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

Plant Physiological Ecology

Weather variability El Niño

Climate change

Stable isotopes: Link carbon and water cycles Trace CO2 processes

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

Summer Winter

6CO2 + 6H2O C6H12O6 + O2 SEM of stomata

Figure 1 Cross section chloroplast

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

Why do different plants grow where they grow?

Why do different plants grow where they grow?

Why do different plants grow where they grow?

Why do different plants grow where they grow?

Why do different plants grow where they grow?

Stable isotopes as indicators of plant-environment interactions Periodic Table

6 C 12.011 Periodic Table

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)

‘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

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

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

Carbon isotope work has dramatically improved crop water use efficiency.

Carbon isotopes in tree rings can be used to reconstruct climate

Why the new money?

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

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.

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.

*= 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.

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

Regional distribution of d18O in surface water

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

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

H218O CO2 H216O

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

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

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

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

Regional distribution of d18O in surface water

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

Global terrestrial biomes Ricklefs

Leaf temperature minus growing season temperature

Mean leaf temperature was 21.4 °C across species

Leaf temperature minus growing season temperature

Smith and Carter 1988

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

Summer Winter

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

CO2 sources are isotopically distinct 45 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)

Summer Winter

CO2 sources are isotopically distinct 45 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)

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…).

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

Source of cocaine growth

Plants Animals

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

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

Plants Animals

Regional distribution of d18O in surface water

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

Figure 1 Cross section chloroplast

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

Thank you!