Oil sands development within the Athabasca Oil Sands Region (AOSR) has accelerated in recent decades, causing alteration to natural ecosystems including wetlands that perform many vital ecosystem functions such as water and carbon storage. These wetlands comprise more than half of the landscape, and their distribution and local hydrology are the result of interactions among a subhumid climate, topography, and spatially heterogeneous surficial and bedrock geology. Since hydrology plays a fundamental role in wetland ecological functioning and determines wetland sensitivity to human disturbances, the characterization of anthropogenic impacts on wetland hydrology in the AOSR is necessary to assess wetland resilience and to improve current best management practices. As such, this paper reviews the impacts of oil sands development and related disturbances including infrastructure construction, gravel extraction, and land clearing on wetland function in the AOSR. Hydrologic disturbances in wetlands in the AOSR include changes to soil hydrophysical properties that control water table position, the interruption of recharge–discharge patterns, and alteration of micrometeorological conditions; these in turn govern wetland ecological structure and wetland ecosystem processes (e.g., evapotranspiration, nutrient cycling). Given that anthropogenic disturbance can affect natural wetland succession, long-term hydrological monitoring is crucial for predicting the response of these ecosystems to varying levels of human impact.

Current efforts to assess changes to the wetland hydrology caused by growing anthropogenic pressures in the Athabasca Oil Sands Region (AOSR) require well-founded spatial and temporal estimates of actual evapotranspiration (ET), which is the dominant component of the water budget in this region. This study assessed growing season (May-September) and peak growing season (July) ET variability at a treed moderaterich fen and treed poor fen (in 2013-2018), open poor fen (in 2011-2014), and saline fen (in 2015-2018) using eddy covariance technique and a set of complementary environmental data. Seasonal fluctuations in ET were positively related to net radiation, air temperature and vapour pressure deficit and followed trends typical for the Boreal Plains (BP) and AOSR with highest rates in June-July. However, no strong effect of water table position on ET was found. Strong surface control on ET is evident from lower ET values than potential evapotranspiration (PET); the lowest ET/PET was observed at saline fen, followed by open fen, moderately treed fen, and heavily treed fen, suggesting a strong influence of vegetation on water loss. In most years PET exceeded precipitation (P), and positive relations between P/PET and ET were observed with the highest July ET rates occurring under P/PET 1. However, during months with P/PET > 1, increased P/PET was associated with decreased July ET. With respect to 30-year mean values of air temperature and P in the area, both dry and wet, cool and warm growing seasons (GS) were observed. No clear trends between ET values and GS wetness/coldness were found, but all wet GS were characterized by peak growing seasons with high daily ET variability.

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The earliest eukaryotes recorded in continental environments are non-pollen palynomorphs (NPP) in Mesoproterozoic strata, and NPP provide our best insights into lacustrine ecosystems through the Paleogene. They have been underexploited in studies of younger lake sediments, either ignored or only qualitatively observed, because many NPP are destroyed by standard processing techniques for pollen and embryophyte spores. The palaeoenvironmental potential of palynomorphs, with representatives from all eukaryotic kingdoms as well as cyanobacteria and from all trophic levels in various lacustrine environments, has been recognized by a few Quaternary palynologists in the past few decades. NPP have proven particularly valuable in archaeological and environmental monitoring studies of human impact on freshwater ecosystems, with spores of some fungi and eggs/ egg cases of some flatworms and roundworms associated with feces of humans and livestock, and the acid-resistant remains of various life stages of cyanobacteria, algae, and their aquatic consumers responding to increased turbidity and nutrient influx associated with permanent human settlements, particularly those associated with agricultural activity. Descriptions of NPP commonly encountered in Quaternary lake sediments and case studies illustrating applications to various research questions should encourage more palynologists that ‘Quaternary non-pollen palynomorphs' deserve our attention!’, to quote Prof. Bas van Geel, undisputed Father of NPP Research.Supplementary material at https://doi.org/10.6084/m9.figshare.c.5244661

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