Changes in Nutrient Concentrations and Limitations of Poyang Lake Associated with Socioeconomic Development in the Watershed from 1978 to 2021

Socioeconomic development often leads to environmental pollution and degradation initially while, beyond a certain point, there is the potential for improvements in environmental quality. In this study, we conducted a comprehensive review of published literature and national data to investigate changes in nutrient concentrations and limitations in Poyang Lake from 1978 to 2021. Our objective was to examine the relationships between these changes and the process of socioeconomic development in the watershed. The findings revealed a rapid socioeconomic development of the Poyang Lake Watershed, showing significant changes in various indexes. For example, population, Gross Domestic Product (GDP), urbanization, grain and meat productions, sewage amount and treatment rate, and forest coverage in the watershed showed increasing trends with different fitting curves, each following distinct fitting curves such as exponential, binary, and linear models. Concurrently, the concentrations of total nitrogen (TN) and total phosphorus (TP) in Poyang Lake exhibited a linear increase over the years, surpassing eutrophication thresholds since the early 1980s. However, TN and TP have shown a decreasing trend in recent years. Notably, the lake displayed co-limitation by N and P, with TN primarily driving the N:P ratio. TN and TP showed a significant “∩” shape with the increase in GDP and urbanization, while they increased with the population. TN:TP showed an increasing pattern with GDP and urbanization but a “U” shape with the population. This research contributes significant insights into the long-term changes in nutrient concentrations, shifts in nutrient limitations, and their associations with socioeconomic development. The findings highlight the need for a balanced and strategic approach to appropriately manage both nutrients for effective eutrophication mitigation.