Multi-marker DNA reveals the diversity of plastic-associated organisms in the Western South Atlantic and Austral Oceans

, Lacerda Ana Luzia, Kessler Felipe, Secchi Eduardo, Proietti Maira, Taylor Joe Daniel.

Floating plastics in aquatic systems act as artificial substrates for a large taxonomic diversity of micro and macro-organisms. As plastics can last for many years in the oceans and be transported between regions, they have the potential to increase dispersal of these species; however, the diversity and ecological function of epiplastic communities are not known for many regions. Our study aimed to identify the diversity of plastic-associated organisms in the Western South Atlantic (WSA) and around the Antarctic Peninsula (AP), and show how plastic characteristics and geographic location may influence community composition. Sampling was conducted in the open ocean using manta net (330µm mesh). The size, color and chemical composition of sampled plastics were characterized. DNA was extracted from the plastics biofilm and a metabarcoding approach targeting both prokaryotes and eukaryotes (16S, 18S and ITS2) was used to characterize the diversity of life associated with plastics. Our data showed a range of different prokaryote (Bacteria and Archaea) and eukaryotes (e.g. Protists, Fungi, Metazoa, Macroalgae) associated with plastics in both regions; in general, plastic characteristics did not influence community diversity, even within regions, contrary to what has been suggested by some colonization studies. We found microbial groups in our oceanic samples that have been previously described, under lab conditions, as plastic biodegraders (Aspergillus and Cladosporium species). We also identified groups that had not been described associated with plastics, and for the first time documented the diversity of plastic-associated fungi in these regions (Lacerda et al., 2020). Our work shows that epiplastic communities within these regions are highly diverse. This work has increased our knowledge about plastic-associated organisms in Southern Hemisphere. It is essential that we continue to monitor these epiplastic communities to better characterize the potential impacts of plastics and their associated biota on marine ecosystems, including bioinvasions.

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