Contract Name: NSRP Lake Paleolimnology Survey Consultant Name: Hutchinson Environmental Sciences Ltd.
This report was commissioned by Alberta Environment and Sustainable Resource Development (now Alberta Environment and Parks) to support both the implementation of the Land-Use Framework and the Cumulative Effects Management System. Recreational lakes within the North Saskatchewan Regional plan boundaries are of high ecological and recreational value. To better understand how to effectively manage cumulative impacts on the lakes, it is necessary to understand conditions in the lakes prior to development. Knowing these pre-development conditions will assist in setting reasonable and achievable goals for lake management.
The paleolimnology study was undertaken by Hutchinson Environmental Sciences Ltd. The objective of the study was to provide a paleolimnological reconstruction of water quality conditions at Pigeon and Wabamun lakes. Sediment cores were collected, sectioned, and analyzed to assess temporal variability in paleolimnological indicators. Based on these results, an overview of anthropogenic impacts on lake water quality was to be provided.
Both Wabamun and Pigeon lakes are productive, alkaline, and polymictic, and are situated within a carbonaceous geological setting. These characteristics are known to influence the interpretation of results and were not sufficiently considered in the report. Future work may be required to further describe the limitations and evaluate the data presented in report.
This report has been completed in accordance with the contract issued by Alberta Environment and Parks (AEP). AEP has closed this project and considers this report final. AEP does not necessarily endorse all of the contents of this report, nor does the report necessarily represent the views or opinions of AEP or stakeholders. The conclusions and recommendation contained within this report are those of the consultant, and have neither been accepted nor rejected by AEP. Until such time as AEP issues correspondence confirming acceptance, rejection, or non- consensus regarding the conclusions and recommendation contained in this report, they should be regarded as information only.
Oct 2016 © 2016 Government of Alberta 1 of 96 Hutchinson Environmental Sciences Ltd.
North Saskatchewan Regional Plan:
Lake Paleolimnology Survey
Prepared for: Alberta Environment and Sustainable Resource Development ESRD Contract Number: 140201 HESL Job #: J130053
December 19, 2014
R24112015_J130053_Alberta_Paleo-Final.docx Hutchinson Environmental Sciences Ltd.
4482 97 St. NW. Edmonton AB, T6E 5R9 │587-773-4850 www.environmentalsciences.ca
December 19, 2014 HESL Job #: J130053
Jason Kerr Limnologist - Red Deer - North Saskatchewan Region Suite 202, 4909 – 49 Street Red Deer, Alberta T4N 1V1
Dear Mr. Kerr:
Re: ESRD Contract 140201: North Saskatchewan Regional Plan: Lake Paleolimnology Survey Final Report
We are pleased to submit this final report to you, presenting the approach and results of the paleolimnological studies of Wabamun and Pigeon Lakes. The report contains detailed descriptions of the methodology, results and interpretation of the study. It closes with a summary section where the key results are presented and interpreted; first for each lake individually and then as a comparison of both. This report is intended for a technically instructed audience, but is the foundation for a public face document that will be submitted under separate cover.
We have addressed the various comments received from ESRD and internal reviewers as well as comments on the second draft, and provided a comment disposition table under separate cover that outlines our approach to address comments.
We thank you for the opportunity to assist with this very interesting project and hope that the report will help promote the further application of the paleolimnological approach to informing Alberta lake management.
Sincerely, Hutchinson Environmental Sciences Ltd.
Original signed by:
Dörte Köster, Ph.D. Senior Aquatic Scientist [email protected]
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Signatures
Report Prepared by:
Original signed by:
Dörte Köster, Ph.D. Senior Aquatic Scientist
Original signed by:
Tammy Karst-Riddoch, Ph.D. Senior Aquatic Scientist
Original signed by:
Kris Hadley, Ph.D. Industrial NSERC Fellow
With contributions from Dr. Isabelle Larocque (The Lakes Institute), Dr. Peter Leavitt (University of Regina) and Dr. Yi Yi (Alberta Innovates and Technology Futures).
Report Reviewed by:
Original signed by:
Neil Hutchinson, Ph.D. Principal Aquatic Scientist
Hutchinson Environmental Sciences Ltd.
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Acknowledgments
We would like to thank Chris Teichreb, at that time AESRD limnologist, for leading this project, helping with field work, core sectioning, water quality data acquisition and report review. We thank Bradley Peter and Elynne Murray from the Alberta Lake Management Society for their assistance with sediment coring and sectioning in the lab and Chris Ware with additional field assistance. The report benefited from detailed reviews of a number of ESRD limnologists.
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Executive Summary
Background
Lakes in the North Saskatchewan Region, including Pigeon and Wabamun Lakes, are among the most heavily used recreational lakes in Alberta, in part due to their proximity to urban centres such as Edmonton. These lakes hold significant value as habitat for aquatic life, water sources for municipalities, industries, and farmers and for their aesthetic and recreational value for homeowners and visitors. Recently, apparent increases in algal blooms and fish kills have threatened the ecological integrity of these systems and may negatively affect their value to users. Pigeon Lake and Wabamun Lake both have an extensive history of regional development, but limnological studies are limited to the past ca. 35 years, leading to uncertainty about the degree to which water quality has changed due to human activities. Alberta Environment and Sustainable Resource Development initiated this paleolimnological study to fill this information gap from historical limnological data preserved in lake sediments.
Objectives
The objectives of the study were to
1. Establish predevelopment baseline limnological conditions in Pigeon Lake and Wabamun Lake,
2. Provide insight into the individual and cumulative effects of different factors on lake water quality,
3. Distinguish between natural and anthropogenic nutrient sources,
4. Distinguish between human impacts that can be actively managed through local land use planning (e.g., nutrient inputs from the watershed) and regional or global impacts (e.g., climate change) that require different management strategies, and
5. Understand how physical, chemical and biological processes in the lakes affect their sensitivity to external factors and therefore their responsiveness to potential management actions.
Methods
Sediment cores were collected from the central deep basin in Pigeon Lake and in the western basin of Wabamun Lake. The sectioned cores were sub-sampled and analyzed for radioisotopes (lead-210, cesium- 137), carbon and nitrogen elemental and stable isotopes, algal pigments, diatom algae and chironomid (midge) communities. Surface water total phosphorus (TP) and conductivity were reconstructed using a diatom-based inference model developed for Alberta lakes. The nature and timing of notable changes in paleolimnological data were compared to known land use histories, measured water quality and climate records to assess any potential causes of changes in lake health.
Results
The 40-cm long core from Pigeon Lake represented approximately the past 120 years and the 41 cm-long Wabamun Lake core covered about 270 years, based on the CRS dating model applied to lead-210 data and confirmed by the cesium-137 peak. Both cores therefore captured the period of major land disturbances
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J130053, Alberta Environment and Sustainable Resource Development North Saskatchewan Regional Plan: Lake Paleolimnology Survey with early agriculture in the 1900s and extensive residential development after 1950, while only the Wabamun Lake core covered the time before the arrival of non-native settlers.
Pigeon Lake
Biotic assemblages and sediment chemistry were relatively stable in the sediment core from Pigeon Lake and indicated only minor changes in lake productivity that were coincident with watershed development in the mid-20th Century. More recent changes in the paleolimnological record are most consistent with physical and chemical changes in the lake resulting from declining lake levels and climate change..
In the 1950s, a few paleolimnological indicators suggested an ecosystem change to slightly more productive conditions, represented by a minor increase in colonial and N-fixing blue-green algal pigments, a subtle increase in eutrophic chironomid and diatom taxa and a slight increase in diatom-inferred TP. These changes were in contrast to a decrease in overall algal productivity as indicated by fossil pigments, possibly indicating a small shift of algal communities to more blue-green algae at the expense of other algal groups.
In the 2000s, diatom assemblages indicated a more thermally stable water column and responded to the measured conductivity increase that most likely occurred as the result of evaporative enrichment from declining lake levels. This recent change in algal communities was not caused by sustained increased nutrient levels, as monitored nutrients during this time did not show any trend. There was, however, a larger variability in measured TP and a strong inverse relationship of TP with conductivity since about 2000, which warrant further investigation. This period coincided with reported increased frequency and severity of blue- green algae blooms, suggesting that the changes in diatoms may be associated with similar factors as algae blooms. Warmer surface water temperatures since the 1980s and declining summer wind gust speeds during the past ca. 60 years may have increased water column stability. Both stability and warmer waters are factors known to favour the development of blue-green algae blooms and therefore may have contributed to recent Pigeon Lake algae blooms. A more detailed collection of temperature profile data and thorough analysis of wind speed and direction data and the exploration of their relationship with algal bloom occurrence as well as a temperature reconstruction using fossil chironomid data collected in this study would be useful to test this hypothesis.
Wabamun Lake
There were few consistent patterns across paleolimnological indicators that would suggest any marked changes in trophic status in Wabamun Lake over the past circa 200 years. Compared to Pigeon Lake, however, the sediment record of Wabamun Lake showed some more obvious responses to watershed development, industrial activities and water management.
Starting in the 1950s, algal communities and sediment accumulation rates recorded a response to watershed development. There were increases in diatom and some blue-green algae pigments, but no indication of increased overall productivity in pigments. Increasing carbon and nitrogen accumulation rates and the increase of the eutrophic diatom Fragilaria capucina var. mesolepta, on the other hand, indicated increased aquatic productivity. The trends in these indicators stabilized during the 1970s-1990s, but continued after decommissioning of the Wabamun powerplant, despite reduced nutrient levels in the lake due to the addition of diverted river water.
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Some indicators showed unexplained changes between the 1970s and the late 1990s, coinciding with reduced ice cover in the East Basin due to heated discharge from coal-fired power plant and lower lake levels. The percent of organic carbon and nitrogen decreased, along with several algal pigments, while chironomids preferring benthic habitat increased. These changes were temporary and occurred in parallel with ongoing increases in eutrophic diatom abundance and sediment accumulation rates, suggesting a response to factors other than nutrient availability. Increased macrophyte growth in response to thermal discharge and possibly higher mineralization rates of sediments may have played a role in these patterns.
The only change that started in the 1970s and continued through to the top of the core was a decrease in δ15N stable isotopes, indicating a new source of nitrogen. The explanation for this change remains unclear, but may include a relative increase in importance of groundwater to the water balance, and after 1995 the new source of water from North Saskatchewan River diversion may have contributed to the maintenance of this pattern through to the present.
During the past 20 years, diatom assemblages indicated increased conductivity and increased water column stability and both trends were supported by measured data. These recent changes, like those observed for Pigeon Lake, are most likely due to climate change.
The oil spill in 2005 left little, if any, traces, in the sediment record. No significant changes in paleolimnological indicators were observed at this time, except for the occurrence of chironomid taxa associated with toxicity and one deformity. The presence of those chironomid taxa, however, was not limited to this time, and one deformity out of 25 specimens of the affected species bears little significance, showing the low importance of this event on the studied algal and chironomid biota.
A large unknown for Wabamun Lake is if the observed trajectory of increased productivity in some sediment indicators before 1970 will continue in the absence of thermal water discharge and once diversion of river water is reduced. The most recent samples in the sediment core appear to indicate such a trend, but are not sufficient to be conclusive and have not been confirmed by measured data.
Conclusion and Implications for Lake Management
Taken together, analysis of two well-dated and highly-resolved sediment cores suggests that these shallow prairie lakes are naturally productive, with highly organic sediments, abundant blue-green and green algae typical of summer blooms along with eutrophic diatom and midge larvae assemblages. However, despite diverse and abundant fossil pigments from nitrogen-fixing and potentially-toxic colonial taxa, there was little evidence of pronounced eutrophication of either lake during the 20th century. Instead, total algal abundance is inferred to have declined during parts of the 20th century, with present-day phytoplankton abundance and composition inferred to lie within the natural historical range of the lakes. Both lakes therefore displayed a comparatively lower susceptibility to ecosystem effects from external nutrient inputs than other lakes in the area, due to their naturally nutrient-rich state, small proportion of external watershed sources in P-budgets and small watershed area relative to lake area. This result confirms previously completed phosphorus budgets for both lakes that indicated relatively small portions of lake nutrients originating from the watershed.
Management of these lakes must therefore be informed by the fact that, for every kilogram of reduced nutrient input from the watershed due to improved nutrient management, the nutrient levels in the lakes will decrease by less and more slowly than in other, well flushed or naturally less eutrophic lakes. Small
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J130053, Alberta Environment and Sustainable Resource Development North Saskatchewan Regional Plan: Lake Paleolimnology Survey increases in productivity indicators in response to watershed development in the 1950s in both lakes, however, indicate that some reduction may be possible. Whether nutrient reduction through management efforts would be sufficient to prevent or significantly lessen the occurrence of algal blooms is uncertain. Control of external nutrient inputs, however, remains an important part of Pigeon and Wabamun Lake management and stewardship activities.
Recently (post-2000) reported increases in frequency and severity of blue-green algae blooms in Pigeon Lake cannot be explained by increased nutrient levels, but rather appear to be related to warmer temperatures and increased thermal stability. It is possible, however, that the increased nutrient loads since the 1950s made the lake more susceptible to climate related blooms. One objective for lake and watershed management could therefore be not to increase loads and try to minimize loads to reduce the nutrient baseline and thereby reduce frequency and severity of blooms. Other management actions should be investigated that would address the stability and thermal conditions that are most likely responsible for the recent increase in blooms. Given that the relative roles of weather, internal nutrient loading, watershed inputs and other factors in the development of algae blooms in Pigeon Lake remain largely unknown, further study into these factors is warranted to inform management plans aimed at reducing algal blooms in Pigeon Lake.
Both Pigeon and Wabamun Lakes displayed increases in conductivity and a resulting significant change in diatom assemblages since 1990. Along with thermal stability, this pattern is another indication that physical factors, such as hydrological regime and climate appear to be as important for Pigeon and Wabamun Lake ecosystems as nutrient loads from the watershed. Water quantity and quality management therefore need to be coordinated to obtain the best possible outcome for sustainable, healthy ecosystems in Pigeon and Wabamun Lakes.
This paleolimnological study has provided valuable information on the history of Pigeon and Wabamun Lakes, by describing the ecological baseline, changes in lake health and the most likely factors contributing to these changes. This knowledge will assist watershed and lake managers in identifying priorities, making informed decisions and defining reasonable expectations in their work towards maintaining and improving lake health.
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Table of Contents
Transmittal Letter Signatures Acknowledgments Executive Summary
1. Introduction ...... 11 1.1 The North Saskatchewan Regional Plan ...... 11 1.2 Why Pigeon and Wabamun Lakes?...... 11 1.3 Background on Eutrophication ...... 11 1.4 Why Paleolimnology?...... 12 1.5 Study Objectives ...... 13 2. Study Sites ...... 13 2.1 Pigeon Lake ...... 13 2.1.1 Site Description and History of Human Activities ...... 13 2.1.2 Pigeon Lake Water Quality ...... 15 2.2 Wabamun Lake ...... 16 2.2.1 Site Description and History of Human Activities ...... 16 2.2.2 Wabamun Lake Water Quality ...... 19 2.3 Summary of Lake Histories ...... 20 3. Approach ...... 22 3.1 Sediment Collection and Processing ...... 22 3.2 Paleolimnological Proxies ...... 23 3.2.1 Radioisotopes ...... 23 3.2.2 Carbon and Nitrogen Geochemistry ...... 24 3.2.3 Pigments ...... 25 3.2.4 Diatoms ...... 27 3.2.5 Chironomids ...... 30 4. Results ...... 31 4.1 Pigeon Lake ...... 31 4.1.1 Chronology ...... 31 4.1.2 Carbon and Nitrogen Geochemistry ...... 34 4.1.3 Pigments ...... 36 4.1.4 Diatoms ...... 37 4.1.5 Chironomids ...... 42 4.2 Wabamun Lake ...... 43 4.2.1 Chronology ...... 43 4.2.2 Carbon and Nitrogen Geochemistry ...... 46 4.2.3 Pigments ...... 47 4.2.4 Diatoms ...... 50 4.2.5 Chironomids ...... 53 5. Summary ...... 54 5.1 Summary of Pigeon Lake Paleolimnology ...... 54
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5.1.1 History of Water Quality and Lake Health ...... 54 5.1.2 Knowledge Gaps ...... 55 5.1.3 Implications for Pigeon Lake Management ...... 56 5.2 Summary of Wabamun Lake Paleolimnology ...... 57 5.2.1 History of Water Quality and Lake Health ...... 57 5.2.2 Knowledge Gaps ...... 58 5.2.3 Implications for Wabamun Lake Management ...... 59 5.3 Regional Patterns ...... 59 6. Conclusion ...... 60 7. References ...... 62
List of Figures
Figure 1. Map of Pigeon Lake and Watershed ...... 14 Figure 2. Lake Levels in Pigeon Lake 1925-2013 ...... 16 Figure 3. Map of Wabamun Lake and its Watershed ...... 17 Figure 4. Wabamun Lake Levels 1915-2014 ...... 19 Figure 5. Coring Location in Pigeon Lake ...... 22 Figure 6. Coring Location in Wabamun Lake...... 23 Figure 7. Lead-210, Lead-214 and Cesium-137 Activity in Pigeon Lake Sediment Core ...... 32 Figure 8. CRS-modeled Sedimentation Rates for Pigeon Lake ...... 33 Figure 9. Two Alternative Sediment Chronologies for Pigeon Lake Based on 210Pb and 137Cs Peak ...... 33 Figure 10. Carbon and Nitrogen Geochemistry in Pigeon Lake ...... 35 Figure 11. Pigments in Pigeon Lake ...... 37 Figure 12. Diatom Assemblages Pigeon Lake ...... 38 Figure 13. Trends in Maximum Wind Gust Speeds at the Edmonton International Airport 1960-2012..... 39 Figure 14. Temperature Contour Plots Derived from Profiles taken in Pigeon Lake (1984 to 2012) ...... 41 Figure 15. Chironomids Pigeon Lake ...... 43 Figure 16. Lead-210 and Cesium-137 Activity in Wabamun Lake core ...... 44 Figure 17. Wabamun Lake Chronology ...... 45 Figure 18. Wabamun Lake Sedimentation Rates ...... 45 Figure 19. Carbon and Nitrogen Geochemistry in Wabamun Lake ...... 47 Figure 20. Pigments in Wabamun Lake ...... 48 Figure 21. Diatoms in Wabamun Lake ...... 51 Figure 22. Temperature Contour Plots for Wabamun Lake (1980 to 2012) ...... 52 Figure 23. Chironomids in Wabamun Lake...... 53 Figure 24. Summary of Key Paleolimnological Indicators for Pigeon Lake ...... 55 Figure 25. Summary of Key Paleolimnological Indicators for Wabamun Lake ...... 58
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List of Tables
Table 1. Pigeon Lake Morphometry and Water Quality ...... 15 Table 2. Wabamun Lake Morphometry and Water Quality (2012) ...... 20 Table 3. Summary of Lake Histories ...... 21 Table 4. Comparison of Model and Study Lakes’ Characteristics ...... 28 Table 5. Alberta Diatom Model Performance in Comparison to Other North-American Diatom Models (modified from Gartner Lee Ltd. (2008)) ...... 29
Appendices
Appendix A. Sediment Chronology Appendix B. Geochemistry Appendix C. Algal Pigments Appendix D. Diatoms Appendix E. Chironomids
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1. Introduction
1.1 The North Saskatchewan Regional Plan
Under the Alberta Land Use Framework (LUF), Alberta was subdivided into seven planning areas for the purpose of land-use planning and management of cumulative effects of anthropogenic activities on natural resources. One of these areas is the North Saskatchewan Region (NSR), which extends from Banff National Park in the South-west to the Alberta-Saskatchewan border in the east, and approximately corresponds to the North Saskatchewan River watershed. In the recent “Water Conversations”, a stakeholder engagement strategy undertaken by Alberta Environment and Sustainable Resource Development (ESRD) to collect public input into water issues, healthy lakes emerged as an important issue, demonstrating the importance of lake and watershed management for the development of Regional Plans under the LUF.
1.2 Why Pigeon and Wabamun Lakes?
Lakes in the North Saskatchewan Region, including Pigeon and Wabamun Lakes, are among the most heavily used recreational lakes in Alberta, in part due to their proximity to urban centres such as Edmonton. These lakes hold significant value as habitat for aquatic life, water sources for municipalities, industries, and farmers and for their aesthetic and recreational value for homeowners and visitors. Recently, apparent increases in algal blooms and fish kills have threatened the ecological integrity of these systems and may negatively affect their value to users. Potential causes of these water quality issues may include: 1) nutrient enrichment (eutrophication) from agricultural and other land uses, discharge of treated sewage, failing sewage treatment systems, cottage development, and shoreline conversions, 2) impacts of climate change, e.g., duration of ice cover, temperatures and thermal stability, or 3) changes in hydrology, e.g., residence times and water levels. Pigeon Lake and Wabamun Lake both have an extensive history of regional development (Donahue et al. 2006), but limnological studies are limited to the past ca. 35 years, leading to uncertainty about the degree to which changes in the lakes are attributable to human activities.
