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The complexity and natural variability of ecosystems present a challenge for reliable detection of change due to anthropogenic influences. This issue is exacerbated by necessary trade-offs that reduce the quality and resolution of survey data for assessments at large scales. The Peace-Athabasca Delta (PAD) is a large inland wetland complex in northern Alberta, Canada. Despite its geographic isolation, the PAD is threatened by encroachment of oil sands mining in the Athabasca watershed and hydroelectric dams in the Peace watershed. Methods capable of reliably detecting changes in ecosystem health are needed to evaluate and manage risks. Between 2011 and 2016, aquatic macroinvertebrates were sampled across a gradient of wetland flood frequency, applying both microscope-based morphological identification and DNA metabarcoding. By using multispecies occupancy models, we demonstrate that DNA metabarcoding detected a much broader range of taxa and more taxa per sample compared to traditional morphological identification and was essential to identifying significant responses to flood and thermal regimes. We show that family-level occupancy masks high variation among genera and quantify the bias of barcoding primers on the probability of detection in a natural community. Interestingly, patterns of community assembly were nearly random, suggesting a strong role of stochasticity in the dynamics of the metacommunity. This variability seriously compromises effective monitoring at local scales but also reflects resilience to hydrological and thermal variability. Nevertheless, simulations showed the greater efficiency of metabarcoding, particularly at a finer taxonomic resolution, provided the statistical power needed to detect change at the landscape scale. [ABSTRACT FROM AUTHOR]

Habitat degradation associated with resource development is a major ecological concern, particularly in Canada's boreal zone where limited information on biodiversity is available. Habitat degradation can lead to reductions in biodiversity and ecosystem function, especially when drivers of variability and diversity patterns have not been identified for a region of interest. In this study, the distribution of diatom genera in the Peace-Athabasca Delta in northeastern Alberta was examined in relation to seasonal, geographic, and alkalinity gradients. Grab samples of six abiotic variables (total dissolved nitrogen, total dissolved phosphorus, dissolved iron, turbidity, pH, and specific conductance (SPC)) were taken from 12 remote wetlands over three sampling periods, and regressed against an ordination of diatom community composition to identify key environmental drivers of diatom community variation. Indirect gradient analysis identified two major gradients among sites. First, separation of sites among sampling periods showed successional seasonal changes in diatom community composition. Second, separation of sites from the Peace sub-delta and Birch sub-delta showed a gradient of geographic separation. Direct gradient analysis failed to explain the underlying drivers of these two gradients, but did show that alkalinity is a key driver of diatom community composition in the Embarras sub-delta, and that these sites could be particularly vulnerable to community changes associated with acidification. [ABSTRACT FROM AUTHOR]

Natural and anthropogenically driven changes in upstream watershed conditions strongly influence the hydrological, geomorphological and ecological processes within downstream riverine and deltaic ecosystems. The goal of our study was to examine temporal trends and spatial patterns in ecologically relevant hydrological variables within the Athabasca River watershed and the downstream Peace-Athabasca Delta (PAD), located in northwestern Canada. Temporal trends for a suite of indicators of hydrologic alteration, appropriate for cold regions environments, were explored using non-parametric Mann-Kendall trend analysis. Results in the Lower Athabasca River (LAR) watershed were placed in a watershed-scale context. Across the two study periods (A - 1958-2009 and B - 1974-2009), results indicated decreasing trends in several key drivers of deltaic system hydrology, including short-term and long-term maximum and minimum runoff. In addition, an increasing trend in hydrograph variability was observed within the watershed. A spatially discrete pattern was apparent from the data, with a greater number of significant trends noted within the headwater region as compared with other areas of the watershed. Although earlier dates of annual freeze-up were observed across the watershed, there were few observable patterns in ice-on/ice-off conditions on the river. If these historical trends in freeze-up continue on the LAR, water levels in the PAD channels and inland wetlands could be affected, leading to reduced habitat diversity and altered ecosystem productivity. The study illustrates significant natural variability in the hydrological regime within the LAR that should be considered in future water management frameworks to ensure the preservation and maintenance of this Ramsar wetland site, particularly in the context of projected climate change and the increased water demands arising from upstream development associated with the Alberta Oil Sands. Copyright © 2012 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]