Micro-litter pollution in the ascidian Cnemidocarpa verrucosa along the Antarctic Peninsula

Antarctic benthic ecosystems are currently threatened by global change and direct human impact. Pollution from local human activities is among the most relevant emerging hazards affecting Antarctic organisms. Micro-litter (ML) has already been found in Antarctic marine ecosystems, including diverse benthic fauna. This study characterised and quantified ML in a common soft-bottom filter-feeding solitary ascidian, Cnemidocarpa verrucosa (Lesson, 1830), along the Antarctic Peninsula from 62° S to 67° S, focusing particularly on Deception Island. Study sites included Johnsons' Bay (Livingston Island), Deception Island (South Shetland Islands), Uruguay Island (Yalour Islands), and Ryder Buttress (Ryder Bay, Adelaide Island). More than half of the analysed organisms contained at least one ML particle, with an average of 0.14 ± 0.26 items per gram (viscera wet weight) and 1.62 ± 1.79 items per individual. Microplastics represented 37 % of the total ML items found. Along the Antarctic Peninsula, significantly higher amounts of ML were found in Johnsons' Bay and Uruguay Island. Within Deception Island, significantly higher ML abundances were found in Murature, at the innermost part of the island. The most common items found were black or blue cellulosic fibres within the smallest size range analysed (100-500 μm). We suggest that variations in ML among sites could be mainly due to the different intensity of anthropogenic activities, although environmental characteristics of the locations (i.e. currents, bottom type) also played a key role in its distribution. To the best of our knowledge, this is the first study to assess ML pollution in an Antarctic ascidian and it also represents the southernmost benthic invertebrate study regarding ML along the Antarctic Peninsula. We believe this research may contribute to the development of policies to protect the Antarctic marine benthos from human pollution and improve their management.