Eco-toxicological Assessment of Metal-Microbiome Dynamics in Freshwater Systems: Bacterial Biodiversity Indices and the Novel Composite Metal–Bacteria Interaction Index (CMBII) in Sulaimani, Iraq
Keywords:
Biodiversity of bacteria, Health risk assessment, Heavy metals, CMBII and Water qualityAbstract
This study evaluates the microbial biodiversity and ecological health of the freshwater distribution system in Chamchamal District, Iraq, through an integrated lens of heavy metal stress and bacterial community structure. Over four seasonal campaigns (January–June 2025), 40 samples from ten sites were analyzed for eleven heavy metals and bacterial abundance (TVC and TC). While the Heavy Metal Pollution Index (HPI) remained below critical thresholds (Mean: 44.23), taxonomic stressors such as Mercury and Lead frequently exceeded national standards. Ecological diversity was quantified using Shannon-Wiener (H′) and Simpson (1–D) indices, revealing significant spatial and temporal shifts in bacterial community structure, with diversity peaking in warmer months. A novel Metal-Bacteria Interaction Index (MBII) was developed (MBII = Cd × log10 (1 + Atotal)) to quantify the combined effects of chemical stressors and microbial richness. MBII identified Sites 4 and 9 as critical ecological hotspots (Class III). Spearman correlations revealed significant positive associations between Nickel and bacterial richness (ρ=0.697), suggesting a selective metabolic advantage for certain taxa under metal stress. This study demonstrates that traditional pollution indices may overlook cumulative ecological risks, and the MBII offers a robust tool for assessing biodiversity stability in anthropogenically stressed aquatic habitats.
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