1. Nichole Holdbak November 2009
Lakes as Records of Past Climates
Nichole Holdbak
November 2009

2. Presentation Outline Background
What is Paleolimnology?
What does it tell us?
Lakes and Climate Variability
Paper 1: Climate-driven regime shifts in the biological communities of arctic lakes
Paper 2: Effects of agriculture, urbanization, and climate on water quality in the northern Great Plains
Closing Statements

3. What is Paleolimnology?
Link between limnology and paleoecology
Using sediment records to reconstruct past conditions
Physical, chemical and biological indicators of climate variation in sedimentary profiles
Background
Paper 1
Paper 2
Conclusions

4. Why are we interested? Background Paper 1 Paper 2 Conclusions
Observation of past response may help infer response to current or future climate shifts
Help clearly understand the long chain of effects of land use and other human impacts
Background
Paper 1
Paper 2
Conclusions

5. Organisms Background Paper 1 Paper 2 Conclusions Diatoms – valves
Chironomids – head capsules
Chrysophytes – scales and stomatocysts
Chitinous invertebrates
Background
Paper 1
Paper 2
Conclusions

6. Climate Influence Background Paper 1 Paper 2 Conclusions
Atmospheric temperature and wind
directly affect water temperature and stratification
Moisture availability (P-E)
primary control on lake level
Temperature and light availability
affect growth rates
All above affect geochemical precipitates and biological fossils in sediments
Background
Paper 1
Paper 2
Conclusions

7. Open vs. Closed Background Paper 1 Paper 2 Conclusions Open Lakes
Freshwater
Water flows through lake system under all climate patterns
Closed Lakes
Saline
Water does not flow through – evaporation is the only exit
Background
Paper 1
Paper 2
Conclusions

8. What can OPEN lakes tell us?
Evaporation only a small portion of water loss
Variation in sediment carbonates mainly a function of lake water composition
Changes in 18O stratigraphy in sediments may reflect a temperature change or change in source area of precipitation
Background
Paper 1
Paper 2
Conclusions

9. What can CLOSED lakes tell us?
Balance between precipitation and evaporation has strong impact on lake level and concentration of dissolved salts
Diatom distribution is correlated with salinity and brine type
shift in composition of population can help qualitatively reconstruct past climates
Background
Paper 1
Paper 2
Conclusions

10. What systems tell us the most?
Systems most sensitive to change are those in extreme environments (high Arctic) or near climatic boundaries (near treeline or prairie-forest border)
Large lakes show climatic extremes
Small lakes show seasonal variability
Midsize lakes and catchment with simple hydrological networks show clearest record of climatic signals
Background
Paper 1
Paper 2
Conclusions

11. Paleolimnology – Big Picture
Brings together historical data and sediment analysis
algal communities, invertebrate communities, pigment abundances, and other indirect measurements
Creates an image of past climates
Shows response to known or measured changes in climate or surrounding environment
May help project future response to environmental shifts
Background
Paper 1
Paper 2
Conclusions

12. Smol, J. P. et al. (2005) Climate-driven regime shifts in the biological communities of arctic lakes
Background
Paper 1
Paper 2
Conclusions

13. Overview Background Paper 1 Paper 2 Conclusions
All sub regions of the Arctic are thought to be ecologically sensitive
Climate warming is amplified in polar regions due to positive feedback mechanisms
Ecological thresholds linked with length of ice-free season
Aquatic community composition predicted to shift towards new states
Background
Paper 1
Paper 2
Conclusions

14. Methods Background Paper 1 Paper 2 Conclusions
Sediments obtained with gravity corers
Geochronology based mainly on 210Pb dating
Beta-diversity calculated from species turnover in the last 150 years
greater turnover = greater beta-diversity
Background
Paper 1
Paper 2
Conclusions

15. Diatom population profiles
Results
Diatom population profiles
Shifts towards taxa that are consistent with longer growing seasons and habitats expanding with warmer conditions (B)
Background
Paper 1
Paper 2
Conclusions

16. Results Background Paper 1 Paper 2 Conclusions
Shifts linked to reduced ice-cover and/or increased thermal stratification (F)
Background
Paper 1
Paper 2
Conclusions

17. Map of site locations
Background
Paper 1
Paper 2
Conclusions

18. Results Background Paper 1 Paper 2 Conclusions
Beta-diversity increases with latitude
Some lakes showing high beta-diversity in close proximity to those showing low beta diversity
Higher sensitivity in some lakes: ex. shallow ponds
Background
Paper 1
Paper 2
Conclusions

