Accumulation of microplastics in relation to the sediment grain size distribution in seagrass meadows in the coastal areas of Tuticorin, southeast coast of India

This research investigated the relationship between microplastic accumulation and the sediment texture in seagrass meadows across the selected coastal regions of Tuticorin. Sixteen sediment samples were collected by SCUBA divers utilizing a stainless steel grab sampler. Findings indicate significantly elevated microplastic concentrations in seagrass sediments when compared to unvegetated areas. In processing the samples, hydrogen peroxide was used to digest the organic matters in the sediments, followed by density separation using NaCl. Microplastic (MP) concentration in the seagrass bed sediments ranged from 13.52 ± 2.11 to 44.52 ± 4.32 items/kg, whereas in areas devoid of seagrass the range was from 4.04 ± 1.22 to 8.52 ± 1.32 items/kg. The predominant types of MPs identified were fibre and fragment with sizes ranging from <0.5 mm to 5 mm. MPs under 0.5 mm constituted 33.16 % of the total. Polyethylene was the most common polymer detected (57.33 %), followed by polypropylene (31.7 %), polyamide (6.41 %), and polystyrene (4.57 %). Sediment texture analysis revealed a prevalence of coarse and medium sand, with significant MP accumulation, likely influenced by sediment pore dimensions. These findings suggest that seagrass meadows capture higher concentrations of MPs than control sites, highlighting the potential of seagrass to trap these pollutants.