Paleolimnology as a Tool for Interpreting Ecosystem Changes

within Freshwater Lakes

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 Vermont2 Allegheny College, Biology Department 3 Rubenstein School of Environment and Natural Resources, University of Vermont4 Vermont Department of Environmental Conservation, Water Quality Division

Heather Burgess1, Andrea Lini1, Milt Ostrofsky2, Suzanne Levine3, Neil Kamman4

1 Department of Geology, University of Vermont2 Allegheny College, Biology Department 3 Rubenstein School of Environment and Natural Resources, University of Vermont4 Vermont Department of Environmental Conservation, Water Quality Division

ObjectivesObjectives

• 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

• 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

Significance of StudySignificance of StudyTo better understand:• Baseline trophic state of Lake

Champlain • Anthropogenic impacts on lake

ecology• Provide information for

restoration and management

To better understand:• Baseline trophic state of Lake

Champlain • Anthropogenic impacts on lake

ecology• Provide information for

restoration and management

Why are Lake Sediments Important?

Why are Lake Sediments Important?

Preserve information about lake history, specifically:

• Land-use changes in watershed

• Ecological changes in lake and watershed

Preserve information about lake history, specifically:

• Land-use changes in watershed

• Ecological changes in lake and watershed

ProxiesProxies

• Organic Carbon

• Total Nitrogen

• C/N

• Stable Carbon Isotopes

• Paleopigments

• P, Si, metals

• Diatom Assemblages

• Organic Carbon

• Total Nitrogen

• C/N

• Stable Carbon Isotopes

• Paleopigments

• P, Si, metals

• Diatom Assemblages

Total Organic Carbon (%C)Total Organic Carbon (%C)

• Total Organic Carbon (TOC)Proxy for organic matter

• Primary productivity• Dilution• Preservation

• Total Organic Carbon (TOC)Proxy for organic matter

• Primary productivity• Dilution• Preservation

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Total Organic Carbon (%)

C/N RatioC/N Ratio

• Indicative of organic

matter source

• C/N algae <10

• C/N terrestrial >20

• Indicative of organic

matter source

• C/N algae <10

• C/N terrestrial >20

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Stable IsotopesStable 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)

• 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

0- ‰ + ‰

Stable Carbon Isotopes and Fractionation

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

• 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

Oligotrophic System

Eutrophic System

13Carbon

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ALGAE

ALGAE

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Stable Carbon Isotopes and Productivity Change

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

• High productivity– Less available DIC– Less fractionation– Algae/OM less negative

• Low productivity– More available DIC– More fractionation– Algae/OM more negative

Sediment ChronologySediment Chronology

•Fundamental to Paleolimnology–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

•Fundamental to Paleolimnology–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

PaleopigmentsPaleopigments

Indicative of :–Total algal abundance

–Specific algal types

–Paleoproductivity

Indicative of :–Total algal abundance

–Specific algal types

–Paleoproductivity

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PhosphorusPhosphorus

• Increases due to

–Cultural inputs

–Upward migration

–Biological uptake

• Increases due to

–Cultural inputs

–Upward migration

–Biological uptake

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Biogenic SilicaBiogenic Silica

• Diatoms, chrysophytes

• Indicator of diatom biomass

• Diatoms, chrysophytes

• Indicator of diatom biomass

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From: Academy of Natural Sciences

Field Methods-SummerField Methods-Summer

Field Methods- WinterField Methods- Winter

Glew gravity corePreserved sediment-water interface

Glew gravity corePreserved sediment-water interface

Piston corePiston core

Lab MethodsLab Methods

C/N ratios

%C and %N

Elemental Analysis

Freeze dried samples

13C

Isotopic

Analysis

Paleo-pigments and

Soft Algae

Nutrients (P, Silica)

Sediment Chronology (210Pb & 14C)

Other

AnalysesOther

Analyses

Historical Record Search

Case Study: Case Study: Lake ChamplainLake Champlain

Case Study: Case Study: Lake ChamplainLake Champlain

Results and Preliminary Interpretations

Results and Preliminary Interpretations

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Modified from LCBP Atlas

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Cole BayCrown Point

Mallett’s Bay

Study Sites

MissisquoiBay

St. AlbansBay

(VT DEC)

(VT DEC)

(VT DEC)

Modified from LCBP Atlas

Crown Point

Point Au Roche

Savage Island

Cole Bay

Mallett’s Bay

Crown Point

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Total Organic Carbon Total Nitrogen C/N Ratio

