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The World of Protozoa, Rotifera, Nematoda and Oligochaeta

Ref ID : 6684

Kurihara Yasushi and Kikuchi Eisuke; Analysis of interactions among biotic and abiotic factors in ricefields, with special reference to the role of Tubificids in the ricefield ecosystem. Tropical Ecology & Development:1017-1019, 1980

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The aim of the present report is to analyse the interactions between biotic and abiotic factors in ricefield, with special references to the role of tubificids in the ricefield ecosystem. This is done by the submerged soil system in vitro, with and without tubificids under LD 12:12 and continuous darkness and soil which is artificially mixed by weak-aeration. The study indicates that weeds thrive in soil without tubificids, (their growth being inhibited by the presence of tubificids), while the Eh values increase and the pH decreases with the growth of weeds. The crustacean zooplankton (Moina sp.) appears more frequently in the presence of tubificids. The number of aerobes is lower in the soil with tubificids than in the soil without tubificids, while the number of sulphate-reducing bacteria is higher in the presence of tubificids. As for nitrifying bacteria, the number is lower in the presence to tubificids. The rise in oxidized nitrogen concentration of the overlying water is delayed in the presence of tubificids while the ammonia contents are higher in the presence of tubificids. Tubificids also affect nitrification by changing the oxidation-reduction conditions in the submerged ricefield soil. The similarities of the results between soil artificially mixed and soil with tubificids indicate that the tubificids in the ricefield soil are aerating the soils.