Ultraviolet radiation dose calculation for algal suspensions using UVA and UVB extinction coefficients

•Extinction coefficients (k) for UVA and UVB were calculated using algal suspensions.•Under controlled growth conditions, k may be estimated using OD750.•Beer–Lambert’s law definite integral was used to calculate average UVR intensity.•UVR dose calculations were 2–40 times more accurate than values obtained with previous approaches.

Although the biological importance of ultraviolet light (UVR) attenuation has been recognised in marine and freshwater environments, it is not generally considered in in vitro ecotoxicological studies using algal cell suspensions. In this study, UVA and UVB extinction were determined for cultures of algae with varying cell densities, and the data were used to calculate the corresponding extinction coefficients for both UVA and UVB wavelength ranges. Integrating the Beer–Lambert equation to account for changes in the radiation intensity reaching each depth, from the surface until the bottom of the experimental vessel, we obtained the average UVA and UVB intensity to which the cultured algal cells were exposed. We found that UVR intensity measured at the surface of Chlamydomonas reinhardtii cultures lead to a overestimation of the UVR dose received by the algae by 2–40 times. The approach used in this study allowed for a more accurate estimation of UVA and UVB doses.