Polymorphic endogenous releases and the responses of aquatic organisms in a rapidly deteriorating shallow lake

Globally, lakes are currently under considerable stress, with endogenous nutrients a critical driver of eutrophication. This study focused on the release of endogenous nutrients and the ecological response mechanisms in degraded shallow lakes, using Honghu Lake as a case study. Ecological surveys and simulation experiments revealed that the average concentrations of total nitrogen, total phosphorus, and organic matter (OM) in the surface sediments of Honghu Lake are 5148.20 ​mg/kg, 688.10 ​mg/kg, and 13.82%, respectively, but varied spatially. The potential diffusion fluxes of NH 4 + -N and PO 4 3- -P at the sediment-water interface ranged from 0.4471 to 2.1938 mg/(m 2 ·day) (average 1.3130 mg/(m 2 ·day)) and 0.0041–0.0482 mg/(m 2 ·day) (average 0.0237 mg/(m 2 ·day)), respectively. The comprehensive release model indicated that elevated temperature enhanced the release of endogenous nutrients from sediments. At 30 ​°C, the release potentials of total nitrogen and total phosphorus were 3.19 ​± ​0.97 ​g/m 2 and 0.17 ​± ​0.07 ​g/m 2 , respectively. Annually, the lake sediments released approximately 192.4 tons of NH 4 + -N and 3.37 tons of PO 4 3- -P, contributing to 79.52% and 5.66% of the needed nitrogen and phosphorus control requirements, respectively. The release of endogenous sediment nutrients played a vital role in influencing the distribution of various aquatic organisms. Notably, the release of endogenous phosphorus significantly affected the distribution of macrobenthos, whereas zooplankton exhibited greater sensitivity to the release of endogenous nitrogen. • Endogenous pollution influenced the distribution of lake organisms. • The release of endogenous phosphorus significantly affected macrobenthos distribution. • Zooplankton exhibited greater sensitivity to the release of endogenous nitrogen. • 79.52% and 5.66% of the nitrogen and phosphorus need to be controlled from lake sediments.