Contrasting Structural Changes in Two Benthic Invertebrate Communities After an Extraordinary Rainfall Event in Liuqiu Island, Taiwan

Abstract

This study compared the changes in benthic community structures of the Shanfu (SF) and Duozaiping (DU) coral reef intertidal zones of Liuqiu Island between 2020 and 2022 after a prolonged precipitation event between late July and early August 2021. The trend of extreme rainfall on the island was also explored using the Standardized Precipitation Index (SPI) for coastal management use. The adjacent study sites of SF and DU have areas of 16,203 and 31,930 m², respectively. Variations in the diversity indexes between sites (SF and DU) and years (2020, 2021, and 2022) were determined by two-way ANOVA tests. SF and DU differed significantly in species density, richness, dominance, diversity, and evenness indexes. Site factor had a more significant effect than year on these indices. The benthic community at DU was distinctly clustered into before, after, and 1-year after rainfall groups, but this was not the case for SF. Echinodermata was the taxon primarily responsible for the differences. Based on the meteorological data from 1997 to 2022, the SPIs varied from -1.83 (severe drought) to +1.90 (severe precipitation). Temporally, precipitation intensity and frequency increased during 2016-2021 compared with 2000-2006, with a peak precipitation event of 1,168 mm rainfall over 14 days in 2021. The broader reef flat at DU may have resulted in thermal and salinity stresses lasting longer for stenohaline echinoderms than at SF. Results from this island highlighted the differential vulnerability of the benthic communities from different sites to natural disturbances for the first time, allowing policymakers and stakeholders to formulate effective regional management strategies to minimize the impact of extreme climate events.

Keywords: Climate change; Diversity index; Echinoderms; Low salinity; SPI; Standardized Precipitation Index.

Fig. 1.

The study area and sampling sites in Liuqiu Island, Taiwan.

Fig. 2.

K-dominance curves of the benthic communities at (a) Shanfu (SF) and (b) Duozaiping (DU) in 2020–2022. (n): the number of species.

Fig. 3.

The composition and density of invertebrate taxa at (a) Shanfu (SF) and (b) Duozaiping (DU) in 2020–2022.

Fig. 4.

Dendrograms of the hierarchical clustering of the benthic communities based on Bray-Curtis similarities at (a) Shanfu (SF) and (b) Duozaiping (DU) in 2020–2022.

Fig. 5.

The contribution of each species in the benthic communities of (a) Shanfu (SF) and (b) Duozaiping (DU) to the first and second principal component scores in 2020–2022.

Fig. 6.

The precipitation records in Liuqiu Island from 1997 to 2022. (a) Annual precipitation (mm) and SPI (standardized precipitation index) values; (b) annually maximum consecutive precipitation days and its total precipitation (mm); (c) daily precipitation (mm) from May to September in 2021. Data source: Central Weather Administration, Taiwan, ROC.