Do polyethylene terephtalate microplastics (PET-µPs) affect or suffer the effects by the sea urchin Paracentrotus lividus?

Microplastic (µPs) contamination in deep marine ecosystems is of growing concern. A number of monitoring surveys have shown that µPs composed by different polymers are floating in surface waters, but many of them sink to deep sediments. However, the information on the toxicity caused by the exposure to µPs reaching deep sediments towards benthic marine organisms is still scant. The aim of this study was to assess the ingestion and the adverse effects caused by a 7-days dietary exposure to three amount (8; 80 and 800 particles/g of food) of irregular shaped polyethylene terephthalate µPs (PET-µPs) in a benthic grazer, the sea urchin Paracentrotus lividus. Histological analyses were carried out to evaluate the occurrence of PET-µPs within the digestive tract of sea urchins, as well as to check for potential tissue alterations to the esophagus. Oxidative stress-related effects were explored in the proximal part of the esophagus. In addition, potential alteration of PET macromolecular chain caused by the ingestion and the permanence of particles within the sea urchin digestive system were investigated. Sea urchins ingested and efficiently egested PET-µPs, which did not provoked any histological alteration to their esophagus. PET-µPs ingestion induced an overproduction of pro-oxidant molecules and modulated the activity of antioxidant enzymes. Interestingly, the time of permanence of PET-µPs within sea urchin digestive tract slightly affected the PET macromolecular chain. Our findings suggest that irregular shaped PET-µPs do not represent a hazard for the health status of a benthic grazer organism, which actually can contribute to the degradation of this polymer in marine ecosystems.