Evaluation of artificial light regimes and substrate types for aquaria propagation of the staghorn coral Acropora solitaryensis

Stony corals are in high demand in the ornamental aquarium industry, underpinning a substantial global trade. Because coral propagation generally has limited success, the bulk of corals is sourced from wild populations, impacting natural coral reefs. Many stony corals contain symbiotic algae and light is therefore a critical factor. Inadequate light (e.g. intensity, spectral composition) may thus be a main reason for death of stony corals in aquaria. The effects of artificial light sources on corals remain, however, poorly documented. Thus, the chief objective of this study was to determine survival and growth of the staghorn coral Acropora solitaryensis under four metal halide lamps with different Kelvin ratings (5000 K, 10 000 K, 14 000 K, 20 000 K). Additionally, the effects of two substrate types (marble or cement) were tested over 85 days. Corals survived better under lamps of higher Kelvin ratings (≥ 14 000 K), but survival was not affected by substrate type. Similarly, coral growth was significantly faster in light treatments with lamps of high Kelvin ratings, and marginally better on cement blocks. Overall, of the treatments examined in this study, the combination of a 20 000 Kelvin light source with fragments grafted onto cement blocks produced the best survival and growth of the staghorn coral A. solitaryensis in aquaria. This study demonstrates that culture regimes can be identified to improve coral propagation, but these are likely to be species-specific and dependent on the types of lamps used. Because of the high popularity of corals as ornamental aquarium species, the aquaculture industry has the potential to make a valuable contribution to the sustainable use of marine resources by developing appropriate culture techniques for stony corals that reduce wild harvests and their negative environmental impacts on coral reefs.