Patterns in the limnology of lakes and ponds across multiple local and regional environmental gradients in the eastern Canadian Arctic

This study examined water chemistry from 113 lakes and ponds across the eastern Canadian Arctic to address the lack of limnological data and understanding of relationships among limnological variables across key local and regional gradients. Environmental and geochemical variables were compared at both the local and regional scale with the use of multivariate analysis. A principal components analysis indicated that there was a primary gradient in temperature, nutrients, and conductivity between sampled regions. In addition, there were significant regional differences observed for nutrients total nitrogen (TN) and total phosphorus (TP), chlorophyll a, and dissolved major ions determined via canonical variates analysis. Across all regions TN:TP ratios were high, indicating phosphorus limitation, and mid-summer surface water temperature was strongly correlated to dissolved nitrogen concentrations. Local landscape characteristics were also examined, with multiple samples from lakes of varying elevations, surface area, and depth within the same area. Shallow pond systems (<2 m depth) were found to have significantly higher variability for major ions, especially in areas with influences from local geology. Likewise, the concentration of nutrients and ions in ponds were strongly correlated to concentrations of dissolved organic carbon, likely indicating the influence of watershed inputs and resuspended sediments on the limnology of ponds. Although there was higher regional variation in the limnology of pond systems than lakes, the general patterns within each region were similar

Physical and Chemical Limnology of a 61-lake Transect across Mainland Nunavut and Southeastern Victoria Island, Central Canadian Arctic

We describe the physical and chemical properties of sixty-one tundra lakes, sampled in a latitudinal transect (65-71°N, 105-108°W) across mainland and island regions of Nunavut, central Canadian Arctic, and examine the influence of geology, geography, climate, and vegetation on lake water chemistry. This dataset complements earlier limnological surveys of the Canadian Arctic and provides valuable information for evaluating the vulnerability of tundra lakes to predicted climate change. Principal components analysis revealed a geographical clustering of lakes; pH, DIC, specific conductivity, and trace metal concentrations reflected major lithological differences between the mainland and Victoria Island. Clustering of mainland lakes by ecoregion was also detected. Lakes of the Queen Maud Gulf Lowland and Garry Lake Lowland ecoregions (north) differed from lakes of the Takijuq Lake Upland ecoregion (south) in depth, pH, and specific conductivity as well as nutrient, DOC, and chlorophyll-a concentrations. Ionic composition of the northern mainland lakes also indicated that the influence of marine aerosols and/or leaching of residual marine salts from post-glacial marine deposits exposed by isostatic rebound. The northern mainland lakes were the most nutrient-rich and biologically productive of the three lake clusters and were characterized by median concentrations of total dissolved nitrogen (518 μg l−1) and chlorophyll-a (1.6 μg l−1) that were higher than previously reported for tundra lakes in the Canadian Arctic. These lakes were chemically similar to lakes of the Tuktoyaktuk Peninsula, in the western Canadian Arctic. Lakes of the southern mainland were dilute, acidic, and nutrient-poor, in accord with earlier limnological surveys in this ecoregion. Concentrations of nutrients, DOC, and chlorophyll-a in Victoria Island lakes fell in the middle of the ranges reported from other islands in the Canadian Arctic. Lithologic and edaphic factors strongly influenced the limnological properties of the tundra lakes surveyed and must be controlled for in order to fully evaluate the influence of future climate and vegetation change

Spatial and temporal patterns in trace element deposition to lakes in the Athabasca oil sands region (Alberta, Canada)

The mining and processing of the Athabasca oil sands (Alberta, Canada) has been occurring for decades; however, a lack of consistent regional monitoring has obscured the long-term environmental impact. Here, we present sediment core results to reconstruct spatial and temporal patterns in trace element deposition to lakes in the Athabasca oil sands region. Early mining operations (during the 1970s and 1980s) led to elevated V and Pb inputs to lakes located <50 km from mining operations. Subsequent improvements to mining and upgrading technologies since the 1980s have reduced V and Pb loading to near background levels at many sites. In contrast, Hg deposition increased by a factor of ~3 to all 20 lakes over the 20th century, reflecting global-scale patterns in atmospheric Hg emissions. Base cation deposition (from fugitive dust emissions) has not measurably impacted regional lake sediments. Instead, results from a principal components analysis suggest that the presence of carbonate bedrock underlying lakes located close to development appears to exert a first-order control over lake sediment base cation concentrations and overall lake sediment geochemical composition. Trace element concentrations generally did not exceed Canadian sediment quality guidelines, and no spatial or temporal trends were observed in the frequency of guideline exceedence. Our results demonstrate that early mining efforts had an even greater impact on trace element cycling than has been appreciated previously, placing recent monitoring efforts in a critical long-term context

Assessing the utility of sulfur isotope values for understanding mercury concentrations in water and biota from high Arctic lakes

