Effects of irradiance and light spectrum on growth of the scleractinian coral Galaxea

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 275-325 mu mol m(-2) s(-1); and LEP (light emitting plasma) at a PPFD of 40-60, 125-150 and 275-325 mu mol m (2) s (1). Specific growth and survival rates were monitored over a 69-day interval. Mean specific growth rates were 0.031 +/- 0.006 day(-1) for the LED 40-60 treatment, 0.030 +/- 0.007 day(-1) for LED 125-150, 0.022 +/- 0.009 day(-1) for LED 275-325, 0.024 +/- 0.011 day(-1) for LEP 40-60, 0.040 +/- 0.008 day(-1) for LEP 125-150, and 0.031 +/- 0.006 day(-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. (c) 2012 Elsevier B.V. All rights reserved