PhD Student, University of Waterloo
I use paleolimnology to evaluate the effects of major energy projects on a downstream landscape
My research combines the fields of paleolimnology and aquatic ecology to evaluate the effects of major energy projects (dams and oil sands), climate change, distributary flow and declining river discharge on lakes in a downstream water-rich northern Alberta landscape called the Peace-Athabasca Delta (PAD). Most of the PAD lies within the borders of Wood Buffalo National Park, Canada’s largest national park and a UNESCO World Heritage Site, and is also recognized as a Ramsar Wetland of International Importance for its ecological, historical and cultural significance. Despite the efforts of federal (Parks Canada, Environment Canada), First Nation (Athabasca Chipewyan, Mikisew Cree), provincial (Alberta) and international agencies (UNESCO, Ramsar Convention) to preserve this world-renowned floodplain landscape, concerns about drying and contamination in the PAD have persisted for decades. A critical aspect for complex landscapes such as the PAD is that disentangling the major drivers causing hydroecological change can be very difficult without sufficient spatial and temporal perspectives, which are often unavailable due to the paucity of long-term and comprehensive monitoring programs. If these drivers are misidentified, misinformed policy can further threaten the integrity of the downstream floodplain, which is the path that has been charted for the PAD. Using dated sediment cores from 10 lakes across the delta and other biological, chemical and physical proxies, my research is providing the critically missing long-term information about directional changes in hydroecological conditions and contaminant deposition of lakes in the PAD for the last 300 years. This research will provide important information that can be used to guide natural resource stewardship decisions by federal (Parks Canada, Environment Canada), First Nation (Athabasca Chipewyan, Mikisew Cree), provincial (Alberta) and international agencies (UNESCO) and industry and determine the extent to which the PAD, a world-renowned national treasure, has become degraded by human activities and climate variations. This early career research prize would be used to travel to the International Paleolimnology Conference in Sweden to explain how sediments cores can be used to create paleohydrological reconstructions and baselines for sediment metal deposition required to assess for evidence of pollution from industry in places that comprehensive monitoring programs were not in place prior to industry.
Abstract: Growing concerns over effects of climate warming and other stressors on shallow Arctic lakes and ponds stimulate the need to develop and implement effective protocols to track changes in ecological integrity. This study assesses seasonal and spatial variability of periphytic diatom communities in a shallow Arctic lake in northern Yukon Territory to establish biomonitoring protocols. Artificial substrate samplers, which mimic macrophytes, allow direct measurement of biotic responses to shifting environmental conditions and control for possible confounding factors (e.g., accrual time and microhabitat type). Artificial substrate samplers were deployed at three locations and retrieved at three times (early, mid, and late) during the ice-free season. Analyses identified that diatom abundance increased exponentially and community composition changed significantly over the ice-free season, despite little variability in water chemistry, but did not differ among the three sampling locations within the lake. Patterns of seasonal succession in diatom community composition were characterized by first arrival of well-dispersed taxa, which included several planktonic taxa, followed by a transitional phase composed of planktonic and periphytic taxa, and culminated with dominance by periphytic species, mainly Achnanthes minutissima (Kützing). Results highlight the role of seasonal succession on artificial substrate colonization and the need to deploy artificial substrate samplers for the duration of the ice-free season to capture peak periphytic algal abundance. Low spatial variability of shallow Arctic lakes allows for samplers to be deployed at one single location to characterize diatom community composition.
