Ecological disturbances and their relative impacts on coral cover: analysis of monitoring data in Sekisei Lagoon (Okinawa, Japan)

Abstract

Using monitoring data from 1998 to 2017, we examined the spatiotemporal pattern of disturbances that occurred in Sekisei Lagoon, surrounded by Iriomote and Ishigaki islands in Okinawa, Japan. Outbreaks of crown- of-thorns starfish ( Acanthaster cf. solaris ), coral bleaching, typhoon damage, snail predation, and occurrences of growth anomalies, black band disease, and white syndrome were investigated using generalized linear models. Likelihood ratio test indicated that the type of coral assemblage, topographic features, and geographic range of research sites affected the occurrence of each disturbance. The sites dominated by Acropora spp. and the sites located in Sekisei Lagoon suffered recurrent and multiple disturbances. The impacts of disturbances on coral cover were evaluated using generalized additive models. Model averaging using Akaike information criteria revealed that a loss of coral cover occurred even when only a few A. cf. solaris were present, when the bleaching rate was sufficiently high, or when typhoon damage was severe. Our study describes spatiotemporal patterns of disturbances over a 20-yr period and reveals their relative impacts on coral cover. Our findings may be useful in predicting the responses of coral communities to future climate change scenarios.