1. University of Pennsylvania
Human and Environmental linkages revealed through stable isotope analysis
Brent R. Helliker
Department of Biology
University of Pennsylvania

2. Plant Physiological Ecology

3. Weather variability
El Niño

4. Climate change

5. Stable isotopes:
Link carbon and water cycles
Trace CO2 processes

6. Fossil Fuel combustion
Photosynthesis:
Plants
6CO2 + 6H2O C6H12O6 + O2
Respiration:
Plants
Animals
Microbes
Oxidation:
Fossil Fuel combustion

7. Summer
Winter

8. 6CO2 + 6H2O C6H12O6 + O2
SEM of stomata

9. Figure 1
Cross section
chloroplast

10. 6CO2 + 6H2O C6H12O6 + O2 Photosynthesis:
Plants taking in carbon to make sugars and
eventually more plant and… seeds!
6CO2 + 6H2O C6H12O6 + O2
Respiration:
Plants
Animals
Microbes

11. Why do different plants grow where they grow?

12. Why do different plants grow where they grow?

13. Why do different plants grow where they grow?

14. Why do different plants grow where they grow?

15. Why do different plants grow where they grow?

16. Stable isotopes as indicators of plant-environment interactions
Periodic Table

17. 6 C
12.011
Periodic Table

18. C ‘Stable’ carbon can differ in number of neutrons, either 12 or 13.
12C = 99 % of all carbon on earth
13C = 1% of all carbon on earth
Atomic number
(protons) 6 C
12.011
Atomic mass
(protons + neutrons)

19. ‘Stable’ carbon can differ in number of neutrons, either 12 or 13.
12C = 99 % of all carbon on earth
13C = 1% of all carbon on earth
Atmospheric CO2
12CO2
13CO2
Photosynthesis discriminates against 13CO2

20. CO2 in air has 13C of -8
CO2 in plants has 13C of -14 to -35
13CO2
12CO2
Plants have less 13C than the atmosphere

21. Photosynthesis discriminates against 13CO2
Plants have less 13CO2 than the atmosphere.
The amount of 13C that plants contain varies by:
Plant type
Plant response to climate: more 13C = more water use efficient = more Carbon gained per H2O lost.
Where they are grown

22. Carbon isotope work has dramatically improved crop water use efficiency.

23. Carbon isotopes in tree rings can be used to reconstruct climate

24. Why the new money?

25. Why the new money?
1920’s
1980’s
1990’s
2000’s

26. Why the new money?
All of the cotton for our money is grown from one region in Texas. It has a distinct 13C signature.
Old counterfeits were grown in central Asia— this could only be determined by stable isotope analysis.

27. O 16O ≈ 99.8 % of all oxygen on earth
Atomic number
(protons) 8 O
15.999
Atomic mass
(protons + neutrons)
Stable oxygen isotopes in water, H216O and H218O, are a great proxy for temperature.

28. *= equilibrium fractionation factor highly temperature dependent
Liquid, more H218O
Vapor, less H218O
The amount of 18O vs. 16O in atmospheric water vapor is a strong and known function of temperature.

29. Oxygen isotopes in ice cores tell us a lot about past climates

32. Regional distribution of d18O in surface water

33. Fossil Fuel combustion
Photosynthesis:
Plants
6CO2 + 6H2O C6H12O6 + O2
Respiration:
Plants
Animals
Microbes
Oxidation:
Fossil Fuel combustion

34. Plant 18O content reflects:
Plant type
Climate of when they grow

36. H218O
CO2
H216O

37. H218O
CO2 + H2O CH2O + O2
sunlight
sucrose
Tree-ring cellulose

38. H218O Plant carbohydrates are ‘labeled’ by leaf-water isotopes
CO2 + H2O CH2O + O2
sunlight
sucrose
Tree-ring cellulose

39. Black dots are hurricanes, reconstructed using oxygen isotopes of tree rings.

40. H218O Plant carbohydrates are ‘labeled’ by leaf-water isotopes
CO2 + H2O CH2O + O2
sunlight
sucrose
Tree-ring cellulose

41. Regional distribution of d18O in surface water

42. 39 tree species from 25 sites covering more the 50° of latitude

43. Global terrestrial biomes
Ricklefs

44. Leaf temperature minus growing season temperature

45. Mean leaf temperature was 21.4 °C across species

46. Leaf temperature minus growing season temperature

47. Smith and Carter 1988

48. More than one isotope (using carbon, oxygen and nitrogen all together) can give us a feel for…

49. Summer
Winter

50. Fossil Fuel combustion
All have distinct isotope ratios
Photosynthesis:
Plants
6CO2 + 6H2O C6H12O6 + O2
Respiration:
Plants
Animals
Microbes
Oxidation:
Fossil Fuel combustion

51. CO2 sources are isotopically distinct45
photosynthesis 40 35
d18O (per mil, V-SMOW) 30
respiration
combustion of
natural gas
combustion
of gasoline 25 20 15
-45
-40
-35
-30
-25
-20
d13C (per mil, PDB)

53. Summer
Winter

56. CO2 sources are isotopically distinct45
photosynthesis 40 35
d18O (per mil, V-SMOW) 30
respiration
combustion of
natural gas
combustion
of gasoline 25 20 15
-45
-40
-35
-30
-25
-20
d13C (per mil, PDB)

57. Prior to industrial revolution, photosynthesis and respiration were approximately balanced globally.
The increase in atmospheric CO2 is undoubtedly due to the burning of fossil fuels.
Half of all fossil fuel CO2 released has been assimilated by photosynthesis (meaning the plants have saved our butts so far…).

58. Measuring more than one isotope (using carbon, oxygen and nitrogen all together) can give us a feel for…
Food adulteration
Drugs
Bombs
Bioterrorism
Migrations

59. Source of cocaine growth

60. Plants
Animals

61. In terms of stable isotopes, you are what you eat.

62. Testosterone for non-cheater (and MVP)
13C content = -26
more 13C
13C content = -30
Low 13C
13C content = -26
more 13C
Testosterone for cheaters
13C content = -30
less 13C
13C content = -30 ppt
Low 13C
less 13C

63. Plants
Animals

67. Regional distribution of d18O in surface water

72. Fossil Fuel combustion
All have distinct isotope ratios
Photosynthesis:
Plants
6CO2 + 6H2O C6H12O6 + O2
Respiration:
Plants
Animals
Microbes
Oxidation:
Fossil Fuel combustion

73. Figure 1
Cross section
chloroplast

74. What have stable isotopes told us about human environment interactions?
Half of all fossil fuel CO2 released has been assimilated by photosynthesis.
Floyd Landis, Justin Gatlin…cheaters
We can ‘geolocate’ your past movements
We know where you’re getting your drugs

75. Thank you!