A simple approach to measuring upper ocean light quality using an underwater camera

Abstract Solar radiation is the fundamental driving force of the Earth’s system. In the upper water column, interactions such as absorption and scattering by water constituents decrease light intensity (photon quantity) and alter light quality (spectral distribution of photons). Although changes in solar intensity have been extensively studied over the years, variations in light quality with depth have received comparatively little scholarly attention. This dearth of research may be due to the lack of simple and cost-effective instruments for measuring light quality, unlike commercial instruments available for measuring solar intensity. In this study, we present a simple approach that uses an underwater camera and a diffuser to measure light quality, represented by the hue angle (HA) of the downwelling irradiance. Our results reveal that the HA from this simple, low-cost device aligns closely with measurements from an expensive hyperspectral radiometer across various water types, ranging from oceanic to coastal waters ( R 2 = 0.94, mean absolute percentage difference = 1.64%). The widespread adoption of this approach could significantly enhance our understanding of the impact of solar radiation on the biogeochemical processes in aquatic environments.