Significant differences in invertebrate assemblages between low- and high-uplifted intertidal shores in the Simeulue Island, Indonesia, after a megathrust earthquake of 2004 and 2005

Abstract

Co-seismic uplift provides significant effects on rocky intertidal assemblages. However, previous studies mainly focused on analysing invertebrate assemblages before and after the uplift event and are conducted in the Pacific Ocean region. The present study evaluated differences in invertebrate assemblages (i.e. species richness, species density, abundance, and composition) between low-uplifted (the uplift of ≤ 75 cm) and high-uplifted (the uplift of > 75 cm) intertidal shores in the Simeulue Island, Indonesia, after a megathrust earthquake of Indian Ocean in 2004 and 2005. The proportion of sediment types (i.e. clay, silt, sand, and gravel) was also analysed to determine their relationships to these assemblages. Invertebrate assemblages on high-uplifted intertidal shores showed lower species richness, higher abundance, and different compositions compared to those on low-uplifted intertidal shores. High-uplifted intertidal shores were dominated by Clypeomorus bifasciata (G.B. Sowerby II, 1855) (a cerithiid gastropod), while low-uplifted intertidal shores were dominated by Calcinus sp. (a hermit crab). Invertebrate assemblages were not significantly influenced by the proportion of most sediment types. These results indicate that co-seismic uplift should be considered in the management of rocky intertidal shores, especially those in the geologically active area.