Ten-year simulations of organic matter concentrations in tropical aquaculture ponds using the multiple pool modeling approach

The accumulation rate of organic matter has been used to develop guidelines on sediment management in tropical aquaculture ponds. However, there is co nflicting evidence as to the rate of sediment organic matter accumulation a nd whether steady state concentrations are achieved in the short term ( < 1 0 years) in aquaculture ponds. A simulation study using the multiple pool m odeling approach (Multi-G model) was conducted to determine the longterm dy namics of sediment organic matter and to establish whether steady state con centrations could be achieved in tropical aquaculture ponds. The Mufti-G mo del, which recognizes the existence of different organic matter pools, each with its own decay rate constant was run as a sub-model of an integrated a quaculture-agriculture system (IAAS) model. The simulation study was conduc ted for representative management scenarios for new integrated ponds receiv ing artificial feed, chicken manure, or a combination of chicken manure and crop wastes. The model was run for 10 years using a 0.125 day time step, a nd each year's simulation consisted of a wet and a dry season, and fallow p eriods between crops that totalled 121 days for the year. Pond sediment org anic matter concentrations increased over time for all input regimes in the following order: chicken manure x plant waste > chicken manure > artificia l feed. Simulated organic matter concentration decreased in the first 4-5 y ears in ponds receiving chicken manure and artificial feed. Contrary to pre dictions of models that used a single decay rate constant for the organic m atter, steady state sediment organic matter were not achieved within the fi rst 5 years of production. These results were consistent with those obtaine d from long term sediment organic matter experiments in tropical aquacultur e ponds. The results show that the multiple pool modeling approach may be m ore applicable to the simulation of pond sediment organic matter dynamics t han those that assume organic matter to consist of a single pool decaying a t a single rate. (C) 2001 Published by Elsevier Science B.V.