Stable Carbon Isotope

Crown PointCrown Point

1982

1849

1958

2002

1781

Modified from LCBP Atlas

Point Au Roche

Savage Island

Cole BayCrown Point

Mallett’s Bay

Cole Bay

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Carbon Total Nitrogen C/N RatioStable Carbon

Isotope

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Modified from LCBP Atlas

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Savage Island

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Mallett’s Bay

Mallett’s Bay

Mallett’s BayMallett’s Bay

Total Organic Carbon

Total Nitrogen C/N Ratio Stable Carbon Isotope

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FF

FFFF

FF

FFF

F

-27.5 -27 -26.5 -26 -25.5 -25 -24.5 -24

2001

1996

1979

1964

1926

1859

1819

Modified from LCBP Atlas

Point Au Roche

Savage Island

Cole BayCrown Point

Mallett’s Bay

Savage Island

FF

FF

FF

FF

FF

FFFFFFF

FFFFFF

FFFF

FFFF

FFF

FFFFFFFFFFFFF

FFFF

FF

FFFFFFFFFF

-30 -29 -28 -27 -26 -25 -24

Savage IslandSavage Island

BB

BBB

BBBB

BBB

BBBB

BB

BBBBB

BBB

BB

BB

BBB

BB

BB

BB

BBBB

BB

BB

BB

BBB

BB

BBB

BB

BBB

B65

60

55

50

45

40

35

30

25

20

15

10

5

0

0 0.5 1 1.5 2 2.5 3 3.5 4

JJ

JJ

JJJ

JJJJJ

JJ

JJ

JJ

JJJ

JJ

JJJ

JJ

JJJJJ

JJ

JJJ

JJJ

JJJ

JJ

JJ

JJ

JJ

JJ

JJ

JJJ

JJJ

J

0 0.050.10.150.20.250.30.350.4 0.450.5

HHHH

HH

HHH

HHHH

HHH

HH

HHHHH

HHH

HH

HH

HH

HH

HH

HH

HHHHH

HH

HH

HH

HHH

HH

HH

HH

HH

HH

H

0 2 4 6 8 10 12 14

Total Organic Carbon Total Nitrogen C/N Ratio

Stable Carbon Isotope

1991

1840

1668

Modified from LCBP Atlas

Point Au Roche

Savage Island

Cole BayCrown Point

Mallett’s Bay

Point Au Roche

BBB

BB

BB

BB

BB

BB

BB

BBB

BBBBBBBBBBBBBBBBBB35

30

25

20

15

10

5

0

0 1 2 3 4 5 6

JJ

JJ

JJ

JJJ

JJ

JJ

JJ

JJJ

JJJJJJJJJJJJJJJJJJ

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7

HH

HHHHH

HH

HHHH

HHH

HHHH

HHH

HHHHHHHHH

HHHH

0 1 2 3 4 5 6 7 8 9 10

FF

FF

FFF

FF

FF

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FF

FFFFFF

FFFF

FFFFF

-30 -29 -28 -27 -26 -25 -24

2002

1984

1957

1917

1845

1764

Point Au RochePoint Au RocheTotal Organic

Carbon Total Nitrogen C/N RatioStable Carbon

Isotope

Nutrient and Pigment Datafor

Crown Point

Nutrient and Pigment Datafor

Crown Point

BB

BB

BB

BB

BBB

BBB

BBBB

BB

BBBBBBBB

BBBBBBBBBBBB

BBB

BBBB

BB

BBB

BBBB

BB

BB

BB

B

65

60

55

50

45

40

35

30

25

20

15

10

5

0

0 0.5 1 1.5 2 2.5 3 3.5 4

Total OrganicCarbon

HH

HHHHHH

HHH

HHH

HHHH

HH

HH

HHH

HH

HH

HH

HHHHHHHHH

HHHH

HHH

HH

HHHH

HHHH

HH

HHHH

65

60

55

50

45

40

35

30

25

20

15

10

5

0

0 1 2 3 4 5 6 7 8 9 10

C/N

F FFF

F FF

FFFFFFF

FFFF

FF

FFFF

F FF

FF

FF

FFFFFF

FFFFFF

FF

FFFF

F FFFFF

FF

FFF

FF F

-29 -28.5 -28 -27.5 -27 -26.5 -26 -25.5 -25

d13C Biogenic Silica

66

66

66

66

66

66

666

6

6

6

6

6

6

6

6

6

0 5 10 15 20 25 30 35 40 45 50

Total Phosphorus

33

33

333

33

33

33

33

33

33

33333333333333333333333333333333333333333333

0 0.5 1 1.5 2 2.5 3

DiatoxanthinMyxoxanthin2002

1958

1804

PP

PP

PP

PPPP

PPPP

PPP

PP

PP

PP

PPP

PP

PP

