Mass brooding of the blue octocoral, Heliopora coerulea on a sedimented equatorial reef

摘要

The octocoral Heliopora coerulea is a gonochoric surface brooder. Although the species is common on shallow Indo-Pacific coral reefs, information on its reproductive biology is limited and spawning timings have only been reported from four locations. We report the first observations of surface brooding in H. coerulea on a sedimented equatorial reef. In April 2014, 46 and 26 brooding colonies were recorded, respectively, from reefs fringing the islands of Kusu and Lazarus in Singapore. The brooded coral larvae were tightly bound to inflated coral polyps, forming a dense white mat which blanketed the brown coral tissue. The inflated polyps also protruded from layers of sediment, which accumulated in colony crevices, such that the brooded larvae were elevated above the settled sediment. Our observations supplement existing knowledge on the reproductive timing of H. coerulea and highlight the adaptations that improve survival of this species on sediment-impacted reefs.