Microbial community shifts in deposits from the 2018 Palu-Donggala tsunami

The 2018 Palu-Donggala earthquake in Indonesia generated a devastating tsunami, despite originating from a strike-slip fault, which typically does not produce significant tsunamis. This tsunami was triggered by a combination of subaerial landslides, liquefaction, and submarine landslides. Here, we present the first application of sedimentary environmental DNA to characterize microbial community changes in deposits from a landslide-triggered tsunami. Sediment samples collected 2 months after the event provide a rare snapshot of the near-immediate microbial response to tsunami disturbance. Microbial assemblages derived from 16S rRNA gene sequencing clearly distinguished tsunami deposits from pre-tsunami samples across three sites in Palu Bay, even where conventional sedimentary evidence was inconclusive. The community composition varied among sites, suggesting site-specific environmental filters, which explain the absence of a universal tsunami microbial signature. Tsunami deposits were associated with microbial communities shaped by strong environmental disturbance linked to saline inundation and geochemical change. Microbial communities in the Palu tsunami deposits provide new insight into early microbial responses to extreme coastal flooding events.