The study of benthic organism is necessary to obtain a comprehensive idea of the fishery potential of any biotope. Benthic research in sedimentary estuarine environments began with an emphasis on descriptions of organism distributions and abundance. The present study area extends over distance of about 35 km and bound between Poompukar in the north and Nagore in the South India. The present study focuses on determining the spatial distribution and structure of the benthic assemblages, and to evaluate the species diversity along the study area, and finally whether there is any impact of black sand distribution on the benthic and pelagic community. A survey of benthic macrofauna at a total of 12 sampling stations from Poompukar to Nagoor was carried out between November 2004 to March 2005. Positions were fixed with a Trimble Global Positioning System (GPS). The sampling stations were chosen to quantify the benthos both within the black sand enrichment areas. The black sand enrichment area like Chandrapadi, Karaikal and Nagoor indicates that the colonisation of macrobenthic fauna is totally absent. This study is carried out on benthos in terms of impact of beach sand extraction and concluded that the white sand constituted more habitats than the black sand area. The sediment grain size particularly in coarse sand having non-black sand shows more interrelationship with macrobenthic faunal diversity which also clearly indicate the supply of organic matter source of food web to the species.