Sedimentary systems are a constantly shifting mosaic of sites that are more or less risky for settling larvae. The infauna move, and the biogenically controlled aspects of the habitat shift with their movements, movements that occur on short temporal scales. The juveniles of many infaunal organisms emigrate in response to such biogenic degradation of the habitat. How important are these movements to the survivorship of the juveniles, how costly are they in terms of growth? These are the central questions of the research proposed herein. Without measurements of the cost and/or benefits of such movements by juveniles, we cannot evaluate our models of recruitment in sedimentary systems. The proposed research will provide those measurements for members of the three dominant infaunal taxa, the bivalves, polychaetes and small crustaceans.