Abstract Exposed sandy beaches comprise three quarters of the world’s shorelines and are a dominant open coast habitat in Southern California. Sandy beaches in Southern California support diverse macroinvertebrates communities. To investigate the influence of marine macrophyte wrack subsidies on community structure, species richness, and abundance of macrofauna were examined on 2 exposed sandy beaches on the Southern California. The beaches sampled, one was non groomed and the other was regularly groomed. . Substantial ecological effects of large scale disturbances and removal of organic material, food resources, and habitat are associated with beach grooming. Overall species richness and abundance, were significantly varied with the standing crop of macrophyte wrack( non groomed) and the groomed beach. Wrack associated macrofauna such as Hoopers, blood worms, polychaete, isopods made up 50 % or more of species on non groomed beaches and comprised more than half of total abundance. Substantial ecological effects of large scale disturbances and removal of organic material, food resources, and habitat are associated with beach grooming. These results suggest that macrophyte wrack subsidies strongly influence macrofaunal community structures, higher trophic levels and ecological processes on exposed sandy beaches. Beach grooming practices that remove wrack may have significant impacts on macrofauna communities. Introduction Sandy beaches comprise approximately three quarters of the world’s shorelines (Dugan 2003). On the mainland coast, 74%, 93% and 66% of Santa Barbara, Ventura, and Los Angeles countries are Sandy beaches(Smith et al 1976 et al. 1998a). Bottom up processes can have important influences on community structure and the flow of energy to higher trophic levels in marine ecosystem (Dugan, Hubbard, 2002). Food availability is a potentially important determinant of abundance in natural communities and growth rates may be positively associated with food supply in a variety of habitats( Hunter & Price 1992). Macrofauna communities inhabiting in sandy beaches are supported almost entirely by inputs of carbon and organic materials because little production occurs on the beach itself(Dugan & Hubbard). In many temperate regions, the major sources of carbon to sandy beach macrofauna are marine macrophytes (macroalgae, seagrasses)( Brown & McLachlan 1990). The production of marine macrophytes is very high in coastal regions and the input of drift macrophytes may represent a major source of carbon and organic materials to macrofa