1.3 Background on Eutrophication
Eutrophication is the enrichment of surface waters with nutrients and the resulting increased productivity. This process remains a significant global threat to the integrity of freshwater resources despite 50 years of research to identify and manage the factors that degrade water quality (Carpenter et al. 1998, Schindler 2006). For example, UNESCO reports that high biomass of cyanobacteria is ubiquitous in 65 countries, including more than 50% of lowland lakes of Europe, Africa, Australia, and China (Codd et al. 2005). Similarly, excess nutrients, algae, macrophytes and associated hypoxia remain common symptoms of water quality loss in the United States and Canada, with particularly pronounced evidence of eutrophication in many agricultural and urban-impacted regions of North America (e.g., Leavitt et al. 2006). Consistent with these trends, recent studies have suggested that water bodies within the Canadian Prairies have experienced cultural eutrophication during the 20th Century due to changes in regional land use (Hall et al. 1999, Schindler et al. 2012, Adams et al. 2014), and now exhibit substantial degradation of water quality (Orihel et al. 2012).
In cases where eutrophication has been caused by nutrient influx from discrete sources (e.g., cities, factory farms) (Schindler 1977), significant improvements in water quality have been achieved following treatment
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J130053, Alberta Environment and Sustainable Resource Development North Saskatchewan Regional Plan: Lake Paleolimnology Survey or diversion of point-source nutrients, particularly when basins also experience rapid hydrologic flushing (Jeppesen et al. 2005). In contrast, eutrophication by diffuse nutrient sources (e.g., agriculture, atmospheric deposition) has been more difficult to quantify and regulate because non-point influxes are often intermittent (Bennett et al. 2001), derived from large-scale land-use practices (Carpenter et al. 1998), or are regulated by opposing management strategies for food production and environmental quality (Bunting et al. 2007, 2011). Unfortunately, such diffuse nutrient inputs are now the primary cause of aquatic pollution in many regions of the world (Smith 2003, Schindler 2006), including the Canadian Prairies (Leavitt et al. 2006, Bunting et al. 2011, Adams et al. 2014).
Previous paleolimnological studies have shown that many prairie and boreal plain lakes in Alberta are naturally nutrient rich, and therefore blue-green algae and low oxygen may be a natural occurrence (e.g., Hickman and Schweger 1991, Köster et al. 2008). A study of a number of Alberta lakes showed that agricultural land use in the watershed explained only 7% of total phosphorus (TP) patterns in polymictic (shallow, well mixed) lakes, versus 39% in dimictic (deep, thermally stratified) lakes, indicating that it may be more difficult to identify causes of water quality deterioration in polymictic lakes like Pigeon and Wabamun Lakes (Taranu et al. 2010). A synthesis of paleolimnological studies conducted in Alberta lakes (Gartner Lee Limited 2007) concluded that many Alberta lakes are naturally eutrophic, that in some cases they have been more productive in past periods of warmer climate and that since European settlement, productivity in most studied lakes increased around the period of the 1950s to 1970s. Land-use changes were suggested as the causal factors, although there was limited information on the link between watershed land use and water quality (Gartner Lee Ltd. 2007).
1.4 Why Paleolimnology?
One way to identify causes of water quality changes is to relate the observed changes to known changes in the watershed at particular times and thereby infer causation. Monitoring data collected in Alberta lakes indicate relatively stable nutrient and productivity levels over the past ca. 30 years (Casey 2011), but data prior to ca. 1970 are generally unavailable. Extensive historical land disturbances in the Wabamun Lake and Pigeon Lake watersheds began as early as 200 years ago with land clearance, followed by agricultural development in the early 1900s. Substantial cottage development in both watersheds also predates the monitoring record, as does significant coal mining and power generation in the Wabamun watershed. The existing monitoring record is therefore insufficient for establishing the range of natural variability in these lakes and determining the extent to which human activities may have affected lake water quality.
Alberta Environment and Sustainable Resource Development initiated this paleolimnological study to fill this data gap and collect historical limnological data from lake sediments. Physical and chemical properties as well as fossil remains of biota in lake sediments can be used to infer past lake conditions, predating and including the period of non-indigenous settlement. Paleolimnological techniques have been used globally and in many different settings for scientific research, for example to reconstruct climate change, landscape ecology and pollution history. Paleolimnology is a powerful tool to track the natural evolution of a lake and to quantify the relative importance of natural versus anthropogenic-driven changes. This information is crucial for setting reasonable, achievable goals for lake management, e.g., water quality objectives or targets, and to assess the sensitivity of a lake to external stressors.
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1.5 Study Objectives
The objectives of this study were to:
1) Establish predevelopment baseline limnological conditions in Pigeon Lake and Wabamun Lake by reconstructing nutrient concentrations (total phosphorus), algae community composition, chironomid (midge larvae) community composition, and some aspects of lake and sediment chemistry including sedimentary pigments from phytoplankton and other algae (carotenoids, chlorophylls, derivatives).
2) Provide insight into the individual and cumulative effects of different factors on lake water quality,
3) Distinguish between natural and anthropogenic nutrient sources,
4) Distinguish between human impacts that can be actively managed through local land use planning (e.g., nutrient inputs from the watershed) and regional or global impacts (e.g., climate change) that require different management strategies, such as adaptation, and
5) Understand how physical, chemical and biological processes in the lakes affect their sensitivity to external factors and therefore their responsiveness to potential management actions.
We designed a paleolimnologcal study to provide observations on past patterns of lake water quality and aquatic biological communities and to investigate and separate possible causes of change by using multiple independent indicators and comparing the observed lake patterns to readily available historical information on external factors, such as land use, development, and climate.
This information will help stakeholders involved with lake management to better understand the factors influencing present day water quality and to weigh management options and their anticipated outcomes in protecting water quality in Wabamun and Pigeon Lakes.
2. Study Sites
2.1 Pigeon Lake
2.1.1 Site Description and History of Human Activities
Pigeon Lake is located in Leduc County, Alberta, 100 km south-west of Edmonton (53° 01′ 49″ N; 114° 03′ 48″ W) and is one of the most intensively used recreational lakes in Alberta (Figure 1). It has a maximum depth of 9.1 m and a surface area of 96.7 km2. The lake’s primary outflow, Pigeon Lake Creek, runs south to the Battle River, a major tributary of the North Saskatchewan River.
The 187 km2 catchment is highly developed, with over 2,300 private cottages in ten summer villages, as well as two Provincial Parks, Pigeon Lake Provincial Park and Ma-Me-O Beach Provincial Park. Lakeshore properties used to be serviced by septic systems, but many summer villages and communities in the Pigeon Lake area have moved toward banning septic fields and grey water release systems (Pigeon Lake Watershed Association
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Soil in the region is dominated by moderately well-drained Orthic Gray Luvisols which have developed on glacial till originating from the regional Paskapoo bedrock formation. The Paskapoo formation contains massive yellowish brown sandstones and sandy shales with a significant carbonate component, resulting in relatively hard water. Approximately half of the drainage basin remains forest-covered, dominated by trembling aspen and, on poorly drained soils, balsam poplar. The remainder of the watershed has been cleared for agriculture (46%) and residential uses (4%).
Agriculture in the Pigeon Lake drainage basin consists predominantly of feed grains and hay, but there are also cow-calf operations, and several small feed lots (Pinkoski 1988, in Prepas and Mitchell 1990). In Wetaskiwin and Leduc Counties, which include the Pigeon Lake watershed, wheat, barley, and oat were among the most important cereal crops in 2001, along with canola, alfalfa, and other herbs (Statistics Canada, 2007, in Aquality 2008). On average, there were 117 cattle per farm and 371 pigs per farm in 2001 (Statistics Canada, 2007, in Aquality 2008).
Additionally, the Pembina and Bonnie Glen oil fields flank Pigeon Lake to the northwest and southeast, respectively (Pigeon L. Study Group 1975).
Figure 1. Map of Pigeon Lake and Watershed
Source: Atlas of Alberta Lakes (Prepas and Mitchell 1990)
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2.1.2 Pigeon Lake Water Quality
Pigeon Lake is an alkaline, eutrophic lake with elevated concentrations of nutrients and algal biomass (Table 1) with frequent recent nuisance algae blooms in 2006, 2007, 2011 and 2012. Monitoring data collected since 1983 by the Alberta government shows that total phosphorus levels have not changed significantly and that total dissolved solids have increased in the lake (Casey 2011). Lake level has declined during the same time (Casey 2011; Figure 2), likely resulting in increased water residence time as well. The long term record also shows, however, a period of low water levels in the late 1950s and 1960s (Figure 2).
Table 1. Pigeon Lake Morphometry and Water Quality
Parameter Units Median* Minimum Maximum
Surface Area km2 96.7
Watershed Area km2 187 Depth m 6.2 pH 8.48 8.4 8.76 Conductivity μS/cm 316.5 311 328 TP mg/L 0.028 0.015 0.042 TN mg/L 0.94 0.47 1.18 Nitrate + Nitrite -N mg/L 0.006 0.006 0.007 Chlorophyll - a mg/m3 23 2 48
Calcium mg/L 25.3 22.5 28.5 Chloride mg/L 3.34 3.23 4.18
* Mean for Lake Depth; Source: ESRD, unpublished data.
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Figure 2. Lake Levels in Pigeon Lake 1925-2013
Pigeon Lake Daily Water Levels (1924 - Oct 7, 2013)
851.0
850.5
850.0
Elevation (m) Elevation FSL = 849.935 m
849.5
849.0 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 00 05 10 15 Year Source: Teichreb et al. 2014
2.2 Wabamun Lake
2.2.1 Site Description and History of Human Activities
Wabamun Lake (53° 31′ 47″ N; 114° 35′ 14″ W) is located in Parkland County, Alberta, approximately 60 km west of the City of Edmonton (Figure 3) and is one of the most studied lakes in Alberta. Wabamun Lake is large (82 km2) and has a similar depth as Pigeon Lake (maximum depth = 11 m). On its northern side, the lake is flanked by two villages (Lakeview and Point Alison), one hamlet (Fallis) and the Village of Wabamun. Two additional summer villages, Seba Beach and Betula Beach, are located on the western and southern shores, respectively. Most residences are serviced by septic systems (Schindler et al. 2004), which were estimated to contribute about 2% of the phosphorus to Wabamun Lake’s total phosphorus budget (Emmerson 2008). Much of the south and north eastern shores of the lake is owned by TransAlta Utilities and used to mine coal for power generation (see Figure 1 in Schindler et al. 2004). Approximately half of the Wabamun watershed is cleared or used for agriculture, particularly for hay, barley, oats and cattle production (Reid, Crowther Partners Ltd. 1973, in Prepas and Mitchell 19990). Wabamun Lake Provincial Park on the western end of the lake includes 318 campsites, extensive day-use areas, hiking trails and a sandy swimming beach.
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Figure 3. Map of Wabamun Lake and its Watershed
Source: Atlas of Alberta Lakes (Prepas and Mitchell, 1990)
Non-native harvesting of fish in Wabamun Lake began in the mid-19th century and fishing pressure on the lake has been heavy since, including one of Alberta’s largest commercial fisheries (Schindler et al. 2004). Settlers from Edmonton and area began visiting the lake around 1910, taking advantage of organized weekend railway excursions (Mitchell and Prepas 1990). Shoreline cottage development started during this period. Summer villages were built at Lakeview on Moonlight Bay and at Kapasiwin.
The percentage of the Wabamun Lake area that was cultivated increased from 8% in ca. 1920 to about 30% in the 1960s and the number of cattle increased from 40,000 to 135,000 (Lindsay et al. 1968). Although these data do not correspond exactly to the watershed area of Wabamun Lake, they are a reflection of land use trends in the area and therefore are likely coarsely representative of the Wabamun watershed.
Coal mining in the Wabamun Lake watershed began with underground operations in 1910, with strip mining beginning in 1948 (Mitchell and Prepas 1990). As these mining activities have moved west, reclaimed land has largely been used for agricultural purposes. TransAlta Utilities Corporation opened the Wabamun Power Plant in 1956, using the locally mined coal and the lake water for cooling and returning the heated effluent directly to the lake via a canal. The heated discharge water from the Wabamun Power Plant was about 10°C above lake temperatures in summer, peaking at about 30°C in August. In winter, the average effluent temperature was about 15°C above lake temperature, and occasionally as high as 24°C (Golder Associates 1997, in Schindler et al. 2004). As a result, an area of 1.2 to 5.4 km2 was kept from freezing
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J130053, Alberta Environment and Sustainable Resource Development North Saskatchewan Regional Plan: Lake Paleolimnology Survey over in winter by the warm water discharge, representing 1.5 % to 7% of the lake’s area. The discharge of cooling water was discontinued when the plant was decommissioned in 2010.
The Sundance Plant was opened in 1970 on the shore opposite the Wabamun Plantand also initially used lake water for cooling purposes, but switched in 1975 to a large cooling pond near the lakeshore with water supplied by and returned to the North Saskatchewan River. In addition to these two plants, the Keephills Plant borders the Wabamun Lake watershed, with the plant being outside the watershed and its cooling pond located within the watershed boundaries.
The operation of coal-fired power plants resulted in heavy metal and PAH contamination of the lake from atmospheric deposition, resulting in up to 4-fold increases of sediment metal concentrations (Donahue et al. 2006). Some metals exceeded sediment guidelines for the protection of aquatic life, but no impacts on aquatic life were detected (Schindler 2004). The surface coal mining at the south shore resulted in reduced lake levels, as all surface runoff from this area, representing about 25% of the Wabamun Lake watershed, was collected for treatment and released to the North Saskatchewan River. In order to counter this undesired hydrological effect, river water from the NSR has been diverted, treated at the Lake Wabamun Water Treatment Plant and added to the lake since 1997, with high initial diversion volumes and smaller volumes recently.
The water level of Wabamun Lake (Figure 4) has been subject to a number of human caused variations during the 20th Century, due to manipulations of the outflow channel and weir height by parties with conflicting interests (Schindler et al. 2004). Lower lake levels observed in 2002-2003 reduced the volume of the lake by 17%, causing considerable loss of fish habitat and increasing salinity of the lake basin. Several years of drought and TransAlta coal mining activities have also contributed to the low water levels during this period. As a result of dry conditions, there has been little runoff entering the lake. The near lack of outflow from the lake causes chemicals that are not biologically or chemically reactive such as sodium and sulfate to become more concentrated as water evaporates. In addition to evaporative enrichment of ions, sodium, sulfate and chloride are added to treat the water discharged to the lake by the WLWTP, further increasing lake concentrations of ions (Schindler et al. 2004).
On August 3rd, 2005 a Canadian National (CN) freight train derailed spilling an estimated 734,000 litres of heavy bunker C fuel oil and 700,000 litres of Imperial Pole Treating Oil into the lake, the latter of which contained naphthalene and other toxic polycyclic aromatic hydrocarbons (PAHs).
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Figure 4. Wabamun Lake Levels 1915-2014
Source: ESRD 2014 (unpublished data). Data were taken from Water Survey Canada (WSC) finalized data at 05DE002 (WABAMUN LAKE AT WABAMUN) Station. The most recent data (2012-2014) is taken from WISKI NRT data and should be considered as preliminary.
2.2.2 Wabamun Lake Water Quality
Wabamun Lake is an alkaline lake that is enriched with ions and nutrients (Table 2). Previous studies have shown that Wabamun Lake is naturally eutrophic with abundant blue-green algae (Hickman and Schweger 1991, Hickman et al. 1984). Phosphorus budgets indicated that about half of the lake phosphorus stems from internal loading (Emmerton 2008). Trend analysis on the ESRD long-term lake monitoring dataset covering the years 1983-2008 indicated that total dissolved solids (TDS) and ammonia-nitrogen (N) increased, while dissolved organic carbon (DOC) and phosphorus (total and dissolved) decreased, with step trends detected in 1999 and 2005 (Casey 2011), the former likely due to the influence of treated diverted water from the NSR.
The effect of the two power plants near the lakeshore, their associated coal mines and the heated effluent on water quality in Wabamun Lake has stimulated much controversy (Reid, Crowther Partners Ltd. 1973; Noton 1974; Beak Consult. Ltd. 1980; Habgood 1983, in Prepas and Mitchell 1990). One hypothesized effect of the extended open-water season was the proliferation of Elodea canadensis, a submerged aquatic plant in the early 1970s, although it declined in abundance starting in 1977.
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The majority of water quality studies on Lake Wabamun were conducted from the mid-1970s to early 1980s. Another burst of activity in the late 1990s and into 2000-2003, was primarily due to public concern about TransAlta’s activities on the lake. Little information is available on the lake prior to 1970, nor are there many data, other than Alberta Environment monitoring data, for a period of approximately 6 years in the mid to late 1980s (Schindler 2004).
Table 2. Wabamun Lake Morphometry and Water Quality (2012)
Parameter Units Median* Minimum Maximum
Surface Area km2 82
Watershed Area km2 259 Depth m 5.1 11 pH 8.47 8.06 8.74 TDS mg/L 353 343 363 Conductivity μS/cm 599 592 616 TP mg/L 0.034 0.023 0.041 TN mg/L 0.99 0.93 1.19 Nitrate + Nitrite -N mg/L 0.0025 0.0025 0.009 Chlorophyll - a mg/m3 8.6 6 17.9 Dissolved Organic Carbon mg/L 11.2 9.7 12.1 Chloride mg/L 13 12.6 14.1
* Mean for Lake Depth: Source: AESRD.
2.3 Summary of Lake Histories
The early history of both lake’s watershed was likely similar, with first settlers arriving in the 1800s and the first significant logging and agriculture beginning in the early 1900s. The settlement history with increased recreational use starting in the early 1900s and significantly increasing in the 1950s is common to both lakes as well. Both have relatively small watersheds compared to their size, and in these moderate amounts of agricultural land use occur. Wabamun Lake, however, has also been significantly influenced by the coal mining and power industries, which affected its hydrology, ice cover and sediment chemistry, while human activities in the watershed of Pigeon Lake have remained predominantly recreational in nature (Table 3).
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Table 3. Summary of Lake Histories
Time Wabamun Lake Pigeon Lake Pre-1800 First Nations First Nations 1800-1900 First Settlers First Settlers 1900s early agriculture early agriculture 1912: Village of Wabamun, Summer Villages 1910 1914 weir built on Pigeon Lake Underground coal mining 1910 Artificial outlet constructed 1920 1927 weir built to recreate natural levels 1924 Ma-Me-O Beach Resort Weir rebuilt in 1939/40 Whitefish, walleye, pike populations 1940 24% of area cultivated by 1944 collapsed due to overfishing (Alberta Environment 2008) 1950 Surface Coal Mining starts 1948 1948 Ma-Me-O Beach Summer Village 1957 Ma-Me-O Provincial Park 32% of watershed area cultivated by 1961 established 1960 Wabamun Coal-Fired Powerplant online Walleye Populations eliminated (Alberta 1963- 2008 Environment 2008) Sundance Coal-Fired Powerplant 1970 Reduced ice cover in eastern basin Increased growth of aquatic macrophytes 1967 Pigeon Lake Provincial Park 1970 & benthic algae (early 1970s) established Increased trace metal and mercury Increasing water levels until early 1980s deposition (Donahue et al. 2006) Increasing water levels until early 1980s 1980s high water levels and erosion In the 1980s, lake levels decreased by problems, lead to clearing of outflow 1980 about 36 inches (0.9 m) because vandals channel dug a ditch to bypass the steel weir. 1986 Alberta Environment replaced the old weir with a new two-bay structure Decreasing water levels due to diversion Decreasing water levels of runoff from surface mining outside Significant increasing trend in TDS 1990s watershed; increased residence time; Walleye successfully re-introduced 1992 to 2004 no outflow occurred (Alberta Environment 2008) 1997 to present NSR water treated and 2000s diverted to Wabamun Lake Algae blooms 2006, 2007 2005 Railway Oil Spill 2010 Wabamun Plant stops discharging 2010s Algae blooms 2011, 2012 cooling water Sources: Alberta Atlas of Alberta Lakes, if not otherwise noted.
