With California Sea Grant support, researchers collected biological data (fecal indicator bacteria, chlorophyll and dinoflagellate counts) as a supplement to an extensive large-scale field project conducted in 2009 at Imperial Beach near the mouth of the Tijuana River with funding from the Nati onal Science Foundation and the Office of Naval Research to study how waves, currents and tides affect ocean pollution. While the physics study has focused on understanding how pollutants are diluted and advected in the surf-zone, the biological study is centered on identifying the sources of fecal indicator bacteria (FIB) and the effects of solar irradiance, particle attachment and microbial food web dynamics on the fate of pathogenic bacteria at the beach. Exchange from the surfzone to inner-shelf waters farther offshore is also being studied, which has important implications for pollution dilution, nutrient delivery, phytoplankton and larval exchange. Among the intended outcomes of the project is a better characterization of the biological and physical processes that create highly “patchy” distributions of pollutants, including fecal indicator bacteria, along the coast. Findings are of relevance to improving coastal water quality.