Retention of microplastics in Halophila decipiens seagrass meadows

Microplastic (MP) trapping and storage by seagrasses and sediments highlight their role as potential long-term reservoirs for plastic particles. This study evaluated the presence of MPs in Halophila decipiens meadows and its associated sediments in two localities, Pichilingue and Los Aripes, in the southwest Gulf of California. At each locality, 12 samples were collected along two 30-m transects: six from vegetated and six from unvegetated sites. At Pichilingue, 93 items were found on H. decipiens, with a maximum of 46 items on roots, with films and fibers being the main MP forms and black the most frequent color. For sediments, an average of 231 ± 145 items kg DW was estimated; the vegetated site showed 406 ± 184 items kg DW, with black films (1016 items) as the most abundant items, while the unvegetated site showed 56 ± 11 items kg DW, with transparent fragments (25 items) as the dominant items. The main MP type was polyethylene (38 items). At Los Aripes, MPs were not found on any structure of H. decipiens; but in sediments, the average was 17 ± 7 items kg DW, with 13 ± 3 items kg DW in the vegetated site and black and blue fibers (seven items each) as the dominant items, and 21 ± 10 items kg DW in the unvegetated site and blue fibers (16 items) as the dominant items. The main MP type was polyethylene terephthalate. This research provides insight into the capacity of sediments and H. decipiens structures (leaves, petioles, rhizomes, and roots) to retain MPs derived from local human activities and the effect of environmental factors.