1. Paleolimnology as a Tool for Interpreting Ecosystem Changes within Freshwater Lakes
Heather Burgess1, Andrea Lini1, Milt Ostrofsky2, Suzanne Levine3, Neil Kamman4
1 Department of Geology, University of Vermont
2 Allegheny College, Biology Department
3 Rubenstein School of Environment and Natural Resources, University of Vermont
4 Vermont Department of Environmental Conservation, Water Quality Division

2. Objectives
To determine pre-settlement trophic conditions in Lake Champlain
To document changes in trophic state and algal assemblages since European settlement
To relate these changes to anthropogenic disturbances within the watershed

3. Significance of Study To better understand:
Baseline trophic state of Lake Champlain
Anthropogenic impacts on lake ecology
Provide information for restoration and management

4. Why are Lake Sediments Important?
Preserve information about lake history, specifically:
Land-use changes in watershed
Ecological changes in lake and watershed
ORGANIC MATTER

5. Proxies Organic Carbon Total Nitrogen C/N Stable Carbon Isotopes
Paleopigments
P, Si, metals
Diatom Assemblages

6. Total Organic Carbon (%C)
Total Organic Carbon (TOC)
Proxy for organic matter
Primary productivity
Dilution
Preservation
(%)

7. C/N Ratio Indicative of organic matter source C/N algae <10
C/N terrestrial >20

8. Stable Isotopes Are naturally occurring Do not radioactively decay
Reported using the ‘ notation’
‰ = [(R sample/R standard) -1] x 1000
where ‘R’ is the ratio of heavy to light isotopes (e.g. 13C/12C)
Less of the heavier isotopes
More of the heavier isotopes
-  ‰
+  ‰

9. Stable Carbon Isotopes and Fractionation
Natural abundance of stable carbon isotopes
12C 98.9%
13C 1.1%
Organisms preferentially take up 12C
Organic matter depleted in 13C
Amount of fractionation based on:
Photosynthetic Pathway
Carbon Availability

10. Stable Carbon Isotopes and Productivity Change
High productivity
Less available DIC
Less fractionation
Algae/OM less negative
Low productivity
More available DIC
More fractionation
Algae/OM more negative
Oligotrophic System
Eutrophic System
-27‰
-30‰
-24‰
ALGAE
Increasing productivity
Terrestrial Plants
13Carbon

11. Sediment Chronology Fundamental to Paleolimnology 210Pb 14C
Determine rates of processes/fluxes
Link disturbance to sediment archive
Determine synchronicity of events
210Pb
14C
Extrapolate 210Pb dates, use 14C to constrain oldest core dates

12. Paleopigments Indicative of : Total algal abundance
Specific algal types
Paleoproductivity
Beta Carotene

13. Phosphorus
Increases due to
Cultural inputs
Upward migration
Biological uptake

14. Biogenic Silica Diatoms, chrysophytes Indicator of diatom biomass
From: Academy of Natural Sciences

15. Field Methods-Summer

16. Field Methods- Winter

17. Preserved sediment-water interface
Glew gravity core
Preserved sediment-water interface
Piston core

18. Lab Methods Other Analyses Freeze dried samples Elemental Analysis
Isotopic
Analysis
Paleo-pigments and
Soft Algae
Nutrients (P, Silica)
13C
Sediment Chronology (210Pb & 14C)
%C and %N
C/N ratios
Historical Record Search

19. Case Study: Lake Champlain

20. Results and Preliminary Interpretations

21. Study Sites St. Albans Missisquoi Bay Bay Point Au Roche Savage Island
Modified from LCBP Atlas
Point Au Roche
Savage Island
Cole Bay
Crown Point
Mallett’s Bay
St. Albans
Bay
Missisquoi
Bay
(VT DEC)
(VT DEC)
(VT DEC)

22. Crown Point Point Au Roche Savage Island Mallett’s Bay Cole Bay
Modified from LCBP Atlas
Crown Point
Point Au Roche
Savage Island
Mallett’s Bay
Cole Bay
Taken north of CP Bridge, near the town of Port Henry, in approx. 9m of water

