1. Class #19 More Ocean Chemistry... NUTRIENT ELEMENTS ORGANIC SUBSTANCES
LONG-TERM CONTROLS ON MAJOR DISSOLVED CONSTITUENTS
"Steady state"
Input processes
Removal processes

4. NUTRIENT ELEMENTS Photosynth. requires ~ 30 nutrient elements
CO2 + H2O + nutrients --> "Organic Matter" + O2
A few things can be "limiting nutrients” i.e., algae grow until they deplete one of these
P -- present as dissolved PO4
N -- as dissolved NO3 (plants can't use N2)
SiO2 -- diatoms need SiO2
Fe -- Iron is not soluble; its scarcity probably limits growth in many places (recent discovery)

5. Photosynthesis removes CO2
So can we “fertilize” the oceans to offset our CO2 emissions?
6CO2 + 6H2O + nutrients + sunlight => 6C6H12O6 + 6O2
The biological CO2 pump
Reading: Section 16.5

6. http://disc. sci. gsfc. nasa

7. Nutrient uptake and the nutrient cycle
Nutrients are easy to identify: Non-conservative
Concentrations vary- controlled by life processes
Photosynthesis -- extracts nutrients
photic zone waters -> nutrient concentrations drop quickly if not replenished
Respiration -- releases nutrients locked up in organic matter (decomposed); concentrations greater in deep water
Upwelling of deep water supplies nutrients to surface layer of the oceans

9. Photic Zone: Nutrients taken up into organic matter
Organic matter sinks; some of it sinks out of the photic zone before it gets eaten/decomposed/recycled
Deeper: Organic matter decomposed- nutrients released