Macroinvertebrate-Based Ecological Health Assessment of Main River and Canal Systems in the Mekong Delta: Challenges and Future Directions

Abstract

Macroinvertebrate-based ecological health assessment (EHA) complements physicochemical monitoring in tropical deltas by integrating cumulative ecological responses to interacting stressors. The Vietnamese Mekong Delta is shaped by monsoonal discharge, tidal mixing, fine-sediment dominance, salinity gradients, and a heavily modified canal network unique conditions that pose significant bioassessment challenges unaddressed by generic, temperate-river frameworks. This review synthesizes approximately 83 peer-reviewed and grey-literature sources (1991–2026) to evaluate the application of macroinvertebrate-based EHA, contrasting evidence from main rivers and artificial canal systems. We identify a fundamental ecological dichotomy: main river assemblages exhibit strong monsoon–tide seasonal turnover, whereas canal networks reflect chronic degradation marked by biotic homogenization and a dominance of pollution-tolerant taxa. Across the literature, current assessments are fundamentally constrained by profound methodological biases, including a geographic underrepresentation of canal systems, a pervasive dry-season sampling bias, a reliance on higher-taxon identification, and the inconsistent transferability of uncalibrated temperate indices. To advance EHA in the Mekong Delta, future research must prioritize typology-based frameworks that explicitly distinguish rivers from canals. Furthermore, we advocate for the integration of trait-based metrics and molecular tools (eDNA/metabarcoding) alongside coordinated, multi-season monitoring to establish robust, locally calibrated pressure–response models for sustainable regional water management.