Anthropogenic influences such as urbanization, agricultural intensification, use of chemical fertilizers,and the release of sewage emit nutrients (nitrogen and phosphorus) into freshwater lakes. Excessiveamounts of nitrogen and phosphorus lead to eutrophication, which is a global water quality concern,with typical impacts such as the growth of harmful algal blooms, hypoxia and fish kills. The currentwater quality indicators used to monitor lake eutrophication focus only on water quality constituents(e.g., total phosphorus and total nitrogen). The response of lakesto nutrient inputs, however, dependson its interaction with climate, basin characteristics that include land use, hydrology andanthropogenic activities. In this study, we present a set of comprehensive indicators that account fornutrient sources and biogeochemical pathways in the lake basins and demonstrate their interactionsusing a causal network. The causal network provides a holistic perspective of nutrient dynamics andthe interactive effects of the indicators on water quality in lake basins, which is key to improving waterquality management. The indicators from this study can be used as proxies to monitor water qualitystatus. The comprehensive indicators improve mechanistic understanding of the lake nutrientdynamics, by systematically considering mechanisms of sources and factors of nutrients emission inthe basin. They can consequently fill the gap in water quality monitoring data, especially in data scarceregions such as Asia and Africa. These indicators can be used to set realistic water quality targets andare therefore beneficial in long-term policy making and sustainable water quality management
