Spatial and Temporal Assessments of Zooplankton Community and Stable Isotope Indicators: Developing A Predictive Understanding of Ecological Dynamics In Boreal Lakes

Date
2019-02
Authors
Mohamed Usoof, Mohamed Anas
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Faculty of Graduate Studies and Research, University of Regina
Abstract

Developing a predictive understanding of processes that regulate lake ecosystem dynamics is crucial in the face of environmental perturbations affecting boreal western Canada, particularly atmospheric pollutant deposition from oil sands operations in Alberta and climate change. Based on spatial and temporal analyses of zooplankton communities and their δ13C and δ15N values, my research sought to 1) assess the biological responses to climate and industrial deposition and 2) develop a holistic understanding of regulatory processes of these indicator dynamics to better assess future impacts. First, a spatial assessment of 97 lakes detected significant correlations of zooplankton community composition to environmental gradients vulnerable to industrial deposition, together with intriguing spatial patterns. Yet, unraveling industrial impacts from natural variability was precluded by lack of regional baselines. The effects of both environmental gradients and dispersal on species composition were scale-dependent, emphasizing the need for explicit consideration of spatial scale in regional bioassessments. Second, a multi-lake paleolimnological study revealed that trajectories of zooplankton community compositional turnover during the past century were largely asynchronous among lakes, indicating dominant local effects over climatic forcing. This cautions against regional extrapolation of site-specific results, highlighting the need for intensive replication in regional bioassessments. Specific changes in trajectories corresponding to intensified oil sands development were not detected, suggesting minimal industrial impacts. Third, evaluation of spatial patterns in δ13C and δ15N of taxon-specific zooplankton from a 233-lake survey revealed that relative effects of lake/catchment-specific factors (water chemistry, hydromorphology and land cover) on stable isotope (SI) variation were more important than potential regional factors (lithology, atmospheric nitrogen deposition). The relative importance of specific lake/catchment-specific predictors of δ13C varied among taxa, likely due to contrasting dietary niches and resulting differences in allochthony. This suggests δ13C may respond taxon-specific to limnological changes. Fourth, analyses of δ13C and δ15N time series of taxon-specific zooplankton subfossils during the 20th century demonstrated that they can better reflect environmental impacts on carbon/nutrient fluxes and trophic dynamics in different lake habitats compared to bulk sediment. Beyond indicating limited current biological impacts of industrial deposition and establishing crucial regional baselines, my research provided a comprehensive understanding of regulatory processes of zooplankton communities and SI dynamics, with broad ecological implications for developing indicator frameworks to assess future environmental perturbations in boreal regions.

Description
A Thesis Submitted to the Faculty of Graduate Studies and Research In Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy in Biology, University of Regina. xv, 253 p.
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