Optimizing sexual reproduction of Montipora capitata for restoration: effects of abiotic conditions and light acclimation on juvenile survival and growth

Abstract

The worldwide decline of coral reefs necessitates development of tools and methods for active conservation of reef structures and their ecological function. Aquaculture of sexually produced corals is a potential strategy for reef restoration efforts, but existing methods require greater scalability and optimization. To address these needs, we reared Montipora capitata larvae from Kāne’ohe Bay and raised them in an ex situ facility to examine patterns of growth and survivorship under different abiotic conditions, building from previous best practices and manipulating light levels during early life-history stages. Larvae were reared using different stocking densities and settled at varied densities (25, 125, and 225 larvae per plug) on conditioned plugs (1 or 4 wk). Juveniles were raised and tracked under different flow, shade, and light acclimation regimes for 135 d. Results show that recruitment increased with settlement density. Juvenile survivorship was maximized in high flow and intermediate shade levels, while growth was maximized by low shade environments in both aggregate and individual settlers. Light acclimation treatments yielded intermediate survivorship and tradeoffs between growth and survival compared to corals reared in static shade conditions. Importantly, no abiotic treatment combinations optimized growth and survivorship simultaneously. This study demonstrates interactions of abiotic factors and provides insight into how they can be manipulated to scale the sexual reproduction of corals for conservation.