Impacts of climate change on wetland habitat for muskellunge and Blanding's turtles in eastern Georgian Bay

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The coastal zone of Georgian Bay (GB), eastern arm of Lake Huron, has been designated by UNESCO as a Biosphere Reserve, where there are 50 species-at-risk including the federally endangered Blanding's turtle. Coastal marshes in eastern GB are used as spawning and nursery habitat by the muskellunge, the largest freshwater sportfish in Canada, and which grows to trophy status in GB and is unique among the Great Lakes in being a self-reproducing population. The greatest threat to coastal wetlands in this region is climate change, whose effects on coastal marshes have not been properly studied. First, there appears to be a change in the interannual fluctuations of water levels. Since 1918, cycles of fluctuations have ranged from 8 to 12 years; beginning in 1999, however, water levels remained near record low for 14 continuous years and then rose to above normal levels for the following 7 years. The terrestrial zone expanded greatly during the initial low-water years, with shrubs and 10-y old pine trees becoming established in former aquatic habitat. The new water-level regime also compressed the plant community and reduced fish species richness and diversity. When water levels abruptly increased in 2014, the trees and shrubs began to die but because of strong root systems, are still standing and have formed a novel "Dead Tree Zone". This novel zone has prevented re-establishment of submergent species that are required by age-0 muskellunge. A second effect of climate change is an increase in intensity and frequency of wildfires. We saw a preview of what's to come when the Parry Sound 33 fire consumed more than 110 km2 of land between Henvey Inlet and the French River during the summer of 2018. This fire burned almost all topsoil, leaving only bare rock in many places. This should have negative implications for Blanding's turtles that use lichen/moss on rocks as nesting substrate. The primary objectives of this proposal are to study the long-term effects of unprecedented water-level fluctuations and wildfire on habitat of Blanding's turtle and the muskellunge in coastal wetlands of Georgian Bay. First, we will conduct a change detection of vegetation zones in GB coastal marshes between the period of sustained low water levels and the recent 7 years of high water levels. We will then assess how these changes have affected the distribution and species composition of plants and fish (particularly muskellunge) in wetlands using a 15-y dataset. We have been tracking the Blanding's turtle in the Henvey Inlet/Key River region since 2020, and we propose to continue monitoring how Blanding's turtles use fire-affected vs unaffected habitat over the next 5 years. These long-term studies provide more appropriate data for assessing landscape-level changes in response to climate change, and inform conservationists how wetland plant structure will affect the long-term viability of the muskellunge and Blanding's turtle populations living in eastern Georgian Bay.