Turbidity and nutrients drive species-specific responses of freshwater plankton in mesocosms
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Authors
Ewins, Carrie
Date
Type
thesis
Language
eng
Keyword
Lake Ecology , Zooplankton , Phytoplankton , Turbidity , Nutrients , Mesocosm Experiment , Multiple Stressors
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Abstract
Freshwater systems are among the most threatened globally despite the important ecosystem services they provide. Among the many ways humans are altering freshwater systems, the impact of elevated turbidity on zooplankton remains relatively understudied, with much research limited to single-species laboratory studies or community-level studies in oligotrophic systems. Nutrients can be delivered to lakes together with sediments, representing a second stressor. I conducted a mesocosm field experiment to explore the independent and interactive effects of increased turbidity and nutrients on freshwater zooplankton and phytoplankton communities. I found that zooplankton and phytoplankton communities changed with both increased turbidity and nutrients, however, I did not detect any interactions between them. As turbidity increased, the abundance of Skistodiaptomus oregonensis, Daphnia mendotae/dentifera, Chydorus sphaericus, and Alonella increased, whereas Daphnia pulex/pulicaria, Monostyla, and total rotifer abundance declined, with no change in total zooplankton abundance, biomass, richness, and diversity. Cryptophyte concentration, a high-quality food source for zooplankton, declined with increasing turbidity, however total chlorophyll a concentration did not change due to stable cyanobacteria and golden-brown algae concentrations. Total zooplankton abundance, richness, total cladoceran, Chydorus sphaericus, and Alonella abundance, and cyanobacteria concentration declined, whereas golden-brown algae concentration increased with increasing total phosphorus (TP). Dissolved oxygen concentrations declined with increasing TP, suggesting zooplankton abundances were controlled by stressful low-oxygen conditions. By finding different and milder impacts of turbidity on zooplankton communities compared to previous studies, my results contribute to our understanding of turbidity as an aquatic stressor in different contexts. My findings suggest that a species-rich and likely more genetically diverse zooplankton community in eutrophic conditions may be more resilient to increased turbidity. However, important zooplankton and phytoplankton taxa still declined with elevated turbidity and nutrients, indicating that we should aim to manage and limit further turbidity and nutrient increases to protect and maintain our lakes.
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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.