Abstract

Eutrophication, driven by nutrient accumulation, alters species composition, food chains, and nutrient cycling in aquatic ecosystems. In the Fushan Ecological Pond, nutrient inputs have led to flourishing aquatic plants, indicating a shift towards eutrophic conditions. This study conducted in October 2020 analyzed water flow, quality, and nutrient concentrations to construct water and nutrient budgets for exploring nutrient stocks and flows in the pond. The results show that the Fushan Ecological Pond was approaching eutrophic condition. The water budget shows that the change of water capacity was 2.95 m3 h-1, and the residence time was as long as 45.7 days, indicating that the water body was poorly flushed. In the nutrient budget, 61% of nitrogen came from the surface runoff, and 92% of the phosphorus input was contributed by the release from sediment. The submerged plant Hydrilla verticillate absorbed most of the nitrogen, and Spirogyra sp. absorbed most of the phosphorus. The nitrogen and phosphorus budgets show that 0.100 g N h-1 and 0.437 g P h-1 were accumulating in the pond. Collectively, this study suggests that future management efforts should focus on reducing N input from the inlets by installing simple constructed wetlands at the inlets to purify the water entering the pond. To mitigate nutrient accumulation, management should reduce nitrogen input via constructed wetlands and prevent sediment disturbance to limit phosphorus release. These actions would help mitigate the ongoing accumulation of nutrients in the pond and improve its ecological condition and function.

Keyword: Eutrophication, nitrogen budget, phosphorous budget, residence time, water budget