Taxonomic Profiling of Bacterial Communities Associated with Metals in the Tar Mats and Cyanobacterial Mats of the Qatar Coast, Arabian Gulf.

Tar mats are the final weathered petroleum residues derived from natural or human-induced incidents that form mats of varying sizes along the intertidal or coastal zones following prolonged environmental exposure. This study investigates the bacterial communities associated with tar mats from two distinct coastal areas of Qatar: Ras Rakan (an uninhabited island) and Al Khor (an anthropogenically influenced coast), using 16 S rRNA gene sequencing of the V3–V4 regions. The results showed the dominance of Proteobacteria across all samples, and notably higher relative abundances of Thermovirga, Salinivibrio, Synechococcus IR11, and Arcobacter in samples from Ras Rakan compared to Al Khor. Elemental analysis of tar mat samples from Ras Rakan showed notable differences in concentrations across sample types, with higher concentrations of the major elements Ca, Mg, Al, and Fe, as well as petroleum-related elements such as Cu, Ni, and V. The occurrence of genera is probably linked to high concentrations of heavy metals, enabling bacteria to respond to the tar-contaminated environment. Positive correlations were observed between heavy metals and several taxa, including Synechococcus spp., highlighting the potential role of cyanobacteria in metal biosorption and hydrocarbon-associated cyanobacterial consortia. The correlation between these metals and cyanobacterial diversity highlights the importance of metal-microbe interactions in understanding the ecological consequences of oil contamination in coastal environments.