before and after dredging. This study first reveals that the rare bacterioplankton exhibits stronger environmental adaptation to dredging disturbance than the abundant bacterioplankton. 

In addition, they also find that stochastic processes dominate community assemblies of both rare and abundant bacterioplankton before and after dredging. Water dissolved oxygen plays decisive roles in adjusting the balance between stochastic and deterministic processes of community assemblies of both rare and abundant bacterioplankton. They have proposed that community assembly can be used a bio-indicator to reflect community function of bacterioplankton.  

These findings provide new insights for diversity maintenance of rare and abundant bacterioplankton, and may enrich the theoretical basis for the environmental policy of dredging measures to mitigate cyanobacterial blooms.  

The research was funded by the National Natural Science Foundation of China and the German Science Foundation. The findings of this research have been published in the SCI Journal of Water Research, with the title of  "Stronger environmental adaptation of rare rather than abundant bacterioplankton in response to dredging in eutrophic Lake Nanhu (Wuhan, China)”. 

Associate professor WAN Wenjie is the first author of this paper, professor YANG Yuyi is the corresponding author, and the Key Laboratory of Aquatic Botany and Watershed Ecology Wuhan Botanical Garden of the Chinese Academy of Sciences is the first institute.  

Rare bacterioplankton exhibits broader environmental breadth and stronger phylogenetic signal than abundant bacterioplankton before and after dredging, while abundant bacterioplankton shows higher functional redundancy than rare bacterioplankton before and after dredging. Water dissolved oxygen shows decisive role in balancing stochasticity and determinism of community assembly, indicating distinct changes in stochasticity with higher dissolved oxygen content (Image by WBG)