Seasonal Drivers of Nutrient Concentration in Lake Ecosystems: Evaluating Climate and Ice Phenology Characteristics in a Shallow Eutrophic Lake

Abstract

Abstract The climate is shifting across the globe and understanding seasonal drivers of nutrient concentration in lake ecosystems is important to further our understanding of drivers of biotic change. Additionally, the degree to which winter dynamics in lake ecosystems respond to climate and ecosystem level factors and their role in influencing nutrient cycling processes is unclear but important for understanding and managing potential changes. The overall objective of this study was to evaluate seasonal water column nutrient concentrations, climatic conditions, and ice phenology characteristics in a small shallow eutrophic lake. Water column nutrients were sampled from October 2009 to September 2020 at two locations at Petit-lac-Saint-François (Lake Inlet and Lake Outlet) in south-central Quebec, Canada. During this sampling period, ice phenology characteristics and phytoplankton samples were also collected. The degree of correlation with nutrient concentrations varied between climate indices across different time scales and monitoring locations. The timing of lake ice varied during the study period ranging from 102 to 166 days of ice coverage with the duration of ice coverage being significantly correlated with dissolved inorganic nutrient accumulation during the ice-on period. Moreover, phytoplankton composition varied between ice-on/off periods and species richness significantly declined. Studies that evaluate winter limnological characteristics are limited but important to understand the seasonal dynamics of nutrient cycling in these systems, especially given how the climate is shifting. Moreover, the climate is a significant driver of lake biogeochemical with respect to both inputs and internal processes.