Figure 1. Light spectra and Symbiodinium absorption.

A) Normalised absorption spectrum of Symbiodinium, and defined scalar irradiance spectra used in the experiments in which the OL 490 light engine was used to simulate the in situ light exposure (‘coral tissue’, blue) and ‘halogen lamp’ (red) exposure (in µmol photons m⁻² s⁻¹ nm⁻¹). The scalar irradiance spectra were normalised to give the same integrated output in µmol photons m⁻² s⁻¹ over PAR (400–700 nm). The absorption spectrum of Symbiodinium was normalised to its peak absorption at 465 nm. B) Photosynthetically usable radiation (PUR; see text).