Metabarcoding reveals unique rhizospheric microbiomes of Rhizophora in Indian Mangroves

Rhizophora species are ecologically significant true mangroves with a broad tropical distribution. We examined the rhizospheric microbiomes of dominant Rhizophora species from two contrasting Indian mangrove ecosystems-Coringa and Pichavaram-using high-throughput metabarcoding. Soil properties differed significantly between sites: Pichavaram exhibited higher electrical conductivity (24.53 dS/m), organic carbon (1.70%), sodium (8811.86 ppm), sodium adsorption ratio (220.15), and exchangeable sodium percentage (64.27%), while Coringa soils showed higher pH (8.01). Sequencing generated 1.31, 1.24, and 1.22 million high-quality reads for archaea, bacteria, and fungi, respectively. Taxonomic profiling revealed Nitrososphaeria (62.3-91.9%), Gammaproteobacteria (16.8-25.1%), and Sordariomycetes (18.6-27.8%) as dominant classes. Core taxa across both sites included Candidatus Nitrosopumilus, Woeseia, and Aspergillus. Alpha diversity indices (Chao1, Shannon, Simpson) indicated significantly higher bacterial richness and evenness in R. apiculata at Coringa (P < 0.001), while archaeal and fungal diversity showed no marked differences. Beta diversity analysis (PCoA, PERMANOVA) revealed distinct community compositions between Coringa and Pichavaram, with stronger segregation in archaeal and bacterial assemblages than in fungi. Differential abundance analysis identified nine archaeal, fifty-nine bacterial, and three fungal genera enriched between sites, with methanogens (Methanosarcina, Methanocella) predominant in Coringa and halophiles (Halococcus, Haloferax) in Pichavaram. Redundancy analysis showed sodium adsorption ratio as the key determinant of microbial assemblages, while electrical conductivity significantly shaped archaeal and fungal communities. These findings provide the first baseline dataset of the Coringa rhizospheric microbiome and new insights into the microbial ecology of Indian mangroves, with implications for ecosystem functioning, methane emissions, and conservation strategies.