INTRODUCTON TO WATER QUALITY IN AQUACULTURE Unit 4:

1
INTRODUCTON TO WATER QUALITY IN AQUACULTUREUnit
4 Dissolved oxygen/aeration
Auburn University Department of Fisheries and
Allied Aquacultures
2
Dissolved oxygen

• Aquatic animals require oxygen, just as air
  breathing animals do.
• The oxygen contained in water is termed
  dissolved oxygen.

3
Dissolved Oxygen

• Managing the dissolved oxygen content of the
  water in a culture system is of critical
  importance both to keep the animals alive and to
  increase the production capacity of the system.

4
Chemical Determination of Dissolved Oxygen

• Accurate
• Water samples can be held for a period of time
  before measurements
• Time consuming with multiple measurements

Dissolved Oxygen Kit
5
Electronic Determination of Dissolved Oxygen

• Accurate
• Multiple measurements are done quickly
• Need to calibrate meter

Electronic dissolved oxygen meter
6
Factors affecting dissolved oxygen concentrations

• Air-water gas transfer
• Sediment oxygen uptake
• Animal and plant respiration
• Photosynthesis

7
Factors affecting dissolved oxygen concentration
Air-water gas transfer

• Factors that influence the transfer of oxygen
• Temperature
• Elevation
• Salinity
• Turbulence

atmosphere
o2
o2
o2
o2
o2
o2
Under saturated
Super saturated
Saturated
water
8
Factors affecting dissolved oxygen concentration
Sediment oxygen uptake
atmosphere
water
O2
O2
O2
O2
O2
O2
O2
O2
O2
Bacterial respiration
sediment
9
Factors affecting dissolved oxygen concentration
Animal and plant respiration
C6H12O6 6O2 ? 6CO2 6H2O heat energy
10
Factors affecting dissolved oxygen concentration
Photosynthesis
6CO2 6H2O light energy ? C6H12O6 6O2
11
Daily fluctuation in surface dissolved oxygen
concentration in a fish pond
12
Stratification and Dissolved Oxygen

• In a pond, distinctive layers of water may form,
  with different temperature and DO
  characteristics.
• This phenomenon can have important implications,
  especially for deeper ponds.

Epilimnion
High temperature High dissolved oxygen
Thermocline
Low dissolved oxygen Low temperature
Hypolimnion
13
Management of dissolved oxygen in ponds

• Control phytoplankton - Chemical

Copper sulfate crystals
Copper liquid
14
Management of dissolved oxygen in ponds

• Control phytoplankton - Biological

Silver Carp
Nile tilapia
15
Management of dissolved oxygen in ponds
Aeration
16
Failure to maintain good Dissolved Oxygen
Fish Kills
17
End of Unit