19. Background
Paper 1
Paper 2
Conclusions

20. Conclusions Background Paper 1 Paper 2 Conclusions
Increased beta-diversity with latitude suggests polar amplification of climate warming
Increased latitude generally coincides with increased remoteness and decreased land use impacts
Shifts in population assemblages not explained by recent colonization events
Taxa recently expanding were found, even in very low numbers, in sediments predating the time of shifts
Represent response to environmental change
Background
Paper 1
Paper 2
Conclusions

21. Hall, R.I., and Leavitt, P.R. (1999) Effects of agriculture, urbanization, and climate on water quality in the northern Great Plains
Background
Paper 1
Paper 2
Conclusions

22. Overview Background Paper 1 Paper 2 Conclusions
Focus on Qu’Appelle Valley drainage system
More than 95% of area composed of agricultural fields and pastures
Low N:P ratios
Water quality in prairie lakes impacted by climate, resource use and urban factors
Lake eutopphication is a widespread problem
Pre-agricultural communities used as a benchmark for change
Background
Paper 1
Paper 2
Conclusions

23. Methods Background Paper 1 Paper 2 Conclusions
Historical data sorted into either climate, resource use or urban categories
Monthly, seasonal and annual precipitation and evaporation
Min and max temps
Length of ice-free season
Sediment cores taken with freeze-core procedures
Pigments extracted and identified
Algal concentrations inferred from this data
Background
Paper 1
Paper 2
Conclusions

24. Results Background Paper 1 Paper 2 Conclusions
Distinct shift in species composition of diatoms after European settlement around 1890
Present day communities remain different from those of pre settlement era
Most algal pigments increased 2-4 fold between
Background
Paper 1
Paper 2
Conclusions

25. Results Background Paper 1 Paper 2 Conclusions
Relative abundance of Chironomus declined between
Absolute sediment density declined rather than reciprocal increases in other species
Background
Paper 1
Paper 2
Conclusions

26. Results Background Paper 1 Paper 2 Conclusions
Community change was low and insignificant before 1890 in diatoms and chironomids  increasing after the onset of European style agriculture
Algal pigments were more variable than diatoms or chironomids pre agriculture but still show increase after this point
Background
Paper 1
Paper 2
Conclusions

27. Background Paper 1 Paper 2 Conclusions Pasqua Lake
may be particularly sensitive to urbanization being directly downstream from Regina and Moosejaw
Background
Paper 1
Paper 2
Conclusions

28. Results Background Paper 1 Paper 2 Conclusions
Increase in algal abundance greatest in Pasqua Lake
Increase was lower both upstream and downstream of Pasqua Lake
Upstream Last Mountain Lake doesn’t receive municipal sewage
Background
Paper 1
Paper 2
Conclusions

29. Conclusions Background Paper 1 Paper 2 Conclusions
Communities of diatoms and chironomids as well as levels of pigments varied little prior to the onset of European style agriculture and settlement
Water quality has declined since human settlement
Declining Chironomus concentrations
Likely due to decreased O2 availability resulting from increased phytoplankton decomposition
Background
Paper 1
Paper 2
Conclusions

30. Conclusions Background Paper 1 Paper 2 Conclusions
Water management will vary with position of the lake within the catchment and what input sources are directly surrounding
Cropland area, livestock abundance and urban nitrogenous waste are all strong controls
Algal and invertebrate populations are very susceptible to environmental changes due to human impact
these impacts may make it difficult to observe the influence of climate change on these communities
Background
Paper 1
Paper 2
Conclusions

31. Closing Statements Background Paper 1 Paper 2 Conclusions
Response to climate shift as well as human impacts
Increased sensitivity due to geography
Large scale differences such as latitude
Small scale differences such as placement within catchment
We have more impact on the environment than most realize...
Background
Paper 1
Paper 2
Conclusions

32. References
Fritz, S.C. (1996) Paleolimnological records of climatic change in North America. Limnol. Oceanogr., 41(5),
Hall, R.I., Leavitt, P.R. (1999) Effects of agriculture, urbanization, and climate on water quality in the northern Great Plains. Limnol. Oeacnogr., 44(3),
Smol, J.P. (1992) Paleolimnology: an important tool for effective ecosystem management. Journal of Aquatic Ecosystem Health, 1,
Smol, J.P. et. al. (2005) Climate-driven regime shifts in the biological communities of arctic lakes. PNAS, 102(12),
Smol, J.P. et. al. (1995) Inferring past climatic changes in Canada using paleolimnological techniques. Geoscience Canada, 21(3),