Floodplains are areas of low lying land that are subject to inundation by lateral overflow water from rivers or lakes with which they are associated. Maintenance of free interconnection between floodplain and river is of significance to maintain high biodiversity and ecological health. In the Yangtze floodplain, to protect villages and cultivated land along the lakeshore from flooding, embankments and sluice gates were constructed between the 1950s and the 1970s. Eventually, most lakes were isolated from the main stem of the river, resulting in biodiversity reduction and biological resources decline. Macrozoobenthos are not only good indicators of long-term changes in environments, but also sensitive to changes in hydrological conditions. Therefore, studies on macrozoobenthos in relation to hydrological connectivity are of great significance to floodplain management and conservation. Then, how would macrozoobenthos respond along the gradient of hydrological connectivity? 

Bao-Zhu Pan, Hai-Jun Wang, Xiao-Min Liang and Hong-Zhu Wang from Institute of Hydrobiology, Chinese Academy of Sciences (IHB) answered this question in a paper entitled “Macrozoobenthos in Yangtze floodplain lakes: patterns of density, biomass and production in relation to river connectivity”, which was recently published on Journal of the North American Benthological Society (2011, 30(2): 589-602).  

Based on the field investigations conducted in more than 30 isolated lakes, 3 connected lakes and 10 mainstream sections of the Yangtze River, the relation between macrozoobenthic assemblages and hydrological connectivity was analyzed. Results showed that at an intermediate level of river connectivity, biodiversity, biomass and production of total macrozoobenthos reached maxima. These results not only confirmed the previous theory that α diversity of macrozoobenthos peaks at moderate connectivity with rivers, but also first proposed the theory that biomass and production of total macrozoobenthos reach maxima at a moderate connectivity. It is suggested that a moderate hydrological connectivity is of critical importance to the maintenance of ecological health of river-floodplain systems. 

The research was funded by National Natural Science Foundation of China and Chinese Academy of Sciences.