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Plastics are artificial substrates in aquatic systems that can host a wide variety of organisms (plastisphere), with complex, yet not well understood, ecological interactions. Data on the diversity and ecological role of the plastisphere is still limited for many environments, including estuaries. Here we investigated the diversity of the plastisphere in Patos Lagoon Estuary (PLE), the world's largest coastal lagoon, through an in situ experiment. Polyethylene (PE) and polypropylene (PP) plates were incubated in shallow waters and sampled after 15, 30, 60 and 90 days of incubation within each season, over one year. A DNA-metabarcoding approach (genes 16S, and 18S-V4 and V9 regions) was used to identify the diversity of taxa. Fifteen prokaryotic phyla and thirty-seven eukaryotic groups were observed in the overall dataset. Between polymer types, the Operational Taxonomic Units (OTUs) richness varied significantly only for eukaryotes within the 18S-V4 dataset, in which PP showed a greater OTU richness. However, community composition was not significantly variable between polymers in any of the datasets. Amongst seasons, only prokaryotes showed significant seasonal variation in OTU richness, which was greater in autumn and winter, corroborating the hypothesis that the bacterial community in the plastisphere is influenced by seasonality. Community composition significantly varied for both prokaryotes and eukaryotes according to season, with higher diversity in autumn and winter. There was no difference in OTU richness or community composition between the different incubation times. We found microbial species (e.g. Vampirovibrio sp. and Acinetobacter sp.) that are putative pathogens for aquatic organisms such as algae, shrimps and fishes, including commercial species. This study is the first to assess - using molecular tools - the diversity and factors that influence the composition of the plastisphere in a subtropical estuary, extending the knowledge on the plastisphere in estuarine regions. Also see: https://micro2022.sciencesconf.org/427273/document, In MICRO 2022, Online Atlas Edition: Plastic Pollution from MACRO to nano

Understanding the impacts of marine litter on fauna is challenging, and for cetaceans the knowledge is scarce. This study aimed to verify the ingestion of marine debris by odontocetes found stranded in the south of Rio Grande do Sul state, Brazil. Between 2018 and 2022, 139 stomachs of six species were obtained during beach monitoring along the southern coast of Rio Grande do Sul ( 360 km). The stomach contents were analyzed following conventional methods, and the debris found were quantified and classified according to material. Plastic items were analyzed by FTIR to identify polymer types. The overall Frequency of Occurrence (FO%) of ingestion was 33.8%, with 47 stomachs presenting debris. Specific FO%s of 20%, 33.3% and 44.9% were found respectively for Steno bredanensis, Delphinus delphis and Pontoporia blainvillei; Tursiops spp., Pseudorca crassidens and Stenella spp. showed no debris in their stomachs. P. blainvillei, a critically endangered species restricted to the Western South Atlantic, represented 70.5% of all stomachs analyzed, and 93.6% of all stomachs with residues. Litter ingestion by this species can be accidental and is possibly linked to its bottom foraging habit, where debris accumulates. Plastic represented 99.3% of the litter found in stomachs, and cloth (cotton string) 0.66%. The most abundant plastic polymer was polypropylene (PP) (40.9%), followed by polystyrene (PS) (20.1%) and polyamide (PA) (20.1%). PP and PS are commonly used in disposable packaging and are among the most abundant in the marine environment, which can increase their ingestion probability. PA is commonly used in the manufacture of nets and ropes used in fishing activities, which are common in the region. These results confirm the interaction between cetaceans and marine litter in South Brazil, and highlight the importance of properly managing litter to reduce its entry and impacts in the marine environment. Also see: https://micro2022.sciencesconf.org/426732/document, In MICRO 2022, Online Atlas Edition: Plastic Pollution from MACRO to nano