might have lost from the system either by ammonia gas volatilization and/or
denitrification in the sediment. Daniels and Boyd (1988) mentioned that the most
probably loss of nitrogen is by ammonia gas volatilization, which is further enhanced
by vigorous aeration and high pH in the tanks. Unaccounted phosphorus is likely to
the result of muds adsorption, as muds were known to have a strong affinity for
phosphorous (Boyd, 1985). However, from the nutrient budget data (Table 3) it is
apparent that larger percentage of the total nutrient inputs went unaccounted in the
treatments with concrete bottom than the muddy bottom treatments; procedural
difference (as explained in the Section 2) in estimating nutrient output in the form of
sediment between the two treatments might have caused this discrepancies. It is likely
that some of the sediment deposited in the concrete bottom tank could have washed
out of the tank with the drained water during harvest, and thus could have went
unaccounted for the nutrient budget.
In conclusion, this study provides valuable information on the management
practice for closed shrimp culture systems, as a viable alternative to the current water
exchange systems. The study demonstrated that closed culture system could
maintain acceptable water quality for shrimp culture, and shrimp could be grown
well at stocking density of 50 juveniles per m2. In addition, the study showed that
closed shrimp culture system can reduce the nutrient loss through pond effluents and
thus minimize the environment impacts of shrimp culture. Nevertheless, the total
quantity of nutrient released in closed shrimp culture system may be same to the
water exchange system, the small volumes of concentrated effluent produced at
harvest in closed system should be easier for the shrimp grower to treat before being
discharged to the external environment.
might have lost from the system either by ammonia gas volatilization and/ordenitrification in the sediment. Daniels and Boyd (1988) mentioned that the mostprobably loss of nitrogen is by ammonia gas volatilization, which is further enhancedby vigorous aeration and high pH in the tanks. Unaccounted phosphorus is likely tothe result of muds adsorption, as muds were known to have a strong affinity forphosphorous (Boyd, 1985). However, from the nutrient budget data (Table 3) it isapparent that larger percentage of the total nutrient inputs went unaccounted in thetreatments with concrete bottom than the muddy bottom treatments; proceduraldifference (as explained in the Section 2) in estimating nutrient output in the form ofsediment between the two treatments might have caused this discrepancies. It is likelythat some of the sediment deposited in the concrete bottom tank could have washedout of the tank with the drained water during harvest, and thus could have wentunaccounted for the nutrient budget.In conclusion, this study provides valuable information on the managementpractice for closed shrimp culture systems, as a viable alternative to the current waterexchange systems. The study demonstrated that closed culture system couldmaintain acceptable water quality for shrimp culture, and shrimp could be grownwell at stocking density of 50 juveniles per m2. In addition, the study showed thatclosed shrimp culture system can reduce the nutrient loss through pond effluents andthus minimize the environment impacts of shrimp culture. Nevertheless, the totalquantity of nutrient released in closed shrimp culture system may be same to thewater exchange system, the small volumes of concentrated effluent produced atharvest in closed system should be easier for the shrimp grower to treat before beingdischarged to the external environment.
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