Environmental DNA Reveals Typhoon-Driven Multitrophic Food Web Reorganization in a Subtropical River

Paired pre- and post-typhoon environmental DNA surveys examined how typhoon disturbance was reflected in multitrophic community and food web organization in the Lianjiang River basin, China. Phytoplankton, zooplankton, benthic macroinvertebrates (benthos), and fish were integrated into an empirically constrained multitrophic network. Within this integrated framework, signed associations, pathway analysis, and the trophic coupling index (TCI) assessed changes in potential trophic associations and trophic coupling across four biological groups. Typhoon disturbance produced little overall change in alpha diversity, whereas beta diversity and taxonomic composition differed between periods, indicating community reassembly across all four groups. This contrast motivated the analysis of trophic organization. The post-typhoon network was denser, with positive edges increasing from 991 to 1769 and negative edges declining from 941 to 772. TCI+ increased from 19.63 to 26.15, whereas TCI– decreased from 23.49 to 13.63, and pathway analysis showed that changes were concentrated in selected trophic pathways. Because the networks represent potential trophic associations rather than direct feeding interactions, they are best used to compare changes in trophic organization under consistent sampling and analytical procedures. This eDNA-derived framework can provide a diagnostic layer for post-typhoon river assessment when alpha diversity alone is weakly responsive.