| Summary: | This thesis explores the ecological impacts of retrogressive thaw slumping on cladocerans (Branchiopoda, Crustacea) in Mackenzie Delta Region (Northwest Territories, Canada) lakes using paleolimnological techniques to answer the following questions: 1) Does thaw slumping increase UV exposure of Chydorus? 2) Are Daphnia absent in slump-affected lakes? I reconstructed UV exposure of Chydorus in a reference and slump-affected lake by measuring carapace absorbances at UV wavelengths. Carapace absorbances in the slump-affected lake were comparable to the reference lake, indicating Chydorus were not exposed to more UV radiation than in the reference lake. I also examined Daphnia ephippia in surface and pre-1850 sediments from 7 slump-affected and 7 unimpacted lakes, to confirm a 2017 zooplankton survey observation that Daphnia were absent in slump-affected lakes. Daphnia were not observed in slump-impacted lake sediments; however low sediment volumes likely underestimate Daphnia presence. My research provides new information on zooplankton biogeography in the Mackenzie Delta region.
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