Coupling Water Column and Sediment Biogeochemical Dynamics: Modeling Internal Phosphorus Loading, Climate Change Responses, and Mitigation Measures in Lake Vansjø, Norway

Abstract

We expanded the existing one‐dimensional MyLake model by incorporating a vertically resolved sediment diagenesis module and developing a reaction network that seamlessly couples the water column and sediment biogeochemistry. The application of the MyLake‐Sediment model to boreal Lake Vansjø illustrates the model's ability to reproduce daily water quality variables and predict sediment‐water column exchange fluxes over a long historical period. In prognostic scenarios, we assessed the importance of sediment processes and the effects of various climatic and anthropogenic drivers on the lake's biogeochemistry and phytoplankton dynamics. First, MyLake‐Sediment was used to simulate the potential impacts of increasing air temperature on algal growth and water quality. Second, the key role of ice cover in controlling water column mixing and biogeochemical cycles was analyzed in a series of scenarios that included a fully ice‐free end‐member. Third, in another end‐member scenario P loading from the watershed to the lake was abruptly halted. The model results suggest that remobilization of legacy P stored in the bottom sediments could sustain the lake's primary productivity on a time scale of several centuries. Finally, while the majority of management practices to reduce excessive algal growth in lakes focus on reducing external P loads, other efforts rely on the addition of reactive materials that sequester P in the sediment. Therefore, we investigated the effectiveness of ferric iron additions in decreasing the dissolved phosphate efflux from the sediment and, consequently, limit phytoplankton growth in Lake Vansjø.

Temperature Sensitivity of Freshwater Denitrification and N2O Emission—A Meta‐Analysis

“…Nitrogen processing models such as Global NEWS (Mayorga et al., 2010) and nutrient loading models such as PCLake+ (Janssen et al., 2019) and VEMALA (Huttunen et al., 2016), often include denitrification as a nitrogen conversion term. Moreover, other ecosystem models such as the MyLake‐Sediment model (Markelov et al., 2019) and the terrestrial NEMIS model (Hénault & Germon, 2000), even use (derivatives of) Q10‐values to describe the temperature sensitivity of denitrification. Our meta‐analytic results provide an overview of in‐situ Q10‐values for a wide range of ecosystems (Table S1 in Supporting Information S1), which can potentially aid the modeling of the temperature sensitivity of denitrification for specific freshwater ecosystems.…”

Warming combined with experimental eutrophication intensifies lake phytoplankton blooms

“…Aim 2: Lake modeling MyLake is a 1D process-oriented model designed to simulate seasonal ice and snow cover, heat exchange and thermal stratification, N and P cycling, phytoplankton growth, oxygen and carbon dynamics, and water-sediment coupling (Saloranta and Andersen 2007;Couture et al 2015;de Wit et al 2018;Kiuru et al 2019;Markelov et al 2019). The model has previously been applied to boreal lakes to simulate the response of P cycling to external P loading and climate change (Couture et al 2014a(Couture et al , 2018.…”

Preface: Restoration of eutrophic lakes: current practices and future challenges

“…For the purpose of planning lake restoration, accounting for hydrodynamics, ecosystem functioning and sediment processes may be necessary (Trolle et al, 2011;Smits & van Beek, 2013;Hipsey et al, 2015;Zhang et al, 2015;Hu et al, 2016). Recently, the coupling of stateof-the-art lake models (Hipsey et al, 2020;Rousso et al, 2020) with sediment diagenetic models (e.g., Gudimov et al, 2016;Matisoff et al, 2016;Doan et al, 2018) has been promoted specifically to address gaps in lake resaturation planning (Markelov et al, 2019;Messina et al, 2020). A key future perspective is thus the improved integration of the required modeling infrastructure to test different restoration scenarios.…”