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3. Approach
3.1 Sediment Collection and Processing
Pigeon Lake and Wabamun Lake were sampled on September 19th and 29th, 2013, respectively. Several sediment cores were collected from the central deep basin in Pigeon Lake (Figure 5) and in the western basin of Wabamun Lake (Figure 6). A 7.6 cm diameter modified KB gravity corer was used to collect cores (Glew 1989). Sediment cores were between 35 and 50 cm in length and the two longest cores with an undisturbed sediment-water interface and minimal smearing at the core tube were selected for the study. The cores were immediately wrapped in black plastic bags, placed on ice, secured in an upright position and transported to the ESRD field centre.
Figure 5. Coring Location in Pigeon Lake
Coring Location
Note: Coring location is approximate and based on field staff personal communication (C. Teichreb).
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Figure 6. Coring Location in Wabamun Lake
Coring Location
Note: Coring location is approximate.
In the laboratory, the cores were sectioned in dampened light using a vertical extruder (Glew 1988) at 0.5- cm (top 10 centimetres) to 1-cm (10 cm and lower) resolution. Sediment samples were stored in industrial grade Ziploc bags. Samples from one core were frozen for archiving purposes and samples from the other core were sub-sampled immediately for pigment, geochemistry and lead-210 analyses. Pigment samples were frozen and shipped on ice to the analytical laboratory in Regina. The remaining material was kept cool and dark for further sub-sampling for diatom and chironomid analysis.
Sub-sampling intervals focussed on a high temporal resolution of recent times, when the largest human impacts would have occurred. In addition, climate data are available at a high resolution for this time period and could potentially allow development of relationships between sediment records and observed climate patterns. Sediments below ca. 30 cm depth were assumed to be of pre-settlement age, based on the common settlement horizon at ca. 25 cm in other Alberta lakes. These sediments were sub-sampled at coarser intervals to ensure information for these times were collected while using project resources carefully.
3.2 Paleolimnological Proxies
3.2.1 Radioisotopes
The age of sediments in the cores was determined by the analysis of lead-210 (Pb-210) and cesium-137 (Cs-137). Lead-210 is a naturally occurring isotope of the Uranium-238 (U-238) decay series. Pb-210 is derived from the decay of gaseous Radon-222 (Rn-222), the daughter of Radium-226 (Ra-226). As Rn-222 diffuses to the atmosphere, Pb-210 is produced and subsequently falls to the surface of soils and sediments. In lake sediments, Pb-210 derived from this atmospheric fallout is termed 'unsupported' Pb-
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210 since it cannot be accounted for by decay of the in situ parent. Sediment age can therefore be determined from the amount of unsupported Pb-210 remaining in the sediment. With a half-life of 22.26 years, the amount of unsupported Pb-210 will approximate supported levels in ~150 years. In addition, peaks of the artificial isotope Cesium-137 (Cs-137), from the period of maximum nuclear weapons testing fallout in ~1963-4 was used to provide an independent age marker to confirm and refine chronologies.
Subsamples from 20 sediment intervals from each core were analyzed for gamma-emitting radioisotopes (Pb-210, Pb-214, Cs-137) by gamma spectrometry at the L.A.N.S.E.T. facility at the University of Ottawa, which specializes in radiometric analysis of natural isotopes for dating sediment and peat cores for use in paleoenvironmental reconstructions. This state-of-the-art laboratory serves academic research at the university as well as the broader Canadian and international scientific community.
Radioisotope activity was determined using an Ortec High Purity Germanium Gamma Spectrometer (Oak Ridge, TN, USA). Certified Reference Materials obtained from International Atomic Energy Association (Vienna, Austria) were used for efficiency corrections, and results were analyzed using ScienTissiME (Barry’s Bay, ON, Canada).
The amount of unsupported Pb-210 in a sediment sample was calculated by subtracting the amount of Pb- 214 from the total Pb-210 activity. Pb-214 is a short-lived daughter product of Ra-226 and therefore assumed to be in radioactive equilibrium with supported Pb-210. Sedimentation rates and age-depth profiles for each sediment core were then developed from changes in the activity of unsupported Pb-210 using the Constant Rate of Supply (CRS) dating model (Appleby 2001). In this model, Pb-210 concentrations are assumed to change due to radioactive decay (aging) and changes in sediment accumulation rate. If the concentrations of unsupported Pb-210 do not decline with depth, the CRS model interprets these changes as fluctuations in the rate of sediment accumulation. In undisturbed systems, an exponential shape of the Pb-210 profile provides assurance that the sediment system is behaving as theory would predict.
Dates for sediment intervals not analyzed were determined by linear interpolation of dates between dated intervals. Sediment samples older than ~150 years (with no unsupported Pb-210 activity) were estimated by linear extrapolation of the mean CRS-modeled dates for the bottom 3 dated intervals to the base of the cores. While a linear fit is not the appropriate model for long sediment chronologies due to the compaction of sediments and potential changes in sedimentation rates over time, it is the simplest available approximation for a short section of sediment, for which compaction would not change significantly over the depth intervals in the bottom sections of the core.
3.2.2 Carbon and Nitrogen Geochemistry
Carbon and nitrogen elementary content and isotope records preserved in lake sediments provide information on the origin of organic matter, variation of lake productivity, availability of nutrients, lake mixing regimes and changes in hydrology and climate, which affect the delivery of organic matter to the lake (Meyers and Ishiwatari, 1993; Talbot 2001; Herczeg et al., 2001). This process-related information can constrain the interpretation of microfossil records and improve the understanding of the impact from anthropogenic activities on a lake ecosystem.
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Preparation of lake sediment samples prior to instrumental analysis closely followed the protocol developed at the Environmental Isotope Laboratory, University of Waterloo (Wolfe et al., 2001). Samples were first sieved to <500 m to eliminate macrofossil plant debris, which are likely of terrestrial origin. A small proportion of fine fraction was reserved for nitrogen (elemental and isotopic) analysis, while the majority of the fine fraction was acidified using hydrochloric acid (HCl), in order to remove inorganic carbon, calcium carbonate (CaCO3). The aliquot of fine fraction, free of carbonate, was then used for carbon (elemental and isotopic) analysis. This procedure ensured that carbon and nitrogen analyses were prepared and completed in a separated manner to avoid potential effects of acidification on the nitrogen content and isotopic composition of the sample (Kennedy et al., 2005). Acidification of the samples was completed as follows:
1. 200 to 300 mg (dry weight) sediments were treated with 1 M HCl at 60°C (water bath) for a minimum of two hours, stirring gently to enhance the contact of sediments with acids. 2. The pH was checked to ensure samples remained acidic. If no acidic or visible reaction occurred upon agitation, supernatant was removed, fresh HCl added, and step #1 repeated. If acidic, supernatant was removed, deionized water added and the sample stirred. 3. Samples were allowed to settle for 24 hours then supernatant was removed, and samples were rinsed repeatedly with deionized water once a day until pH was neutral. 4. Supernatant was removed and samples were frozen and freeze-dried for organic carbon elemental and isotope analyses.
The instrumental arrangement for elemental and isotopic analysis was a NA1500 Fisions Elemental Analyzer (EA) interfaced to Isotope Ratio Mass Spectrometer (MAT253, Thermo Scientific) in continuous flow modes. Approximately 2 mg of sample material were weighted and dropped into the elemental analyzer for combustion at 900°C. Organic materials in the sediment were completely converted to CO2 and N2 in the EA and then carried by helium flow to a mass spectrometer for isotopic determination. The carbon (or nitrogen) content of the sample was measured based on the peak area of CO2 (or N2) gas eluted from the EA and reported in percentage (%) relative to the accurate weight of the sample. The stable isotopic 13 12 15 compositions were determined by measuring CO2 and CO2 species for the carbon isotope and N2 and 14 N2 species for the nitrogen isotope in the mass spectrometer. Results were reported in the notation as the isotopic ratios in the sample (Rsample) relative to that of a standard (Rstd) in per mil (‰) (Meyers and Teranes, 2001).
푅푠푎푚푝푙푒 훿푠푎푚푝푙푒 = 1000 ( − 1). 푅푠푡푑
Vienna Pee Dee Belemnite (VPDB; Craig 1957) and AIR (Mariotti 1983) are standards used for carbon and nitrogen results, respectively. The reproducibility of C and N content is better than ±0.1%; the uncertainties for 13C and 15N results are ±0.1‰ and ±0.18‰ respectively.
3.2.3 Pigments
Historical changes in the abundance and gross community composition of primary producers were quantified using fossil pigments derived from algae and phototrophic bacteria (Leavitt and Hodgson 2001). Previous validation of this approach in whole-lake experiments has demonstrated that these pigments are deposited in lake sediments in direct proportion to their abundance in the water column (Leavitt and Hodgson 2001). Consequently, the amount and types of fossil pigments in each sediment layer can be
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J130053, Alberta Environment and Sustainable Resource Development North Saskatchewan Regional Plan: Lake Paleolimnology Survey used to assess past changes in algal community characteristics including past abundance of total algae, total cyanobacteria, colonial cyanobacteria, Nostocales cyanobacteria, N2–fixing cyanobacteria, green algae, cryptophytes, diatoms alone, all siliceous algae, and dinoflagellates (Leavitt 1993; Leavitt and Hodgson 2001). The majority of our data were derived using the classic HPLC method, which allows detailed analysis of many different pigments. It was complemented for Wabamun Lake by a more recent method that is less labour-intensive than HPLC and non-destructive, which provides data on total algal biomass through chlorophyll-a spectral reflectance.
3.2.3.1 HPLC Analysis
Sedimentary pigments were extracted, filtered and dried under N2 gas following the procedures of Leavitt and Hodgson (2001) at Environmental Quality Analysis Laboratory (EQAL) at the University of Regina. Briefly, lipid-soluble pigments were extracted from the bulk sediments by soaking freeze-dried sediments in a mixture of acetone : methanol : water (80 : 15 : 5, by volume) for 24 h in darkness and under an inert N2 atmosphere at 4°C. Pigment concentrations were quantified by reversed-phase high performance liquid chromatography (RP-HPLC). Specifically, carotenoid, chlorophyll (Chl), and pigment-derivative concentrations were quantified using an Aligent 1100 HPLC system following the reversed-phase procedure of Leavitt and Hodgson (2001). The Agilent 1100 system was equipped with a C-18 column (5- μm particle size; 10-cm length), and an Agilent model 1100 photodiode array spectrophotometer (435-nm detection wavelength). An internal reference standard (3.2 mg L-1) of Sudan II (Sigma Chemical Corp., St. Louis, MO) was injected in each sample.
Pigments isolated from sediments were compared to those from unialgal cultures and authentic standards obtained from US Environmental Protection Agency and other suppliers (Leavitt and Hodgson 2001). Pigment identity was based mainly on spectral characteristics and chromatographic mobility of pigments from all sources. Pigment analysis was restricted to taxonomically-diagnostic carotenoids characteristic of the following algal groups; diatoms, chrysophytes and some dinoflagellates (fucoxanthin,), mainly diatoms (diatoxanthin), cryptophytes (alloxanthin), chlorophytes (pheophytin b), chlorophytes and cyanobacteria (lutein-zeaxanthin), filamentous or colonial cyanobacteria (myxoxanthophyll), Nostocales cyanobacteria (canthaxanthin), potentially N2-fixing cyanobacteria (aphanizophyll), Oscillatoriaceae (oscillaxanthin), all cyanobacteria (echinenone) and the major a, b, and c-phorbins (Chls and derivatives), although not all compounds were recorded in every sample. Pigment concentrations were expressed as nmol pigment g-1 total carbon (TC). Estimates of TC content were derived from stable isotope determinations. Estimates of post-depositional pigment degradation were derived from analysis of ratios of labile precursor, Chl a, to chemically-stable product, pheophytin a, as described by Leavitt and Hodgson (2001). Finally, estimates of historical changes in the penetration of ultraviolet radiation (UVR) was estimated using a ratio of a cyanobacterial photo-protective compound to the sum of carotenoids derived from cryptophytes, diatoms, chlorophytes and cyanobacteria (alloxanthin, diatoxanthin, lutein-zeaxanthin). This UVR ratio increases as a linear function of the exposure of algae to UVR in whole-lake experiments (Leavitt et al. 1997).
3.2.3.2 Spectrally-inferred Chlorophyll a
As a novel method to track temporal changes in the whole-lake primary productivity of Wabamun Lake, we used spectral analysis to infer trends in sedimentary chlorophyll a (Chl a) concentration. Briefly, this analysis infers [Chl a] based on a unique trough found in the 650-700nm range of the spectral profile of the lake sediments (Michelutti et al. 2005). The area of this trough has been correlated to the concentration of
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Chl a and its derivatives in the sediment, providing a rapid, non-destructive method for estimating primary productivity. Following the development of this technique, research has demonstrated the applicability of the method in a variety of ecological settings (Michelutti et al. 2010). Sedimentary spectral profiles were obtained using a FOSS NIRSystems Model 6500 series Rapid Content Analyzer, operating over the range of 400 to 2500 nm.
3.2.4 Diatoms
Diatoms are a group of microscopic algae that have been widely used in paleolimnological studies due to their ubiquitous distribution, defined ecological preferences and thoroughly-studied taxonomy. Their siliceous cell walls are usually well preserved in lake sediments and provide a record of past water quality, such as pH, conductivity and trophic status. Diatoms were chosen as paleoindicators for this study as they have proven useful for the reconstruction of past trends in lake productivity, which is one of the main objectives of this study. Based on the relative abundance of diatom species with different nutrient preferences, we can describe past productivity trends in a qualitative way, but also quantitatively by application of models to reconstruct water quality parameters (see section 3.2.4.1).
Sediment subsamples were shipped to LABIAQ inc., (Laboratoire d'analyse de bioindicateurs aquatiques de Québec), in Charny, Québec, Canada, for diatom slide preparation. This laboratory specializes in processing sediments for paleolimnological analyses. A minimum of 1 mL of wet sediment from each sampling interval was processed for diatoms using standard strong acid digestion techniques as outlined in Pienitz and Smol (1993), but using concentrated sulfuric and nitric acids instead of potassium dichromate and sulphuric acid. An aliquot of the resulting slurry was evaporated onto coverslips and then mounted onto glass microscope slides with Naphrax®, a highly refractive mounting medium (refractive index = 1.74). The diatom slides were scanned with a microscope at 1,000x magnification to ensure even distribution of diatoms across the coverslip with a maximum concentration of approximately 10 valves in a single field of view.
Diatom identification and enumeration was completed by Dr. Tammy Karst-Riddoch, with input on taxonomy by Drs. Dörte Köster and Kristopher Hadley. Drs. Karst-Riddoch and Köster are experienced paleolimnologists and senior aquatic scientists at HESL, each with more than 15 years of experience in diatom identification and enumeration. Dr. Hadley is a post-doctoral research fellow at HESL (in partnership with Queen’s University, Kingston, ON, Canada) with 8 years of experience in diatom identification and enumeration.
A minimum of 300 diatom valves were identified and enumerated for each sediment sample along random transects of the coverslips under oil immersion using a Nikon microscope fitted with differential interference contrast (DIC) optics at 1,500x magnification. The slides were counted in random order to prevent bias in taxonomic identification of the diatoms.
Diatom data were expressed as taxon relative abundances (%) of the total sum of the diatom valves in each sample. Principal Component Analysis (PCA) was used to summarize the variation in diatom assemblages over time with depth in core. Zones in the core with similar diatom flora were determined by depth- constrained cluster analysis (Constrained Incremental Sum of Squares, CONISS) with the broken-stick model to identify significant partitions using the “rioja” package (Juggins, 2009) in R v. 2.13.2. For both the PCA and CONISS, diatom abundance data were square-root transformed to stabilize variance and
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J130053, Alberta Environment and Sustainable Resource Development North Saskatchewan Regional Plan: Lake Paleolimnology Survey downweight the influence of dominant taxa, and rare taxa (with a maximum abundance of <1%) were excluded to eliminate their influence on the analyses. PCA analysis and plotting of the diatom profiles were performed using specialized software for ecological and palaeoecological data analysis and visualisation (C2 Version 1.5; Juggins (2007)).
3.2.4.1 Diatom-based TP and Conductivity Reconstructions
Diatom-based models can be used to reconstruct water quality parameters quantitatively from fossil diatom samples analyzed in sediment cores. Such models are developed using diatoms found in modern, surface sediments of large sets of lakes (usually between 30 and 100 lakes) and statistically relating these recent diatom species assemblages to measured water chemistry in the water column. Using a variety of multivariate statistics, the strength and nature of relationships of diatom assemblages with water quality variables can be described and a regression-like model established. This model can then be applied to fossil diatom assemblages found in older sediment samples to reconstruct numeric values for the water quality variables of interest for times represented by the sediment core, most importantly, times for which no measured values exist. These models are also called diatom-inference models and the reconstructed values are commonly referred to as diatom-inferred values.
The conductivity model applied here was developed for Alberta Environment in 2008 (Gartner Lee Ltd. 2008) and the TP model was the result of further analysis of the same dataset after completion of that report (Köster and Prather 2008). These models were developed from Alberta lakes with similar lake and watershed characteristics to the study lakes (Table 4) and have strong predictive capabilities that are comparable or stronger than published models from other areas (Table 5) and are therefore considered to provide reliable reconstructions.
Table 4. Comparison of Model and Study Lakes’ Characteristics
Pigeon Wabamun Variable Conductivity Model TP Model Lakea Lakeb Number of Lakes 112 46 - - 0.21 – 96.7 Surface Area (km2) 0.18 – 96.7 (2.3) 96.7 79 (7.9) 6.0 – 60.0 Maximum Depth (m) 0.5 – 60.0 (3.6) 9.1 10.9 (10.7) Mean Depth (m) - - 6.2 5.1 10 – 2,816 Conductivity (S/cm) 28-2,816 (335) 283 [164] 489 (214) Total Phosphorus (g/L) 4 – 442 (50) 4 – 106 (33) 29-35 [26.7] 30 0.35 – 2.7 910-1,100 Total Kjeldahl Nitrogen (mg/L) 0.41 – 2.26 (1.15) - (0.98) [785] TN:TP 12.8 – 69.7 (33.8) 8 – 90 (28) 30 30c Notes: afrom Aquality (2008), values in square brackets represent average 2013 values reported by Teichreb et al. (2014); bfrom Aquality (2013); ccalculated from reported average TN of 900 ug/L and TP of 30 ug/L; values in round brackets indicate the median.
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Table 5. Alberta Diatom Model Performance in Comparison to Other North-American Diatom Models (modified from Gartner Lee Ltd. (2008))
2 Model performance (r jack or boot) Authors Location No. of sites Zmax Cond pH TP TN
Gartner Lee Ltd. 2008 Alberta 113 (26) 0.60 0.67 0.56 0.731 0.482 Köster and Prather 2008 Alberta 46 - - - 0.653 - Bradbury 2002* British Columbia 111 - - - 0.47 - Hall and Smol 1996 Ontario 54 - - 0.82 0.41 - Werner and Smol 2005 Ontario 101 - - - 0.47 0.42 Reavie et al. 2001 Ontario 64 0.38 0.52 0.49 0.47 0.38 Philibert and Prairie 2002 Quebec 76 - - 0.69 0.51 0.36 Siver 1999 Connecticut 50 - 0.78 0.81 - 0.47 Gregory-Eaves et al. 1999 Alaska 51 0.53 - - 0.52 - Dixit et al.1999 New England (U.S.) 238 - - 0.89 0.55 - Ponader et al. 2007 New Jersey (streams) 45 - - - 0.69 0.50 Western North Adams et al. 2014 271 (266) 0.47 0.693 America Tremblay et al. 2014 Ontario and Quebec 55 - - - 0.71 - *using a subset of lakes from a model published by Cumming and Smol (1993); 1subset of 23 lakes with maximum depth >6 m dimictic lakes; 2subset of 26 lakes; 3subset of 266 lakes
The conductivity model is a weighted-averaging model based on a set of 112 Alberta lakes that ranged in 2 conductivity from 10 to 2,800 uS/cm (r boot = 0.67, RMSEP = 0.30 uS/cm, maximum bias = 0.64 uS/cm). Among 13 variables analyzed (Area, Ca, CI, conductivity, maximum depth, Mg, pH, SO4, TDS, alkalinity, TP, TKN, latitude, longitude, TN:TP), conductivity was the variable that displayed the strongest relationship with diatom assemblages, and was therefore an excellent candidate for model development. The model is most reliable in the low and middle range of the conductivity gradient (<1,000 uS/cm), as indicated by trends in residuals of the relationship between measured and predicted values, using a rigorous re-sampling method to test model performance (bootstrapping).
