As the abundance of plastic increases in marine systems, the potential risks of adverse biological and ecological effects of plastics of various size classes (macro-, micro-, nano-) need to be evaluated. EPA’s Office of Research and Development (ORD) has spearheaded methods development for extraction and characterization of microplastics (MPs) and works collaboratively with many agencies and organizations to better understand the sources, fate, and transport of MPs. Additionally, ORD research assesses ecological and human health impacts of MPs, supported by the development of analytical methods to detect MPs in a variety of environmental samples. This talk will cover three topics: 1) background information on MPs, including source and prevalence in the marine environment, 2) current research investigating the impacts of MPs on stony coral, and 3) recent studies assessing the impacts of nanoplastics to communities of benthic marine fauna.