Marine turtles as bio-indicators of plastic pollution in the eastern Mediterranean
Emily M. Duncan, Hasan Deniz Akbora, Patrizia Baldi, Damla Beton, Annette C. Broderick, Burak Ali Çi̇çek, Charlotte Crowe-Harland, Sophie Davey, Tess DeSerisy, Wayne J. Fuller, Julia C. Haywood, Yu Jou Hsieh, Ecem Kaya, Lucy C. M. Omeyer, Meryem Özkan, Josie L. Palmer, Emma Roast, David Santillo, Matthias Schneider, Robin Snape, Katrina C. Sutherland, Brendan J. Godley
Abstract
The loggerhead turtle (Caretta caretta) has been suggested as a bio-indicator species for plastic pollution. However, detailed investigations in the eastern Mediterranean are limited. Here, we present data from loggerhead turtles (2012-2022; n = 131) of which 42.7 % (n = 57) had ingested macroplastic (pieces ≥ 5 mm). Frequency of occurrence (%) was not found to have changed over time, with body size (CCL cm), between stranded or bycaught turtles, or with levels of digesta present. The characteristics of ingested plastic (n = 492) were largely sheetlike (62 %), clear (41 %) or white (25 %) and the most common polymers identified were Polypropylene (37 %) and Polyethylene (35 %). Strong selectivity was displayed towards certain types, colours and shapes. Data are also presented for posthatchling turtles (n = 4), an understudied life stage. Much larger sample sizes will be needed for this species to be an effective bio-indicator, with the consideration of monitoring green turtles (Chelonia mydas) for the eastern Mediterranean recommended allowing a more holistic picture to be gathered.