Supervised by:

Jérôme Comte (Regular Member (Co-researcher))

Research project description

Indirect impacts of climate change on small Arctic lakes: How changes in spatial connectivity will affect bacterial community structure and functioning?

Introduction

The Arctic regions contain many small lakes where life thrives in its microbial form. The particularly fast climate warming in the Arctic is currently promoting both the expansion and shrinkage of lakes, altering connectivity among aquatic systems. Such indirect effects will affect the movement of microorganisms in the landscape and modify terrestrial inputs, with largely unknown repercussions for microbial diversity, let alone for the functions they provide. Aquatic bacterial communities play a crucial role in nutrient recycling, contribute to the biodiversity of these ecosystems through their place at the base of the food web. Additionally, these lakes are a source of greenhouse gases, whose emissions are regulated by microbial communities.

Objectives

With the present project, I intend to evaluate the consequences of climate-induced changes in the connectivity of Arctic freshwater lakes on microbial communities and the ecosystem functions they support. To address this challenge, I will: 1) Assess the taxonomic and functional diversity of bacterial communities by metagenomics and barcoding and measure multiple ecosystem functions simultaneously along local connectivity gradients, 2) Compare bacterial diversity and ecosystem functions at two sites with contrasting regional connectivity and 3) Examine the mechanisms controlling ecosystem functioning.

Study Sites

The study is based on the sampling of 2 sites in continuous permafrost regions of the Arctic. The first site, “Camp 1” on Bylot Island, is located in Nunavut territory. The study site is right next to the camp, in the polygonal landscape. The numerous shallow ponds, more or less distant, lends themselves self well for the study of connectivity. These ponds are also diverse in terms of abiotic properties. In this area, the number of waterbodies is increasing, enhancing connectivity. The second site, the indigenous and territorial protected area Ts’udé Nilįné Tuyeta, is located in the Northwest Territories. Numerous lakes are located west of the Mackenzie River and the community of Fort Good Hope. In contrast with the site in Bylot Island, lakes are shrinking in this area, sometimes even disappearing completely.

Material and methods

First, we will define local connectivity gradients for each site, from satellite or drone images. The spatial connectivity between surface waters will be assessed with an index borrowed from network theory, the “closeness centrality” which measures the closeness of waterbodies against each other. Regional connectivity will be evaluated with the “characteristic path length” which designates the mean of all the shortest paths between waterbodies in a given area. About 20 lakes will be sampled in each site in order to assess bacterial diversity with metagenomic and barcoding techniques. Multiple functional properties of each waterbody will be measured, such as respiration, greenhouse gas emissions and pathogenic potential, with the aim of estimating the multifunctionality of these ecosystems. Contextual abiotic data will also be collected.

References

Giling, D. P., Beaumelle, L., Phillips, H. R., Cesarz, S., Eisenhauer, N., Ferlian, O., Gottschall F., Guerra C., Hines, J., Sendek, A., Siebert, A., Thakur, M.P. and Barnes, A. D. (2019). A niche for ecosystem multifunctionality in global change research. Global Change Biology, 25(3), 763-774. Hector, A., and Bagchi, R. (2007). Biodiversity and ecosystem multifunctionality. Nature, 448(7150), 188- 190 Mony, C., Uroy, L., Khalfallah, F., Haddad, N., and Vandenkoornhuyse, P. (2022). Landscape connectivity for the invisibles. Ecography, 2022(8), e06041. Saros, J.E., Arp, C.D., Bouchard, F., Comte, J., Couture, R.M., Dean, J.F., Lafrenière, M., MacIntyre, S., McGowan, S., Rautio, M. and Prater, C. (2022). Sentinel responses of Arctic freshwater systems to climate: linkages, evidence, and a roadmap for future research. Arctic Science, 9(2), 356-392.