Anthropogenic microparticles, including microplastics, are commonly found in nearshore environments, where they may be entrained in coastal waters, sequestered in sediments, or ingested by a variety of organisms. We assessed the distribution of microparticles in coastal California and examined bioavailability to foundational species such as zooplankton and invertebrate infauna. Our findings, indicating high abundance of very small and bioavailable microparticles, are concerning because of the potential impact to nearshore communities at multiple trophic levels.