AbstractsGeography &GIS

Integration of paleolimnological and contemporary hydroecological analyses to decipher effects of multiple stressors on water-rich northern landscapes

by Lauren Ashley MacDonald




Institution: University of Waterloo
Department:
Year: 2015
Keywords: Paleolimnology; Carbon; Wapusk National Park; Old Crow Flats; Slave River Delta; Thermokarst lakes; Lesser Snow Goose; Metals; Giant Mine
Posted: 02/05/2017
Record ID: 2088432
Full text PDF: http://hdl.handle.net/10012/9672


Abstract

Northern freshwater ecosystems provide important habitat and resources which support abundant wildlife and waterfowl populations and the traditional lifestyle of many First Nation communities. However, concerns have been mounting regarding the effects of multiple stressors, including climate change and other human-related activities in these regions. In order to understand the consequences of stressors, information on both present and past conditions is needed. This thesis addresses knowledge gaps by using a combination of contemporary and paleolimnological methods to characterize lake and pond responses to different stressors in three northern landscapes. A paleolimnological record in combination with aerial images was used to investigate causes of lake-level changes at a lake in the Old Crow Flats (OCF). Contemporary measurements were used to identify how hydrological and limnological conditions of coastal ponds in Wapusk National Park (WNP) differ seasonally and with disturbance from Lesser Snow Geese (LSG). Paleolimnological studies were also used in this landscape to determine how hydroecological conditions have changed during the past few centuries in response to climate warming and LSG population expansion. At a lake in the Slave River Delta (SRD), paleolimnological studies of hydrology and contaminant deposition were used to establish baseline concentrations and assess if temporal changes have occurred in response to northern industrial development. Together, these studies provide a detailed record of environmental changes in response to stressors at three large northern freshwater landscapes. Recent studies using remote sensing analysis of lake-rich thermokarst landscapes have documented evidence of declining lake surface area in response to recent warming. However, images alone cannot identify whether these declines are due to increasing frequency of lake drainage events associated with accelerated thermokarst activity or to increasing evaporation in response to longer ice-free season duration. In Chapter 2, the potential of combining aerial photograph time series with paleolimnological analyses to track changes in hydrological conditions of a thermokarst lake in the OCF and to identify their causes was explored. Images showed water level in lake OCF 48 declined markedly sometime between 1972 and 2001. In a sediment core from OCF 48, complacent stratigraphic profiles of several physical, geochemical and biological parameters from ~1874-1967 indicated hydrolimnological conditions were relatively stable. From ~1967-1989, declines in organic matter content, organic carbon isotope values and pigment concentrations were interpreted to reflect an increase in supply of minerogenic sediment, and subsequent decline in aquatic productivity caused by increased thermo-erosion of shoreline soils. Lake expansion was likely caused by increased summer rainfall, as recorded by increased cellulose-inferred lake-water oxygen isotope compositions. Stratigraphic trends defining the lake expansion phase terminated at ~1989,…