Photodegradation is a natural process that strongly a↵ects the chromophoric fraction of dissolved organic matter (DOM), especially in surface water of the oceans. In the euphotic zone, the concentration and quality of DOM are mostly dependent on primary production by phytoplankton. The e↵ect of photodegradation on algal DOM has not been investigated as much as on terrestrial DOM. In this study, we explored the e↵ect of di↵erent spectral regions (i.e., full sun spectrum, visible light, 295-800 nm, 305-800 nm, and 320-800 nm) on algal exudates by Emiliania huxleyi, a ubiquitous coccolithophore. The optical properties (absorption and fluorescence) of algal DOM were investigated before and after irradiation with the di↵erent spectral regions. The absorption and fluorescence spectra were compared before and after irradiation. The results showed an increase in the e↵ect of photobleaching with increasing irradiation energy for all of the absorbance indices. Similarly, the protein-like fluorescence decreased at increasing irradiation energy. The humic-like fluorescence, which was the most a↵ected, did not show a linear trend between photobleaching and irradiation energy, which suggested that irradiation mainly determined a change in these molecules' quantum yield.