The TP model was constructed from a subset of 46 lakes from the 112 Alberta lake set, including only lakes with a maximum depth greater than 6.5 m. In the complete dataset including all lakes, diatom assemblages did not a display strong relationship with TP, but they did with maximum depth suggesting that the TP– diatom relationship was masked by a large influence of depth. By removing shallow lakes (<6 m) and thereby reducing the influence of depth, the diatom-TP relationship emerged more strongly and resulted in 2 a model with statistical performance (r boot = 0.65, RMSEP = 0.16 (log10) ug/L, maximum bias = 0.60 (log10) ug/L) similar or superior to other published diatom TP models (Table 3). The hampering effect of shallow lakes on TP model performance may be explained by larger variability in both TP and diatom communities in shallow lakes due to unpredictable mixing events and changing nutrient limitation over the course of the year (with nitrogen limitation occurring in summer in highly eutrophic lakes) as well as the strong influence
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J130053, Alberta Environment and Sustainable Resource Development North Saskatchewan Regional Plan: Lake Paleolimnology Survey of benthic habitat availability. In fact, mass TN:TP ratios indicating nitrogen limitation (<14) only occurred in 3 lakes (6%) in the TP model dataset had, in contrast to 18 lakes (16%) in the complete dataset.
There are other diatom calibration sets available that have been published in the scientific literature (e.g. Cumming and Smol 1993 and expanded by Moos et al. 2009) and used to develop and apply nutrient inference models to Alberta lakes (e.g., Adams et al. 2014), but they have the disadvantage of not being developed from Alberta lakes. Local models usually have a better representation of local conditions, such as climate and soils, and better species analogues (similarity) between the model and fossil assemblages. Application of the Alberta TP model to sediment core samples from mesotrophic to eutrophic lakes in the Beaver River Basin (Moose, Wolf, and Kehewin Lakes) for example, showed much better agreement of diatom-inferred TP with measured values than if using the published larger BC model of Cumming and Smol (1993), supporting the hypothesis that the Alberta model is more applicable to Alberta lakes (Köster and Prather 2008).
Applicability of the conductivity and phosphorus models for use with the study lakes is supported by the good representation of fossil diatoms in the training set samples. Minimum dissimilarity coefficients (DCs, Bray and Curtis) between the fossil and model diatom assemblages are below the 20th percentile of the DCs for both models and the fossil samples are therefore considered to have good analogues in the calibration sets. Furthermore, the majority of taxa in the fossil samples are present in the training sets representing at least 82% and 93% of the diatoms in any one fossil assemblage for Pigeon Lake and Wabamun Lake, respectively.
In summary, the combination of models that have strong predictive capability and that are representative of local conditions of the study lakes and their diatom flora provides for confident reconstructions of conductivity and TP.
3.2.5 Chironomids
Chironomids (non-biting midges) are flying insects (adult phase) with larval phases living in most water bodies. The head capsule of the larvae is made of chitin, a substance that preserves in lake sediments for thousands of years. It can be isolated from the sediment matrix and identified, usually to the level of genus, by light microscopy. The larval development is mostly influenced by nutrients, levels of oxygen and temperature (Brodersen and Lindegaard 1999) and as such, chironomids have been previously described as one of the most powerful tools to reconstruct changes in these parameters in paleolimnological studies (Battarbee 2000). Chironomid analysis provides another independent proxy of changes in lake productivity along with the diatoms, pigments and stable isotopes. More importantly, as sensitive indicators of oxygen and temperature, the chironomids can provide valuable information on aquatic habitat conditions, water mixing regimes, the potential for internal phosphorus loading from the sediments due to anoxia and the role of climate change and variability on water quality of the study lakes.
Sediment samples were freeze-dried and mailed to The L.A.K.E.S Institute in Switzerland. Samples were placed in a solution of 10% KOH overnight, and then sieved with a 90-µm mesh. The remnant was poured into a Bogorov tray and observed under a stereomicroscope at 10X magnification. Each head capsule was picked with tweezers and mounted on a microscope slide in a drop of Hydromatrix. The head capsules were then identified under a light microscope at 40-100X magnification. The taxonomy followed Larocque and Rolland (2006), Brooks et al. (2007) and Larocque (2014).
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Chironomid data were expressed as taxon relative abundances (%) of the total sum of the chironomids in each sample. The relative abundance of eutrophic and anoxic taxa was determined based on known ecological preferences of taxa following Brookes et al., (2007). Principal Component Analysis (PCA) was used to summarize the variation in chironomid assemblages over time with depth in core. Zones in the core with similar chironomid assemblages were determined by depth-constrained cluster analysis (Constrained Incremental Sum of Squares, CONISS) with the broken-stick model to identify significant partitions using the “rioja” package (Juggins, 2009) in R v. 2.13.2. PCA analysis and plotting chironomid profiles were performed using specialized software for ecological and palaeoecological data analysis and visualisation (C2 Version 1.5; Juggins (2007)).
4. Results
4.1 Pigeon Lake
4.1.1 Chronology
210Pb activity varied in the top 5 cm of the sediment core, (Figure 7), likely indicating sediment mixing in the oxygenated part of the sediment, which was also highly liquid (water content of 94-95%, Appendix A). Total 210Pb activity declined near exponentially from 5 cm to ~18 cm depth as expected from radioisotope decay. Between 19 cm and 29 cm it varied between zero and 50 Bq/kg, similar to background levels, as indicated by the parent isotope 214Pb. At 32 cm, total 210Pb activity increased above background to 100 Bq/kg and then returned to low background levels at 36 and 39 cm.
The maximum 137Cs activity occurred at depths of 12.5 and 15.5 cm (Figure 7), which would correspond to the 1963 peak in nuclear weapons testing.
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Figure 7. Lead-210, Lead-214 and Cesium-137 Activity in Pigeon Lake Sediment Core
Pigeon Lake 800
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Activity Activity (Bq/kg) 200
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0 0 5 10 15 20 25 30 35 40 45 -100 Depth (cm)
210-Pb 214-Pb 137-Cs
Note: The grey shaded box indicates the area where low total 210Pb occurred.
The sediment depth at which 210Pb reaches background levels is key for developing a chronology based on the constant-rate-of-supply method. Based on the activity profile, two possible depths for background were identified: 17.5 cm and 35.5 cm. Background 210Pb at 17.5 cm assumes lower sedimentation rates with the increase in 210Pb at 32.5 cm due to measurement error or sample contamination with more recent sediments (Figure 8). If background 210Pb is at 35.5 cm, the low activity between 17.5 and 32.5 cm is inferred to occur due to rapid sedimentation rates or a dilution event over that sediment interval (Figure 8). Chronologies were developed for both scenarios and plotted against the 137Cs peak that occurred at 12.5 and 15.5 cm depth (Figure 9). The cesium peak corresponded best with the chronology based on 35.5 cm background. Based on this line of evidence, we selected the latter chronology for discussing paleolimnological indicators in the Pigeon Lake core but note that either chronology is possible. Both chronologies provide very similar dates for the past ~30 years before they begin to deviate. Dates older than ~1980 should be interpreted with caution recognizing the potential that they may be considerably older.
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Figure 8. CRS-modeled Sedimentation Rates for Pigeon Lake
Note: Sedimentation rates cannot be modeled where no 210Pb activity is detected (at 19.5 cm and 28.5 cm)
Figure 9. Two Alternative Sediment Chronologies for Pigeon Lake Based on 210Pb and 137Cs Peak
Pigeon Lake 2020
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CRS Year ([email protected] cm) CRS Year ([email protected]) Cesium Peak (1963)
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4.1.2 Carbon and Nitrogen Geochemistry
Geochemical analyses of carbon and nitrogen confirmed that sediments from Pigeon Lake are rich in organic matter that originates primarily from in-lake productivity. Overall, patterns in elemental and isotopic carbon and nitrogen did not suggest any significant change in lake productivity over time beyond a possible slight trend of increasing aquatic productivity since the early 1900s.
The organic rich nature of the sediments from Pigeon Lake was reflected by the relatively high organic carbon (C) content that varied between 10% and 17% (Figure 10). Nitrogen (N) content ranged between 1.2% and 2.5% resulting in C/N ratios less than 10 (Figure 10). Organic matter produced within a lake (autochthonous) is usually characterized by low C/N ratios between 4 and 10 because algal biomass is rich in N-rich protein but poor in C-rich lignin (Meyers and Ishiwatari, 1993; Herczeg et al., 2001). Vascular plants, on the other hand, which dominate terrestrial habitats and are cellulose C-rich and protein-poor, contribute organic matter that usually has much higher C/N ratios of 20 and greater. The low C/N ratios in the Pigeon Lake sediments therefore suggested the predominance of autochthonous organics in the lake, and were consistent with the productive status (mesotrophic to eutrophic) and the small watershed to lake- surface ratio of Pigeon Lake.
Variations of C and N contents in the sediments closely tracked each other, and both displayed a general increasing trend over time since ~1900 (Figure 10). N content nearly doubled from the bottom to the top of the core, while C content increased by ~60%. Accordingly, C/N ratios decreased over time beginning ~1920, which could indicate an overall trend to a larger aquatic carbon source from greater algal productivity.
The13C and 15N signatures of sediment organic matter are strongly controlled by production of organic matter from dissolved inorganic carbon (DIC) and dissolved inorganic nitrogen (DIN) in the water column. Changes of 13C and 15N in DIC and DIN affect the final isotopic signature of organic matter. Phytoplankton preferentially utilize light isotopes (12C and 14N) to produce organic matter. When high primary productivity raises the demand for DIC and DIN, algae may be forced to increasingly rely on the heavier isotope for primary production resulting in an increase in 13C and 15N. In the Pigeon Lake sediments, only minor variations occurred in 13C (-26.6‰ to -27.7‰) and 15N (4.1‰ and 4.7‰) (Figure 10) suggesting no significant change in lake productivity.
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Figure 10. Carbon and Nitrogen Geochemistry in Pigeon Lake
%C %N C/N delta-13C delta-15N
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1890 9 11 13 15 17 0 1 2 4 6 7 8 9 -29 -28 -27 -26 4 5 per mil per mil
Preservation (or the post-depositional diagenesis) is another major process that can alter the elemental composition and isotopic signatures of organic matter in the early stage of deposition and sedimentation. Organic matter in lake sediments consists of a spectrum of constituents that vary in resistance to degradation and that have a range of 13C values. In general, protein and carbohydrates are isotopically (13C) heavy, while cellulose and lipids are dominated by carbon that is relatively light in 13C. In the early stage of diagenesis, selective loss of labile organics (e.g., proteins and carbohydrates) would leave residue organics isotopically lighter with higher C/N ratios (Shelske and Hodell, 1991; Meyers and Ishiwatari, 1993; Spike and Hatch, 1994; Lehmann et al., 2002). This pattern was not observed in the Pigeon Lake core (lower 13C values generally corresponded to lower C/N ratios), suggesting that there were no significant changes in degradation of organic matter.
In addition to these primary factors, changes in pH, temperature, nutrient limitation, and growth rate could also affect the isotopic signature of organic matter produced by phytoplankton (Fogel and Cifuentes, 1993; Laws et al., 1995). Over time, the isotope and elemental signatures of sedimentary organic matter may change as a consequence of a shift in one or more of the above-mentioned processes. All in all, the interpretation of 13C (and 15N) record alone does not provide conclusive answers and requires integration with other proxies.
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4.1.3 Pigments
Sedimentary pigment analysis revealed little evidence of marked historical changes in total algal abundance within Pigeon Lake during the past ca. 150 years (Figure 11). Concentrations of chemically-stable pheophytin a and β-carotene declined slowly and irregularly during the period of time encompassed by the core, with no evidence of lake eutrophication. Fossil concentrations of chemically-labile pigments (Chl a, fucoxanthin) declined monotonically in a pattern consistent with slow changes in pigment preservation. Consistent with this interpretation, Chl a : pheophytin a ratios followed the decline in absolute Chl a content, reaching stable baselines in the mid-20th Century (Figure 11). The observation that other, chemically-stable pigments did not record this trend demonstrates that Chl a is not a reliable metric of past algal abundance in Pigeon Lake. Similarly, relatively high inter-decadal variation in concentrations of ubiquitous pheophytin a and β-carotene were difficult to interpret, as they may have reflected either low signal-noise ratios in the fossil record or actual, but transient, changes in inferred lake production.
Fossil pigments from phytoplankton known to bloom in spring (cryptophytes, diatoms) exhibited few consistent temporal trends (Figure 11). Concentrations of diatoxanthin from diatoms increased slightly in the early 20th century (ca. 1930-1945), while there were no substantial changes in abundance of the cryptophyte pigment, alloxanthin (Figure 11).
Fossil concentrations of pigments from phytoplankton common during summer (chlorophytes, cyanobacteria) revealed few consistent changes in Pigeon Lake during the past ~125 years that would suggest significant eutrophication (Figure 11). Concentrations of carotenoids from colonial cyanobacteria th (myxoxanthophyll) and N2-fxing forms (aphanizophyll) increased during the 20 Century (ca. 1940 and ca. 1970 respectively) while pigments from the Nostocales group (canthaxanthin), chlorophytes (pheophytin b), and a mixture of chlorophytes and cyanobacteria (lutein-zeaxanthin) varied little since ca. 1900. Although increases in abundance of colonial and N2-fixing cyanobacteria are often consistent with eutrophication, the observation that total abundance of phytoplankton (as pheophytin a, β-carotene) actually declined through the same period suggests that summer blooms were not as severe as those noted in other prairie lakes (Hall et al. 1999, Bunting et al. 2011) and that changes in colonial cyanobacteria did not regulate overall lake production. In fact, aphanizophyll was the only pigment that clearly showed highest levels in the 2000s compared to the remainder of the sediment core, a pattern supported by the biomass dominance of the associated Aphanizomenon species in a Pigeon Lake phytoplankton survey in 2008 (ESRD, unpublished data). The increase in colonial and N2-fixing cyanobacteria is therefore more likely associated with factors such as thermal stability rather than overall nutrient enrichment that favour these forms over other summer blooming algae.
Ultraviolet radiation (UVR) indices were too low to interpret reliably, despite apparently sudden changes in the mid-20th century. The pattern is consistent with higher exposure of algae to UVR, however the low absolute index may indicate either only modest changes in transparency, or an increase in phytoplankton exposure to UV associated with enhanced surface blooms.
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Figure 11. Pigments in Pigeon Lake
fucoxanthin (siliceous)diatoxanthin (diatoms,alloxanthin chrysophytes) (cryptophytes)pheophytin B (green)lutein-zeaxanthinmyxoxanthophyll (green, blue-green)canthaxanthin (colonial blue-green) aphanizophyll(colonial blue-green) (potentiallyechinenone N (total fixers)Chl blue-green)a (all algae)pheophytin a (chlbeta-carotene a derivative) Chl(all algae)a: pheo a ratioUV-Index (preservation)
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1890 0 100 50 100 50 100 100 200 300100 150 0 20 40 50 60 70 80 0 150 30020 40 60 0 150 300100 200 0 100 2000 1 2 3 0 4 8 nanomoles per g organic carbon 4.1.4 Diatoms
Generally the diatom assemblages were quite stable for the period covered by the core (Figure 12). The diatom community has always been dominated by small benthic Fragilaria species, which tolerate a wide range of environmental conditions and are therefore poor indicators of lake trophic status (Bennion et al. 2010). These species are often associated with physically disturbed environments as they quickly colonize new habitats. This may include a shallow, frequently mixed, environment such as Pigeon Lake.
The first noticeable change in diatom assemblages occurred ca. 1950s, with the appearance of Aulacoseira granulata, a species indicative of eutrophic conditions, and the relative increase in some of the above noted Fragilaria species at the expense of other small benthic species. The magnitude of this change was small, but represented the largest community change as indicated by PCA Axis 1 sample scores (Figure 12). It likely represented a small, but permanent step increase in Pigeon Lake nutrient concentrations, as indicated by a parallel small increase in diatom-inferred TP.
Another important change in diatom assemblages was the post-2000 increase in Fragilaria crotonensis. There are several possible explanations for the increase in this planktonic diatom including nutrient enrichment, increased water depth and hence the availability of planktonic habitat, and physical changes of the water column related to climate change (e.g., lengthening of the growing season, increased thermal stability). F. crotonensis is widely accepted as an indicator of nutrient (P) enrichment in temperate lakes (e.g., Reavie et al. 1995, Kingston 2003) and nitrogen enrichment in oligotrophic alpine lakes (Saros et al. 2005). It has increased in abundance after about 1960 in Lac St. Anne, another eutrophic lake in the North Saskatchewan River watershed (Blais et al. 2000). Nonetheless, monitoring data and diatom-inferred TP do not support nutrient enrichment in Pigeon Lake since ~2000, when the F. crotonensis increase occurred. Lake levels in Pigeon Lake were lower in the 1990s and 2000s than in the previous decades (Figure 2),
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J130053, Alberta Environment and Sustainable Resource Development North Saskatchewan Regional Plan: Lake Paleolimnology Survey eliminating the hypothesis of larger depth for planktonic habitat as an explanation for the increase in this diatom. The most probable explanation, therefore, relates to physical changes in the water column (e.g., thermal stability and mixing, temperature) due to climate change and variability.
Figure 12. Diatom Assemblages Pigeon Lake
CocconeisNavicula disculus scutelloidesFragilaria leptostauronAmphora pediculusFragilaria brevistriataFragilaria construensFragilaria construensFragilaria pinnata var. venterAulacoseiraFragilaria granulata crotonensisNaviculaPCA subrotundata Axis 1 SamplePCA Axis Scores 2 SampleDI-TP Scores DI-ConductivityMeasured ConductivityMeasured TP
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1890 0 0 20 0 20 0 20 0 20 40 0 20 0 20 0 20 40 0 0 20 0 -1 0 1 2 -1 0 1 2 20 25 30100 200 300 250 300 35010 50 90 Relative Abundance (%) ug/L uS/cm uS/cm ug/L
Note: The measured water quality data were annual averages of multiple measurements throughout the open-water season (source: Alberta ESRD).
Warming due to climate change can result in a complex array of physical and chemical changes in lakes to which diatom assemblages respond. Recently published studies report late-20th and 21st century increases in Fragilaria crotonensis in temperate Canadian lakes (Rühland et al. 2010; Hyatt et al. 2011; Enache et al. 2011; Hadley et al. 2013; Cumming 2014). In general, increased relative abundance of this and other planktonic algae has been attributed to climate-driven changes in the physical properties of lakes, including a lengthening of the ice-free season, and the timing, duration and strength of thermal stratification. In deep, dimictic Elk Lake, Minnesota, F. crotonensis dominated assemblages when spring circulation periods were short (Bradbury et al. 2002) supporting their ability to compete under conditions of reduced mixing. The high surface area to volume ratio of these diatom taxa allow them to stay higher in the water column, while less buoyant taxa sink out of the photic zone when water column stability is high. Although Pigeon Lake is generally well-mixed throughout the water column, short periods of water column stability may occur in warm summers, which, together with available nutrients, may cause the preferential growth of F. crotonensis. This is supported by biweekly phytoplankton data collected in 2013, showing peak biomass of this species in late July and mid-August (Teichreb et al. 2014).
Preliminary evidence for reduced mixing of the water column in summer can be found in historical wind records. Maximum gust speeds for all three summer months (July, August, September) measured at the Edmonton International Airport showed a declining trend from the early 1960s to 2012 (Figure 13). There
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J130053, Alberta Environment and Sustainable Resource Development North Saskatchewan Regional Plan: Lake Paleolimnology Survey was a lot of year-to year variation in wind speeds, however, and further analysis is required to assess if there is a relationship between wind speeds at Pigeon lake and water column stability.
Figure 13. Trends in Maximum Wind Gust Speeds at the Edmonton International Airport 1960- 2012
July Speed of Maximum Gust (km/h) 120 110 100 y = -0.4821x + 1030.9 90 R² = 0.3003 80 70 60 50 40 1960 1970 1980 1990 2000 2010
Spd of Max Gust (km/h) Linear (Spd of Max Gust (km/h))
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Temperature profiles, which are the most direct way to measure thermostability, were collected at numerous occasions in Pigeon Lake and indicated somewhat warmer and stable conditions in the most recent decade (Figure 14). Besides favouring the diatom, F. crotonensis, these factors were the second-most important factors explaining high blue-green algae biomass in a cross-Canadian analysis of blue-green algae models (Beaulieu et al. 2014). Increased thermostability and temperatures in Pigeon Lake in the past decade could therefore explain the observed increased abundance of F. crotonensis, the increased relative importance of cyanobacteria inferred from pigment concentrations and increased bloom activity in the past decade.
