This paper increases knowledge on litter transfer from sediments towards the trophic web throughout sea cucumbers, key protected benthic species. In October, sediment and holothurian samples from seventeen sampling sites from Croatian Islands characterized by different levels of protection (Silba n = 7; Telašćica MPA n = 10) were collected. Collected particles ranged in sediments within 113.4–377.8 items/kg d.w., and in holothurians within 0.6–9.4 items/animal, showing sizes within 1.4–10,493 μm. In holothurians, cellulose and cellulose acetate (non-synthetic materials) mean percentages were within 5.0–12.7% of the total amount of particles. Nylon fibres ranged within 0–26.7%; while PP, PE, PA, and PS% were more abundant than in sediments. Among factors of variability tested, “island group” and “level of protection” resulted to affect plastic composition in sediments. Otherwise, other environmental factors (i.e. orientation, morphology of sampling site, P. oceanica) were significantly related to chemical composition of microplastic ingested by holothurians.
