Development and application of aquatic ecosystem monitoring approaches for the Peace-Athabasca Delta and Whooping Crane Nesting Region of Wood Buffalo National Park

Abstract

Shallow waterbodies are abundant in northern regions where their small water volume and large surface area-to-volume ratio make them vulnerable to effects of climate change, natural resource development and long-distance transport of contaminants. Canada’s largest national park, Wood Buffalo National Park, spans the NWT-Alberta border and contains two Ramsar Wetlands of International Importance: The Peace-Athabasca Delta (PAD) and the Whooping Crane Nesting Region (WCNR; hereafter referred to as the Whooping Crane Summer Range (WCSR)). These aquatic landscapes play vital roles in supporting biodiversity and traditional livelihoods of Indigenous Peoples of the region, and in providing habitat for the threatened wood bison (Bison bison athabascae) and the endangered whooping crane (Grus americana). They also underpin the park’s designation as an UNESCO World Heritage Site. Despite these recognitions, increasing concern over aquatic ecosystem degradation due to climate change and industrial development prompted UNESCO to evaluate the park’s status in 2017 and whether it should be downgraded to ‘World Heritage in Danger’. In response, Parks Canada developed an Action Plan in 2019, which was supported by federal investment of $87 million towards its implementation. Key actions include the development and implementation of an integrated aquatic ecosystem monitoring program for the PAD and WCSR to assess how aquatic ecosystems in these landscapes respond to multiple potential stressors – a need that has long been recognized. Monitoring aquatic ecosystems in remote, hydrologically diverse landscapes poses significant challenges, particularly in balancing the need for comprehensive spatial and temporal data with logistical and financial constraints. Effective sampling methodologies that can track changes across a range of timescales (e.g., from hours to years) at a landscape scale can help overcome these barriers and generate critical knowledge to support aquatic ecosystem monitoring programs. At the PAD and WCSR, hydrological processes strongly influence the physical, chemical, and biological conditions of waterbodies. Thus, tracking these processes across space and time must serve as the cornerstone of an aquatic ecosystem monitoring program designed to address longstanding concerns about reduced freshwater availability due to hydroelectric regulation of the Peace River by the WAC Bennett Dam and potential contamination from upstream Alberta Oil Sands operations. This thesis reports results obtained during 2015-2022 using integrated, multi-faceted field-sampling approaches to investigate the responses of shallow waterbodies in two ecologically significant landscapes to anthropogenic stressors. Given the foundational role of hydrology in shaping these aquatic ecosystems, a multi-method approach was used to characterize influential hydrological processes, including episodic river flooding at the PAD, groundwater discharge in the WCSR, as well as precipitation and evaporation. The sampling spanned from continuous hourly water depth measurements to systematic seasonal (spring, summer, fall) measurement of water isotope tracers and water chemistry surveys at ≥60 waterbodies across both landscapes over multiple consecutive years. Additional approaches were employed to assess enrichment of nickel and vanadium, key oil sands indicators, at lakes across the PAD. Key findings presented in this thesis are organized across three data chapters, each contributing advancements to understanding the hydrological processes shaping shallow waterbodies in the PAD and WCSR, as well as contaminant enrichment in fluvial-derived sediment to lakes in the PAD. In Chapter 2 continuous water depth measurements were used to develop a new lake classification scheme for the PAD based on four distinct depth variation patterns associated with a singular, dominant hydrological process: 1) ‘Drawdown’ (≥15 cm decline) by evaporation and/or outflow after ice-jam floods, 2) ‘Stable’ lake levels (<15 cm change) sustained by rainfall, 3) ‘Gradual Rise’ by inundation from the open-drainage network, and 4) ‘Rapid Rise’ by input of river floodwater. River flooding during the open-water season has not been well recognized as an important recharge mechanism for lakes in the PAD, yet it occurred extensively in the Athabasca sector in 2018 and 2019. Retrospective analysis of past peak summer levels of the Athabasca River revealed that open-water flooding equivalent to that of 2018 has likely occurred during 16 years since 1982 (42% of the years). Thus, open-water flooding, a phenomenon rarely reported on in the scientific literature, is a common hydrological process affecting broad areas of the Athabasca sector of the delta. Chapter 3 synthesizes evidence gathered during a 7-year research program at the PAD (from which Chapter 2 emerged) to explore the associations between lake ecosystem processes in the PAD and climate indices, assess if upstream industrial activities have enriched concentrations of substances of concern, and provide a foundation for multi-faceted aquatic ecosystem monitoring at the PAD. Integration of evidence from key metrics, including isotope-inferred lake water balance, water chemistry and contaminant enrichment, was used to identify status and trends over space and time and assist with identifying causes of change. The research coincided with a period of marked climatic variation, which provided opportunity to evaluate the effectiveness of the methodologies and responses of lakes to changes in hydrology and climate. Four key recommendations are provided to operationalize the methodologies and approaches presented in Chapter 3, which strive to maximize the information content of cost-effective measurements to sustain a long-term monitoring program. Chapter 4 extends use of the methodologies beyond the PAD to 63 shallow ponds in the WCSR, to characterize key hydrological processes and their spatial and seasonal patterns in 2022. Peak water levels occurred in spring when consistently low isotope compositions and low concentrations of major nutrients and ions reveal widespread, profound influence of snowmelt runoff. Spatial variability of these measurements increased during summer and fall as connectivity to groundwater waned and influence of evaporation increased at some waterbodies. Water level drawdown was less at waterbodies with strong versus weak groundwater connectivity (median = 23% vs 44% of initial depth, respectively). Geospatial interpolation of a multi-metric ‘Vulnerability Index’, based on isotope-inferred evaporation-to-inflow ratios, water-level drawdown and water chemistry ordination sample scores, identified that Whooping Crane nest locations in 2022 cluster within areas where waterbodies retained strong connectivity to groundwater. Collectively, this research aims to inform the design and implementation of sustainable, long-term monitoring programs for shallow aquatic ecosystems in the PAD and WCSR to enable rapid detection of changes and their causes in the face of accelerating industrial development and climate change. The knowledge gained can be used to guide policy decisions under the WBNP Action Plan, and the methodologies may be applied at other remote, water-rich landscapes to evaluate for changes caused by multiple potential stressors.