[Research progress on techniques for artificial propagation of corals]

The natural coral reef resources degrade rapidly because of climate change, environmental pollution and exploitation of aquarium species. Artificial propagation is an effective way to facilitate the reduction of wild harvesting, reef restoration, preservation of biodiversity. This paper reviewed the technique and research progresses focused on coral artificial propagation. We compared the advantages and disadvantages of sexual reproduction and asexual reproduction as well as in situ and ex situ propagation. Moreover, we summarized the important roles of irradiation, flow rate, nutrients, feed and other factors in coral propagation within recirculating aquaculture system (RAS). Irradiation is the key to successful ex situ coral culture and different species show different needs of radiation intensity and light spectrum. Therefore, artificial lighting in RAS, as well as. power and maintenance costs, are very important for ex situ coral aquaculture. In addition, corals are very sensitive to NH4+, NO3-, NO2- as well as phosphate in RAS, and many physical, chemical and biological methods are acquired to maintain low nutrients condition. Although RAS has progressed a lot in terms of irradiation, flow rate and nutrient control, future studies also should focus on sexual reproduction, genetic modification and disease control.