Fatty acid signatures of sediment microbial community in the chronically polluted mangrove ecosystem

Highlights: • Microbial lipids and sediment geochemistry in polluted mangrove sediment of Thane were evaluated. • Sediment harboured 40 different PLFA representing 11 microbial functional groups. • Predominance of anaerobes and microalgal remains indicated reduced condition. • Geochemical characteristics best explained the variation in the microbial community. • Shift from G⁺ to G^– microbial community indicated a stressful ecological niche. Phospholipid fatty acid (PLFA) analysis was used to examine variation in the distribution of microbial communities in heavily polluted mangrove sediments of Thane creek, west coast of India. A total of 40 individual PLFAs representing 11 functional groups were identified in the sediment and were mainly dominated by saturated fatty acids (anaerobic prokaryotes) >50%. Significant dominance of PUFA, 16:3 ω6c (34.2%) indicators of micro-eukaryotes, in subsurface depth (p 0.05) suggests input from the remnants of marine microalgae. Declined mean relative abundance of fungi (1), B/F (>1) and G⁺/G^– (<1) ratio and prolonged hypoxia to be prevalent in the creek during the study. In conclusion, PLFA signatures can thus be used as potential biomarkers of environmental monitoring and proxy for interpreting ecosystem health.