Contrasting consequences of seabed liquefaction on juvenile and adult bivalves during a mega earthquake sequence

Abstract

Mega earthquakes and associated disasters such as seabed liquefaction and tsunamis can have profound impacts on coastal ecosystems. However, the mechanisms underlying these impacts are difficult to identify because of the extreme difficulty of in-situ field observation during a disaster. In this study, we examined the processes by which an earthquake and accompanying seabed liquefaction could affect the Manila clam Ruditapes philippinarum by using a shaking table with control of seismic waveforms and an experimental tank. The clams floated up to the sediment surface (i.e., were expelled from the sediment) during seabed liquefaction because of their low body density in comparison to the density of the liquefied sediments. The magnitude of the liquefaction effect was affected by the clam's body size. Juvenile clams tended to be more affected by ground shaking and liquefaction but were able to quickly reburrow. By contrast, adult bivalves were rarely affected by liquefaction, but if affected they were less able to recover.