23. Crown Point Stable Carbon Isotope Total Organic Carbon C/N Ratio
Total Nitrogen
2002
1982
1958
1849
1781

24. Cole Bay Point Au Roche Savage Island Mallett’s Bay Cole Bay
Crown Point
Modified from LCBP Atlas

25. Cole Bay Total Organic Carbon Stable Carbon Isotope Total Nitrogen
C/N Ratio
2000
1959
1980
1917
1811
1760
1711

26. Mallett’s Bay Point Au Roche Savage Island Mallett’s Bay Cole Bay
Crown Point
Taken in outer malletts bay july 2002
Modified from LCBP Atlas

27. Mallett’s Bay Total Organic Carbon Stable Carbon Isotope
Total Nitrogen
C/N Ratio
2001
1996
1979
1964
1926
1859
1819

28. Savage Island Point Au Roche Savage Island Mallett’s Bay Cole Bay
Crown Point
Modified from LCBP Atlas

29. Savage Island Total Organic Carbon Stable Carbon Isotope
Total Nitrogen
C/N Ratio
1991
1840
1668

30. Point Au Roche Point Au Roche Savage Island Mallett’s Bay Cole Bay
Modified from LCBP Atlas
Point Au Roche
Savage Island
Cole Bay
Crown Point
Mallett’s Bay

31. Point Au Roche Stable Carbon Isotope Total Organic Carbon
Total Nitrogen
C/N Ratio
2002
1984
1957
1917
1845
1764
Can I relate decrease in OC and TN at top to decrese P???

32. Nutrient and Pigment Data for Crown Point
Total Organic
Carbon
Total Phosphorus
C/N
d13C
Biogenic Silica
Myxoxanthin
Diatoxanthin
2002
1958
1804

33. Watershed Development
Date
Disturbance
Geochemical Trend
Prior to 1780
Pre-settlement
Stable
1780- early 1900
Settlement, Deforestation,
Agriculture
Trend toward Eutrophication
1950
Chemical Fertilizer, Development
More rapid trend toward eutrophication

34. Summary Very little change prior to 20th century
Post-1950s
Overall increase in organic matter deposition in upper portion of cores
Possibly indicative of increased productivity

35. Possible Implications for Lake Management
Historical variability
Rates of change
Lag time
Effects of remediation

36. Thanks USGS Neil Kamman and the VT DEC Vermont Geological Society
Andrea Lini, Milt Ostrofsky and Suzanne Levine
University of Vermont Geology Department

39. Stable Carbon Isotopes and Bioavailable Phosphorus
From Schleske and Hodell, 1995

40. Savage Island Total Phosphorus
Total Phosphorus mg/gdry sediment

41. Diatom Assemblages Algae with siliceous cell walls
Different assemblages based on:
Location in lake, i.e. planktonic vs. benthic
Productivity, pH, DOC within lake
Therefore useful indicators of environmental conditions
through time
From: Academy of Natural Sciences

42. Trophic Status and Phosphorus
Trophic state often based on phosphorus concentration (mg/l)
Oligotrophic 0-10
Mesotrophic 10-20
Eutrophic >20
Trophic state measurements are often based on phosphorus levels, because P is a limiting nutrient in most lacustrine systems, which essentailly means that as P levels increase, productivity increases.
P is measured in mg/L, and defines the 3 states:
Oligotrophic lakes have low algae growth and high water clarity, with p levels between 0 and 10 mg/l
Mesotrophic lakes have some algae growth and lower water clarity, with P levels between mg/l
Eutrophic lakes have very high algae growth and very poor water clarity, with P levels greater than 20 mg/l
This map shows the different trophic states across lake champain based on P concentrations…

43. Total Organic
Carbon
C/N
d13C
Biogenic Silica
Total Phosphorus
Diatoxanthin
Myxoxanthin

44. Stable Carbon Isotopes
Indicative of:
Changes in productivity
Source of terrestrial or
aquatic OM

45. C/N ratio vs. 13C
13C
C/N
C/N