1. Nutrient Cycles in Marine Ecosystems – Part 2

2. Surface Layer of Ocean Dissolved nutrients
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)

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
1. Copy this table.
2. Create a bar graph from the information above

5. Surface Ions
Those ions, together with nitrate and phosphate ions form nutrients for growth of algae and other producers
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

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
N gas is fixed by blue-green algae in intertidal zones
Forms nitrogen-containing organic compounds
How nitrogen enters marine ecosystems

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

15. Recall

16. Limited Productivity
Inorganic nutrients (ex: nitrate and phosphate ions) are essential for growth of primary producers
Productivity of primary producers will affect productivity of higher trophic levels
Example: upwelling – high productivity

17. Benguela upwelling system

18. Removal of Nutrients Sink to sea floor In feces
Detritus (decaying organic materials); organisms die
Loss of nutrients from surface water
Will only return to surface by upwelling
Slow decomposition on sea bed (floor) due to cold/lack of oxygen

20. Removal of Nutrients Incorporated into coral reefs
Deposition of calcium carbonate for growth of corals

21. Removal of Nutrients Removed by harvesting
Removing/eating fish and other marine organisms

23. Nutrient Biological Uses
Nitrogen
Make proteins; synthesis of amino acids
Carbon
Synthesis of all organic materials (ex: carbohydrates, proteins)
Magnesium
Make chlorophyll for plants
Calcium
Production of bones, corals and shells
Phosphorus
Production of bones and synthesis of DNA

24. Summary of ways in nutrients are cycled in marine systems
Nutrients derived from both
Removal (3)
Summary of ways in nutrients are cycled in marine systems

25. In Summary
Fertilizers, like nitrogen (N), phosphorous (P), and potassium (K), are important for plant growth and are called 'nutrients.' The level of dissolved nutrients increases from animal feces and decomposition (bacteria, fungi). Surface water often may be lacking in nutrients because feces and dead matter tend to settle to the bottom of the ocean. Most decomposition is thus at the bottom of the ocean. In the oceans most surface water is separated from bottom water by a thermocline (seasonal in temperature and marginal polar regions, constant in tropics) which means that once surface nutrients get used up (by the plants there) they become a limiting factor for the growth of new plants. Plants must be at the surface for the light. Nutrients are returned to surface waters by a special type of current called 'upwelling' and it is in these areas of upwelling that we find the highest productivity of marine life.