Outbreak of white syndrome in Acropora spp., temperate region of Japan

Abstract

Coral diseases are a growing concern worldwide, posing another threat to a system already plagued by bleaching and predation. White syndromes (WS) are tissue loss diseases causing mortality on corals globally (e.g., Willis et al. 2004). In Japan,WSwas initially reported in the nation’s largest coral reef area around the Ishigaki-Iriomote Islands (Nature Conservation Bureau 2004) and has since been observed sporadically in northern Japan. This study describes an outbreak of WS in the temperate region of Japan. Hermatypic corals are distributed around Ohshima Island (31°31′N, 131°24′E) (southeast of the main island of Kyushu, Japan), where there is no coral reef development. Conspicuous signs of WS were recognized around this island in July 2014, primarily spreading to the dominant species of the area, Acropora solitaryensis (Fig. 1) and A. japonica, which form large colonies. Almost 25 % of the colonies (41 of 164 colonies examined) of Acropora spp. from shallow to deep water (7–14 m depth) were affected by WS in November 2014. For A. japonica, 50 % colonies were affected. Even in winter (February 2015), when water temperatures dropped to 15 °C, WS-infected corals were still observed. Turbinaria peltata, another dominant coral in this area, has been affected bywhite spot syndrome (Yamashiro and Fukuda 2009), but no WS infections have been observed in this species to date. The water temperature in July and August 2014 was 27 °C, which was lower compared to 2013; however, two strong typhoons hit this region in July (on 10th and 28th), causing heavy turbidity (observation by M.F.). Four typhoons landed on Kyushu in 2014, the most in a decade (mean 2.2 per year; data from Japan Meteorological Agency). Although there is no direct evidence of a causal agent for WS in this area, sedimentation/ turbidity appears to be one possible driver of coral disease, as recently observed in Australia (Pollock et al. 2014).