INVESTIGATING LAKE ECOSYSTEM RESPONSE TO INCREASED TEMPERATURE AND WILDFIRE OCCURRENCE

Air temperatures in the boreal forest have increased about twice that of the global average and are contributing to increases in the frequency and intensity of wildfires. How these changes will impact lakes in the boreal region remains unclear. In this study we use paleolimnological methods to determine the impacts of warming and wildfire on six boreal lakes located near Yellowknife, Canada. The lakes were selected to help determine factors affecting lake resiliency, and include deep (>5 m) and shallow (<3 m) lakes, with recent (<5 yrs prior to sediment retrieval) and historically (>20 yrs ago) burned catchments. Based on ²¹⁰Pb and ¹⁴C dating, the sediment records span the past ~500 to ~1200 years. To investigate the effects of warming and wildfire on lakes, we measured sedimentary chlorophyll-a, biogenic silica, and stable C and N isotopes, inferred past lake-water TOC, and identified diatom community composition. Cluster and rate of change analysis and generalized additive models were used to identify significant changes in the diatom community composition and timing of change in the other proxies, respectively. No long-term changes were linked to wildfire, even in lakes with severely burned catchments, but were linked to the onset of rapid warming. Changes in shallow lakes were much more pronounced than in deep lakes, highlighting the sensitivity of shallow, boreal lakes to rising temperatures. Our findings show with warmer temperatures, shallow boreal lakes will increase in primary production with the potential for irreversible regime shifts in these aquatic ecosystems.

Primary Presenter: Kevin Ng, University of Western Ontario (kng342@uwo.ca)

Authors:

Kevin Ng, University of Western Ontario  (kng342@uwo.ca)

Katrina Moser, University of Western Ontario  (kmoser@uwo.ca)

Maria Eloisa Sia, University of Victoria  (mesia@uvic.ca)

Michael Pisaric, Brock University  (mpisaric@brocku.ca)

Carsten Meyer-Jacob, Université du Québec en Abitibi-Témiscamingue  (carsten.meyer-jacob@uqat.ca)

John Smol, Queen's University  (smolj@queensu.ca)

Fred Longstaffe, University of Western Ontario  (flongsta@uwo.ca)