1. Nutrient Cycles in Marine Ecosystems Part I
Section 4

2. Surface Layer of Ocean Dissolved nutrients (N,*P)
Elements/compounds that are
essential to life
Recall: algae require light for photosynthesis
Intensity of light as depth
Restricted to surface layer (photic zone)
Depth 30 m to 150 m
Obviously less in turbid water (high turbidity)
*there due to animals releasing ammonia

3. What is an ion?
atom or molecule in which the total number of electrons is not equal to the total number of protons, giving the atom a net positive (+) or negative (-) electrical charge.

4. SOME Surface Layer Ions

5. Surface Ions
Those ions, together with nitrate and phosphate ions form nutrients for growth of algae and other producers
Unit of measurement: ppm
Nitrate and phosphate ions occur in low concentrations in seawater
Nitrate = 0.5 ppm
Phosphate = 0.07 ppm

6. Replenishment of dissolved nutrients (3)
1. Upwelling – movement of water from deep in the ocean to the surface layer, where nutrients become available to primary producers
Replenishment=bringing back to use
Wind driven
Movement of dense water
Movement of cooler water

7. Causes of Upwelling Deflection of deep water currents upwards
Nutrients sunk to sea floor brought back up to surface of ocean
Movement of water away from the coast by wind

8. 2. Run-off from land Part of hydrological cycle
Water leach nutrients (including nitrates and phosphates) from soil

9. 3. Atmospheric Gases
CO2 dissolved in seawater forming hydrogencarbonate ions (HCO3-)
AKA bicarbonate
Makes CO2 available for fixation in photosynthesis for primary producers
*Ocean acidification
N gas is fixed by blue-green bacteria in intertidal zones
Forms nitrogen-containing organic compounds
How nitrogen enters marine ecosystems
*Show ocean acidification lesson

10. Intertidal Zone
Area above water during low tide but underwater during high tide

11. Nitrogen Cycle

12. Recycled
Nutrients like nitrates and phosphates are recycled at the ocean surface by excretion from zooplankton

13. Depletion of dissolved nutrients
Uptake by primary producers like phytoplankton
Synthesis of organic substances
Example: nitrate ions used for synthesis of amino acids and proteins
Phytoplankton  zooplankton  small fish
Proteins passed to next trophic level and so forth