Evaluation of the Potential Release Risk of Internal N and P from Sediments—A Preliminary Study in Two Freshwater Reservoirs in South China

Abstract

Growing evidence has demonstrated the influence of internal nitrogen (N) and phosphorus (P) on harmful algae blooms in eutrophic freshwater ecosystems. However, the main controlling factors for internal N and P release risks, and whether these factors vary as environmental conditions change, remains poorly understood. We evaluated potential release risks of N and P from sediments in two freshwater reservoirs in Beihai City, southern China, by evaluating apparent nutrient fluxes during simulated static incubation experiments at two temperatures (15 °C and 25 °C). Sediments were analyzed to determine their basic properties as well as N and P fractions. Results showed that the main controlling factors of the apparent fluxes in dissolved total P, soluble reactive P, total N, and ammonium were related to sediment adsorption properties, redox properties, and microbial-mediated properties (e.g., water-extractable P, total inorganic N, redox-sensitive P, total organic carbon, organic P). The primary controlling factors for apparent N and P fluxes were dependent on the form of N and P and changed with temperature. The results suggest that care should be taken when simply using total N and P contents in sediments to evaluate their internal nutrient release risks.

Exploring the Drivers of Spatiotemporal Patterns in Fish Community in a Non-Fed Aquaculture Reservoir

“…The study was performed at Hongchaojiang Reservoir in the Guangxi Zhuang Autonomous Region, China (21 • 52 5 N, 109 • 7 35 E). To reduce the risks of eutrophication and algal blooms, non-fed aquaculture was implemented in the reservoir, with abundant filter-feeding fish such as Hypophthalmichthys molitrix and Hypophthalmichthys nobilis stocked from 2012 [27,29,38].…”

“…The Hongchaojiang Reservoir was originally one of the typical large aquaculture reservoirs. With the recent expansion of aquaculture production, aquaculture effluents result in eutrophication and environmental degradation, which increasingly reduces ecosystem productivity and resilience of ecosystems [27][28][29][30][31]. High concentrations of inorganic anions, such as phosphates, nitrates, and ammonia, coupled with organic nitrogen and/or heavy metals have been found in the sediment of the water body [32].…”

A Comparison Study of the Nutrient Fluxes in a Newly Impounded Riverine Lake (Longjing Lake): Model Calculation and Sediment Incubation

“…Flux studies were effective methods used as an assessment of the risk associated with contaminated sediments [9,10]. There were mainly two kinds of methods to determine the fluxes of compounds released from the SWI [11].…”