Large Porites microatoll found by aerial survey at Sesoko Island, Okinawa, Japan
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The hermatypic coral, Porites, grows into a large, solid or flat-topped microatoll, typically comprised of a single coral colony, usually round, and with a flat or concave upper surface devoid of living polyps (Stoddart and Scoffin 1979). The largest reported Porites microatoll in fossil records from the Pacific and southern China was ca. 9 m in diameter (Woodroffe and Webster 2014).
The length of the longest axis is 11.1 m, and the circumference is 33.7 m. The living part of the microatoll (on the outer edge) is circular and 0.5–1.5 m in width. The estimated growth rate of P. australiensis at Sesoko Island is 2.6–10.8 mm yr−1 (Hayashi et al. 2013). At this growth rate, the age of the microatoll is between 500 and 2100 yr. The stable environment at the site could lead to such longevity. Our study highlights the usefulness of drone surveys in the study of coral reef topography.
Comments from Dr. A. Suzuki improved the manuscript. The study was partially supported by JSPS KAKENHI (No. 15K12253).