Ch. 9. Aquatic ecosystems and Physiology: Energy Flow Productivity Dissolved Oxygen Fig. 9.1. Hypothetical Trophic Structure Model. Boxes are filled with functional groups, measured as calories of energy, or moles of chemicals, biomass, or numbers.
Fig 1.14a. Energy flow model of Cedar Bog Lake, Minnesota (Lindeman 1942)
Boxes are filled with SPECIES. Food Web Model: Boxes are filled with SPECIES.
Fig 1.14b. Energy flow model of Silver Springs, Florida (Odum 1971)
PRIMARY PRODUCTIVITY: PHOTOSYNTHESIS NPP = GPP – Respiration Fig. 9.4.
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 http://www.globalchange.umich.edu/globalchange1.html 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
Horne and Goldman 1994
Horne and Goldman 1994
Kalff 2002
Horne and Goldman 1994
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
Photo-inhibition
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 = 0.375 mg C fixed Examples of productivity measurement techniques: Light - dark bottles Diel cycles in oxygen levels 14C uptake
PN=PG-R R Lingeman and Ruardij, 1981
Kalff 2002
Kalff 2002
Kalff 2002