In the Weeds: Multiple stressors drive long-term invertebrate dynamics in two Great Lakes Areas of Concern (Cornwall and the Bay of Quinte)
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Authors
Armstrong, Isaac Arthur
Date
2024-07-29
Type
thesis
Language
eng
Keyword
Paleolimnology , Cladocera , Chironomids , Great Lakes , Legacy contamination , Community ecology , Dreissenids
Alternative Title
Abstract
The Great Lakes experienced severe twentieth-century anthropogenic impacts whose legacies are now interacting with invasive species and climate warming. Long-term data are needed to characterize the environmental effects of multiple interacting stressors and inform management objectives in designated Areas of Concern. Aquatic invertebrates are established water quality indicators and important to ecosystem function, however there are few data available pre-1970s on invertebrate dynamics in response to historic anthropogenic impacts within the Great Lakes. I used paleolimnological techniques to assess long-term change in invertebrate assemblages from two Great Lakes Areas of Concern. First, I analyzed spatial and temporal trends in chironomid assemblages in relation to historic industrial discharges in the St. Lawrence River at Cornwall, Ontario. Species distribution in surface-sediment samples from the Cornwall waterfront was significantly related to sedimentary Zn, potentially reflecting a legacy effect of textile mill effluent. Sediment cores showed a near absence of chironomid head capsules during the period of sedimentary contamination. As contaminant concentrations declined, there was a corresponding increase in chironomid abundance, diversity, and the relative abundance of pollution-sensitive taxa. I also investigated long-term effects of nutrient enrichment and dreissenid invasion on cladoceran assemblages in four sediment cores representing morphometrically distinct basins of the Bay of Quinte, Lake Ontario. Prior to the acceleration of eutrophication in the early 1900s, assemblages indicated a mesotrophic, piscivore-dominated system with diverse shoreline habitat. Cultural eutrophication was marked by increases in the relative abundance of Bosmina longirostris, Chydorus sphaericus, and Eubosmina. coregoni, while Daphnia longispina complex declined to very low relative abundances (0-5%). The dreissenid invasion c. 1994 and associated water clarity increase led to varied trophic responses across the Bay related to environmental legacies and subsequent biological invasions. Since ~2010, sediment cores show a widespread increase in the relative abundance and sedimentary flux of large littoral taxa and small generalist taxa, while large pelagic grazers remain impaired. Overall, my results suggest that remedial actions in Cornwall have allowed ecological recovery of benthic invertebrates, while pelagic zooplankton in the Bay of Quinte are being adversely impacted by multiple stressors.
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ProQuest PhD and Master's Theses International Dissemination Agreement
Intellectual Property Guidelines at Queen's University
Copying and Preserving Your Thesis
This publication is made available by the authority of the copyright owner solely for the purpose of private study and research and may not be copied or reproduced except as permitted by the copyright laws without written authority from the copyright owner.
Attribution 4.0 International