Author(s): Parag Deka, MM Goswami

Abstract: Seasonal variation of phosphorus was studied in two perennial aquaculture ponds of the Aquaculture and Biodiversity Campus of Zoology Department, Gauhati University, Guwahati, Assam, India. One of the experimental ponds is manually managed with the application of lime and other inorganic and organic fertilizer and the other is a naturally maintained pen culture pond, which is recovered from a part of reed swamp and maintained without addition of any fertilizer. The reclaimed zone of the pen culture pond is separated from the perennial swamp by bamboo screens. The unrecovered zone of pen culture pond is infested with Phragmites karka. The pen culture pond is dominated by Eichhornia crassipes, which is a free floating macrophyte.In comparison to manually managed pond, macrophytic growth is more and phytoplankton density is less in the natural pen culture pond. Both the ponds maintain acidic profile in soil phase; but manually managed pond maintains higher profile than natural pond. The total and available forms of soil phosphorus of the two ponds show similar trend of seasonal fluctuation with higher profile in natural pond. In water phase, however, it is interesting that the artificial pond maintains higher profile in both the form of phosphorus. Major portion of Phosphorus, which is not available for the water phase especially in natural pond are found to be in bounded form mainly with iron, calcium and aluminium.

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