Paleolimnological Study of Chironomidae (Diptera) Assemblage Responses to Multiple Stressors in Lake Nipigon (Northwestern Ontario)

Abstract

Lake Nipigon is a large, deep lake in northwestern Ontario that has experienced over a century of environmental disturbance linked to hydroelectric development, mining, and climate change. This thesis applied paleolimnological methods to reconstruct historical chironomid assemblages and their responses to multiple stressors in nearshore areas, as limnological data for Lake Nipigon is only sparsely available. Core surveys conducted show generalist and moderately tolerant taxa that suggest moderately warm, vegetated, and nutrient-rich conditions in the nearshore areas, with generally favourable oxygen conditions. Chironomid subfossil assemblage changes in Gull Bay were relatively muted, while recent increases in the warm-adapted taxon Stempellina in South Bay suggest a response to warming in the nearshore environment. South Bay also documented declines in cold, oxygen-sensitive Heterotrissocladius grimshawi-type. This study established the first paleolimnological baseline for Lake Nipigon, which is intended to provide a foundation for future Indigenous-led lake monitoring efforts that reflect both western scientific and Indigenous knowledge systems.