The biodegradability of dissolved organic matter （DOM） is a crucial factor in assessing the carbon balance and ecosystem equilibrium of freshwater lakes. It is closely linked to regional hydrological characteristics and biochemical processes. Taking cyanobacterial bloom-dominated bays in Lake Taihu as the research object, combined with characterization by ultraviolet absorption, three-dimensional fluorescence spectroscopy, and bioassay experiments, this study analyzed the temporal and spatial variations of DOM concentration, structural composition, and biodegradable dissolved organic carbon （BDOC） during the rainy and bloom season and the dry and post-bloom season. The results showed that during the bloom season, the release of cyanobacterial-derived organic matter led to a significant increase in DOM concentration in Meiliang Bay and Gonghu Bay, which was mainly composed of protein components, such as tyrosine and tryptophan （>
70%） with a lower aromaticity （SUVA