A minor, short-term increase in Navicula scutelloidis during the 1940s may have indicated an increased availability of the preferred habitat of this algae, which is epipsammic, i.e., on sediments, or a decreased importance of alternative habitat. The increase in this taxon was coincident with the period of increased sedimentation rates from the CRS dating model. This would support an influx of sediment carrying this benthic diatom and the choice of the deeper background 210Pb value.
Diatom-inferred TP was relatively stable, ranging between 22 and 26 µg/L. There was an indication of slightly higher TP levels after 1950, as discussed above, with the 1950-2012 average diatom-inferred TP of 25 µg/L compared to 23 µg/L before 1950. This change coincided with increased recreational development, as indicated by the incorporation of Ma-Me-O-Beach summer village. The periods before and after 1950 displayed relatively stable diatom-inferred TP, confirming that the more recent changes in diatom assemblages after 2000 were not related to nutrient changes. The most recent diatom-inferred TP levels were similar to measured spring TP levels in Pigeon Lake (20-30 µg/L), while in summer, TP usually increased to about 40 µg/L (Teichreb et al. 2014). Diatom species dominate Pigeon Lake phytoplankton mainly in spring and are replaced by green and blue-green algae in summer, indicating that the diatom- inferred values of the model likely reflected spring TP concentrations. Both diatom-inferred and measured TP did not show any directional trend in the past ca. 30 years.
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Figure 14. Temperature Contour Plots Derived from Profiles taken in Pigeon Lake (1984 to 2012)
Note: Black arrows indicate dates for which profiles were available.
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The measured TP data showed a large increase in inter-annual variations since 2000, and measurements were strongly inversely correlated with measured conductivity from 2003-2013 (r2 = 0.94, n = 7, p < 0.001). This suggests that although no long-term TP trend has been detected, other nutrient dynamics may have changed. These changes coincided with the most recent change in diatom assemblages and increased algal bloom activity, indicating that factors controlling conductivity, such as increased run-off during wet years, may also have influenced lake productivity. The relationship between conductivity and algal bloom dynamics warrant further investigation.
Diatom-inferred conductivity was ~200 µS/cm in the early 20th century, was variable in the mid-20th Century and increased considerably after 1990 to values above 300 µS/cm. The appearance of the brackish-water species Navicula subrotundata in 2000 is an example of how diatom communities responded to this change. This increase in conductivity is confirmed by measured data, which increased from around 280-300 µS/cm in the 1980s to 300-320 µS/cm after 1990 (Figure 12). Increased conductivity was likely the result of increased evaporative enrichment with declining lake inflows and levels during this time, supporting physical lake changes (e.g., increased thermal stability, increased evaporation) related to climate (warmer weather, reduced wind speeds) as the most likely explanation for the increase in F. crotonensis.
4.1.5 Chironomids
Forty eight taxa were found in the sediments of Pigeon Lake, but only 29 taxa were common, occurring in at least three samples and with a maximum abundance of at least 2%. The chironomid community composition was remarkably stable with no statistically significant changes over the period of record for which chironomids were analyzed (1903-2013) based on constrained cluster analysis (CONISS).
The main patterns of change in chironomid communities as represented by PCA Axis 1 were fluctuations with no clear directional change that could be attributable to land use history or other factors (Figure 15). These results were consistent with chironomid analyses in prairie lakes of the Saskatchewan Qu’Appelle Valley, where rates of community change did not increase significantly after onset of agriculture (Quinlan et al. 2002) and with the very little changes observed in the paleolimnological study of Lac St. Anne and Lake Isle, Alberta (Blais et al. 2000).
Minor changes were observed ca. 1967, when anoxic and eutrophic taxa proportions were generally at or above average for this dataset (Figure 15). Oscillations in eutrophic taxa abundance of the same magnitude occurred afterwards, however, potentially indicating short-term changes, but no consistent long-term trend towards increasing or decreasing importance of eutrophic taxa.
A secondary pattern in community composition as represented by PCA axis 2 showed a shift in chironomid communities in the 1940s to a slightly different state than pre-1940. This shift was mainly driven by a slight increase in Procladius, which is usually associated with reduced oxygen availability in the bottom waters (Clerk et al. 2000).
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Figure 15. Chironomids Pigeon Lake
ChironomusChironomus anthracinusCladopelma plumosusCryptotendipesDicrotendipes lateralisGlyptotendipesPolypedilumTanytarsini barbipes Cladotanytarsusnubeculoseum sp PseudochironomusTanytarsus no Tanytarsusspur Tanytarsus lugensPentaneuriniProcladius sp B Anoxic TaxaEutrophic TaxaPCA axis 1 PCA axis 2
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1900 0 20 0 20 0 0 0 0 20 0 0 20 0 20 0 0 20 40 0 20 0 0 0 20 0 20 40 0 20 40 -1 0 1 2 -1 0 1 2
% Abundance Sample Scores Note: The vertical lines in the Anoxic Taxa and Eutrophic Taxa profiles represent the average relative abundance.
4.2 Wabamun Lake
4.2.1 Chronology
In Wabamun Lake sediments, 210Pb activity was variable in the very liquid top 6 cm, but then declined as expected from radioisotope decay with sediment age (Figure 16). The 137Cs peak was relatively well defined and occurred at 24 cm depth. The chronology based on 210Pb activity and the CRS model was in close agreement with the 137Cs-derived date for 1963 (Figure 17), providing a high confidence in the estimated sediment dates.
CRS-modelled sedimentation rates displayed an overall increasing trend until the 1980s when sedimentation rates declined and stayed relatively constant until the early 2000s (Figure 18). In the 2000s, sedimentation rates varied, but this is likely an artefact of sampling (some loss of sediment or water is likely in very liquid surface sediments like those of Wabamun Lake).
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Figure 16. Lead-210 and Cesium-137 Activity in Wabamun Lake core
Wabamun Lake 900
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Figure 17. Wabamun Lake Chronology
Figure 18. Wabamun Lake Sedimentation Rates
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4.2.2 Carbon and Nitrogen Geochemistry
Sediments from Wabamun Lake were rich in organic matter with consistently high C content between 19% and 23%. Organic nitrogen content (N) varied little within a range of 2.3% and 2.9%. C/N ratios in all sediment intervals were close to 10 reflecting a predominantly aquatic source of organic matter to the sediments over the past ~300 years (Figure 19).
Overall, variations of elemental and isotopic C and N indicate that there have been no ecologically significant changes in primary productivity in Wabamun Lake since the 1700s. This is supported by the similar patterns of C and N, and hence little variation in C/N, as well as by stable 13C values that varied by only ~1‰. Changes in C and N accumulation, while small in magnitude, however, suggest that the lake has become slightly more productive from ~1950 to ~1990. Both percent C and N in sediments declined over this period reaching minimum values in the early 1990s. This change occurred during a time of increasing sedimentation rates such that despite the relative decline in C and N, their accumulation rates increased, suggesting increased algal productivity over that time period. A similar increase in C and N accumulation rates occurred over the past ~5 years which may suggest further increases in productivity, or may be an artefact of incomplete decomposition in the uppermost sediments.
The most prominent change in the geochemical record from Wabamun Lake was a large decrease in the 15N signature (>1.5‰) from the 1970s to the 1990s, generally coinciding with increased lake productivity inferred from C and N accumulation rates (Figure 19). This decrease is substantial in magnitude and indicates a new source of dissolved inorganic nitrogen (DIN) to algae in Wabamun Lake.
There are several possible sources of DIN that could have contributed to the depleted 15N signatures observed in the late 20th century, including atmospheric N assimilated by nitrogen-fixing cyanobacteria, fertilizer inputs, groundwater or diverted river water. Previous studies found that 15N of plankton declined when eutrophic lakes become hyper-eutrophic because of N2 fixation by cyanobacteria in these highly productive systems (e.g., Gu et al. 1996). Wabamun Lake is not hyper-eutrophic and a corresponding increase in the relative contribution of N-fixing cyanobacteria to algal production was not observed in the pigment data (Figure 20); this is therefore unlikely to be the main cause for the depleted 15N signature. 15 Synthetic fertilizer is generally labelled with N of 0‰, as it is derived from atmospheric N2 (Bateman and Kelly 2007), however, N transformations (e.g., volatilization and denitrification) occurring after N application are well known to result in further elevation of the remaining unreacted N in ground waters and surface waters (Anderson and Cabana 2005), so fertilizer inputs would be expressed as increased 15N signatures in the lake. Fertilizer therefore does not seem to be the reason for decreasing 15N signatures in Wabamun Lake after 1970.
The proportion of groundwater as a water source may have increased when surface water runoff in the southern portion of the watershed was diverted away from the lake for the surface coal mines, but the N isotope signature in the basin is unknown. Further, the addition of treated water from the North Saskatchewan River to Wabamun Lake starting in 1995 may have also contributed to the maintenance of depleted 15N in the more recent sediments. Still, the decrease in 15N in Wabamun Lake since the 1970s remains unresolved.
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Figure 19. Carbon and Nitrogen Geochemistry in Wabamun Lake
%C %N C/N delta-13C delta-15N C Accumulation Rate N Accumulation Rate
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1740 19 21 23 2.2 2.4 2.6 2.8 7.8 8.1 8.4 8.7 -31 -30 -29 -28 2 3 4 5 0.0 0.4 0.8 0.00 0.05 0.10 per mil per mil g/cm^2/yr g/cm^2/yr
4.2.3 Pigments
Analysis of ubiquitous algal pigments (pheophytin a, β-carotene) by high performance liquid chromatography suggested that there had not been a systematic increase in total algal abundance during the past 300 years in Wabamun Lake (Figure 20). For example, although concentrations of chemically- stable pheophytin a increased nearly two-fold after ca. 1990, this increase appeared to record a return to values observed during the 19th and early-20th centuries, after lowest-on-record values were measured from ca. 1970-1990. The timing and magnitude of changes in pigment-inferred total algal abundance were similar when calculated with equally widespread and chemically-stable β-carotene and using the spectral chlorophyll a method (Figure 20), suggesting that this pattern was robust to the choice of fossil biomarker. In contrast, labile Chl a was not well preserved in Wabamun Lake sediments, as recorded by the near- exponential decline in sediment concentration from top to bottom sediments over the 20th century. As a result of these latter declines, precursor : product ratios of Chl a : pheophytin a also exhibited marked changes during the past ca. 300 years, suggesting historical variation in the preservation environment (Leavitt and Hodgson 2001). In particular, lake conditions appeared to favour preservation of easily- degraded pigments after ca. 1980, whereas there were few changes in Chl : pheophytin ratios between ca. 1750 and ca. 1980 (Figure 20).
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Figure 20. Pigments in Wabamun Lake
fucoxanthin (siliceous)diatoxanthin (diatoms,alloxanthin chrysophytes) (cryptophytes)Pheophytin B (green)lutein-zeaxanthinmyxoxanthophyll (green and canthaxanthinblue-green) (colonial blue-green) aphanizophyll(colonial blue-green) (potentiallyechinenone N (total fixers)Chl blue-green)a (all algae)pheophytin a (chlbeta-carotene a derivative) Chl(all algae)a: pheo a ratioUV-Index (preservation)Spectral-inferred Chlorophyll a
2000 1980 1960 1940 1920 1900 1880 Year 1860 1840 1820 1800 1780 1760 1740 0 50 100 150 250 100 300 100 200 300 500 0 50 100 50 100 0 100 20050 100 0 200 400 100 200 100 400 0 1 2 0 10 0.06 0.09 0.12 nanomoles per g organic carbon
At present, we cannot reliably evaluate how land use changes associated with agricultural or shoreline development may have impacted phytoplankton abundance in the early 20th century. Total algal abundance is inferred to have declined ca. 1970-1990, in sharp contrast to patterns of 20th century eutrophication seen in other prairie lakes (e.g., Hall et al. 1999, Bunting et al. 2011). Shading by nuisance growth of Elodea canadensis in the early 1970s (Prepas and Mitchell 1990) or top-down food-web control as a result of a “cold shock” fish kill episode, which occurred in February 1973, and resulted in the loss of an estimated 250 pike and 250,000 spottail shiners (Schindler et al. 2004), are some possible reasons for this decline in algal abundance.
Shallow prairie lakes are known to be naturally eutrophic (Blais et al. 2000, Adams et al. 2014), however, some of these systems also experienced substantial water quality degradation due to the influences of non- aboriginal agricultural practices in the late 19th century (Hall et al. 1999, Bunting et al. 2011), concomitant urban development (Leavitt et al. 2006), and more recent changes in land use (Blais et al. 2000, Adams et al. 2014). Although climatic warming during the 20th century is thought to enhance algal production (Paerl and Huisman 2008), most paleolimnological research to date suggests that climate change since the Little Ice Age has had little effect on prairie water quality relative to that associated with development of European-style agriculture or urbanization (Hall et al. 1999, Leavitt et al. 2009, Bunting et al. 2011). Unfortunately, high variability in fossil pigment concentration during ca. 1750-1900, combined with low sample frequency, make it difficult to quantify baseline conditions in Wabamun Lake prior to ca. 1900 (Figure 20).
Analysis of taxon-specific biomarker pigments suggested that the abundance of spring-blooming phytoplankton has not increased notably during the past 300 years (Figure 20). Comparison of vernal taxa
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J130053, Alberta Environment and Sustainable Resource Development North Saskatchewan Regional Plan: Lake Paleolimnology Survey revealed that cryptophyte abundance (as alloxanthin) varied little between ca. 1750 and ca. 2000, before increasing to an historical maximum in sediments deposited during the past decade. In contrast, concentrations of chemically-stable diatoxanthin from diatoms increased during the first half of the 20th century before declining ~30% to a minimum at the start of the 21st century. Selective increases in diatom abundance in the early 20th century have occurred in both Lake Winnipeg (Bunting et al. 2011) and Lake Manitoba (Leavitt et al. unpublished data) mainly in response to crop production and increased influx of nutrients. In contrast, low-light adapted cryptophytes often exhibit little change in abundance in response to regional development of agriculture (Hall et al. 1999, Bunting et al. 2011), possibly reflecting differences in mineral nutrient requirements of diatoms and cryptophytes. In particular, diatoms but not cryptophytes require Si for cell wall construction, and so may be more responsive to changes in soil erosion associated with agriculture. The increase in diatoxanthin between 1920 and 1960 may therefore be an indication of increased diatom productivity in response to increasing agricultural activity in the watershed at that time, as indicated by the increasing coverage of cultivated land and rising numbers of life stock (see section 2.2.1).
Analysis of fossil pigments from summer taxa (chlorophytes, cyanobacteria) suggested that the abundance of summer bloom-forming phytoplankton had changed little since ca. 1750 (Figure 20). Carotenoids from the cyanobacteria (myxoxanthopyll, canthaxanthin, aphanizophyll, oscillaxanthin, echinenone) were consistently abundant during the past 300 years, suggesting that Wabamun Lake is naturally eutrophic. In particular, elevated concentrations of aphanizophyll and canthaxanthin demonstrate that colonial, potentially-N2-fixing, and often toxic cyanobacteria are a common component of the phytoplankton. This conclusion is consistent with prior analysis of pigments in Wabamun Lake sediments which showed that cyanobacteria have been abundant in this basin for millennia (Hickman and Schweger 1991). In general, abundance of cyanobacterial biomarkers exhibited few pronounced trends during the 20th century, other than a transient increase in potentially N2-fixing taxa (as aphanizophyll) and mixed markers of cyanobacteria and chlorophytes (lutein-zeaxanthin) during ca. 1940-1960. Instead, concentrations of most pigments from cyanobacteria pigments and those derived exclusively from green algae (pheophytin b) declined during much of the 20th century to reach an historical minimum ca. 1990. Thereafter, historical patterns varied among biomarkers, with continued declines in the abundance of the Oscillatoriaceae (oscillaxanthin) and N2-fixing taxa (aphanizophyll), and increases in total cyanobacteria (echinenone), colonial cyanobacteria (myxoxanthophyll) and chlorophytes (pheophytin b, lutein-zeaxanthin) during the past ~15-20 years. Together, these analyses suggest that while summer bloom-forming phytoplankton are common in the lake, their modern abundance is within the historical range recorded since ca. 1750.
Pigment analyses suggest that plankton exposure to UV radiation has been low during the period of time encompassed by the core (Figure 20). Although exposure to UVR appeared to increase after ca. 1965, roughly concomitant with the commissioning of the Wabamun power plant and changes in ice cover during winter (Hickman 1974, Donahue et al. 2006), UVR indices were ~10-fold lower than those recorded in highly transparent lakes with elevated exposure to UVR (Leavitt et al. 1997). Furthermore, as increases in UVR index corresponded closely with changes in preservation environment inferred from Chl : pheophytin ratios (see above), we suggest that historical patterns of UVR index are not subject to simple interpretation.
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4.2.4 Diatoms
During the early and mid-20th century, Wabamun Lake diatom assemblages were dominated by Aulacoseira spp., indicating a well-mixed water column, and small Fragilaria spp., an indicator of the availability of benthic (shallow water) habitat (Figure 21).
In the 1970s and 1980s, the small Fragilaria species F. pinnata increased, possibly indicating the increase in shallow water habitat. F. capucina var. mesolepta, a larger, tychoplanktonic species (living both in attached and planktonic forms) that is usually associated with eutrophic conditions (e.g., Gregory-Eaves et al. 1999) increased in abundance as well, at the expense of Aulacoseira species, indicating increased productivity due to nutrient enrichment, as observed elsewhere (e.g., Pienitz et al. 2006).
In the 1990s, the planktonic species Stephanodiscus minutulus, F. crotonensis and Asterionella formosa as well as F. capucina var. mesolepta increased in relative abundance, while the small Fragilaria species and Aulacoseira species declined in relative terms. This trend continued more so in the 2000s, resulting in another significant change in diatom assemblages as identified by cluster analysis (CONISS, see section 3.2.4). Relative increases of these species have previously been associated with nutrient enrichment of lakes (e.g., Pienitz et al. 2006), but in Wabamun Lake were not accompanied by increases in phosphorus concentrations, which actually declined during that period (Casey 2011). This is confirmed by generally stable diatom-inferred TP concentrations and results in other paelolimnological indicators, such as pigments and geochemical indicators (see section 5.2), which did not display consistent indication of increased productivity.
Alternatively, increases in F. crotonensis and Asterionella formosa have been interpreted as indicators of increased water column stability, as discussed in Pigeon Lake (Rühland et al. 2010; Hyatt et al. 2011; Enache et al. 2011; Hadley et al. 2013; Cummings 2014). In fact, the patterns of increased abundance of F. capucina var. mesolepta, F. crotonensis and Asterionella formosa after 1950 and their further increase after 2000 resemble patterns observed in polymictic Kehewin Lake (Alberta), which were strongly correlated with climate records, i.e. ice-out date, precipitation and tree-ring records (Köster et al. 2004). Temperature profile data from Wabamun Lake east basin, although incomplete, indicate an increase in water temperature and water column stability from the 1980s to the 2010s (Figure 22), supporting the hypothesis that physical lake characteristics have played a role in the recent diatom assemblage changes.
Diatom-inferred conductivity increased at the same time, in accordance with conductivity monitoring data (Figure 21), suggesting that increased ion content was another driving factor for the diatom assemblage changes. The same climatic factors, however, may have affected both the physical environment (thermostability) and chemical lake characteristics through evaporative enrichment.
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Figure 21. Diatoms in Wabamun Lake
CyclotellaAulacoseira bodanica ambigua var. lemanicaAulacoseira granulataFragilaria brevistriataFragilaria construensFragilaria pinnataCyclotellaDiatoma ocellataStephanodiscus tenuis Fragilaria minutulus crotonensisFragilaria capucina var. mesoleptaAsterionellaDiatom-Inferred formosa Diatom-Inferred TP Measured Conductivity MeasuredTP Conductivity 2020 3 2000 1980 2
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1800 1780 0 0 20 40 0 20 0 20 0 20 0 20 0 0 0 20 0 20 0 20 40 60 0 2020 30 40200 400 60015 25 35 400 600 Relative Abundance (%) ug/L uS/cm ug/L uS/cm
Note: The measured water quality data were annual averages of multiple measurements of Main Basin composites throughout the open-water season from 1983 to 1998, 2010 and 2012 and averages of East and West Basin Composite for 1981, 1982, and 1999- 2008 (source: Alberta ESRD). The numbered column indicates groups of samples that are significantly different from each other, as indicated by stratigraphically constrained cluster analysis (CONISS).
