The factors which control the distribution and rate processes of phytoplankton, bacteria and higher trophic levels in the coastal environment are of particular importance to the proper characterization and management of our nation's land-margin systems. Dr. Simenstad and colleagues will study the dynamics and impact of anthropogenic effects upon the estuarine turbidity maximum (ETM) in the Columbia River. The ETM is hypothesized to promote and control microbial conversion of entrapped organic material and to facilitate the maintenance of dense populations of primary consumers, which exploit the microbial loop for food. This well experienced team will undertake a multi-disciplinary effort focusing on the physics and biology of the system. It is expected that the effort will provide valuable information about the physical processes which may ultimately control the retention and recirculation of the biological components within the estuary.