2-Dr Boyd-1
Transcript of 2-Dr Boyd-1
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Claude E. Boyd
School of Fisheries, Aquaculture and Aquatic Sciences
Auburn University, Alabama 36849 USA
The Theory and Practice of Shrimp PondBottom Soil Management
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Basic Soil Science Concepts for
Aquaculture
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Holds pond water (not water quality issue)
Accumulates sediment
Exchanges cations with water
Removes phosphorus from water
Source of combined nitrogen to water
Removes oxygen from water column
Source of potentially toxic microbial metabolites
Soil acidity neutralizes alkalinity in water
Source of nutrients in water via dissolution ofminerals
Habitat for benthic food organisms
Harbors pathogens
Role of Pond Soil
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Soil triangle. To use, mark percentage clay and percentage sand on the
appropriate axes. From these points, project a line inward from the
clay axis and parallel to the sand axis and another line from the sand
axis parallel to the silt axis. The interaction of the two projected lines
will denote soil texture.
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Pond on Sandy Soil
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Turbid Water Supply
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Pond Filled with Sediment
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Average rate of sediment accumulation isroughly 1.0 cm/yr, but is much faster during the
first 2 or 3 years that a pond is used.
Sediment accumulates forming a unique profile
with distinct horizonsupper 4 or 5 cm effects
water quality.
Heavy mechanical aeration may greatly
accelerate erosion.
Comments on Sedimentation
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HORIZONS IN SEDIMENT PROFILE
FLOCCULENT LAYER
MIXED
SEDIMENT
LAYER
Oxidized (aerobic)
Reduced
(anaerobic)
MATURE STABLE
SEDIMENT
TRANSITIONAL
LAYER
ORIGINAL, UNDISTURBED
POND BOTTOM
PO
ND
SOILPROFILE
WATER HORIZON CHARACTERISTICS
F
S
M
T
P
Water with high concentration of mineral
and organic solids, aerobic
Sediment with high water content and
low dry bulk density, abundant organic
matter, well stirred by physical and
biological agents, thin aerobic surface
but anaerobic below
Sediment with medium water content
and intermediate dry bulk density,
abundant organic matter, not stirred,
anaerobic
Transition between M and P horizonswith characteristics intermediate
between M and P horizons, not stirred,
anaerobic
Low water content and high bulk
density, usually compacted, low organic
matter, not stirred, anaerobic
}So
Sr
}MT
PT
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Brown Oxidized soil
Black Reduced soil underneath
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Aerobic Saprophytic
MicroorganismsThese organisms use oxygen in
respiration to decompose organic
matter to carbon dioxide, mineralnutrients, and water. The typical
equation for aerobic decomposition is:
Organic Matter + O2 CO2+ H2O + Mineral
Nutrients
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Fermentation
When anaerobic conditions exist, some
organisms can use intermediate organic
metabolites as electron acceptors. An
example of a fermentation reaction is:
C6H12O6 2CH3CH2OH + 2CO2
Also, can have end products such as
formate, propionate, lactate, etc.
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Denitrification
Some bacteria can use oxygen from
nitrate when no dissolved oxygen is
available as illustrated by the followingreaction:
6NO3-
+ 5CH3OH 5CO2+ 3N2+ 7H2O +6OH-
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Reduction of Ferric Hydroxide and
Manganese Oxide
Some bacteria can derive oxygen from
iron and manganese compounds.
CH3COOH + 2H2O 2CO2+ 8H+
Fe(OH)3+ 3H+ = Fe2++ 3H
2O
MnO2+ 4H+= Mn2++ 2H2O
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Sulfate Reduction
Sulfate-reducing bacteria use
sulfate as an oxygen source asshown below:
SO42-+ 4H+ S2-+ 4H2O
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Methane Bacteria
Methane-producing bacteria use
oxygen from carbon dioxide asillustrated in the following
equation:
8H++ CO2 CH4+ 2H2O
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Date
7/05 9/05 11/05 1/06 3/06 5/06
P
otassium
(mg/L)
0
10
20
30
40
50
60
70First treatment
Second treatment
Third treatment
Changes in potassium concentration following three potassium
additions of 50 mg/L each in laboratory soil-water systems.
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Potassium loss from water and adsorption by soil
over 8 months in laboratory soil-water systems with
56 L of water and 9.6 kg soil.
Variable Average
Potassium loss from water
(mg/L) 89
(mg/tank) 4,982
Exchangeable potassium adsorption by soil
(mg/kg) 136
(mg/tank) 1,284Potassium fixed by nonexchange process
(mg/kg) 390
(mg/tank) 3,568
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Number of Consecutive Exposures
0 2 4 6 8 10 12 14
Potass
ium
adsorbedbyso
il(mg/kg)
0
100
200
300
400
500
Potassium adsorption by samples of original pondsoil from an inland shrimp farm in Alabama.
Samples were exposed twelve consecutive times to
50 mg/L potassium (potassium chloride in distilled
water) in a shaker trial.
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Soil is source of substances to water viadissolution of minerals. Possibly, most
important are carbonate and silicate minerals
that dissolve to give alkalinity as illustrated with
calcium carbonate and silicate:
CaCO3+ CO2+ H2O Ca2++ 2HCO3
CaSiO3+ 2CO2+ 3H2O Ca2++ 2HCO3-+ H4SiO4.
Dissolution of Minerals
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Neutralization of Exchangeable Acidity in Soils
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Mangroves
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Mangrove Soil
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Pyrite Formation
2CH2O + SO42- H2S + 2HCO3
Fe(OH)2+ H2S FeS + 2H2O
FeS + S FeS2
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Pyrite Oxidation
FeS2+ 3.75O2+ 3.5H2O Fe(OH)3+ 2SO42-
+ 4H+