Environmental DNA metabarcoding reveals the impact of glacier melt-induced ionic pulses on multitrophic communities in the source region of the Yangtze River

Glacier melt-induced ionic pulses significantly alter river physicochemistry and trigger cascading effects on aquatic communities. However, their impacts on multitrophic community structure and ecological networks remain insufficiently understood. In this study, environmental DNA (eDNA) metabarcoding was applied to explore how ionic pulses influence multitrophic communities in the Source Region of the Yangtze River. The results show that the ionic pulse caused a turnover of dominant taxa among algae, invertebrates, and fish. In addition, bacterial α-diversity declined during the pulse due to ionic stress but recovered afterward; the β-diversity of aquatic communities decreased during the pulse due to homogenization, then increased after the pulse as communities underwent reassembly driven by both species loss and replacement. Co-occurrence network analysis showed that networks were simplified during the pulse but became more complex and modular afterward, with an increase in keystone taxa across trophic levels; however, network stability declined. Water temperature, pH, electrical conductivity (EC), and nutrients are key drivers of these changes. The findings elucidate the important impacts of ionic pulses on aquatic communities in glacier-fed rivers and provide theoretical support for ecological protection and management in high-altitude regions.