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TL PhD Comprehensive Exam
  • Introduction
  • Tasklist
  • 1. Basics
    • 1.1 Basic Biology Review
    • 1.2 Basic Genetics Review
    • 1.3 Light & Photosynthesis
  • 2. Coral Biology
    • 2.1 Basic Coral Biology
      • 2.1a Food Webs
    • 2.2 Reef Structure
    • 2.3 Growth & Reproduction
    • 2.4 Morphology
    • 2.5 Physiology
    • 2.6 Mixotrophy & Energy
    • 2.7 Symbiosis
    • 2.8 Reef Mortality
      • 2.8a Conservation
  • 3. Ecology & Evolution
    • 3.1 Evolution & Plasticity
    • 3.2 General Ecology
    • 3.3 Species
    • 3.4 Cryptic Species
  • 4. Isotopes
    • 4.1 Isotope Basics
      • 4.1a Instrumentation & methodology
      • 4.1b Environmental O & H
      • 4.1c Environmental C and N
      • 4.1d Organismal Isotopes
    • 4.2 Fractionation in Corals
    • 4.3 Trophic Niche Analysis
    • 4.4 CSIA
      • 4.4a C: Essential vs. Nonessential
      • 4.4b N: Trophic vs. Source
  • 5. Other
    • 5.1 Science & Society
    • 5.2 Stats
  • 6. Summary & Resources
    • 6.1 Glossary
    • 6.2 Resources
    • 6.3 Questions From Exam
    • 6.4 Recommendations & Reflections
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  1. 4. Isotopes
  2. 4.1 Isotope Basics

4.1c Environmental C and N

Last updated 1 year ago

Carbon

  • global δC in phytoplankton shows strong relationship to upwelling and latitude

  • surface ocean has equilibrium fractionation with the air (DIC)

  • Photosynthesis preferentially takes up 12CO2 making residual CO2 more 13C enriched

  • Respiration preferentially releases 12CO2 so water DIC has lower 13C values

  • The biologial pump controls vertical 13C DIC gradient, with more 13C in surface where photosynthesis occurs, and less in pycnocline where respiration is more common

  • Upwelling brings low 13C DIC to surface at equator and continental boundaries

  • Seuss Effect: as CO2 concentrations have increased, δ13C has decreased drastically in the atmosphere due to burning of fossil fuels. These fossil fules are primarily preserved 12C.

Nitrogen

  • There's a general relationship between DIN and phosphate in the ocean: N* = (N-16*P)

  • δ15N increases with depth in ocean

  • Denitrification drives really high δ15N values in areas of very high productivity

  • N can be used as a land use tracer (manure, sewage, fertilizer)