Pub.: 03 Dec '11, Pinned: 29 Aug '17
Abstract: We conducted multi-proxy geochemical analyses (including measurements of organic carbon, nitrogen and sulphur stable isotope composition, and carbonate carbon and oxygen isotope composition) on a 13.5 m sediment core from Lake Bliden, Denmark, which provide a record of shifting hydrological conditions for the past 6,700 years. The early part of the stratigraphic record (6,700–5,740 cal year BP) was wet, based on δ18Ocarb and lithology, and corresponds to the Holocene Thermal Maximum. Shifts in primarily δ18Ocarb indicate dry conditions prevailed from 5,740 to 2,800 cal year BP, although this was interrupted by very wet conditions from 5,300 to 5,150, 4,300 to 4,050 and 3,700 to 3,450 cal year BP. The timing of the latter two moist intervals is consistent with other Scandinavian paleoclimatic records. Dry conditions at Lake Bliden between 3,450 and 2,800 cal year BP is consistent with other paleolimnological records from southern Sweden but contrasts with records in central Sweden, possibly suggesting a more northerly trajectory of prevailing westerlies carrying moisture from the North Atlantic at this time. Overall, fluctuating moisture conditions at Lake Bliden appear to be strongly linked to changing sea surface temperatures in the Greenland, Iceland and Norwegian seas. After 2,800 cal year BP, sedimentology, magnetic susceptibility, δ13CORG, δ13Ccarb and δ18Ocarb indicate a major reduction on water level, which caused the depositional setting at the coring site to shift from the profundal to littoral zone. The Roman Warm Period (2,200–1,500 cal year BP) appears dry based on enriched δ18Ocarb values. Possible effects of human disturbance in the watershed after 820 cal year BP complicate attempts to interpret the stratigraphic record although tentative interpretation of the δ18Ocarb, magnetic susceptibility, δ13CORG, δ13Ccarb and δ18Ocarb records suggest that the Medieval Warm Period was dry and the Little Ice Age was wet.
Pub.: 25 Apr '09, Pinned: 29 Aug '17
Abstract: Systematic variability occurs between the oxygen isotopic composition of lake water sampled in mid-summer 1993 and cellulose extracted from surficial sediments of a suite of lakes spanning the forest-tundra transition near Noril'sk, Russia. Some tundra and all forest-tundra lakes show greater deviation from expected cellulose-water isotopic separation than forest lakes, apparently because of greater sensitivity to 18O-depleted snowmelt contributions. Cellulose derived from aquatic plants naturally integrates fluctuations in lake water δ18O, providing a signal that is inherently more representative of average thaw season lake water δ18O than the measure of instantaneous δ18O obtained from an individual sample of lake water. Thus, indiscriminate use of empirical cellulose-water relations derived from ‘calibration’ samples could lead to erroneous assessment of paleohydrology from the oxygen-isotope stratigraphy of sediment cores from arctic lakes. However, deviation from the expected cellulose-water fractionation is a source of lake-specific hydrologic information useful for qualifying paleoenvironmental interpretations and possibly constraining non-isotopic methods that rely on surface-sediment calibrations.
Pub.: 01 Oct '97, Pinned: 29 Aug '17
Abstract: Inadequate knowledge of baseline conditions challenges ability for monitoring programs to detect pollution in rivers, especially where there are natural sources of contaminants. Here, we use paleolimnological data from a flood-prone lake (“SD2”, informal name) in the Slave River Delta (SRD, Canada), ∼500 km downstream of the Alberta oil sands development and the bitumen-rich McMurray Formation to identify baseline concentrations and proportions of “river-transported bitumen-associated indicator polycyclic aromatic compounds” (indicator PACs; Hall et al. 2012) and processes responsible for their deposition. Results show that indicator PACs are deposited in SD2 by Slave River floodwaters in concentrations that are 45 % lower than those in sediments of “PAD31compounds”, a lake upstream in the Athabasca Delta that receives Athabasca River floodwaters. Lower concentrations at SD2 are likely a consequence of sediment retention upstream as well as dilution by sediment influx from the Peace River. In addition, relations with organic matter content reveal that flood events dilute concentrations of indicator PACs in SD2 because the lake receives high-energy floods and the lake sediments are predominantly inorganic. This contrasts with PAD31 where floodwaters increase indicator PAC concentrations in the lake sediments, and concentrations are diluted during low flood influence intervals due to increased deposition of lacustrine organic matter. Results also show no significant differences in concentrations and proportions of indicator PACs between pre- (1967) and post- (1980s and 1990s) oil sands development high flood influence intervals (t = 1.188, P = 0.279, d.f. = 6.136), signifying that they are delivered to the SRD by natural processes. Although we cannot assess potential changes in indicator PACs during the past decade, baseline concentrations and proportions can be used to enhance ongoing monitoring efforts.
Pub.: 12 Apr '16, Pinned: 29 Aug '17
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