Understanding the plastisphere community: biofilm formation on polystyrene microplastics alters the uptake, toxicity and immune response in Mediterranean sea urchin Paracentrotus lividus. The effect of microplastics on Mediterranean sea urchin

The present study is intended to assess the effects of colonized microbeads on P. lividus. We tested the hypothesis that biofilm formation affects the uptake, biodistribution and immune response in sea urchins. Animals were exposed to fluorescent-labelled polystyrene microbeads incubated in natural seawater from a polluted coastal site in the Gulf of Naples. The microbial community attached to the beads was characterized by SEM and DNA sequencing analyses to detect the formation of the biofilm and to identify the most abundant families present on the beads. Microbeads internalization in different tissues as well as their ejection rate were measured in sea urchins exposed to colonized microbeads compared to control animals treated with virgin one. The redox status of the microparticles-incorporating tissues was assessed by examining a series of biochemical markers. Moreover, the immune response of sea urchins was evaluated by measurements of different morphological and biochemical parameters of coelomocytes, including total count, cell type and oxidative stress status determination.