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

Abstract

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 5months to a photoperiod of 12h light with an irradiance of 120μmolquantam−2s−1. Fragments were then distributed by three light treatments (50, 80 and 120μmolquantam−2s−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 5months in fragments exposed to 50 and 80μmolquantam−2s−1, while Fv/Fm and pigment concentration decreased under the highest light intensity (120μmolquantam−2s−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.