Key Takeaways & Executive Findings
- •• • M-IBI core parameters (Chao1, Sobs, Acinetobacter relative abundance, hgcl-clade relative abundance) were identified through rigorous screening, providing a standardized, multi-metric index for river health. • • Seasonal M-IBI scores followed winter > autumn > summer > spring, indicating significant temporal variability in microbial community integrity, with winter exhibiting highest health status. • • Spatial analysis revealed downstream water quality superior to upstream, suggesting longitudinal gradients in pollution load and recovery capacity. • • WQI and M-IBI results were spatially and seasonally concordant, yet M-IBI demonstrated higher sensitivity to human disturbance and environmental changes, offering earlier warning signals for ecological degradation.
Abstract
Urban river ecosystems are increasingly threatened by anthropogenic activities, necessitating comprehensive health assessments beyond conventional water quality metrics. This study evaluates the ecological health of the Zhongshan South Road reach in Wuhu, China, by integrating microbial community integrity with physicochemical parameters. Nine monitoring sections were established, considering land use, pollution sources, and seasonal hydrology. Over four seasons, eight water quality parameters and microbial indicators were systematically monitored. A Microbial Index of Biotic Integrity (M-IBI) was developed through candidate parameter screening, interference response analysis, and discriminant ability assessment. Core metrics included Chao1 index, Sobs index, and relative abundances of Acinetobacter and hgcl-clade genera. M-IBI scores were standardized and classified into health levels, with results compared against the Water Quality Index (WQI). Findings revealed seasonal M-IBI variation: winter > autumn > summer > spring, with downstream water quality superior to upstream. Spatial and seasonal patterns of WQI and M-IBI were largely concordant, though discrepancies arose from differential microbial responses to environmental factors and heightened sensitivity to human disturbance. The M-IBI approach demonstrated robust applicability for river health assessment, offering a sensitive, integrative tool for urban water management.
1. Introduction
Conventional river health assessments rely heavily on physicochemical water quality indices (WQI), which, while effective for regulatory compliance, often fail to capture the ecological integrity of aquatic ecosystems. These indices overlook the biological community's response to cumulative stressors, leading to underestimation of ecological degradation. The need for bioassessment tools that integrate structural and functional aspects of aquatic life has become critical, particularly in urban rivers subjected to complex pollution sources and hydrological alterations.
This study addresses this gap by employing the Microbial Index of Biotic Integrity (M-IBI), which leverages the sensitivity of microbial communities to environmental perturbations. Unlike traditional WQI, M-IBI incorporates multiple microbial metrics, providing a holistic view of ecosystem health. By comparing M-IBI with WQI across seasons and spatial gradients, this research demonstrates the added value of microbial indicators in detecting subtle ecological changes, thereby offering a more robust framework for urban river management and restoration.
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FAN Tingyu, WAN Yi, WANG Shun, WANG Xingming, LU Akang (2026). River Ecological Health Assessment Based on Microbial Integrity Index and Water Quality Index. Environmental Chemistry. https://doi.org/10.7524/j.issn.0254-6108.2024110703
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Frequently Asked Questions
What are the specific microbial metrics used in the M-IBI and how were they selected?
The M-IBI incorporated Chao1 index (species richness), Sobs index (observed species), and relative abundances of Acinetobacter and hgcl-clade genera. These were selected through candidate parameter screening, interference response analysis, and discriminant ability assessment, ensuring they effectively differentiated between disturbed and reference sites.
How does M-IBI compare with WQI in terms of sensitivity to environmental stressors?
M-IBI exhibited higher sensitivity to human disturbance and environmental changes compared to WQI. While both indices showed concordant spatial and seasonal patterns, M-IBI detected more pronounced variations, indicating its potential to serve as an early warning indicator for ecological degradation.
What were the seasonal trends in M-IBI scores and what factors contributed to these patterns?
M-IBI scores followed winter > autumn > summer > spring. This trend likely reflects seasonal variations in temperature, hydrological conditions, and pollution loads, which influence microbial community composition and function. Winter's higher scores suggest lower anthropogenic stress and more stable environmental conditions.
Can the M-IBI approach be applied to other urban rivers with different pollution profiles?
The M-IBI framework is transferable, but core metrics may need recalibration based on local microbial communities and environmental conditions. The methodology—screening candidate parameters and validating discriminant ability—ensures adaptability to diverse river systems.
What are the implications of this study for urban river management?
Integrating M-IBI with WQI provides a comprehensive assessment, enabling managers to identify not only water quality issues but also ecological health degradation. This dual approach supports targeted restoration efforts and prioritization of pollution control measures, particularly in upstream areas where M-IBI indicated lower health.
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