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)
Fig 1.14b. Energy flow model of Silver Springs, Florida (Odum 1971)
PRIMARY PRODUCTIVITY: PHOTOSYNTHESIS
Fig. 9.4.
NPP = GPP – Respiration
Horne and Goldman 1994
Horne and Goldman 1994
Kalff 2002
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. 16) and thus the solubility of redox-sensitive materials
• May be used to estimate ecosystem productivity
Horne and Goldman 1994
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
Lingeman and Ruardij, 1981
PN=PG-R
R
Kalff 2002
Kalff 2002
Kalff 2002
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