Marine litter as a potential dispersal vector of non-native bryozoans along the Brazilian coast

Bryozoans are common organisms in marine encrusting communities that can colonize both natural and artificial substrata. Some taxa are known for their high invasive potential, including exotic and cryptogenic (of unknown biogeographical origin) species being recorded in ports and bays worldwide. With the increase in marine pollution, artificial substrata, including marine litter, are becoming increasingly available in environments. In addition to the pollution itself, the litter can facilitate the dispersal of encrusters, allowing them to reach regions where they would not naturally occur, thus contributing to bioinvasions. Here, we report the occurrence of non-native bryozoan in marine litter from 6 states in northeastern Brazil: Maranhão, Piauí, Rio Grande do Norte, Paraíba, Pernambuco, and Bahia. Collections were made between 2017 and 2026 from 14 urban beaches with high human activity, located within 20km of ports. The marine litter was manually collected by actively searching the intertidal zone of the beaches, including the sandy strip and rocky outcrops, during the 2 hours of low tide. Items with bryozoans were photographed and measured. Bryozoans were identified by recognizing, under a stereomicroscope, diagnostic characteristics of zooids, following recent literature. A total of 62 bryozoans were identified, including 22 cryptogenic, 9 exotic, and 2 invaders: Biflustra okadai Almeida, Souza & Vieira, 2017, and Schizoporella errata (Waters, 1878). These species were recognized as invasive in Brazil only in 2024 and 2019, respectively, due to a large increase in records and their dominance in encrusting communities. Taxa were associated with 8 main types of litter: plastic, ceramics/glass, rubber, wood, metal, clothing/textiles, paper/cardboard, and construction. Most bryozoans were found in association with plastic, and apparently, none showed a preference for a particular type of debris. Due to the buoyancy of debris and the sharing of fauna among the beaches, there is a high likelihood that marine litter serves as a dispersal vector for bryozoans in the area. Therefore, the results presented here are alarming and indicate the need to develop strategies for waste management and for preventing bioinvasions.