Sediment Phosphate Release Flux Under Hydraulic Disturbances in the Shallow Lake of Chaohu, China

Quantifying the effect of hydraulic disturbances on sediment phosphate release is a key issue in the water quality assessment of lakes, especially for the shallow lakes which are susceptible to winds and waves. Here, we sampled the original sediment columns from 12 positions in the eastern, central, and western areas of the Chaohu Lake, a representative shallow lake in China, and observed phosphate release under three levels of hydraulic disturbances in the laboratory. When the disturbance was weak and the surface sediment of bottom mud moved individually (the Individual Motion Mode), sediment phosphate release rate was insignificant (0.24 mg/m2/d). When the disturbance was medium and only a small percentage (<16%) of surface sediment started to move (the Small Motion Mode), phosphate release rate sharply increased to 4.81 mg/m2/d. When the disturbance was further strengthened and most (≥16%) of the surface sediment moved (the General Motion Mode), phosphate release rate was more than doubled (10.23 mg/m2/d). With the increase of hydraulic disturbance intensity, the variation range of phosphate release also became wider. Spatial distribution showed that the release rate varies the most in the western area, followed by the eastern and the central areas. By extrapolating the experimental results to the real scale, we found the phosphate release fluxes would probably fall within a wide range between 203.43 kg/d to 7311.01kg/d under different levels of hydrodynamic disturbances with considerably affects phosphate release from shallow lakes. This study also has implications for the pollutant management in other shallow lakes.

Dynamics and Economics of Shallow Lakes: A Survey

We provide an overview of the results devoted to the analysis of the dynamics and economics of shallow lakes, spanning the period from 1999 until now. A shallow lake serves as a typical representative of an ecological system subject to (possibly irreversible) regime shifts. The dynamics of a shallow lake are described by a non-linear model with multiple steady states and multiple domains of attraction and is thus suitable to model the evolution of an ecosystem featuring both resilience within a domain of stability and an abrupt regime shift outside of it. Beyond this, the shallow lake model can also be viewed as a metaphor for many other ecological problems. Due to the broad applicability of this model, there is substantial interest in the management of shallow lakes and both their optimal regulation and competitive usage.