Innovative methods for the mass production of brooding coral via sexual propagation

Over the past few decades, coral reefs have been rapidly degrading, impacted by climate change, pollution, and tourism, to name a few. In nearly all regions where coral reefs are found, coral cover has declined by 50-75%. One approach to restore coral reefs involves the mass production and subsequent release or transplanting of corals that build reef structures onto degraded reefs. Coral can be mass produced by either asexual (fragmentation) or sexual propagation (the process where an egg is fertilized by a sperm and consequently develops into a larva). The mass production of coral via sexual reproduction maintains the genetic variation, but it is more challenging than the production of corals via fragmentation.
We describe innovative methods to mass produce the brooding coral Stylophora pistillata via sexual propagation. Our focus is primarily on the circumvention of naturally occurring bottlenecks. We describe aspects such as the timing of larval release and their preference when attaching to substrate, as well as growth, caging and orientation in a midwater coral nursery. Efforts are undertaken to reduce the laboratory aspects of coral production and produce corals entirely in the field via the use of a “coral settlement box”.
Tools such as the coral settlement box that can harness the potential of sexual propagated larvae in order to mass produce corals in the field are an invaluable addition to the existing tools available to restore degraded reefs.