A new paper published in Journal of Geophysical Research: Biogeosciences presents the results of analyses of two sediment cores from Lake Wilcox, a kettle lake located in the greater Toronto area. The chemical variables analyzed include various fractions of phosphorus (P), chlorophyll-a, and the radioisotope lead-210, which gives the age of the sediment deposited. The depth profiles enabled the reconstruction of historical phosphorus (P) accumulation rates over time and the estimation of the historical P budgets of the lake for 4 distinct periods of land use/land cover: the period of initial European settlement and farm development, the period of intense farming, the implementation of agricultural best management p A new paper published in Journal of Geophysical Research: Biogeosciences presents a sediment core analysis for Lake Wilcox, an urban kettle lake located in Richmond Hill, Ontario, Canada. The analysis of depth profiles of chemical variables including phosphorus (P), chlorophyll-a, and the radioisotope lead-210, which gives the age of the sediment deposited, enabled the reconstruction of historical phosphorus (P) accumulation rates over time, as well as historical P budgets for the lake for 4 distinct periods of land use/land cover: the period of initial European settlement and farm development, the period of intense farming, the implementation of agricultural best management practices to limit P runoff, and the recent period of significant urban development. The paper is authored by ERG members Steph Slowinski, Jovana Radosavljevic, Fereidoun Rezanezhad, former ERG research assistant Alyssa Graham, now a Masters student in Biology at Waterloo, Mahyar Shafii, ERG adjunct professor Chris Parsons and Philippe Van Cappellen along with other collaborators.
The results of the study show how the external P loading to the lake changed with time because of changes in land use/land cover. What was especially interesting was that the high sediment P burial rates during the period of intense agricultural land use subsequently dropped as best management practices for P were implemented in the watershed between the 1970s and 1990s. In addition, the sediment P burial rates further dropped in the intensive urban development phase due to the installation of stormwater management infrastructure in the watershed. Yet, as the external P loading decreased, internal P loading from the sediments increased in the recent urban phase. The relative increase in the internal P loading is driven by the salinization of the lake which is caused by continued high road salt application rates in the lake’s watershed during the winter. Altogether, the results give insight on the impacts of land use/land cover changes on lake P biogeochemistry, and into the impact of road salt-caused salinization on lake ecosystems.
The published paper is open access and can be found online: "Contrasting Impacts of Agricultural Intensification and Urbanization on Lake Phosphorus Cycling and Implications for Managing Eutrophication."