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The reduction in benthic light from natural sediment resuspension events, dredging activities and clouds was quantified over multiple time periods (days to weeks) from a 3-year in-situ field study in the inshore turbid-zone coral communities of the Great Barrier Reef. The results were then used to examine the tolerance levels of three coral species and a sponge to light reduction and associated changes in spectral light quality (in conjunction with elevated sediment concentrations) in a 28-day laboratory-based study. All species survived the exposures but sub-lethal responses involving changes in pigmentation, lipids and lipid ratios were observed. A pocilloporid coral was the most sensitive taxon, with a 28-d EC10 value for bleaching (dissociation of the symbiosis) of 2.7 mol photons m² d⁻¹. The possibility of such light reduction levels occurring naturally and/or during maintenance dredging activities was then …