Effects of vertical orientation on the photo-physiological health, growth, morphology and survival of intertidally transplanted corals

Coral transplantation on coastal defence structures is an emerging ecological engineering strategy. While past research has focused on transplant suitability and survivability, there is limited knowledge on optimizing seawall designs to accommodate coral transplants. This study investigates the effects of three orientations (horizontal 0°, sloping 45°, and vertical 90°) on the photo-physiological health, growth, morphology and survival of Dipsastraea cf. lizardensis, Platygyra spp. and Porites lutea transplanted intertidally at 0.5–0.6 m above chart datum (CD). After 4.5 mo post transplantation, mortality, growth, coral morphometrics, photosynthetic efficiency (F_v/Fm), total Symbiodiniaceae, and total chlorophyll a were recorded. Results indicate that transplants at 0° grew significantly less and had significantly lower Symbiodiniaceae density and chlorophyll a per cm² as compared to corals transplanted at 45° and 90°. Our findings indicate that Dipsastraea cf. lizardensis and Platygyra spp. are potential candidates for transplantation at 0.5–0.6 m above CD, but not Porites lutea due to high mortality. Future seawalls that are designed to incorporate coral transplants should consider including attachment surfaces angled at 45°or 90°.