Tsunami Impacts on Biodiversity of Seagrass Communities in the Andaman Sea, Thailand: (2) Abundance and Diversity of Benthic Animals

Abstract

Seagrass beds support highly productive and diverse animal communities. Extreme physical disturbances such as tsunamis are expected to affect the abundance and diversity of both the seagrass and the infaunal community. To examine the effects of a tsunami on infaunal seagrass communities, we compared the communities in seagrass beds before and after the tsunami that hit the Andaman Sea coast of Thailand on December 26th, 2004. Infauna were collected in 2001 and again in 2005 from inside and outside seagrass vegetation. Polychaetes were the most abundance taxa, followed by crustaceans. Density of macrobenthic animals varied greatly among sites, among areas inside and outside the vegetated areas and between the two years. The density increased over time in the areas with seagrass while it deceased in the non-vegetated areas, suggesting that the tsunami impacted the two areas differently. Multivariate analysis on the polychaete assemblage revealed that temporal changes in assemblage structure differed between vegetated and non-vegetated areas, and that the degree of temporal changes in assemblage structure was not necessarily related to the magnitude of the tsunami.