Hope for coral reef rehabilitation: massive synchronous spawning by outplanted corals in Okinawa, Japan
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KeywordsCoral Reef Scleractinian Coral Full Moon Average Water Temperature Larval Supply
Here, we report large-scale synchronous spawning of approximately 2800 colonies of outplanted Acropora tenuis (Dana, 1846) in Maeganeku, Onna, Okinawa. On 26 June 2015, 25 nights after the full moon, almost all outplanted colonies released bundles synchronously for approximately 5 min starting at 1947 hrs, 21 min after sunset (Fig. 1b). Average water temperature from the surface to 4 m depth was 29.4 °C.
There have been concerns about reduction in genetic diversity in reef rehabilitation using asexual propagation methods; however, sexual reproduction by synchronized spawning of outplanted colonies should ensure levels of genetic variation equal to those of natural spawning. Along with increasing larval supply, habitat restoration is crucial for maintaining healthy coral reefs, and under unfavorable environmental conditions, coral larval supply cannot be enhanced efficiently by transplantation and outplanting (Ferse et al. 2013). Continuous observation of recruitment, post-settlement survivorship, and growth in recipient habitats will be needed to determine the effects of spawning events such as that reported here.
The authors thank members of Onna Village Fisheries Cooperative, especially Mr. Masami Yamashiro, Mr. Munekazu Mekaru, and Mr. Yoshimi Higa, and members of Okinawa Prefectural Institute of Health and Environment, especially Mr. Tomofumi Nagata, for field observations. We also thank Dr. Steven D. Aird (OIST) for editing the manuscript.
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