ABSTRACT
The 26th December 2004 Indian Ocean Tsunami (IOT) emanated from an Mw 9.2 earthquake that generated a 1600 km-long rupture along the Sumatran Megathrust and generated tsunami waves up to 30 m high. The IOT directly impacted the Bay of Bengal and east Africa, with over 283,000 people perishing. At the time, this catastrophic event was considered unprecedented and sparked intense investigations to test this claim. It is now believed that four pre-2004 IOT events have occurred in the last 2500 years, recurring every 550 to 700 years. Much of this information comes from Phra Thong Island, Thailand, where a sequence of four stacked sandsheets separated by organic units has been recognised and compared to the 2004 IOT event. Recently, ground-penetrating radar on Phra Thong Island identified a region that could not be explained by the known stratigraphy. The stratigraphy of the area was investigated from auger cores and pits, and several previously-unrecognised sandsheets were identified and compared to the known tsunami sandsheets. The proximity of the newly-recognised sandsheets to the palaeo-coastline of Phra Thong Island does not preclude the impacts of localised storms in sandsheet emplacement or that tsunamigenic earthquake recurrence may have been more frequent in the past.
ABSTRACT
The effects of tsunamis on microbial ecologies have been ill-defined, especially in Phang Nga province, Thailand. This ecosystem was catastrophically impacted by the 2004 Indian Ocean tsunami as well as the 600 year-old tsunami in Phra Thong island, Phang Nga province. No study has been conducted to elucidate their effects on microbial ecology. This study represents the first to elucidate their effects on microbial ecology. We utilized metagenomics with 16S and 18S rDNA-barcoded pyrosequencing to obtain prokaryotic and eukaryotic profiles for this terrestrial site, tsunami affected (S1), as well as a parallel unaffected terrestrial site, non-tsunami affected (S2). S1 demonstrated unique microbial community patterns than S2. The dendrogram constructed using the prokaryotic profiles supported the unique S1 microbial communities. S1 contained more proportions of archaea and bacteria domains, specifically species belonging to Bacteroidetes became more frequent, in replacing of the other typical floras like Proteobacteria, Acidobacteria and Basidiomycota. Pathogenic microbes, including Acinetobacter haemolyticus, Flavobacterium spp. and Photobacterium spp., were also found frequently in S1. Furthermore, different metabolic potentials highlighted this microbial community change could impact the functional ecology of the site. Moreover, the habitat prediction based on percent of species indicators for marine, brackish, freshwater and terrestrial niches pointed the S1 to largely comprise marine habitat indicating-species.
