RESPONSE OF FUNCTIONAL COMMUNITY DIVERSITY OF MACROINVERTEBRATES IN ASHI RIVER TO ECOLOGICAL ENVIRONMENT AND OPTIMIZATION STRATEGY

Abstract

To clarify functional feeding group (FFG) response mechanisms to environmental changes and support ecological restoration, 27 sampling sites were established along the Ashi River, with seasonal investigations conducted in 2022. A total of 52 taxa (50 families + 2 classes: Hirudinea, Oligochaeta) were identified, categorized into 6 FFGs: Collector-Gatherers (CG, 42%), Predators (PR, 29%), Scrapers (SC, 13%), Shredders (SH, 10%), Collector-Filterers (CF, 3%), and Omnivores (OM, 2%). Significant spatiotemporal variations were observed: CG dominated anthropogenically disturbed middle-lower reaches, while PR, SH, and SC were more abundant in low-disturbance upper reaches. Seasonally, the ShannonWiener index of FFG diversity peaked in autumn and was lowest in summer. Redundancy Analysis and Spearman correlation identified water temperature (WT), dissolved oxygen (DO), turbidity (NTU), total nitrogen (TN), and water depth (D) as key drivers. PR and SH were positively correlated with DO and negatively with WT/NTU; CG was positively correlated with DO and negatively with NTU/NO3-; SC correlated positively with pH; OM correlated positively with D/Secchi depth. FFG composition was dominated by pollution-tolerant groups, reflecting agricultural and urbanization impacts. This study provides the first FFG-based assessment in the Ashi River, integrating seasonal dynamics, spatial heterogeneity, and multivariate environmental drivers to support functional ecology research in temperate rivers.