AUTHOR=Cohen Itay , Dubinsky Zvy , Erez Jonathan TITLE=Light Enhanced Calcification in Hermatypic Corals: New Insights from Light Spectral Responses JOURNAL=Frontiers in Marine Science VOLUME=2 YEAR=2016 URL=https://www.frontiersin.org/journals/marine-science/articles/10.3389/fmars.2015.00122 DOI=10.3389/fmars.2015.00122 ISSN=2296-7745 ABSTRACT=

Light enhanced calcification (LEC) is a well-documented phenomenon in reef-building corals. The main mechanism proposed for LEC is that photosynthetic CO2 uptake by the algal symbionts elevates the pH and thus enhances calcification. We evaluated the role of light and of photosynthesis on calcification by assessing the response of the corals Porites lutea and Acropora variabilis to different components of the light spectrum. Calcification and photosynthesis of both species decreased under “lagoon” blue, green and red light (peaks at 500, 550, and 600 nm, respectively). However, blue light (peak at 455 nm) enhanced calcification rates of P. lutea and A. variabilis (up to 4.1- and 10.5-fold of dark values, respectively) reaching levels comparable to those measured under full spectrum illumination. However, contrary to our expectations, photosynthetic oxygen production was considerably reduced under blue light, to the extent that it remained below the compensation point even under illumination as high as 400 μmol photons m−2 s−1. It is the first time that a direct effect of light not mediated by the photosynthetic process has been demonstrated to trigger LEC in corals. We propose that blue light signaling, and animal receptors thereof may be involved in the enhancement of calcification by hermatypic corals.