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Figure 22. Temperature Contour Plots for Wabamun Lake (1980 to 2012)
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4.2.5 Chironomids
Forty-three taxa were found in the samples from Wabamun Lake with 30 common taxa (i.e., present in at least 3 samples and with a maximum abundance of at least 2%). Since the late 1700s, the assemblages were dominated by anoxic and eutrophic indicator taxa including Chironomus spp. and Tanytarsus spp. suggesting that Wabamun Lake is naturally productive (Figure 23). Only minor changes occurred in the record and no significantly different zones were detected in the fossil chironomid record using stratigraphically constrained cluster analysis (CONISS).
The most obvious change in assemblages occurred between ca. 1973 and 1990, when the proportion of eutrophic/anoxic taxa decreased. As anoxic taxa and eutrophic taxa are mainly represented by the Chironomus types, which are also profundal taxa, we interpret this decrease as associated with lower lake levels or improved oxygen conditions due to the lack of winter ice cover in the east basin.
Since 2003, new taxa appeared in the chironomid community, such as Cryptotendipes, Stichtochironomus, Tanytarsus lactescens-type and Tanytarsus pallidicornis-type. Posthuma et al. (2010) found increases in Cryptotendipes following an increase in toxicity. The observed increase in Cryptotendipes might therefore be associated with the oil spill of 2005. Furthermore, one head capsule of Chironomus had a mentum (mouthpart) deformation, which is an indicator of pollution (MacDonald and Taylor 2006), although it was only one out of 25 Chironomus head capsules, suggesting only minor effects, if any. Stichtochironomus, Tanytarsus lactescens-type and Tanytarsus pallidicornis-type are all littoral taxa (Armitage et al., 1995; Brooks et al., 2007) which might suggest an increase in near-shore productivity.
Figure 23. Chironomids in Wabamun Lake
Chironomus ChironomusanthracinusCladopelma plumosusCladotanytarsus lateralisCryptotendipesParatanytarsus mancusPentaneuriniPolypedilumProcladius nubeculoseumStictochironomusTanytarsiniTanytarsus sp no Tanytarsusspur Tanytarsus glabrescensTanytarsus lactescensTanytarsus lugensTanytarsus mendaxAnoxic pallidicornis Taxa Eutrophic TaxaPCA axis 1 PCA axis 2
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1770 0 20 40 0 20 40 0 20 0 20 0 0 0 0 0 20 0 0 20 0 20 40 0 20 0 0 20 0 20 0 0 20 40 60 20 40 60 -1 0 1 2 -1 0 1 2 % Abundance Sample Scores Note: The vertical line in the Anoxic Taxa and Eutrophic Taxa profiles represents the average relative abundance.
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5. Summary
This section summarizes and discusses results of key indicators together for each lake. By visualizing similarities and differences and their coincidence with historical information, past changes in lake water quality can be inferred along with possible causal factors. Limitations of our study and persisting knowledge gaps are presented, as well as potential means of filling these gaps.
5.1 Summary of Pigeon Lake Paleolimnology
5.1.1 History of Water Quality and Lake Health
The sediment record from Pigeon Lake showed relatively stable biotic assemblages and sediment chemistry throughout the core, but minor changes in paleolimnological indicators coincided with watershed development and recent chemistry changes associated with lake level declines.
The only sedimentary patterns indicating ecosystem change included a small shift in diatom assemblages, a minor increase in colonial blue-green algae and N-fixing algae, a slight, non-significant increase in eutrophic chironomid taxa and a slight increase in diatom-inferred TP in the 1950s. These changes were in contrast to a decrease in overall algal productivity, possibly indicating a minor contribution of these algae groups to total annual algal productivity. The small shift of algal communities to more blue-green algae at the expense of other algal groups is represented by sediment samples at an annual to multi-year scale, however, so it does not exclude the possibility of more significant changes on shorter time scales, such as months or weeks, which were not resolvable with this sediment record.
In the 2000s, diatom assemblages indicated a more stable water column and responded to the measured conductivity increase that occurred as the result of evaporative enrichment from declining lake levels. This recent change in algal communities was not caused by sustained increased nutrient levels, as monitored nutrients during this time did not show any trend. There was, however, a larger variability in TP and a strong inverse relationship of TP with conductivity since about 2000, which warrant further investigation. This period coincided with reported increased frequency and severity of blue-green algae blooms, suggesting that the changes in diatoms may be associated with similar factors as algae blooms. Warmer surface water temperatures since the 1980s and declining summer wind gust speeds during the past ca. 60 years may have increased water column stability. Both stability and warmer waters are factors known to favour the development of blue-green algae blooms and therefore may have contributed to recent Pigeon Lake algae blooms.
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Figure 24. Summary of Key Paleolimnological Indicators for Pigeon Lake
Geochemistry Pigments Biota Water Quality
Sediment compositionPercent (C:N Organic Ratio)All Carbon Algae (Beta-carotene)Blue-green Algae Nutrient-tolerant(Myxoxanthophyll) MidgeFr. crotonensis Larvae (a Inferredsummer Totalalgae) PhosphorusInferred Conductivity
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5.1.2 Knowledge Gaps
The uncertainty related to the Pigeon Lake chronology places some limitations on the interpretation of the study. Observed changes may have occurred at different times, limiting our ability to correlate them with human activities or weather patterns. This uncertainty is low in the most recent sediments, however, and increases with depth, so correlations with recent monitoring data can still be regarded as reliable. If using the alternative chronology, the changes in trophic indicators currently placed at ca. 1950, would be placed at the early 20th century, which could be related to early clearing and agriculture. This uncertainty would not change the overall conclusion of the study that the Pigeon Lake trophic status has changed little during the 20th century and that there is no evidence of recent eutrophication that could have led to the observed increased frequency and severity of algal blooms.
In the absence of recent trends in monitored and diatom-inferred nutrient concentrations, additional factors that can create favorable conditions for algal blooms need to be considered. It has commonly been reported that prolonged periods of calm and warm weather favour the development of blue-green algae blooms (e.g., British Columbia Ministry of Environment 2014). Our preliminary analysis of water temperatures indicated a recent trend towards warmer waters and a decreasing trend in maximum wind gust speeds. A more detailed collection of temperature profile data and thorough analysis of wind speed and direction data and
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J130053, Alberta Environment and Sustainable Resource Development North Saskatchewan Regional Plan: Lake Paleolimnology Survey the exploration of their relationship with algal bloom occurrence as well as a temperature reconstruction using fossil chironomid data collected in this study would be useful to test this hypothesis. Other changes in the lake ecosystem that were concurrent with recent algal bloom activity are lower lake levels, higher ion concentrations, larger variations in surface water TP, and a strong negative correlation of TP with ion concentrations. These patterns should also be investigated for their potential role in algal bloom formation and their link with watershed activities.
5.1.3 Implications for Pigeon Lake Management
Overall, Pigeon Lake water quality and biota have changed relatively little over the past 150 years. It appears that human activities in the watershed had only minor impacts on the lake’s long-term trends in trophic (nutrient) status, and that these impacts were mostly seen as a small shift around the 1950s, with minor changes in diatom algae and benthic communities, increased relative abundance of blue-green algae, and somewhat more organic sediments. These changes indicate that there is a potential for nutrient controls from the watershed to help reduce lake nutrient levels. It also shows that further increases in nutrient inputs could result in further, albeit small increases in trophic state of the lake. These in turn could cause more severe impacts to lake health, such as more algal blooms and fish kills, highlighting the need to prevent any further increases in nutrient load to the lake.
Recently (post-2000) reported increases in frequency and severity of blue-green algae blooms cannot be explained by increased lake trophic status, which has remained stable since the 1950s. Rather, there is indication that coinciding increasing water temperatures and altered wind patterns create increased water column stability that are known to promote the formation of blue-green algae blooms. Strongly correlated, larger inter-annual variations in conductivity and TP during that same time period indicate that water balance and nutrient dynamics are closely linked, but the roles of weather, internal nutrient loading and watershed inputs in these patterns are currently unknown, as are the precise mechanisms leading to bloom formation in Pigeon Lake. While many unknowns remain, any of these factors add to the existing plentiful nutrient levels that fuel algal blooms, so nutrient management on the watershed and lake level may reduce the likelihood of bloom occurrence. Given the large uncertainties about bloom-promoting factors and the natural occurrence of bloom-forming algae in Pigeon Lake, there is no guarantee that nutrient reductions will prevent future blooms entirely. Additional studies are required to predict the reduction in algal biomass that could be afforded by nutrient management.
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5.2 Summary of Wabamun Lake Paleolimnology
5.2.1 History of Water Quality and Lake Health
There were few consistent patterns across paleolimnological indicators that would suggest remarkable changes in trophic status in Wabamun Lake over the past circa 200 years. Compared to Pigeon Lake, however, the sediment record of Wabamun Lake showed some more obvious responses to watershed development, industrial activities and water management.
Algal communities and sediment accumulation rates recorded a response to watershed development starting in the 1950s. There was an increase in diatom and some blue-green algae pigments, but no indication of increased overall productivity in pigments. Increasing carbon and nitrogen accumulation rates and the increase of the eutrophic diatom Fragilaria capucina var. mesolepta, on the other hand, indicated increased aquatic productivity. The trends in these indicators were stabilized during the 1970s-1990s, but continued after decommissioning of the Wabamun powerplant, despite reduced nutrient levels in the lake due to the addition of diverted river water.
Some indicators showed unexplained changes between the 1970s and the late 1990s, coinciding with reduced ice cover in the East Basin due to heated discharge from coal-fired power plant and lower lake levels. The percent of organic carbon and nitrogen decreased, along with several algal pigments, while chironomids preferring benthic habitat increased. These changes were temporary and occurred in parallel with ongoing increases in eutrophic diatom abundance and sediment accumulation rates, suggesting a response to other factors than nutrient availability. Increased macrophyte growth in response to thermal discharge and possibly higher mineralization rates of sediments may have played a role in these patterns.
The only change that started in the 1970s and continued through to the top of the core was a decrease in δ15N stable isotopes, indicating a new source of nitrogen. The explanation for this change remains unclear, but may include a relative increase in importance of groundwater to the water balance, and after 1995 the new source of water from North Saskatchewan River diversion may have contributed to the maintenance of this pattern through to the present.
During the past 20 years, diatom assemblages indicated increased conductivity and increased water column stability and both trends were supported by measured data.
The oil spill in 2005 left little, if any, traces, in the sediment record. No significant changes in paleolimnological indicators were observed at this time, except for the occurrence of chironomid taxa associated with toxicity and one deformity. The presence of those chironomid taxa, however, was not limited to this time, and one deformity out of 25 specimens of the affected species bears little significance, showing the low importance of this event on the studied algal and chironomid biota.
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Figure 25. Summary of Key Paleolimnological Indicators for Wabamun Lake
Geochemistry Algal Pigments Biota Water Quality
% Organic CarbonCarbon Accumulationd15N Rate Myxoxanthophyll (blue-greenBeta carotene algae) (all Eutrophicalgae) chironomidFragilaria taxa capucinaDiatom-Inferred var. mesolepta TPDiatom-Inferred Conductivity
2000
1980
1960
1940
1920
1900
1880
1860
Sediment Date Sediment 1840
1820
1800
1780
1760
1740 17 19 21 23 250.0 0.4 0.8 2 3 4 5 0 50 100 0 200 400 600 0 20 40 60 80 0 20 40 6025 30 35 40200 400 600 % g/cm2/yr ‰ nmol/g C n mol/g C % % ug/L uS/cm
5.2.2 Knowledge Gaps
An increased sample frequency in the 19th and early 20th century could have provided more insight into the effects of early European settlement in the area, but would not affect the main conclusions of the study. Analysis of sediment cores from the eastern basin may be useful to investigate more local effects of thermal and ash-lagoon discharges. While differences in water chemistry do exist between both basins, for example a 7 ug/L difference in annual mean TP was observed in 2007, and effects of thermal discharge were well detected in the western basin core used in this study, so we assume that the overall effects on the lake were well represented in our results. Reasons for changes in carbon and nitrogen isotope signatures, however, were not entirely resolved. For example, data on isotopic signatures from local groundwater and the North Saskatchewan River would be required to confirm the impact of river and groundwater inputs on the Wabamun Lake nitrogen isotopic signatures.
A large unknown for Wabamun Lake is if the observed trajectory of increased productivity in some sediment indicators before 1970 will continue in the absence of thermal water discharge and once diversion of river water is reduced. The most recent samples in the sediment core appear to indicate such a trend, but are not sufficient to be conclusive and have not been confirmed by measured data.
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5.2.3 Implications for Wabamun Lake Management
Small nutrient impacts to Wabamun Lake from watershed activities were recorded after 1950, but were somewhat confounded by the effects of power plant cooling water discharge and NSR water diversion. Once these influences are removed in the future, nutrient inputs from the watershed may re-gain importance and provide the potential to impact Wabamun Lake water quality. Control of external nutrient inputs is therefore important to prevent the post-1950 trend of more productive conditions from continuing. As long as nutrient-poor river water is diverted to Wabamun Lake, these effects may still not be obvious, but once a desired natural water balance is restored, external nutrient inputs will gain in relative importance again and will need to be managed carefully.
The impact of changing hydrological regime from an open to a closed, evaporative system, has resulted in significant conductivity increases, which appear to be one major impact of human activity on Wabamun Lake water quality thus far. Restoration of a near-natural water budget would therefore be desirable for achieving a healthy Wabamun Lake ecosystem.
5.3 Regional Patterns
Wabamun and Pigeon Lakes are similar in their location, history of human activities and relative size of the watershed to the lake surface. These similarities resulted in somewhat similar water quality histories. They both are naturally rich in nutrients and displayed overall small changes in lake productivity over the past 200 years. Productivity indicators increased slightly in both lakes around 1950, a pattern found by a number of other paleolimnological studies in Alberta lakes (Gartner Lee Limited. 2007). These changes were relatively minor, however, likely in part due to the large relative importance of internal nutrient loading to their total nutrient budgets (Emmerson 2008, Teichreb 2014). Eutrophication signals in Lake Isle and Lac St. Anne, for example, which are situated in close vicinity to Wabamun Lake, were more pronounced in both the pigment and diatom records, but these lakes have watershed-to-lake area ratios of 11 and 6, as opposed to 3 and 2 in Wabamun and Pigeon Lake, suggesting a larger watershed influence on their water and nutrient budget.
Another striking resemblance between Wabamun and Pigeon lakes is the very recent change in diatom assemblages with increased abundance of the same species, e.g., F. crotonensis and A. formosa, along with increased measured and diatom-inferred conductivity, lower water levels and increased thermal stability. While lake levels are susceptible to the overall water balance that is related to a number of factors, the thermal stability is most likely related to warmer summers. The coincidence of this change with increased algal bloom occurrence in Pigeon Lake in the absence of nutrient concentration trends indicates that climate factors and water balance are important factors in lake health.
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6. Conclusion
Taken together, analysis of two well-dated and highly-resolved sediment cores suggests that these shallow prairie lakes are naturally productive, with highly organic sediments, abundant blue-green and green algae typical of summer blooms along with eutrophic diatom and midge larvae assemblages. However, despite diverse and abundant fossil pigments from nitrogen-fixing and potentially-toxic colonial taxa, there was little evidence of pronounced eutrophication of either lake during the 20th century. Instead, total algal abundance is inferred to have declined during parts of the 20th century, with present-day phytoplankton abundance and composition inferred to lie within the natural historical range of the lakes. Both lakes therefore displayed a lower susceptibility to ecosystem effects from external nutrient inputs than other lakes in the area, due to their naturally nutrient-rich state, small proportion of external watershed sources in P- budgets and small watershed/lake ratio. This result confirms previously completed phosphorus budgets for both lakes that indicated relatively small portions of lake nutrients originating from the watershed.
Management of these lakes must therefore be informed by the fact that, for every kilogram of reduced nutrient input from the watershed due to improved nutrient management, the nutrient levels in the lakes will decrease by less and more slowly than in other, well flushed or naturally less eutrophic lakes. Small increases in productivity indicators in response to watershed development in the 1950s in both lakes, however, indicate that some reduction may be possible. Whether nutrient reduction through management efforts would be sufficient to prevent or significantly lessen the occurrence of algal blooms is uncertain. Control of external nutrient inputs, however, remains an important part of Pigeon and Wabamun Lake management and stewardship activities.
Recently (post-2000) reported increases in frequency and severity of blue-green algae blooms in Pigeon Lake cannot be explained by coincidently increased nutrient levels in the lake, but rather appear to be related to warmer temperatures and increased thermal stability. It is possible, however, that the increased nutrient loads since the 1950s made the lake more susceptible to climate related blooms. One objective for lake and watershed management could therefore be not to increase loads and try to reduce loads to lower the nutrient baseline and thereby reduce frequency and severity of blooms. Other management actions should be investigated that would address the stability and thermal conditions that are most likely responsible for the recent increase in blooms. Given that the relative roles of weather, internal nutrient loading, watershed inputs and other factors in the development of algae blooms in Pigeon Lake remain largely unknown, further study into these factors is warranted to inform management plans aimed at reducing algal blooms in Pigeon Lake.
Both Pigeon and Wabamun Lakes displayed increases in conductivity and a resulting significant change in diatom assemblages since 1990. Along with thermal stability, this pattern is another indication that physical factors, such as hydrological regime and climate appear to be as important for Pigeon and Wabamun Lake ecosystems as nutrient loads from the watershed. Water quantity and quality management therefore need to be coordinated to obtain the best possible outcome for sustainable, healthy ecosystems in Pigeon and Wabamun Lakes.
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This paleolimnological study has provided valuable information on the history of Pigeon and Wabamun Lakes, by describing the ecological baseline, major changes in lake health and the most likely contributing factors to these changes. This knowledge will assist watershed and lake managers in identifying priorities, making informed decisions and defining reasonable expectations in their work towards maintaining and improving lake health.
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Talbot, M.R. 2001. Nitrogen isotopes in palaeolimnology. Tracking environmental change using lake sediments. Volume 2. Physical and geochemical methods (ed. by W.M. Last and J.P. Smol), pp. 401-439. Kluwer Academic Press, Dordrecht.
Taranu, Z., D. Köster, R.I. Hall, T. Charette T, F. Forrest F, L. Cwynar, I. Gregory-Eaves. 2010. Contrasting responses of dimictic and polymictic lakes to environmental change: A spatial and temporal study. Aquat Sci. 72(1):97–115.
Teichreb, C. 2014. Pigeon Lake phosphorus budget. Alberta Environment and Sustainable Resource Development.
Teichreb, C., B.J. Peter and A.M. Dyer, 2014. 2013 Overview of Pigeon Lake Water Quality, Sediment Quality, and Non-Fish Biota. Alberta Environment and SustainableResources Development. 84 pp.
Vincent, W.F. 2009. Cyanobacteria. In: Likens, G.E. (ed.) Encyclopedia of Inland Waters vol. 3, Elsevier, Oxford U.K., pp 226-232.
Werner, P. and J.P. Smol, 2005. Diatom-environmental relationships and nutrient transfer functions from contrasting shallow and deep limestone lakes in Ontario, Canada. Hydrobiologia 533, 145-173.
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Wolfe B.B., Edwards T.W.D., Elgood R.J., Beuning K.R.M., 2001 Carbon and oxygen isotope analysis of lake sediment cellulose: methods and applications. In: Last W.M., Smol J.P. (Eds.), Tracking Environmental Change Using Lake Sediments. Volume 2: Physical and Chemical Techniques, Developments in Paleoenvironmental Research. Kluwer Academic Publishers, Dordrecht, pp. 373-400.
