Zonation-dependent distribution of microplastic occurrence in Patella caerulea from Mersin Coast, Türkiye

Increasing plastic pollution has become a critical environmental issue, leading to challenges in management. Specifically, microplastics (MPs) are of particular concern because they can persist in aquatic ecosystems and adversely affect marine organisms. The objective of this study was to assess the occurrence of MPs in the soft tissues of Patella caerulea (Linnaeus, 1758) collected from the Mersin Viranşehir coastal area. As no specimens were found in the supralittoral zone, the decision was taken to conduct sampling only in the mediolittoral and infralittoral zones. The total sampling area was 24 m2 divided into three 4-m2 plots in each zone. A total of 80 individuals were collected. The mean (SE) MP concentration in the soft tissues of P. caerulea was 17.05 MPs/g wet weight (ww) (16.84) in the mediolittoral zone and 10.88 MPs/g ww (8.02) in the infralittoral zone. MPs identified in soft tissues ranged from 0.1 to 5 mm. The mean abundance of MPs per gram of soft tissue varied by morphological type: fragments (31.85 MPs/g ww (6.39)) were the most dominant, followed by granules (10.64 MPs/g ww (1.97)), filaments (8.59 MPs/g ww (1.15)), and films (4.46 MPs/g ww (0.91)). Polymer composition analysis showed that MPs were primarily composed of polyethylene (PE), polypropylene (PP), polystyrene (PS), polyester/ polyethylene terephthalate (PES/PET), nylon-6, and cellulose. Notably, the proportions of PE, PP, and PS were higher in the infralittoral zone compared to the mediolittoral zone. These findings highlight the extent of MP contamination in P. caerulea and the influence of coastal zonation on MP accumulation in marine gastropods.