Effects of irradiance and light spectrum on growth of the scleractinian coral Galaxea fascicularis — Applicability of LEP and LED lighting to coral aquaculture

Abstract

Due to global degradation of coral reefs and high demand for scleractinian corals, aquaculture of these marine organisms is gaining importance. To make coral aquaculture economically viable, optimisation of culture protocols is vital. We determined the effects of irradiance and light spectrum on the growth of a model scleractinian coral species, Galaxea fascicularis (Linnaeus 1767). Single polyps (n=10) were cultured under six different treatments; LED (light emitting diode) at a PPFD of 40–60, 125–150 and 275–325μmolm−2s−1; and LEP (light emitting plasma) at a PPFD of 40–60, 125–150 and 275–325μmolm−2s−1. Specific growth and survival rates were monitored over a 69-day interval. Mean specific growth rates were 0.031±0.006day−1 for the LED 40–60 treatment, 0.030±0.007day−1 for LED 125–150, 0.022±0.009day−1 for LED 275–325, 0.024±0.011day−1 for LEP 40–60, 0.040±0.008day−1 for LEP 125–150, and 0.031±0.006day−1 for LEP 275–325. Coral survival rate at the end of the growth interval was 95%. A significant main effect of irradiance on coral specific growth rate was found (factorial ANOVA, P=0.018), whereas spectrum did not show a significant main effect (factorial ANOVA, P=0.085). A significant interactive effect between irradiance and spectrum was found (factorial ANOVA, P=0.013), as LEP lighting resulted in higher coral growth rates at the two higher irradiance levels applied. The effect of irradiance and its interaction with spectrum were likely modulated by water flow rates. Our results show that balanced as well as light sources skewed towards the blue part of the spectrum result in high coral growth. Specifically, LEP and LED have shown to be suitable lighting technologies for coral aquaculture, where LEP yields higher G. fascicularis growth rates at higher irradiance levels.