Styrofoams are widely used as floats and are likely to be damaged by burrowing animals in mariculture. However, the fate of fragmented Styrofoams and their interaction with organisms are not clear in coastal environments. In the present study, field investigations were conducted in 14 sites along the coast of China from July 2023 to October 2024. Results showed that Styrofoams were buried by sand or soil at a depth of up to 50-60 cm in patchy and belted distribution patterns. The abundances of Styrofoams in the deep layer of sediments ranged from 94 to 3042 items/kg. The buried Styrofoams were bunched by roots of six plant species in three ways, i.e., wrapping, crossing, and clinging. The abundance of bunched foams ranged from 1 to 495 items/plant. Simulation experiments in the laboratory showed that plant roots could interact with Styrofoams after 14 days of exposure and tended to cross through the gaps of foam materials. Our study indicates that the fragmented Styrofoams coming from mariculture floats could remain in the sediments due to the physical and biological factors, providing new insight into the biogeochemical cycle of plastic debris.