1. Ch. 9. Aquatic ecosystems and Physiology: Energy Flow  Productivity  Dissolved Oxygen
Fig Hypothetical Trophic Structure Model. Boxes are filled with functional groups, measured as calories of energy, or moles of chemicals, biomass, or numbers.

2. Fig 1.14a. Energy flow model of Cedar Bog Lake, Minnesota (Lindeman 1942)

3. Boxes are filled with SPECIES.
Food Web Model:
Boxes are filled with SPECIES.

4. Fig 1.14b. Energy flow model of Silver Springs, Florida (Odum 1971)

5. PRIMARY PRODUCTIVITY: PHOTOSYNTHESIS
NPP = GPP – Respiration
Fig. 9.4.

6. The world's ecosystems vary tremendously in productivity.
In terms of NPP per unit area, the most productive systems are estuaries, swamps and marshes, tropical rain forests, and temperate rain forests
To calcualte the total amount of NPP in the world, these values must be multiplied by the area that the various ecosystems occupy.
The most productive systems are open oceans, tropical rain forests, savannas, and tropical seasonal forests

7. Horne and Goldman 1994

8. Horne and Goldman 1994

9. Kalff 2002

10. Horne and Goldman 1994

11. Importance of dissolved oxygen in aquatic systems
Affect the distribution of aerobic heterotrophic life
Impacts the solubility of phosphorus and other nutrients
Influences redox potential (Ch. 10) and thus the solubility of redox-sensitive materials
May be used to estimate ecosystem productivity

12. Photo-inhibition

13. Productivity may be measured in units of mgC volume-1 time-1
Because it takes two moles of O2 to fix 1 mole of C, productivity may also be measured in units of mgO2 volume-1 time-1
CO2 + H2O CH2O + O2
Ratio of moles of C to moles of oxygen = 12/32 = 0.375; i.o.w. 1 mg O2 produced = mg C fixed
Examples of productivity measurement techniques:
Light - dark bottles
Diel cycles in oxygen levels
14C uptake

14. PN=PG-R R
Lingeman and Ruardij, 1981

15. Kalff 2002

16. Kalff 2002

17. Kalff 2002