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Conditions for Life in the Sea

Consider the main biochemical reaction for life in the sea, and on earth in general:

6H₂O + 6CO₂ + energy + nutrients = C₆H₁₂O₆ + 6O₂

Focus on left side of equation

What is in short supply in the sea and thus limits the amount of life in the ocean??

Absorbing Nutrients

Most important primary producers of complex sugars and oxygen

Nutrients absorbed by plants through diffusion across a semi-permeable membrane

Diffusion

Which Nutrients are in Short Supply?

Phosphorus (P) as Phosphate PO4 (-2)

Silicon (Si) as Silicate SiO4 (-2)

Phosphate and Nitrate in the Pacific

Silicate in the Pacific

Biolimiting Nutrients

Essential to the growth of phytoplankton

If these biolimiting nutrients increase in sea water, life increases

If these biolimiting nutrients decrease in sea water, life decreases

Where would you expect to find the highest biomass in the Pacific??

CZCS Global Primary Production

How Does Nutrient Distribution Compare w/Dissolved Oxygen?

Dissolved O2 reverse of Nutrients

O2 is high in the surface and mixed layer

O2 decreases to a minimum at base of thermocline

O2 then steadily increases with depth

Why is the Concentration of Oxygen High in the Mixed Layer??

How and where is oxygen produced in the sea???
6H2O + 6CO2 + energy + nutrients = C6H12O6 + 6O2

How can oxygen be mixed downward from the atmosphere into the ocean?

How is Oxygen Removed from the Thermocline & Slightly Below??

Dead and decaying organic matter sinks downward from surface waters

Material decays (oxidizes) at the thermocline, which strips O2 out of the water and returns nutrients to the sea

Cold, nutrient-rich water of the thermocline is returned to sunlit surface waters by way of upwelling

Last update: May 13, 1999
http://dusk.geo.orst.edu/oceans/lec23.html