Modeling the Interplay between Phosphorus Dynamics and Sediment Diagenesis in a Eutrophic Lake

Abstract

In this study, we investigated phosphorus cycling in the Bay of Quinte, an embayment of Lake Ontario, Canada. Despite the large decline in external P loading to the Bay of Quinte during the last decades, it still experiences harmful cyanobacterial algal blooms, which may be connected to nutrient loading from sediments. Nevertheless, the dynamics of nutrient loading from sediments remains mostly unknown. Thus, we applied a non-steady-state diagenesis reaction–transport model to evaluate the impact of organic matter loading on oxygen demand and to conduct specific modeling scenarios to investigate the impact of organic matter loading on the seasonal dynamics of phosphorus release, and burial efficiency in three different basins of the bay: Belleville, Napanee, and Hay Bay. Our modeling framework integrates physical and biogeochemical processes at the sediment–water interface and incorporates dynamic boundary conditions, such as oxygen, soluble reactive phosphorus concentrations, and organic matter sedimentation at the sediment–water interface. Our scenarios suggested that phosphorus release and burial efficiency can profoundly respond to shifts in sedimentation conditions. At all three studied stations, phosphorus burial efficiency did not change significantly after the scenario year 2034, when we reduced the flux of organic matter by 20%. Meanwhile, phosphorus release at stations Belleville and Napanee was significantly reduced in 2034 compared with the present condition. The 20% reduction in the flux of organic matter at station Hay Bay may not be large enough to remarkably reduce phosphorus release.

Keywords: Eutrophic lakes, phosphorus release; phosphorus burial efficiency, sediments; diagenetic modelling.