Vertical distribution and abundance of sediment dwelling macro-invertebrates in an estuarine mangrove biotope - southwest coast of India

26-30Depth wise distribution of macro-invertebrates in sediments of intertidal areas of Cochin mangroves were studied. The fauna mainly composed of polychaetes, crustacerans and molluscs. At all tidal levels the macro-fauna tended to be concentrated at the top 0-5 cm layer substratum (65%) and they substantially decreased towards deeper levels. The polychaete, Marphysa gravelyi was abundant below 10 cm depth. The aggregation and coexistence of organisms were perceptible in the apex (0-5 cm) soil. Stability of the community structure of infauna was far pronounced in the surface layer zone than the deeper. Anoxic condition of the deep soil and the availability of food in the atop soil determines the vertical distribution of the fauna