Meiofaunal biofouling on the marine plastic debris washed ashore in pollution-hot-spots of Korea

Abstract

We investigated the abundance and species composition of meiofaunal biofouling (40-1,000 µm) attached on the marine plastic debris (MPD), in order to understand relationship between characteristics of the biofouling and polymer types of the plastic as well as difference in the abundance between sampling regions. MPDs were collected from 3 sea area [Southwest(SW), Southeast(SE), and Jeju zone] as a lot of macro-debris frequently accumulated on beaches after rainy season in Korea from 26th of August to 5th of September. MPDs were collected and classified to six types of polymer (PP, PET, PS, LDPE, HDPE and EPS) based on the RIC code. Size of sampled meiofaunal biofouling ranged 40-1,000 µm that were subdivided into size groups of 40-60 µm, 60-300 µm, and 300-1,000 µm. Meiofaunal biofouling sampled from the all MPD was classified into 16 taxa. According to the polymer types, PP showed the highest abundance (933 inds./0.1m2) where Bivalves were dominant (48.1%) and HDPE had the lowest abundance (17 inds./0.1m2) where Nematodes were dominant (71.4%). In 40-60 µm, Nematodes were dominant in all types of polymer (mean: 90.6%), in which PP had the highest dominance (97.1%). In 60-300 µm of all types of polymer, other taxa [Bryozoa(statoblast) and Tanaids] dominated (mean: 37.4%), but in PS, Bivalves dominated (mean: 72.2 %). In the case of 300-1,000 µm, the dominant taxa were different in each type of polymers. The dominant taxa for PP, EPS, and PS and LDPE was Bivalves (PP: 78.2%), Retaria (EPS: 66.7%), and Gastropods (PS: 47.1%, LDPE: 50.0%), respectively. Among the three sea area, the SE zone had the highest abundance (mean: 2,518 inds./0.1m2), where Nematodes (30.2%) and Bivalves (27.9%) dominated. Jeju zone had the lowest abundance (mean: 253 inds./0.1m2) where Retaria dominated (43.4%). There was no significant difference between the average abundance of the sea area (P=0.188). This study shows that the dominant taxa of meiofaunal biofouling differs by the size groups in each polymer type. Nematodes tended to dominate (mean: 34.0%) in all comparison groups (by polymer type, size group, and sea area), and in particular, Nematodes in the size of 40-60 µm was extremely dominant (90.6%). Although no significant difference was found between the sea area, there was a large difference in the average abundance. This suggests that PP may be a favorable habitat for meiofaunal biofouling and Nematodes appears ubiquitously in all polymer types, and gives insight on the degree of dispersion in meiofaunal biofouling according to the sea area.