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Burgeoning populace and industrial activities generate different types of anthropogenic wastes that are discharged in the sea with lasting signatures in the coastal sediments. This edaphic study focused on the physicochemical characteristics, heavy metals and microplastics in the mangrove sediments (up to 50 cm depth) at six locations of Mumbai Metropolitan Region (MMR). The results suggest significant anthropogenic pollution with varying contamination levels in sediments of mangrove habitats. Most sampling locations recorded a high Electrical Conductivity (EC) ranging from 18.07 to 6.50 mS cm−1 and Bulk Density (BD) > 1.0 g cm−3. Heavy metal concentrations were significantly distinct between the study locations (pseudo-F = 9.05). Microplastics (MPs) varied in their distribution – Polyethylene (PE: 11.1% to 50%), Polyvinyl chloride (PVC: 20% to 25%) and nylon (11.1% to 28.6%), with unique severity of contamination. Evidence of interactions between heavy metals and microplastic spectral signatures yielded significant positive correlations of C-Cl stretch with Zn (r = 0.843), Cu (r = 0.825) and Cr (r = 0.945) as well as C-H bend (aromatic) with Ca (r = 0.996) and Fe (r = –0.991) that can exacerbate the impacts of pollution. Serene shoreward habitat scored high on the Functional-group Degradation Index (FDI = 0.530) while landward sediments trailed in this metric. Principal Component Analysis (PCA) explained 69.9% variance and confirmed the diverse composition (PC1 = 42.2%) with significant environmental weathering and degradation (PC2 = 27.1%) of MPs. Such pollutant diversity and interactions can coerce marine ecosystems, particularly mangroves and its microbiota, to reduced ecosystem services. Further research can collect evidences for ecotoxicological implications on ecosystem productivity and biodiversity.
Mansuri et al. (Tue,) studied this question.