Comparative performance of light emitting plasma (LEP) and light emitting diode (LED) in ex situ aquaculture of scleractinian corals

Abstract

Ex situ aquaculture of scleractinian corals is considered as a sustainable solution to fulfill the growing demand of these highly priced organisms by themarine aquarium industry. The economic feasibility of ex situ coral aquaculture is strongly dependent on the trade-offs achieved between coral production and energy costs, namely those directly resulting from the need to employ artificial lighting systems. In the present study, we hypothesize that light spectrum can influence the growth performance of cultured scleractinian corals when these are exposed to identical photosynthetically active radiation (PAR) intensities. To test our hypothesis we evaluated the effect of contrasting light spectra delivering an identical PAR of 250 ?? 10 ??mol quantam-2 S-1emitted by T5 fluorescent lamps (used as a control treatment), Light Emitting Plasma(LEP) and Light Emitting Diode (LED) on the photobiology, growth, and protein concentration of two commercially important scleractinian corals: Acropora formosa and Stylophora pistillata. Replicated coral fragments of both species were exposed to the three types of illumination for a period of 5 months after which the following features were determined: maximum quantum yield of PSII (Fv/Fm) (monitored non-intrusively through Pulse Amplitude Modulation fluorometry, PAM), chlorophyll a content (also determined non-destructively by using the spectral reflectance index Normalized Difference Vegetation Index, NDVI), growth and protein content. Coral fragments of both species cultured under LEP lighting, presented significantly higher values of Fv/Fm when compared intraspecifically with coral fragments cultured with T5 or LED lighting. Fragments of S. pistillata cultured under LEP illumination presented significantly higher NDVI values than fragments grown with T5 or LED. No significant differences were found on the protein concentration of A. formosa under different light treatments, while fragments of S. pistillata grown with LED illumination presented a significantly higher concentration of protein than those cultured with T5 or LEP illumination. Both LED and LEP technologies have shown to be interesting alternatives to provide artificial lighting for coral aquaculture ex situ, with the blue light spectrum of LED promoting high growth performances for both coral species and a lower energetic cost per m2 of production area (0.71 ??? m-2 day-1 for T5, 0.38 ??? m-2 day-1 for LEP, and 0.28 ??? m-2 day-1 for LED).