WATER QUALITY IN
AQUACULTURE
Introduction
Part 1
Aquaculture and Seafood
Capture from the
oceans is maximized.
Aquaculture is
growing as a source
of the world’s
seafood supply.
Benefits of Aquaculture
Ability to bring
fresh, or even
live, seafood
to market at a
specific time
and quantity.
Asian fresh seafood market
US seafood market
Aquaculture is based on water
The key to the
successful culture of
aquatic organisms is
maintenance of water
quality.
Fish ponds in China
Poor water quality =
poor harvest.
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
Source
From where?
underground
surface
Source
well
reservoir
spring
How much?
irrigation canal
stream
Source
pasture
quality
Red tide
unpopulated
forested
underground
populated
Water Quality
Clear water
During culture
Fertile water
Turbid water
Water Quality
Discharge
Shrimp pond
Catfish pond
Factors that influence water quality
Photosynthesis/Respiration
Water temperature
Fertilization
Feeds
Aeration
Water exchange
Photosynthesis/Respiration
photosynthesis
6CO2 + 6H2O + light energy  C6H12O6 + 6O2
respiration
C6H12O6 + 6O2  6CO2
+ 6H2O + heat energy
Water temperature
=
active
zz
z
=
z z
inactive
z
Fertilization
organic
inorganic
Feed
Marine shrimp
Common carp
Rainbow trout
Channel catfish
Aeration
Aspirator
Pond aeration
Defused air
paddlewheel
Water exchange
Salmon cages
Catfish raceways
Trout raceways
Carp cages
Testing Water Quality
Water quality parameters
often tested are:
Dissolved oxygen
Water temperature
pH
Total Ammonia Nitrogen
Nitrite/Nitrate
Alkalinity/Hardness
Salinity
Water test kit
How water quality values are
expressed
Parameter
Value
Dissolved oxygen
Water temperature
pH
mg/L O2
C (Celsius)
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
Oxygen meter
temperature
dissolved oxygen and water
temperature usually vary
over a 24 hour cycle.
Surface dissolved oxygen, mg/L
Surface water temperature, C
15
31
10
29
27
summer
5
25
0
6 a.m.
noon
6 p.m.
midnight
6 a.m.
Dissolved oxygen and water
temperature
Stratification can cause dissolved oxygen and
temperature to vary at different depths in the
same system.
Epilimnion
High temperature
High dissolved oxygen
Thermocline
Hypolimnion
Low dissolved oxygen
Low temperature
pH
pH is a measure of acidity (hydrogen
ion concentration) in water or soil.
pH = - log [
0
1
2
3
acid
4 5
6 7
neutral
8
+
H ]
9 10 11 12 13 14
alkaline
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.
90 %
80 %
60 %
50 %
40 %
30 %
20 %
10 %
pH of water
9.8
9.4
9
8.6
8.2
7.8
0%
7.4
Ammonia as a % of
total ammonia nitrogen
at 20 C
at3 0C
7
NH3 as % of TAN
70 %
Nitrite/Nitrate
feces
NH4+ +1.5 O2 + Nitrosomonas
Bacterial
decomposition
NO2- + 0.5 O2 + Nitrobacter
NO3-
Alkalinity and Hardness
hardness
alkalinity
Total titratable bases
bicarbonate
carbonate
HCO3CO23-
Total divalent salts
calcium
magnesium
Ca2+
Mg2+
Calcium bicarbonate Calcium carbonate Magnesium
bicarbonate
CaCO
Ca( HCO )
3 2
3
Mg( HCO3 )2
Magnesium
carbonate
Mg CO3
Alkalinity and Hardness
The form alkalinity takes is linked to pH of the system.
Alkalinity and Hardness
Alkalinity buffers against diurnal variations in pH.
Salinity
Brackish water is 2 g/L to 34 g/L
Freshwater is less than 2 g/L
Sea water is more than 34 g/L
NaCl
End of Introduction
Part 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/Pen
Cages in lake
Cages in ocean
Pen
Type of culture unit: Tank
Rectangular tank
Circular 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 management
Chemical fertilizer
Supplemental feeds
Animal manures
Intensive management
Aeration in ponds
Water exchange in tanks
Nutritionally complete
pelleted feeds
Public perceptions of aquaculture
Water quality concerns:
• Water pollution
• Salinization
• Sedimentation
• Spread of disease
Other concerns:
• Wetland destruction
• Wasteful of resources
• Biodiversity
• Land conversion
• Social impacts
Water quality concerns
Cages in Indonesia
Shrimp pond effluent
in Thailand
Other concerns
Preservation of saltwater mangrove
Preservation of freshwater wetlands
End