Levels and oxidative toxicity of microplastics and perfluoroalkyl substances (PFASs) in different tissues of sea cucumber (Holothuria tubulosa)

Nowadays, marine pollution is a global problem which finds in microplastics (MPs) and emerging pollutants, such as perfluoroalkyl substances (PFASs), two of the main culprits. Sea cucumbers are a group of marine benthic invertebrates that show ecological, economic and social relevance. As deposit/suspension feeders, sea cucumbers show high susceptibility to bioaccumulate marine pollutants, including PFASs and MPs. In this study, we describe the presence and the effects of MP and PFAS accumulation on gastrointestinal tract (GIT) and coelomic fluid of sea cucumber (Holothuria tubulosa) specimens through the assessment of oxidative stress biomarkers. The MP abundance in the GIT ranged from 3 to 20 particles animal^-1, while the extracted MPs from the coelomic fluid ranged from 0 to 7 particles animal^-1, thus confirming a probable transfer through the respiratory tree. The MPs were identified by FT-IR and Raman analyses, and the polymer types were mainly polyethylene (PE) and polypropylene (PP). The concentrations of nineteen perfluoroalkyl sulfonic acids (PFSAs) were measured in the body wall of sea cucumbers. We found up to seven out of the nineteen PFASs. The Σ₁₉PFAS were in the range 0.083-0.620 μg kg^-1 and the maximum concentrations of individual PFASs in all the samples varied from 0.010 (PFHxA, PFHpA) to 0.390 (PFBS). Pearson coefficients showed a positive correlation among MPs and most of the oxidative stress parameters (i.e. catalase, glutathione S transferase, malondialdehyde and DNA damage) suggesting, however, a potential tissue-related response. This study thus revealed that MPs, and partially PFASs, induce oxidative imbalance in H. tubulosa, and pointed up the importance of different tissues in mediating dose/time-related responses to oxidative stress. Sea cucumbers prove to be very promising model organisms for ecotoxicological investigation.