Fig. 1: The study sites at Phra Thong Island (Thailand) and Cuddalore (India) that were both impacted by the 2004 Indian Ocean Tsunami (2004 IOT). Subsequently, in 2007, an unnamed tropical depression caused a storm overwash in the Thailand and in December 2011, the Indian site was inundated by a very severe tropical cyclone Thane.

Location map ((a) is created in QGIS v3.10 while (b) and (e) are satellite images courtesy of Google Earth Pro v7.3.3.7786, Image data © 2019 Terra Metrics, Maxar Technologies) of Phra Thong Island (a, b(i), b(ii)) and Cuddalore, India (a, e(i), e(ii)). The stratigraphy (created in Adobe Illustrator v25.2.1) and the microbial sample collection depths (white dots) from a backdune pit and sediment cores from two swales (Swale X and Swale Y) are illustrated in (c) (top panel). f (bottom panel) shows the stratigraphy and microbial sample depths (white dots) from the backdune pit at Cuddalore. The grain size analysis (Mean (phi) and sorting) of the sediments are included on the right side of the respective stratigraphic diagrams. Environmental samples such as beach, intertidal, lagoon (only for Cuddalore), and marine sediment samples were also collected from both sites (Phra Thong Island: b(ii), d; Cuddalore: e(ii), g). Marine sediment and water samples were collected at 2 m (M1) and 20 m (M2) water depths offshore of Phra Thong Island, and marine sediment and water samples from offshore of Cuddalore were collected at 5 m (m1), 9.5 m (m2), and 15 m (m3) water depths. A schematic cross-section of the study site (created in Adobe Illustrator v25.2.1) is included on the bottom panel for Phra Thong Island (d) and Cuddalore (g). A detailed sample description is listed in Supplementary Data 1.