<p>Algal organic matter (AOM) originates from algal metabolism or the decomposition and release of intracellular substances, constituting a primary component of natural dissolved organic matter in eutrophic water with algal blooms. Recently, researches have increasingly focused on the high reactivity of AOM in complexation, photosensitization, and electron transfer processes. AOM has been suggested as a key player in the fate of contaminants and the biogeochemical cycle of aquatic environments. However, the understanding of the migration and transformation of AOM and its association with water eutrophication remains fragmentary. This study systematically reviewed the photosensitivity, bioavailability, and heterogeneity in molecular characteristics of AOM. It summarized the relationships between AOM and the macro- and micronutrients essential for maintaining normal physiological functions of algae during eutrophic algal blooms. Specifically, the constituents and physicochemical attributes of AOM are closely correlated with the algal species, growth stages, and nutrients. AOM can modulate nitrogen and phosphorus fluxes in sediments and the cycling of iron and manganese, thereby providing conditions for the sustainable algal blooms. Moreover, the contaminant assimilative capacity of eutrophic waters is enhanced due to photosensitization and redox conversion of micronutrients, which are regulated by AOM. The investigation on the properties and environmental behavior of AOM is expected to further clarify the causes of lake eutrophication and internal cycling mechanisms, aiding the integrated management of lake environments.</p>