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Appendix A. Sediment Chronology
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Wabamun Lake Chronology
Total CRS Year Midpoint 214-Pb 210-Pb Water Cum. Dry Dry 137-Cs "Sed. Rate "Error 214-Pb 210-Pb ([email protected] 137-Cs Depth (error) (error) Content Mass Mass (error) (CRS)" (CRS)" Activity cm) [cm] [Bq/kg] [Bq/kg] [Bq/kg] [Bq/kg] [y] [g/cm^2] [g/cm^2] [Bq/kg] [Bq/kg] [g/cm^2/y] [g/cm^2/y] 0.5 42.59 8.43 739.70 73.85 2013.4 0.985 0.007 0.007 71.53 8.18 0.0265 0.0028 1.5 39.23 7.85 680.56 66.61 2012.7 0.976 0.027 0.020 72.34 7.90 0.0283 0.003 2.5 41.54 8.27 614.13 66.92 2011.8 0.972 0.053 0.026 78.85 8.21 0.0307 0.0036 3.5 34.47 8.01 659.84 66.56 2010.8 0.969 0.083 0.030 83.27 8.32 0.0275 0.003 4.5 39.63 7.80 700.56 65.76 2009.5 0.968 0.115 0.032 90.32 8.64 0.0249 0.0025 5.5 39.27 7.65 745.21 69.13 2008.0 0.963 0.150 0.035 95.63 8.72 0.0222 0.0022 7.5 37.42 7.55 717.47 67.14 2004.4 0.961 0.228 0.078 85.30 8.15 0.0206 0.0021 9.5 34.57 7.59 617.28 63.13 2000.4 0.959 0.311 0.083 93.58 8.83 0.0214 0.0024 11.5 44.06 7.71 520.23 60.43 1996.5 0.956 0.399 0.088 96.13 8.73 0.0227 0.0029 13.5 47.43 7.64 518.80 59.83 1992.0 0.951 0.494 0.095 116.03 10.07 0.0198 0.0025 15.5 33.53 7.62 339.16 56.32 1987.6 0.951 0.594 0.101 133.44 10.43 0.0277 0.0053 17.5 48.25 7.86 348.98 55.10 1983.4 0.946 0.700 0.106 165.74 12.12 0.0235 0.0042 19.5 44.37 8.12 356.49 55.43 1978.3 0.947 0.811 0.110 189.86 13.48 0.0196 0.0035 21.5 32.39 7.43 300.49 52.15 1972.8 0.948 0.919 0.109 201.01 13.96 0.02 0.0041 23.5 37.76 7.61 322.84 51.76 1966.7 0.949 1.025 0.106 211.81 14.62 0.0153 0.0028 25.5 48.13 7.87 319.46 52.66 1959.4 0.953 1.126 0.101 180.11 13.13 0.0123 0.0024 28.5 37.71 7.71 347.33 55.55 1944.1 0.954 1.269 0.143 121.05 9.79 0.0069 0.0013 31.5 36.88 7.70 230.88 58.58 1919.8 0.951 1.415 0.146 29.31 6.07 0.0052 0.0017 35.5 29.01 7.66 160.92 49.65 1822.4 0.954 1.611 0.196 42.76 6.33 0.0004 0.001 40.5 34.88 7.60 24.30 48.61 1742.2* 0.947 1.866 0.255 2.67 5.12 NaN NaN
* Extrapolated
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Pigeon Lake Chronology
CRS CRS Total Year "Cumul. Midpoint 214-Pb 210-Pb Year Water 137-Cs "Sed. Rate "Error 214-Pb 210-Pb (BG@ Dry- Dry Mass 137-Cs Depth (error) (error) (BG@ Content (error) (CRS)" (CRS)" Activity 35.5 Mass" 17.5) cm) [cm] [Bq/kg] [Bq/kg] [Bq/kg] [Bq/kg] [y] [y] [g/cm^2] [g/cm^2] [Bq/kg] [Bq/kg] [g/cm^2/y] [g/cm^2/y] 0.5 54.47 11.62 515.32 90.29 2012.9 2012.8 0.957 0.022 0.022 106.31 14.69 0.0328 0.0058 1.5 58.77 11.46 562.54 86.4 2011.3 2010.9 0.946 0.072 0.050 106.65 13.57 0.0286 0.0044 2.5 50 11.11 558.05 86.66 2009.1 2008.3 0.936 0.133 0.083 114.35 13.83 0.0269 0.0042 3.5 39.64 10.72 602.68 86.06 2006.4 2005.1 0.936 0.200 0.116 108.02 13.23 0.0229 0.0033 4.5 50.31 10.57 602.18 82.9 2003.3 2001.4 0.934 0.267 0.151 108.85 13.23 0.0208 0.0029 5.5 48.29 10.69 426.32 80.55 2000.4 1997.7 0.933 0.337 0.186 108.76 13.11 0.0268 0.0051 7.5 56.24 10.9 466.68 81.46 1994.3 1989.8 0.931 0.479 0.293 111.07 14.37 0.0203 0.0036 9.5 42.62 10.65 416.71 84.66 1986.6 1979.2 0.930 0.625 0.332 124.42 14.51 0.0179 0.0037 12.5 47.59 11.26 323.80 78.78 1972.4 1955.6 0.924 0.856 0.524 141.78 15.91 0.0148 0.0037 15.5 54.65 11.79 148.94 85.82 1956.3 1909.0 0.915 1.111 0.587 141.71 16.2 0.0195 0.0114 17.5 41.91 10.46 51.88 69.29 1949.2 1889.4* 0.911 1.295 0.708 70.08 11.13 0.0449 0.0601 19.5 52.24 10.6 0.00 67.7 1947.1 1866.0* 0.912 1.482 0.775 19.33 8.54 NaN 21.5 40.94 10.55 10.98 64.3 1946.6 1842.7* 0.905 1.677 0.903 14.2 8.23 0.1952 1.1435 23.5 63.81 11.03 15.57 68.5 1945.3 1819.3* 0.902 1.883 0.980 3.32 7.97 0.1322 0.5819 25.5 47.68 11.19 49.14 71.42 1941.7 1795.9* 0.893 2.101 1.121 2.93 8.14 0.0374 0.0547 28.5 63.07 11.3 0.00 70.95 1936.5 1760.8* 0.885 2.460 1.338 1.62 7.45 NaN 31.5 53.05 10.83 100.78 68.19 1920.7 1725.7* 0.877 2.846 1.508 12.48 8.18 0.0095 0.0071 35.5 53.12 10.5 13.97 66.77 1908.4* 1678.9* 0.876 3.382 1.874 0 7.73 NaN NaN 39.5 55.1 11.29 34.66 65.92 1894.4* 1632.1* 0.876 3.918 2.045 0.4 8.36 NaN NaN * Extrapolated
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Appendix B. Geochemistry
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Wabamun Lake Sediment Geochemistry
Sample Top Bottom Sample Depth d15N N d13C C C/N C/N ID cm cm mid point (cm) vs air % vs VPDB % atomic mass W-01 1 2 1.5 2.65 2.77 -29.40 23.00 9.71 8.32 W-02 2 3 2.5 2.67 2.89 -29.42 22.96 9.26 7.94 W-03 3 4 3.5 2.70 2.87 -29.47 23.03 9.37 8.03 W-04 4 5 4.5 2.50 2.78 -29.50 23.48 9.85 8.44 W-05 5 6 5.5 2.48 2.82 -29.51 23.09 9.55 8.19 W-06 6 7 6.5 3.35 2.63 -29.11 21.64 9.62 8.24 W-07 7 8 7.5 2.50 2.82 -29.51 22.98 9.53 8.16 W-08 8 9 8.5 3.27 2.62 -29.35 21.91 9.77 8.37 W-09 9 10 9.5 2.49 2.72 -29.58 21.87 9.40 8.05 W-10 10 11 10.5 3.57 2.63 -29.34 20.84 9.26 7.94 W-11 11 12 11.5 2.88 2.68 -29.65 21.91 9.52 8.16 W-12 12 13 12.5 3.75 2.41 -29.34 19.93 9.67 8.28 W-13 14 15 14.5 3.65 2.34 -29.39 19.69 9.82 8.42 W-14 16 17 16.5 3.94 2.25 -29.20 19.03 9.85 8.44 W-15 18 19 18.5 3.97 2.33 -29.16 19.20 9.63 8.25 W-16 20 21 20.5 4.22 2.38 -29.14 20.06 9.84 8.43 W-17 22 23 22.5 4.43 2.52 -29.01 20.54 9.52 8.16 W-18 24 25 24.5 4.50 2.60 -28.75 20.72 9.30 7.97 W-19 26 27 26.5 4.44 2.56 -28.67 21.11 9.63 8.25 W-20 28 29 28.5 4.24 2.67 -28.85 22.24 9.72 8.33 W-21 31 32 31.5 4.32 2.73 -29.03 22.84 9.78 8.38 W-22 34 35 34.5 4.74 2.58 -29.11 22.57 10.20 8.74 W-23 37 38 37.5 4.55 2.62 -29.14 22.41 9.99 8.56 W-24 40 41 40.5 4.55 2.56 -29.33 22.19 10.11 8.66
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Pigeon Lake Sediment Geochemistry
Sample Top Bottom Sample Depth d15N N d13C C C/N C/N ID cm cm mid point (cm) vs air % vs VPDB % atomic mass P-01 1 2 1.5 4.63 2.46 -27.25 16.51 7.82 6.70 P-02 2 3 2.5 4.19 2.39 -27.41 16.54 8.08 6.93 P-03 3 4 3.5 4.28 2.36 -27.48 16.13 7.98 6.83 P-04 4 5 4.5 4.28 2.19 -27.43 14.97 7.97 6.83 P-05 5 6 5.5 4.72 2.13 -27.47 14.02 7.69 6.59 P-06 6 7 6.5 4.43 2.01 -27.47 13.67 7.94 6.80 P-07 7 8 7.5 4.26 2.17 -27.53 14.93 8.03 6.88 P-08 8 9 8.5 4.31 2.15 -27.31 14.96 8.10 6.94 P-09 9 10 9.5 4.14 2.10 -27.73 15.12 8.39 7.19 P-10 10 11 10.5 4.33 1.99 -27.46 13.73 8.06 6.91 P-11 12 13 12.5 4.14 2.03 -27.55 14.29 8.20 7.03 P-12 14 15 14.5 4.23 2.02 -27.22 14.51 8.39 7.19 P-13 16 17 16.5 4.22 1.72 -27.07 12.63 8.59 7.36 P-14 18 19 18.5 4.31 1.69 -27.46 13.12 9.06 7.76 P-15 20 21 20.5 4.40 1.79 -27.06 13.35 8.73 7.48 P-16 22 23 22.5 4.42 1.77 -26.97 13.21 8.72 7.47 P-17 24 25 24.5 4.28 1.68 -26.89 12.84 8.93 7.65 P-18 26 27 26.5 4.35 1.69 -26.76 13.06 9.01 7.72 P-19 28 29 28.5 4.19 1.68 -26.66 13.14 9.14 7.83 P-20 30 31 30.5 4.36 1.57 -26.62 11.83 8.80 7.54 P-21 32 33 32.5 4.26 1.19 -26.89 9.72 9.53 8.17 P-22 34 35 34.5 4.12 1.30 -27.14 10.76 9.64 8.26 P-23 36 37 36.5 4.55 1.35 -26.96 11.04 9.57 8.20 P-24 38 39 38.5 4.33 1.36 -27.02 11.14 9.56 8.19
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Appendix C. Algal Pigments
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Wabamun Lake Pigments (by HPLC)
Sample Year Lutein, Fuco- Aphani- Diadino- Myxo- Allo- Diato- Cantha- Depth (BG@3 Zea- xanthin zophyll xanthin xanthopyll xanthin xanthin xanthin (cm) 5.5 cm) xanthin 2-3 2012 103.7 156.0 28.7 63.1 372.1 269.2 575.3 92.3 3-4 2011 84.0 50.4 35.8 91.7 318.7 241.8 554.7 88.3 4-5 2010 39.5 38.9 27.6 53.7 245.2 196.0 492.6 81.3 5-6 2008 49.3 45.8 32.5 76.1 246.2 193.9 480.8 87.5 6-7 2006 46.5 73.7 32.9 70.2 244.1 192.0 483.6 90.5 7-8 2004 41.1 71.8 32.1 105.2 248.8 201.0 504.1 99.9 8-9 2002 29.8 79.7 25.1 63.8 220.8 184.9 449.3 91.6 9-10 2000 21.2 92.2 21.8 73.5 209.0 190.0 453.5 92.7 10-11 1998 25.6 100.7 23.8 60.5 206.1 187.6 450.6 94.4 11-12 1996 15.0 107.9 19.9 49.3 203.7 192.2 462.9 99.9 12-13 1994 13.2 103.1 19.0 60.7 178.6 176.0 403.3 90.5 13-14 1992 17.4 119.0 21.9 49.6 199.9 198.5 440.6 100.6 14-15 1990 16.2 108.3 19.9 45.9 192.6 199.9 430.6 103.5 16-17 1986 15.0 68.6 21.6 43.6 177.4 214.3 404.2 106.5 18-19 1981 17.2 117.7 21.6 52.8 185.8 241.9 457.8 119.5 20-21 1976 16.4 122.8 18.0 43.8 163.6 236.4 435.3 107.7 22-23 1970 19.9 132.2 24.3 64.8 198.8 261.0 522.3 116.4 24-25 1963 24.3 175.2 25.7 75.6 206.0 280.2 564.7 111.0 26-27 1954 24.3 159.6 29.4 69.4 211.2 280.4 584.4 107.7 28-29 1944 30.3 132.0 24.3 68.5 211.3 271.0 526.9 100.7 31-32 1920 20.4 115.7 21.3 62.4 186.9 233.6 473.5 122.7 34-35 1853 20.9 138.6 16.4 58.3 183.2 223.7 452.9 113.6 37-38 1790 23.3 120.7 22.2 57.5 190.2 228.1 488.0 136.4 40-41 1741 19.4 96.5 17.8 37.0 166.5 193.4 462.8 118.8 All data in nmol/g organic Carbon, except UV Index, which is unitless
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Wabamun Lake Pigments (by HPLC) (continued)
Sample Year Depth ([email protected] Chlorophyll -b Chlorophyll -a Echinenone Phaeophytin B Phaeophytin A Betacarotene UV-Index (cm) cm) 2-3 2012 42.7 483.4 104.1 264.3 254.3 339.5 8.2 3-4 2011 35.2 360.6 80.7 203.8 225.9 412.9 12.5 4-5 2010 28.0 281.3 59.9 181.3 183.2 323.5 12.3 5-6 2008 29.4 233.9 61.2 140.0 183.1 409.4 11.9 6-7 2006 26.7 205.6 66.2 150.6 163.2 315.0 13.2 7-8 2004 29.9 194.9 82.3 245.3 186.5 452.5 10.7 8-9 2002 24.1 155.7 68.1 160.3 158.0 328.1 8.5 9-10 2000 24.5 145.7 84.8 140.0 162.3 349.5 12.0 10-11 1998 22.3 121.0 75.0 117.7 122.4 235.7 6.9 11-12 1996 23.4 121.4 81.7 140.3 165.6 409.2 8.4 12-13 1994 22.0 91.2 63.0 117.0 102.1 141.4 7.5 13-14 1992 26.8 99.1 82.1 188.5 139.6 326.3 3.6 14-15 1990 24.9 90.7 75.5 140.3 118.7 213.3 4.3 16-17 1986 25.3 77.9 74.2 134.2 141.7 217.6 3.5 18-19 1981 33.3 75.5 77.7 206.2 172.3 377.5 2.3 20-21 1976 38.3 68.0 73.9 196.9 155.4 271.1 2.1 22-23 1970 29.7 84.0 87.2 234.5 197.1 393.7 2.0 24-25 1963 49.9 96.0 92.1 165.0 192.1 357.5 0.0 26-27 1954 38.6 100.6 91.9 185.5 177.4 283.2 0.0 28-29 1944 35.6 93.7 95.9 195.9 196.6 472.2 0.0 31-32 1920 45.1 79.2 110.9 256.8 237.5 538.5 0.0 34-35 1853 39.4 69.4 96.4 191.9 155.4 365.0 0.0 37-38 1790 45.2 72.8 121.5 235.2 239.3 574.6 0.0 40-41 1741 35.8 56.2 80.1 191.0 162.7 353.4 0.0 All data in nmol/g organic Carbon, except UV Index, which is unitless
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Pigeon Lake Pigments (by HPLC)
Sample Year Fuco- Diadino- Myxo- Diato- Lutein, Cantha- Depth ([email protected] Aphanizophyll Alloxanthin xanthin xanthin xanthopyll xanthin Zeaxanthin xanthin (cm) cm) 2-3 2009.1 142.4 177.5 10.5 27.7 107.0 78.0 143.6 74.8 3-4 2006.4 127.2 226.0 13.4 42.9 113.9 89.7 146.9 84.9 4-5 2003.3 93.1 215.7 11.3 25.0 100.1 86.3 131.5 77.6 5-6 2000.4 118.6 229.7 18.1 41.9 106.6 90.0 135.6 82.6 6-7 1997.3 103.7 285.9 15.0 41.1 104.9 97.1 140.8 81.4 7-8 1994.3 55.4 181.1 10.7 42.8 97.0 83.9 150.1 78.3 8-9 1990.4 26.1 136.3 10.7 26.4 79.2 79.5 129.0 67.2 9-10 1986.6 35.8 109.9 9.2 44.6 88.1 85.0 148.7 72.1 10-12 1981.8 27.8 131.0 11.0 41.7 92.6 83.2 155.4 73.3 12-13 1972.4 21.4 143.1 11.3 43.5 92.2 85.4 163.8 74.5 13-14 1967.0 20.8 132.9 10.6 38.7 94.0 82.6 173.0 76.0 14-15 1961.7 34.5 19.0 13.5 43.2 96.0 79.7 174.9 75.4 16-17 1952.8 8.8 48.7 5.8 35.7 80.1 80.6 167.4 64.1 18-19 1948.2 7.8 49.7 5.9 24.5 73.8 73.3 144.9 55.2 20-21 1946.8 9.0 53.1 6.3 20.2 83.4 88.2 156.9 61.4 22-23 1945.9 10.0 67.4 8.0 29.4 90.2 102.5 167.1 67.1 24-25 1943.5 9.5 88.7 7.0 36.8 92.3 112.0 176.5 70.4 26-27 1939.9 13.9 101.3 8.0 24.6 95.8 115.9 174.4 73.1 28-29 1936.5 8.9 105.0 5.5 19.4 81.0 107.0 166.8 68.6 30-31 1925.9 8.6 70.0 3.7 16.7 71.9 91.1 147.0 60.6 32-33 1917.6 8.0 95.6 4.1 17.9 77.4 95.8 154.9 74.1 34-35 1911.5 7.6 80.9 4.3 17.2 71.8 85.9 143.6 65.6 36-37 1904.9 8.0 87.9 3.0 24.5 71.2 84.5 137.2 64.2 38-39 1897.9 9.4 79.9 4.2 22.3 83.5 99.8 168.3 68.3 All data in nmol/g organic Carbon, except UV Index, which is unitless
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Pigeon Lake Pigments (by HPLC) (continued)
Sample Year Depth Chlorophyll b Chlorophyll a Echinenone Phaeophytin B Phaeophytin A Betacarotene UV-Index ([email protected] cm) (cm) 2-3 2009.1 22.8 284.3 36.2 93.9 149.2 79.9 3.2 3-4 2006.4 26.6 313.5 40.3 132.2 153.2 83.8 3.8 4-5 2003.3 24.3 284.8 36.8 135.9 174.2 108.7 3.7 5-6 2000.4 30.0 220.5 42.4 167.6 154.8 151.5 7.6 6-7 1997.3 26.1 228.8 39.2 114.0 149.0 88.6 7.2 7-8 1994.3 29.4 177.6 33.7 190.0 151.7 125.1 3.2 8-9 1990.4 19.4 125.1 27.1 116.7 142.3 102.1 7.4 9-10 1986.6 22.0 130.2 34.1 158.1 168.6 62.2 6.2 10-12 1981.8 21.9 114.0 39.7 156.9 175.9 84.1 7.2 12-13 1972.4 21.2 103.1 39.2 134.8 147.0 96.6 7.6 13-14 1967.0 22.3 103.3 49.2 173.2 159.5 138.6 5.5 14-15 1961.7 24.2 78.1 45.0 185.5 183.5 127.5 6.6 16-17 1952.8 17.5 54.0 39.9 129.0 121.5 57.3 3.7 18-19 1948.2 0.0 41.6 44.0 110.1 117.2 142.6 0.0 20-21 1946.8 0.0 44.8 45.8 156.2 175.9 78.7 0.0 22-23 1945.9 0.0 51.3 54.9 190.4 184.3 139.3 0.0 24-25 1943.5 0.0 51.3 55.3 198.1 184.6 89.2 0.0 26-27 1939.9 0.0 51.5 60.5 238.0 202.2 198.4 0.0 28-29 1936.5 0.0 45.4 57.1 198.9 169.6 168.5 0.0 30-31 1925.9 0.0 42.1 46.5 181.3 170.7 154.4 0.0 32-33 1917.6 0.0 50.6 54.7 210.7 185.5 82.3 0.0 34-35 1911.5 0.0 52.3 49.9 220.3 192.3 131.9 0.0 36-37 1904.9 0.0 48.7 51.7 196.1 185.6 138.6 0.0 38-39 1897.9 0.0 55.2 53.4 290.7 223.3 178.5 0.0 All data in nmol/g organic Carbon, except UV Index, which is unitless
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Wabamun Lake Pigments (by VNIRS)
