Ex situ reproduction and recruitment of scleractinian coral Galaxea fascicularis

Sexual reproduction plays an important role in population and community structure maintenance in scleractinian corals, particularly in growth and development after larvae settlement. Despite this, only a few studies have been conducted to monitor the post-settlement growth and development of scleractinian coral larvae. Our study aimed to inform this question by collecting adult Galaxea fascicularis colonies from Weizhou Island (21°00′–21°10′ N, 109°00′–109°15′ E) and recording their early life cycle, from fertilization to recruitment, for one year ex situ. The results demonstrated that G. fascicularis could reproduce sexually when reared in a pond for 2 y. The spawning occurred in April and May, in synchrony with wild corals. Larvae showed association with zooxanthellae 9 d after spawning (4 d after settlement) and completed metamorphosis after 1 month. The mean diameter of G. fascicularis recruits was 4.74 ± 1.12 mm in the first year, which was lower than that reported in the literature for other broadcast corals. The recruits’ survival rate decreased continuously every month, with the most severe decline occurring in the second month, from 80.87% to 50.82%. By the end of the first year, the final survival rate was 5.46%, which may be attributed to their competition with algae. This study improved our understanding of the early life cycle of scleractinian corals.