4.1c Environmental C and N

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)