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Arctic lakes possess the unique characteristic of being covered by a thick layer of ice for most of the year. In summer, the increased heat input results in thinning of this ice and melting of the margins, which opens up the littoral zone. Global warming observed over the last few decades could potentially intensify the thinning and contraction of the surface area of the lake ice. Hence, the littoral zone would benefit from increased availability of solar energy, resulting in enhanced productivity and greater interactions with the atmosphere.
The littoral zones of lakes in subarctic, temperate and tropical regions are defined by the presence of macrophytes and periphyton. However, High Arctic lakes contain few macroscopic plants, mainly mosses that persist to the bottom of the lake (Sand-Jensen et al. 1999). The objective of my thesis is to identify criteria that can be used to define the littoral zone of Arctic lakes and to evaluate the influence of the loss of the ice cover on the littoral food web dynamics and their interactions with the offshore, pelagic zone. My central hypothesis is that the transition from the littoral zone to the pelagic zone is characterized by an abrupt change in limnological properties (e.g., underwater light, temperature structure, dissolved oxygen, chlorophyll concentrations) where the ice cover ends. Thus, the benthic microbial food web in the littoral zone would have a markedly different structure than the benthic microbial food web in the pelagic zone of the lake. I also will test the hypothesis that loss of ice cover will stimulate the production of microbial mats and mosses of the bottom of the lake due to an increase in photosynthetically available radiation, and that an increase in ultraviolet radiation exposure will modify the quality of dissolved organic carbon quality that is released in the water column.
This research will take place on two High Arctic lakes. Ward Hunt Lake (85°05’N, 74°10’W) experienced a massive reduction of its ice cover thickness and area over the past few years after more than 50 years of stability, and completely lost its ice cover during the summers of 2011 and 2012 (Paquette et al. 2015). My research will focus on this lake as an excellent model to study the benthic zone and its relation with ice cover variations, with comparative analyses of the much deeper Lake A on northern Ellesmere Island (Comeau et al. 2012). I will apply a broad range of methods including satellite image analysis, physico-chemical profiling, sediment sampling, and plankton, pigment, lipid and stable isotope analysis, with the aim to develop an integrative, conceptual model of the littoral zone in Arctic lakes.
References: Comeau A. et al., 2012. Scientific Reports, 2:604; Paquette M. et al., 2015. Geophys. Res. Lett.. 42:1433-1440; Sand-Jensen K. et al. 1999. Can. J. Fish. Aquat. Sci. 56:388-393.
Bégin, P.N., Lebedeva, L., Tashyreva, D., Velazquez, D., Blaen, P.J., 2017. Future priorities for Arctic freshwater science from the perspective of early career researchers. Arctic Science, 3(4): 661-671. DOI: 10.1139/AS-2016-0028.
Bégin, P.N., Vincent, W.F., 2017. Permafrost thaw lakes and ponds as habitats for abundant rotifer populations. Arctic Science, 3(2): 354-377. DOI: 10.1139/as-2016-0017.