Methylmercury (MeHg) biomagnifies through aquatic food webs resulting in elevated concentrations in fish globally. Stable carbon and nitrogen isotopes are frequently used to determine dietary sources of MeHg and to model its biomagnification. However, given the strong links between MeHg and sulfur cycling, we investigated whether sulfur isotopes (δ34S) would improve our understanding of MeHg concentrations ([MeHg]) in Arctic lacustrine food webs. Delta34S values and total mercury (THg) or MeHg were measured in water, sediments and biota from 6 lakes near Resolute Bay, Nunavut. In two lakes impacted by historical eutrophication, aqueous sulfate δ34S was ~8‰ more positive than sedimentary δ34S, suggestive of bacterial sulfate-reduction in the sediment. In addition, aqueous δ34S showed a significant positive relationship with [MeHg] across lakes. Within taxa across lakes, [THg] in Arctic char muscle and [MeHg] in their main prey, chironomids, were positively related to their δ34S values across lakes, but inconsistent relationships were found across entire food webs among lakes. Across lakes, nitrogen isotopes were better predictors of biotic [THg] and [MeHg] than δ34S within this dataset. Our results show significant linkages between Hg and S biogeochemistry in high Arctic lakes which is an important consideration given anticipated climate-mediated changes in nutrient cycling.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

Data from: Recent Warming, Rather than Industrial Emissions of Bioavailable Nutrients, is the Dominant Driver of Lake Primary Production Shifts across the Athabasca Oil Sands Region

Freshwaters in the Athabasca Oil Sands Region (AOSR) are vulnerable to the atmospheric emissions and land disturbances caused by the local oil sands industry; however, they are also affected by climate change. Recent observations of increases in aquatic primary production near the main development area have prompted questions about the principal drivers of these limnological changes. Is the enhanced primary production due to deposition of nutrients (nitrogen and phosphorus) from local industry or from recent climatic changes? Here, we use downcore, spectrally-inferred chlorophyll-a (VRS-chla) profiles (including diagenetic products) from 23 limnologically-diverse lakes with undisturbed catchments to characterize the pattern of primary production increases in the AOSR. Our aim is to better understand the relative roles of the local oil sands industry versus climate change in driving aquatic primary production trends. Nutrient deposition maps, generated using geostatistical interpolations of spring-time snowpack measurements from a grid pattern across the AOSR, demonstrate patterns of elevated total phosphorus, total nitrogen, and bioavailable nitrogen deposition around the main area of industrial activity. However, this pattern is not observed for bioavailable phosphorus. Our paleolimnological findings demonstrate consistently greater VRS-chla concentrations compared to pre-oil sands development levels, regardless of morphological and limnological characteristics, landscape position, bioavailable nutrient deposition, and dibenzothiophene (DBT)-inferred industrial impacts. Furthermore, breakpoint analyses on VRS-chla concentrations across a gradient of DBT-inferred industrial impact show limited evidence of a contemporaneous change among lakes. Despite the contribution of bioavailable nitrogen to the landscape from industrial activities, we find no consistency in the spatial pattern and timing of VRS-chla shifts with an industrial fertilizing signal. Instead, significant positive correlations were observed between VRS-chla and annual and seasonal temperatures. Our findings suggest warmer air temperatures and likely decreased ice covers are important drivers of enhanced aquatic primary production across the AOSR

Deposition and Source Identification of Nitrogen Heterocyclic Polycyclic Aromatic Compounds in Snow, Sediment, and Air Samples from the Athabasca Oil Sands Region

Polycyclic aromatic compounds (PACs) can have multiple sources in the Athabasca Oil Sands Region (AOSR). The current study was designed to identify and explore the potential of nitrogen heterocyclic PACs (NPACs) as source indicators in snowpack, lake sediment and passive air samples from the AOSR during 2014-2015. Source samples including petroleum coke (petcoke), haul road dust, and unprocessed oil sands were also analyzed. Samples were analyzed using comprehensive two-dimensional gas chromatography time-of-flight mass spectrometry, and liquid chromatography-high resolution Orbitrap mass spectrometry. Over 200 NPACs were identified and classified into at least 24 isomer groups, including alkylated carbazoles, benzocarbazoles, and indenoquinolines. Levels of NPACs in environmental samples decreased with distance from the main developments and with increasing depth in lake sediments but were detected within 50 km from the major developments. T

VRS-chlorophyll-a data from 23 sediment cores from study lakes in the Athabasca Oil Sands Region, Alberta, Canada

VRS-chlorophyll-a data from 23 sediment cores from study lakes in the Athabasca Oil Sands Region, Alberta, Canad

Nutrient (TN, DIN, TP, TDP, SRP) data from snowpack samples in the Athabasca Oil Sands Region, Alberta, Canada

Nutrient (TN, DIN, TP, TDP, SRP) data from snowpack samples in the Athabasca Oil Sands Region, Alberta, Canad

Deposition map of total dissolved phosphorus in 2014 snowpack.

<p>Interpolated loads of total dissolved phosphorus (TDP) (mg/m²) to the Athabasca Oil Sands Region in March 2014. Sedimentary VRS-chl<i>a</i> enrichment factors and DBT enrichment factors from each study lake are overlain.</p

Alternative field curve modelling approach : regional models

In this thesis, we focus on thorough yield curve modelling. We build on extended classical Nelson-Siegel model, which we further develop to accommodate unobserved regional common factors and principal components. We centre our discussion on central European currencies' yield curves: CZK, HUF, PLN and SKK. We propose two novel models to capture regional dynamics; one based purely on state space formulation and the other relying also on principal components of the regional yield curves. Moreover, we supplement the models with two application examples in risk management and structural break detection. The main contribution of this thesis is a creation of a complete framework that enables us to analyse yield curves, to design risk scenarios and to detect structural breaks of various types