Bioturbation effect of mud lobster on the nutrient dynmicis in mangrove ecosystem

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Results of field investigations and physico-chemical analyses of the soil mounds built by mud lobster, Thalassina anomala Herbst. Were as follows :1) The domed mound of the mud lobster is 98 cm high on the average, has a basal diameter of 108 cm and weighs 1412kg. There wee 380 mounds/ha in the Rhizophora apiculata dominant forest. The total soil weight of Thalassina anomala mounds was approximately 40 ton/ha, corresponding to a surface layer of soil approximately 6 cm thick, if the mounds were leveled off.2) The mud lobsters carry on the top of mound, subsoil rich in neutral pyrite FeSィイD22ィエD2, that becomes strongly acidic with aeration and shows decreasing trends in total C, N, P and basal contents and as well as electric conductivity in mound soil.3) Weekly measurements using a 10kg spring scale of the amount carried to the surface from the subsoil was estimated to be approximately 20.3 ton dry soil/ha/yr ; the mound soil turnover ratio was estimated to be 0.045 annually, indicating that appreciable amounts of available nutrients would be released from mud lobster activity to the surrounding mangrove ecosystem.