Assessment of hydroecological changes at the Slave River Delta, NWT, using diatoms in seasonal, inter-annual and paleolimnological experiments

• Main Author: Sokal, Michael Andrew
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: University of Waterloo 2007
• Subjects: Aquatic Ecology; Paleolimnology; Biology; Northwest Territories; Canada; Great Slave Lake; Slave River
• Online Access: http://hdl.handle.net/10012/3364

Relationships between hydrology, limnology and ecology are analyzed in a comprehensive study of water bodies in the Slave River Delta, Northwest Territories, Canada, at a variety of temporal and spatial scales, including seasonal, inter-annual and multi-decadal timescales at individual sites to delta-wide perspectives. Water chemistry and surface sediments were analyzed from 41 shallow lakes representing three previously-defined hydrological categories in the Slave River Delta, in order to identify relationships between hydrological and limnological conditions and their associations with recently deposited diatom assemblages. Evaporation-dominated lakes are physically removed from the influence of the Slave River, and are characterized by high alkalinity and high concentrations of nutrients and ions. In contrast, flood-dominated lakes tend to receive a pulse of floodwater from the Slave River during the spring thaw and have low alkalinity and low concentrations of most nutrients and ions. Exchange-dominated lakes are variably influenced by floodwaters from the Slave River and seiche events from Great Slave Lake throughout the spring thaw and open-water season, and are characterized by a broad array of limnological conditions that are largely dependent on the strength of the connection to these sources of floodwater. Specific diatom ‘indicator’ taxa have been identified that can discriminate these three hydrological lake categories. Evaporation-dominated lakes are associated with high relative abundance of common epiphytic diatom taxa, while diatoms indicative of flood- and exchange-dominated lakes span a wide range of habitat types (epiphytic, benthic) but also include unique planktonic diatoms (Stephanodiscus and Cyclostephanos taxa) that were not found in surface sediments of evaporation-dominated lakes. Water chemistry, diatom phytoplankton communities and macrophyte biomass were monitored seasonally over three years (2003-05) from six hydrologically-diverse lakes of varying flood susceptibility to determine ...