Effect of light intensity on post-fragmentation photobiological performance of the soft coral Sinularia flexibilis

The soft coral Sinularia flexibilis is currently considered as a suitable candidate for aquaculture. This soft coral is commonly traded for marine aquariums, is used in reef restoration efforts, as well as in the bioprospecting of marine natural products. The production of this coral under controlled laboratory conditions may be the best option for a sustainable and continuous supply of its biomass. It is known that the fragmentation of corals harboring photosymbiotic unicellular dinoflagellates of genus Symbiodinium, commonly termed zooxanthellae, can be influenced by light, as the photosynthetic performance of zooxanthellae can affect coral physiology and growth. This study aimed to investigate the effect of different light intensities on the photobiology of S. flexibilis following ex situ fragmentation. S. flexibilis mother colonies were fragmented after being acclimated for 5 months to a photoperiod of 12 h light with an irradiance of 120 ??mol quanta m-2 s-1. Fragments were then distributed by three light treatments (50, 80 and 120 ??mol quanta m-2 s-1) for monitoring of their photosynthetic performance, photosynthetic and accessory pigment concentration, zooxanthellae density, and growth. No significant differences were recorded one month post-fragmentation on the maximum quantum yield of PSII (Fv/Fm), neither on zooxanthellae density, between fragmented corals placed under tested light intensities. However, zooxanthellae density significantly increased after 5 months in fragments exposed to 50 and 80 ??mol quanta m-2 s-1, while Fv/Fm and pigment concentration decreased under the highest light intensity (120 ??mol quanta m-2 s-1). This study showed that the use of low light levels after fragmentation, in the absence of heterotrophic feeding, do not significantly affect coral growth. Moreover, light levels used after fragmentation should be adjusted according to the intended stocking time of produced coral fragments.The authors would like to thank Jörg Frommlet (SeReZoox project — PTDC/MAR/113962/2009, funded by Fundação para a Ciência e Tecnologia, Portugal) for helping with Symbiodinium genotyping and Catarina Cúcio for her support on the sampling procedures. Rui J. M. Rocha and Miguel C. Leal were supported by a PhD scholarship (SFRH/BD/46675/2008 and SFRH/BD/63783/2009, respectively) funded by Fundação para a Ciência e Tecnologia, Portugal (QREN-POPH — Type 4.1 — Advanced Training, subsidized by the European Social Fund and national funds MCTES). We also thank two anonymous reviewers for their valuable comments to improve the manuscript.publishe