Nutrient sources and composition of recent algal blooms and eutrophication in the northern Jiulong River, Southeast China

► Eutrophication has been accelerated by human activities worldwide. ► TN:TP mass ratios in nutrient sources and river water were compared in study sites. ► Both external loading and internal nutrient release contributed to algal blooms. ► Damming altered internal nutrient cycles and fueled eutrophication of river waters.