Macrofouling on marine litter in a Southwest Atlantic urban tropical bay and surrounds

Rafting is the transport of marine litter by organisms, influenced by substrate characteristics such as degradation, shape, surface orientation, color, and polymer type. This study focuses on rafting in the Southwest Atlantic, characterizing biofouling on different materials across high- and low-energy beaches. Conducted in Guanabara Bay and Niteroi's oceanic beaches, sampling focused on strandlines. Litter was categorized by material, shape, degradation, surface orientation, color, and polymer, with fouling organisms identified to the lowest taxonomic level. Flechas, Icaraí, and Itaipu beaches had the highest litter concentrations due to their geographic orientation and wind exposure. Biofouling was more frequent on intact litter with cylindrical or irregular shapes, rough surfaces, and white, red, or green PET or PP plastics. Polychaetes, bryozoans, and barnacles were the most common organisms. These findings highlight substrate and environmental conditions that influence rafting in the region, underscoring the role of plastic waste as novel ecological substrate in coastal ecosystems.