Area Area Peak Inferred Midpoint Depth under under area Chl a depth curve line 1-2 4.95 3.75 1.20 0.11 1.5 2-3 6.67 5.56 1.11 0.10 2.5 3-4 10.11 9.09 1.01 0.09 3.5 4-5 8.28 7.34 0.94 0.09 4.5 5-6 9.76 8.81 0.95 0.09 5.5 7-8 9.30 8.44 0.86 0.08 7.5 9-10 9.30 8.45 0.85 0.08 9.5 11-12 9.50 8.67 0.84 0.08 11.5 13-14 8.40 7.70 0.70 0.07 13.5 15-16 11.34 10.51 0.83 0.08 15.5 17-18 10.09 9.30 0.79 0.07 17.5 19-20 9.65 8.85 0.81 0.08 19.5 21-22 11.63 10.72 0.91 0.08 21.5 23-24 10.83 9.86 0.97 0.09 23.5 25-26 7.72 6.75 0.97 0.09 25.5 28-29 10.15 9.16 0.99 0.09 28.5 31-32 11.89 10.89 1.00 0.09 31.5 35-36 12.68 11.68 1.01 0.09 35.5 40-41 12.46 11.51 0.95 0.09 40.5
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Appendix D. Diatoms
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J130053, Alberta Environment and Sustainable Resource Development North Saskatchewan Regional Plan: Lake Paleolimnology Survey
Wabamun Lake Raw Diatom Counts
Interval Midpoint (cm) Diatom Species 0.5 1.5 2.5 3.5 4.5 5.5 6.5 7.5 8.5 9.5 10.5 11.5 12.5 14.5 16.5 18.5 22.5 26.5 31.5 34.5 37.5 Achnanthes clevei 1 1 3 2 1 2 3 1 1 3 Achnanthes conspicua 1 1 1 1 Achnanthes exigua 2 Achnanthes lanceolata ssp. 1 2 2 1 2 1 1 3 1 frequentissima Achnanthes lanceolata ssp. 2 robusta Achnanthes lanceolata var. 1 rostrata Achnanthes unidentified 2 2 3 2 2 1 Achnanthes laterostrata 2 2 Achnanthes lauenburgiana 1 Achnanthes minutissima 6 2 2 2 2 1 2 3 4 2 1 Achnanthes ziegleri 1 2 3 6 2 1 1 Amphipleura pellucida 1 Amphora lybica 1 2 2 1 Amphora pediculus 1 9 3 5 1 4 3 2 4 9 4 3 17 10 2 7 Amphora inariensis 8 1 Amphora veneta 2 Asterionella formosa 30 66 18 8 39 15 11 9 11 11 10 7 5 7 3 2 2 1 5 Aulacoseira ambigua 6 10 7 10 10 48 23 48 20 27 28 61 42 58 33 39 51 94 99 103 Aulacoseira crenulata 2 Aulacoseira granulata 9 10 12 15 32 26 35 38 33 31 26 39 23 49 42 61 90 51 77 71 Aulacoseira lirata 2 1 1 1 1 Aulacoseira perglabra 1 4 Aulacoseira subarctica 2 4 1 1 2 Cocconeis disculus 1 1 1 1 2 1 Cocconeis neodiminuta 1 2 2 2 1 3 1 2 5 3 5 Cocconeis placentula var. 1 1 1 1 1 2 euglypta
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J130053, Alberta Environment and Sustainable Resource Development North Saskatchewan Regional Plan: Lake Paleolimnology Survey
Interval Midpoint (cm) Diatom Species 0.5 1.5 2.5 3.5 4.5 5.5 6.5 7.5 8.5 9.5 10.5 11.5 12.5 14.5 16.5 18.5 22.5 26.5 31.5 34.5 37.5 Cocconeis placentula var. 1 1 2 lineata Cocconeis placentula 2 (raphid) Cyclotella bodanica var. 1 5 3 4 7 7 13 9 6 8 4 21 22 26 8 8 3 7 lemanica Cyclotella comensis 3 8 2 Cyclotella menenghiniana 1 2 Cyclotella michiganiana 4 2 7 1 1 7 5 6 2 1 1 1 1 1 Cyclotella ocellata 2 5 4 9 17 10 2 15 6 6 11 4 6 6 9 6 2 2 Cyclotella stelligera 1 1 Cymbella falaisensis 2 Cymbella minuta 3 Cymbella proxima 2 Cymbella schimanskii 1 Cymbella silesiaca 2 2 Diatoma tenuis 4 9 2 13 5 6 7 9 4 19 10 4 3 4 2 Diploneis marginestriata 1 Epithemia adnata 4 Fragilaria arcus var. recta 1 Fragilaria brevistriata 10 6 9 6 28 16 39 21 31 29 21 17 32 24 38 25 55 21 23 15 13 Fragilaria capucina var. 128 145 158 121 90 39 36 63 12 51 36 42 42 21 36 21 8 7 mesolepta/ bidens Fragilaria capucina var. 6 vaucheriae Fragilaria construens 16 10 11 10 11 10 15 25 22 26 35 26 17 26 41 42 16 27 33 36 Fragilaria construens f. 2 binodis Fragilaria construens var. 3 1 4 4 6 8 3 4 15 2 12 6 3 2 venter Fragilaria crotonensis 32 34 12 55 15 40 15 10 5 8 6 22 3 3 6 6 5 6 Fragilaria cyclopum 1 Fragilaria lata 2
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J130053, Alberta Environment and Sustainable Resource Development North Saskatchewan Regional Plan: Lake Paleolimnology Survey
Interval Midpoint (cm) Diatom Species 0.5 1.5 2.5 3.5 4.5 5.5 6.5 7.5 8.5 9.5 10.5 11.5 12.5 14.5 16.5 18.5 22.5 26.5 31.5 34.5 37.5 Fragilaria leptostauron 2 2 1 2 6 4 8 3 6 4 Fragilaria nanana 5 3 4 4 Fragilaria parasitica 2 2 4 2 2 Fragilaria pinnata 19 22 14 26 30 37 49 24 48 46 57 50 47 46 61 46 39 41 28 32 28 Fragilaria pinnata var. 2 intercedens Fragilaria 2 2 1 pseudoconstruens Fragilaria tenera 3 3 2 2 2 Frustulia rhomboides 1 Gomphonema acuminatum 2 Gomphonema angustatum 2 1 Gomphonema olivaceum 2 Gomphonema pumilum 1 3 3 2 Gomphonema unidentified 2 2 2 Gyrosigma acuminatum 1 Hantzschia amphioxys 1 Navicula cari 2 Mastogloia elliptica 2 Navicula cryptocephala 2 1 Navicula oblonga 1 Navicula pseudoventralis 2 Navicula pupula 1 1 Navicula scutelloides 1 1 2 2 2 3 2 4 1 6 3 6 8 9 Navicula subminiscula 2 Navicula submuralis 1 1 Navicula subrotundata 1 5 2 2 Navicula spp. (unidentified) 1 Navicula vitabunda 2 2 Nitzschia amphibia 1 2 2 Nitzschia angustatum 2 1 Nitzschia fonticola 1 Hutchinson Environmental Sciences Ltd.
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J130053, Alberta Environment and Sustainable Resource Development North Saskatchewan Regional Plan: Lake Paleolimnology Survey
Interval Midpoint (cm) Diatom Species 0.5 1.5 2.5 3.5 4.5 5.5 6.5 7.5 8.5 9.5 10.5 11.5 12.5 14.5 16.5 18.5 22.5 26.5 31.5 34.5 37.5 Nitzschia frustulum 1 1 1 Nitzschia gracilis 1 Nitzschia palea 2 2 2 Nitzschia recta 2 Nitzschia spp. (unidentified) 1 1 Pinnularia interrupta 1 Pinnularia microstauron 1 Pinnularia viridis 1 1 Stephanodiscus minutulus 36 75 38 49 46 32 37 31 44 33 37 6 21 8 12 9 5 4 22 6 6 Stephanodiscus niagarae 1 1 4 3 5 2 8 4 7 1 3 7 2 1 8 6 2 5 1 3 Stephanodiscus parvus 1 Surirella minuta 1 Syndedra ulna 1 Total 316 390 294 346 321 302 321 312 310 320 312 296 324 200 330 297 353 303 321 304 308 # of Taxa 23 20 21 26 24 32 29 30 23 25 26 31 22 18 23 22 22 25 25 22 22 Cysts 6 6 8 9 22 16 35 6 43 43 37 13 48 30 59 76 104 85 115 101 92 Chrysophyte scales 6 11 5 9 4 8 10 4 3 1 3 0 1 2 1 1 0 1 1 0 0
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J130053, Alberta Environment and Sustainable Resource Development North Saskatchewan Regional Plan: Lake Paleolimnology Survey
Pigeon Lake Raw Diatom Counts
Interval Midpoint (cm) Diatom Species 0.5 2.5 3.5 4.5 5.5 7.5 8.5 11 15 17 19 25 27 35 39 Achnanthes clevei 4 1 3 1 3 5 3 4 3 4 2 4 Achnanthes conspicua 9 4 1 3 0 Achnanthes exigua 4 1 1 3 2 1 1 Achnanthes lanceolata ssp. frequentissima 5 6 2 1 1 1 0
Achnanthes lanceolata ssp.robusta Achnanthes unidentified 3 2 2 1 2 0 0 Achnanthes joursascense 1 1 2 1 3 Achnanthes laterostrata 1 Achnanthes minutissima 2 Achnanthes subatomoides 2 Achnanthes ziegleri 2 1 1 Amphora lybica 5 1 1 2 1 1 2 0 Amphora pediculus 32 22 30 29 30 23 6 11 20 11 6 20 22 18 27 Amphora inariensis 3 1 Amphora thumensis 1 3 1 Asterionella formosa 1 1 Aulacoseira ambigua 1 1 0 Aulacoseira crenulata 1 Aulacoseira granulata 4 4 7 2 8 2 6 11 2 2 2 1 Aulacoseira lirata 1 Aulacoseira subarctica 2 1 7 1 2 2 0 Cocconeis disculus 1 1 1 1 1 1 0 4 1 2 1 4 0 Cocconeis neodiminuta 4 2 3 1 3 4 1 1 1 1 Cocconeis placentula var. euglypta 2 1 3 1 1
Cyclotella bodanica var. lemanica 1 2 2 3 1 1 0 Cyclotella ocellata 1
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J130053, Alberta Environment and Sustainable Resource Development North Saskatchewan Regional Plan: Lake Paleolimnology Survey
Interval Midpoint (cm) Diatom Species 0.5 2.5 3.5 4.5 5.5 7.5 8.5 11 15 17 19 25 27 35 39 Cymbella ehrenbergii 2 Diploneis parma 2 Epithemia adnata 1 0 Fragilaria brevistriata 44 69 56 79 49 75 54 51 66 24 15 53 36 39 47 Fragilaria capucina var. mesolepta 1 Fragilaria construens 32 24 32 38 42 27 8 20 64 13 10 32 34 41 77 Fragilaria construens f. binodis 2 2 1 3 3 6 1 2 Fragilaria construens var. venter 36 17 25 2 29 25 12 22 17 2 4 17 18 11 36 Fragilaria crotonensis 45 31 13 15 9 6 1 0 0 Fragilaria leptostauron 10 1 7 11 9 6 2 3 10 11 5 7 8 7 16 Fragilaria parasitica 8 5 10 6 13 4 5 2 0 Fragilaria pinnata 106 89 92 83 102 107 66 90 108 31 19 88 67 54 108 Fragilaria pinnata var. intercedens 4 4 1 Fragilaria pseudoconstruens 6 7 6 9 5 2 Fragilaria robusta 4 Fragilaria virescens var. exigua 2 0 0 Frustulia rhomboides 1 Gomphonema unidentified 1 Navicula cari 2 2 Navicula clementis 1 Navicula cocconeiformis 3 2 1 0 Navicula cryptocephala 1 1 0 0 Navicula cryptotenella 2 Navicula elginensis 1 1 Navicula ignota 1 1 1 1 Navicula minima 5 2 2 1 1 0 Navicula pseudoventralis 2 Navicula pupula 1 1 1 Navicula rhyncocephala 1 0 0 Navicula schoenfeldii 2 Navicula scutelloides 1 1 1 2 3 2 4 6 4 10 18 10 19 21 Navicula seminulum 4 2
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J130053, Alberta Environment and Sustainable Resource Development North Saskatchewan Regional Plan: Lake Paleolimnology Survey
Interval Midpoint (cm) Diatom Species 0.5 2.5 3.5 4.5 5.5 7.5 8.5 11 15 17 19 25 27 35 39 Navicula subminiscula 2 2 1 0 Navicula submuralis 5 2 8 2 1 1 Navicula subrotundata 3 9 14 8 6 1 2 0 Navicula spp (unidentified) 1 Nitzschia fonticola 1 Stauroneis anceps 1 Stephanodiscus minutulus 1 Stephanodiscus niagarae 6 5 5 3 4 1 1 0 Total 374 307 318 312 324 324 167 234 350 109 84 246 209 201 352 # of Taxa 26 26 24 29 21 30 16 21 33 16 16 14 16 12 38 Cysts 20 21 17 19 15 19 16 18 17 20 16 79 54 37 34
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J130053, Alberta Environment and Sustainable Resource Development North Saskatchewan Regional Plan: Lake Paleolimnology Survey
Appendix E. Chironomids
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J130053, Alberta Environment and Sustainable Resource Development North Saskatchewan Regional Plan: Lake Paleolimnology Survey
Wabamun Lake Raw Chironomid Counts
Top of Interval (cm) Chironomid Taxa 0 1 2 3 4 5 6 7 8 9 10 11 12 14 16 18 20 22 24 26 28 30 32 34 36 38 Chironomini 2 1 Chironomus 2 2 3 2 1 1 2 Chironomus anthracinus 6 2 8 5 8 7 6 18 7 8 6 9 11 5 9 1 14 5 13 15 20 13 9 11 27 11 Chironomus plumosus 3 2 5 11 7 6 10 8 10 11 13 5 3 5 2 7 8 5 7 12 29 12 8 9 16 Cladopelma lateralis 1 1 4 1 1 2 8 6 1 4 9 2 6 3 3 2 5 2 1 2 Cryptochironomus 1 1 1 3 1 2 1 1 1 Cryptotendipes 1 1 1 1 1 1 Dicrotendipes 1 2 1 2 2 3 3 9 5 Einfeldia 1 4 1 Endohironomus albipennis 2 2 1 1 1 Endochironomus tendens 1 1 1 1 1 1 Glyptotendipes 1 1 1 1 Microtendipes 1 2 1 1 1 Parachironomus varus 2 Paratendipes 2 1 1 Phaenopsectra flavipes 1 Polypedilum nubeculoseum 1 2 1 4 2 1 1 1 1 1 Sergentia 1 Stictochironomus 2 1 1 1 Cladotanytarsus mancus 1 2 2 1 7 4 4 7 6 3 1 6 3 1 7 6 5 1 3 1 3 Micropsectra radialis 1 Paratanytarsus 2 1 3 1 1 2 1 1 1 Paratanytarsus sp A 1 Tanytarsini sp 4 6 1 5 2 2 5 5 6 1 3 7 11 7 6 2 1 5 2 1 9 Tanytarsus no spur 4 2 10 5 14 6 14 20 9 14 10 12 17 8 18 7 17 14 18 16 18 10 4 4 16 14 Tanytarsus glabrescens 1 2 1 Tanytarsus lactescens 1 1 Tanytarsus lugens 2 1 1 3 4 1 1 1 1 6 1 1 4 3 1 1 Tanytarsus mendax 1 2 2 2 2 3 2 2 1 1 1 1 3 1 1 2 1 1 Tanytarsus pallidicornis 1 1 2 1 1 Hutchinson Environmental Sciences Ltd.
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J130053, Alberta Environment and Sustainable Resource Development North Saskatchewan Regional Plan: Lake Paleolimnology Survey
Top of Interval (cm) Chironomid Taxa 0 1 2 3 4 5 6 7 8 9 10 11 12 14 16 18 20 22 24 26 28 30 32 34 36 38 Pseudochironomus 1 1 Brillia 1 Corynoneura edwardsi 1 1 2 Cricotopus laricomalis 1 1 1 1 1 1 1 1 Cricotopus trifasciata 1 1 Nancladius 1 Psectrocladius sordidellus 1 Pseudosmittia 1 Smittia 1 1 Synorthocladius 1 Ablabesmyia 1 1 1 Monopelopia 1 Procladius 2 4 1 7 8 8 1 6 7 4 6 1 2 6 7 4 7 1 5 2 3 5 4 5 Pentaneurini 1 1 TOTAL 24 18 24 30 55 45 56 74 39 57 58 61 46 27 66 37 73 54 59 57 79 84 38 35 74 69
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J130053, Alberta Environment and Sustainable Resource Development North Saskatchewan Regional Plan: Lake Paleolimnology Survey
Pigeon Lake Raw Chironomid Counts
Top of Interval (cm) Chironomid Taxa 1 2 3 4 5 6 7 8 9 10 12 14 16 18 20 30 34 39 Chironomini 1 4 3 1 1 1 1 Chironomus 3 1 2 Chironomus anthracinus 7 5 6 4 4 1 6 2 2 3 4 3 3 2 1 2 5 Chironomus plumosus 20 11 28 8 24 13 22 3 24 20 11 3 6 4 5 11 11 13 Cladopelma lateralis 6 5 8 2 7 1 5 4 4 1 4 3 4 2 3 8 7 Cryptochironomus 2 2 3 1 1 1 1 3 1 1 1 1 1 Cryptotendipes 1 1 1 Dicrotendipes 5 1 2 3 3 3 1 3 2 2 1 3 1 1 1 1 8 5 Einfeldia 1 1 3 Endochironomus albipennis 1 2 1 3 1 3 1 1 1 2 5 6 Glyptotendipes barbipes 1 3 2 4 5 2 1 1 1 1 2 6 1 Lauterborniella 1 Microchironomus 1 Microtendipes 5 1 1 1 1 Parachironomus 1 1 Paracladopelma 1 1 1 Paratendipes nubisquama 1 1 1 1 1 1 1 2 Phaenopsectra A 1 Polypedilum nubeculoseum 2 2 5 3 4 3 3 5 5 2 3 1 1 2 3 5 4 Tanytarsini sp 7 2 9 1 5 4 8 1 2 6 3 4 4 1 3 14 28 12 Cladotanytarsus 10 3 4 3 2 2 3 1 8 2 2 2 1 11 7 7 Corynocera oliveri 2 3 1 3 1 Paratanytarsus 2 2 1 1 1 1 1 1 1 1 2 1 1 1 Pseudochironomus 2 4 3 2 4 2 4 1 5 2 8 5 4 3 1 1 4 6 Stempellinella 1 1 1 Tanytarsus no spur 31 59 62 19 26 12 36 20 20 46 15 21 22 18 15 24 40 31 Tanytarsus with spur 1 1 1 1 Tanytarsus chinyensis 1 1 1 Tanytarsus gracilentus 1 1 3 1 Tanytarsus glabrescens 1 2 1 2 3 3 2 1 1 1 1 4 Tanytarsus lugens 4 2 2 4 13 7 3 3 11 6 1 3 3 1 4 6 4 Tanytarsus pallidicornis 1 2 3 2 1 1
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J130053, Alberta Environment and Sustainable Resource Development North Saskatchewan Regional Plan: Lake Paleolimnology Survey
Top of Interval (cm) Chironomid Taxa 1 2 3 4 5 6 7 8 9 10 12 14 16 18 20 30 34 39 Tanytarsus sp B 3 6 2 8 1 4 4 5 3 3 5 1 1 8 12 Allopsectrocladius 1 Chaetocladius 1 Corynoneura 2 Cricotopus 3 1 2 1 1 1 1 Orthocladius 1 1 1 Parakiefferiella 1 Parasmittia 1 Psectro sordidell 1 1 Smittia 1 1 1 1 1 Ablabesmyia 1 2 1 Pentaneurini 1 1 1 1 1 1 Procladius 25 26 27 20 25 11 24 4 22 22 23 12 10 6 10 6 12 16 TOTAL 129 142 161 96 143 83 127 53 117 136 96 74 73 56 49 87 148 143
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