A toxicity-integrated trait-based framework for ecological vulnerability assessment of Korean freshwater communities exposed to heavy metals.

Conventional ecological risk assessment (ERA) relies on standardized laboratory toxicity data for a limited number of test species and fails to capture the ecological complexity of natural freshwater communities. This study developed an integrated trait- and toxicity-based ecological vulnerability assessment (EVA) framework for Korean freshwater communities exposed to cadmium (Cd), copper (Cu), lead (Pb), and zinc (Zn). Nationwide biomonitoring data (2008-2017) from four major Korean river basins yielded 292 species (209 macroinvertebrates and 83 fish), characterized across 15 biological and ecological traits (80 modalities) using fuzzy coding and hierarchically aggregated from 11 indicators into three functional vulnerability categories: exposure, recovery, and sensitivity. The trait-based assessment identified annelids (Clitellata) as the most vulnerable group (mean = 0.638 ± 0.034), driven by tegumental respiration, ovoviviparous reproduction, and depositional habitat preference, whereas chordates (fish) showed the lowest vulnerability (mean = 0.365 ± 0.048), given high locomotion capacity and large body size. Adding metal-specific toxicity data as a fourth independent category markedly shifted group rankings: bivalves ranked most vulnerable to Zn due to the anomalous sensitivity of Limnoperna fortunei, annelids remained most vulnerable to Cd, Pb, and Cu, and fish vulnerability increased for Cd. Biological traits and toxicity indicators capture complementary dimensions of ecological risk-neither alone is sufficient for community-level characterization. The dual-pathway EVA framework offers a transferable, data-efficient basis for prioritizing at-risk taxa, refining water quality criteria, and guiding ecosystem-based management of Korean river systems.