| Sumario: |
This study quanti¢ed the accumulation of nitrogen (N) in the water column, sediments, ¢sh and seepage water during a production cycle of Colossoma macropomum. By combining estimates of the deposition rates of uneaten feed, faeces and dead phytoplankton with measurements of N accumulation in the sediment, the rate of decomposition of organic matter in the sediment was estimated. The ¢rst-order rate
constant for organic matter decomposition was 0.237 0.019 day 1. Total N recovery during the ¢rst weeks of the experiment was about 65%. Later, the Nrecovery was close to100%.The cumulative recovery at the end of the experiment was almost 100%, meaning that the N budget in the system studied can be fully explained without consideration of N volatilization, due to either denitri¢cation or ammonia volatilization. In the beginning of the growth cycle, the major £ux of N was sedimentation. Intensive
microbial degradation process occurred about 3^4 weeks later, leading to a release of inorganic N and an approach towards a steady state as to the accumulation of organic N. Feedwas irregularlyapplied during the experiment but ¢sh growthwas constant,
showing that the ¢sh utilized detrital or planktonic feed during periods of low feeding. Nitrogen accumulated in the pond during periods of excessive feeding and was utilized by the ¢sh during periods of low feeding. This cycling should be further studied and may be an important pond management technique.
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