WATER QUALITY IN AQUACULTURE Introduction Part 1
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Transcript of WATER QUALITY IN AQUACULTURE Introduction Part 1
WATER QUALITY IN AQUACULTURE
Introduction Part 1
Aquaculture and Seafood
Aquaculture is growing as a source of the world’s seafood supply.
Capture from the oceans is maximized.
Benefits of AquacultureAbility to bring
fresh, or even live, seafood to market at a specific time and quantity.
US seafood market
Asian fresh seafood market
Aquaculture is based on water
The key to the successful culture of aquatic organisms is maintenance of water quality.
Poor water quality = poor harvest.
Fish ponds in China
Water Quality
• Source • During culture• Discharge
“Water quality issues should be taken into account at every point of the aquaculture cycle.”
Dr.Claude E. Boyd
SourceFrom where?
underground
surface
Source
How much?
reservoir
irrigation canal
stream
spring
well
Sourcequality
populated
Red tide
underground
unpopulated
forested
pasture
Water QualityDuring culture
Turbid water
Clear water
Fertile water
Water QualityDischarge Catfish pond
Shrimp pond
Factors that influence water quality
Photosynthesis/RespirationWater temperature FertilizationFeedsAerationWater exchange
Photosynthesis/Respiration
6CO2 + 6H2O + light energy C6H12O6 + 6O2
photosynthesis
respiration
C6H12O6 + 6O2 6CO2 + 6H2O + heat energy
Water temperature
=
=
active
inactive
zz z
zzz
Fertilization
organic inorganic
FeedCommon carp
Marine shrimp
Rainbow trout
Channel catfish
AerationAspirator Defused air
Pond aeration paddlewheel
Water exchange
Salmon cages
Carp cages
Catfish raceways
Trout raceways
Testing Water QualityWater quality parametersoften tested are:
Dissolved oxygenWater temperaturepHTotal Ammonia NitrogenNitrite/NitrateAlkalinity/HardnessSalinity
Water test kit
How water quality values are expressed
Parameter Value
Dissolved oxygen mg/L O2
Water temperature C (Celsius) pH
Total ammonia nitrogen mg/L N
Nitrite mg/L NO2-
Nitrate mg/L NO3-
Alkalinity/Hardness mg/L CaCO3
Salinity g/L salt
Dissolved oxygen and water temperature
dissolved oxygen and water temperature usually vary over a 24 hour cycle.
6 a.m. 6 a.m.midnight6 p.m.noon
0
15
10
5
Surface dissolved oxygen, mg/L
25
27
29
31
Surface water temperature, C
summer
Oxygen meter
Stratification can cause dissolved oxygen and temperature to vary at different depths in the same system.
Dissolved oxygen and water temperature
Epilimnion
Thermocline
Hypolimnion
High temperatureHigh dissolved oxygen
Low dissolved oxygenLow temperature
pH = - log [ H+ ]
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14
acid alkaline
pH pH is a measure of acidity (hydrogen
ion concentration) in water or soil.
neutral
Total Ammonia Nitrogen Total ammonia nitrogen ( TAN ) is a measure of the ammonia (NH3) and ammonium levels (NH4
+) in the water The ratio of ammonia and ammonium varies in an
equilibrium determined by pH and water temperature.
0%10%20%
30%40%50%60%
70%80%90%
7 7.4
7.8
8.2
8.6 9 9.4
9.8
pH of water
NH 3
as %
of T
AN
at 20Cat30C
Ammonia as a % of total ammonia nitrogen
Nitrite/Nitrate
NH4+ +1.5 O2 + Nitrosomonas NO2
- + 0.5 O2 + Nitrobacter NO3
-
feces
Bacterialdecomposition
Alkalinity and Hardness
alkalinity hardnessTotal titratable bases Total divalent salts
HCO3-
bicarbonateCO2
3-
carbonate calcium magnesiumMg2+Ca2+
Calcium bicarbonate
Ca( HCO3 )2
Calcium carbonateCaCO3
Magnesiumbicarbonate
Mg( HCO3 )2
Magnesium carbonateMg CO3
.
4 5 6 7 8 9 10 11pH
0.00
0.25
0.50
0.75
1.00
mol
e fra
ctio
n
H2CO3 andfree CO2
HCO3 - CO32-
bicarbonate carbonateCa(HCO3) 2 CaCO3
Alkalinity and HardnessThe form alkalinity takes is linked to pH of the system.
Alkalinity and HardnessAlkalinity buffers against diurnal variations in pH.
Salinity
Freshwater is less than 2 g/L
Brackish water is 2 g/L to 34 g/L
Sea water is more than 34 g/L
NaCl
End of IntroductionPart 1
Good Water Quality = Good Harvest
WATER QUALITY IN AQUACULTURE
Introduction Part 2: Applications
Classification of aquaculture systems
• Salinity of culture water.• Producer/consumer
relationship. • Type of culture unit.• Species• Management intensity
Salinity• Freshwater has a low ionic
concentration (i.e. streams, rivers, ponds and lakes).
• Saltwater has a high ionic concentration (ocean waters).
• Brackishwater has an ionic concentration between freshwater and saltwater ( mangroves ).
Producer/consumer relationship
• Commercial aquaculture
• Subsistence aquaculture
Type of culture unit
• Many different culture units are used to grow aquatic organisms.
• The culture unit selected is based on economic, space and water concerns.
• The type and size of the culture unit will determine water quality management.
Type of culture unit:Earthen Pond
Levee ponds
Reservoir Pond
Type of culture unit: Cage/PenCages in lake
Cages in ocean
Pen
Type of culture unit: Tank
Circular tank
Rectangular tank
Raceway culture
Trout farms using raceways
Species• The species cultured will determine
stocking density, water quality levels desired and the most appropriate system to use.
Management intensity
Levels of aquaculture management are closely tied to water quality.
Extensive management – no control of water quality
Semi-intensive management – some control of water quality
Intensive management – control of water quality
Extensive management
Marine shrimp
Semi-intensive managementChemical fertilizer
Supplemental feeds
Animal manures
Intensive managementAeration in ponds
Water exchange in tanks
Nutritionally completepelleted feeds
Water quality concerns:• Water pollution• Salinization• Sedimentation• Spread of disease
Other concerns:• Wetland destruction• Wasteful of resources• Biodiversity• Land conversion• Social impacts
Public perceptions of aquaculture
Water quality concerns
Shrimp pond effluent in ThailandCages in Indonesia
Other concerns
Preservation of freshwater wetlands
Preservation of saltwater mangrove
End