Supervised by:

Milla Rautio (Regular member)

Research project description

Connecting under-ice physical processes with under-ice ecosystem structure

IntroductionAlthough nearly half of the world’s lakes freeze annually, winter is still rarely included in scientific studies. A frozen surface prevents gas exchange with the atmosphere and can block up to 100% of incoming solar radiation. These physical processes can have cascading effects on the overwintering plankton food web, as well as the spring and early summer community structure. ObjectivesThis project aims to study zooplankton community structure and interactions, including how they are enabled and driven by changing biogeochemistry and hydrodynamics during winter. The relative abundance and biomass of rotifer, cladoceran and copepod species is used to characterize zooplankton populations. Bacterioplankton, autotrophic picoplankton and mixotrophic nanoflagellates are also considered and used as a proxy to study lake metabolism and energy pathways. Study sitesLake Simoncouche (Saguenay, Québec) was chosen for this study. This boreal lake is located in the teaching and research forest Simoncouche (FERS) of UQAC. It is a dimictic and mesotrophic lake with a mean depth of 2.2 m and a maximum depth of 8 m. Lake Simoncouche is usually covered in ice between mid-November and early May. Material and methodsSampling dates were chosen to correspond with early, mid and late winter, in addition to the period of ice melting and the fall and spring overturns. Five sampling depths were chosen to represent the whole water column. Samples were taken at 0 m (immediately below ice), 1.5 m, 3 m, 4.5 m and 7 m. All samples were collected at the point of maximum depth.The biological variables are the abundance (ind. m^-3) of bacterioplankton, picoplankton, nanoflagellates and zooplankton, as well as the chlorophyll-a concentration (μg/L). Biomass (μgC/L) is also calculated for zooplankton, bacteria, picoplankton and nanoflagellates, as a function of their abundance and average biovolume. A wide range of environmental variables was also considered, including ice and snow thickness (cm), temperature (°C), oxygen concentration (mg/L), PAR (μm m^-3 s^-1), total phosphorus (μg/L), total nitrogen (mg/L), pH and DOC (mg/L).ReferencesCavaliere E et al. 2021. The lake ice continuum concept: influence of winter conditions on ecosystem dynamics. Journal of Geophysical Research: Biogeosciences. Hampton SE et al. 2017. Ecology under lake ice. Ecology Letters, 20: 98-111.18 Jansen J, MacIntyre S, Barrett D, Chin Y, Cortés A, Forrest A, Hrycik A, Martin R, McMeans B, Rautio M and Schwefel R. 2021. Winter limnology: how do hydrodynamics and biogochemestry shape ecosystems under ice? Journal of Geophysical Research: Biogeosciences, 126. Powers S and Hampton S. 2016. Winter limnology as a new frontier. Limnology and Oceanography Bulletin, 25: 103-108.

Research Site Coordinates