Integrated environmental, phytochemical, and genetic assessment of Avicennia marina populations along the Arabian Gulf coast of eastern Saudi Arabia

Avicennia marina dominates mangrove communities along the hypersaline Arabian Gulf, yet links among local habitat conditions, secondary metabolite profiles, and genetic structure remain poorly characterized. This study examined four A. marina stands—Tarout (P1), Saihat (P2), Al Qatif (P3), and Safwa (P4)—near Dammam, eastern Saudi Arabia, integrating field observations, water and pore-soil physico-chemical analyses, GC–MS/MS profiling, SCoT markers, and rbcL barcoding. Sites differed strongly in stand structure, water chemistry, and sediment ion loading, with Tarout, Saihat, and Safwa exhibiting marine–hypersaline waters and Al Qatif more dilute, high-alkalinity conditions but highly saline sediments. GC–MS/MS revealed 27 compounds and a shared flavonoid-rich baseline dominated by 7,3’,4’,5’-tetramethoxyflavanone, superimposed on distinct site-specific terpenoid and phenolic signatures. SCoT markers detected moderate nuclear diversity and clear genetic differentiation among populations, while rbcL sequences, though conservative, resolved low but informative chloroplast structuring. Collectively, the environmental, chemical, and molecular evidence indicates that A. marina in this region comprises a mosaic of locally differentiated, genetically structured stands with distinct chemotypes, providing a preliminary basis for managing these stands as locally differentiated conservation units rather than a single homogeneous resource.