Dominant and keystone genera of microorganisms dominate the multi-trophic aquatic ecological integrity of the Yangtze finless porpoise reserve.

Abstract

Aquatic ecological integrity is a critical attribute to sustain a vibrant ecosystem, which reflects of the intricate balance among various trophic levels, ensuring the prosperity of the aquatic fauna. The Yangtze finless porpoise (Neophocaena asiaeorientalis), a flagship species in the Yangtze River ecosystem, has been grappling with the degradation of its aquatic habitat due to anthropogenic activities, but the current state of the ecosystem remains uncertain since the implementation of the initial 10-year period of the fishery ban. In this study, we evaluated the ecological integrity of the Yangtze finless porpoise Tongling Nature Reserve (including core zone, experimental zone, buffer zone, and semi-natural zone (artificial feeding zone)) by using a multi-trophic index of biological integrity (MT-IBI) involving phytoplankton, zooplankton, and microorganism. We found that the ecological status was relatively favorable both in experimental and core zones. However, the ecological conditions in the buffer zone and artificial feeding zone were significantly poorer. Hydraulic conditions, including flow velocity and water depth, along with nutrient concentrations such as chemical oxygen demand, and total nitrogen, were critical drivers influencing the MT-IBI values. It was particularly worth noting that the integrity of the aquatic ecosystem is largely affected from the presence of key microbial genera Pseudarthrobacter and Rhodococcus, which play a pivotal role in shaping polytrophic communities. This study provides a foundational understanding for the conservation of Yangtze finless porpoise habitat, and underscore the potential of the MT-IBI as a valuable tool for assessing ecosystem health across various aquatic environments in the future.