T86 Advances and New Voices in Marine and Coastal Geoscience

Monday, 16 October 2023
8:00 AM - 12:00 PM
325

USING ENVIRONMENTAL DNA TO INVESTIGATE HISTORICAL RECORD OF STORMS AND TSUNAMIS

Paper number: T86-10
Program: Technical Sessions
Time: 10:10 AM – 10:30 AM

Authors

Abstract

Studying geological records of storms and tsunamis events is essential for understanding coastal long-term risk and vulnerability. However, distinguishing storm and tsunami deposits in the records is challenging due to their similar features, and the post-depositional deterioration of indicators. To address this, we explore using environmental DNA (eDNA) analysis in coastal hazard geological records. eDNA analysis allows simultaneous detection of multiple organisms using samples from the environment, such as sediment, soil, and water. Taking advantage of this innovation, we conducted a comprehensive investigation in three case studies from Asia.

First, we investigate eDNA approach’s ability to differentiate storm and tsunami overwash deposits. We collected sediment samples from Phra Thong Island, Thailand, and Cuddalore, India, where both locations were impacted by the 2004 Indian Ocean Tsunami followed by a storm. The multivariate analysis showed significant microbial community differences between overwash deposits and non-overwash soil and sediment (p-value < 0.0001).

Second, we examine the capability of the eDNA approach in characterizing tsunami deposits when there is limited grain size evidence. We collected sediment samples from Palu, Indonesia, impacted by the 2018 Palu-Donggala earthquake and tsunami. Our results showed significant microbial community differences between tsunami and pre-tsunami layers (p-value = 0.003).

Third, to address the preservation limitation of tsunami indicators, we extend our eDNA analysis to a sequence of palaeotsunami deposits in Phra Thong Island, Thailand. We found distinct microbial communities in the tsunami deposits compared to the overlying and underlying mud layers (p-value = 0.0269). However, these differences faded in sediment layers > 2,800 years.

In conclusion, our studies demonstrate the potential of eDNA analysis in advancing storm and tsunami reconstructions from geological records. By integrating eDNA as a proxy, we overcome some limitations associated with other indicators, allowing precise differentiation between storm and tsunami overwash deposits. Although challenges persist in distinguishing older overwash deposits, our work represents a significant step in documenting prehistorical coastal hazards and their impact on coastal communities throughout history.

Geological Society of America Abstracts with Programs. Vol. 55, No. 6

doi: 10.1130/abs/2023AM-395477

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