PP

PPP

PP

PP

PPPPPPPP

0 20 40 60 80 100 120

PP

PP

PP

PP

PP

PPPP

PP

PP

PPPPP

PPPPPPP

PPPPP

PP

PP

PPP

PP

PPP

0 20 40 60 80 100 120

Watershed DevelopmentWatershed DevelopmentDate 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

Summary 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

• 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

Possible Implications for Lake Management

Possible Implications for Lake Management

•Historical variability

•Rates of change

•Lag time

•Effects of remediation

•Historical variability

•Rates of change

•Lag time

•Effects of remediation

ThanksThanks• USGS• Neil Kamman and the VT DEC• Vermont Geological Society• Andrea Lini, Milt Ostrofsky and Suzanne

Levine• University of Vermont Geology Department

• USGS• Neil Kamman and the VT DEC• Vermont Geological Society• Andrea Lini, Milt Ostrofsky and Suzanne

Levine• University of Vermont Geology Department

Stable Carbon Isotopes and Bioavailable Phosphorus

Stable Carbon Isotopes and Bioavailable Phosphorus

QuickTime™ and aTIFF (LZW) decompressor

are needed to see this picture.

From Schleske and Hodell, 1995

Savage Island Total Phosphorus

QuickTime™ and aTIFF (LZW) decompressor

are needed to see this picture.

Total Phosphorus mg/gdry sediment

Diatom AssemblagesDiatom 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

• 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

Trophic Status and

Phosphorus

Trophic state often based on phosphorus concentration (mg/l)

•Oligotrophic 0-10

•Mesotrophic 10-20

•Eutrophic >20

Trophic state often based on phosphorus concentration (mg/l)

•Oligotrophic 0-10

•Mesotrophic 10-20

•Eutrophic >20

BB

BB

BB

BB

BBB

BBB

BBBB

BB

BBBBBBBB

BBBBBBBBBBBB

BBB

BBBB

BB

BBB

BBBB

BB

BB

BB

B

65

60

55

50

45

40

35

30

25

20

15

10

5

0

0 0.5 1 1.5 2 2.5 3 3.5 4

Total OrganicCarbon

HH

HHHHHH

HHH

HHH

HHHH

HH

HH

HHH

HH

HH

HH

HHHHHHHHH

HHHH

HHH

HH

HHHH

HHHH

HH

HHHH

65

60

55

50

45

40

35

30

25

20

15

10

5

0

0 1 2 3 4 5 6 7 8 9 10

C/N

F FFF

F FF

FFFFFFF

FFFF

FF

FFFF

F FF

FF

FF

FFFFFF

FFFFFF

FF

FFFF

F FFFFF

FF

FFF

FF F

-29 -28.5 -28 -27.5 -27 -26.5 -26 -25.5 -25

d13C Biogenic Silica

66

66

66

66

66

66

666

6

6

6

6

6

6

6

6

6

0 5 10 15 20 25 30 35 40 45 50

Total Phosphorus

33

33

333

33

33

33

33

33

33

33333333333333333333333333333333333333333333

0 0.5 1 1.5 2 2.5 3

PP

PPP

PP

PP

PP

PPPP

PP

PP

PPPPP

PPPPPPP

PPPPP

PP

PP

PPP

PP

PPP

0 20 40 60 80 100 120

Diatoxanthin

PP

PP

PP

PPPPP

PPPP

PPP

PP

PP

PP

PPP

PP

PP

PP

PPP

PP

PP

PPPPPPPP

0 20 40 60 80 100 120

Myxoxanthin

Stable Carbon IsotopesStable Carbon Isotopes

• Indicative of:–Changes in productivity

–Source of terrestrial or

aquatic OM

• Indicative of:–Changes in productivity

–Source of terrestrial or

aquatic OM

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FF

FF

FFFFFF

FFFFF

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45

40

35

30

25

20

15

10

5

0

-29

-28

-27

-26

-25

-24

-23

-22

-21

-20

De

pth

(cm

)d 13 Carbon

C/N

C/N ratio vs. 13CC/N ratio vs. 13C1

3C

C/N