Predicted shifts in microbial functional potential across the late glacial to holocene transition: a 16S rRNA-based inference from southeastern Arabian Sea sediments.

Marine sediments preserve valuable records of ancient microbial communities. In this exploratory study, direct environmental amplicon sequencing reconstruction is often constrained by DNA degradation. In this exploratory study, we applied predictive functional profiling (PICRUSt2) to 16S rRNA gene amplicon data from five discrete sediment horizons spanning ~14.400 years (Bølling-Allerød, Younger Dryas, Early Holocene, Mid-Holocene, and Late Holocene) in the southeastern Arabian Sea. Inferred functional profiles based on Clusters of Orthologous Groups (COGs) pointed to variations in the predicted abundance of genes associated with carbon metabolism-specifically COG0183 (Acetyl-CoA acetyltransferase) and COG1024 (Enoyl-CoA hydratase/carnitine racemase)-and transport systems. Notably, the predicted potential for carbon metabolism reached its peak during the early Holocene, suggesting possible changes in carbon cycling dynamics during this warming phase. Principal component analysis accounted for 68.7% of the variance in predicted functions across time periods. While these findings are predictive and rely on amplicon-based inference, they provide a preliminary model of microbial functional reorganisation during major climate transitions, offering hypotheses for future high-resolution metagenomic validation.