Assessing hitchhikers of marine plastic debris

Abstract

Plastic debris in the marine environment continues to increase, which acts as a vector for transportation of hitchhikers. The marine plastic debris(MPD) are mainly litter that are discarded at sea or reaching the sea through waterways by currents and wind. The MPD gives opportunity for dispersal of hitchhikers including mesozooplankton and larvae of macrobenthic organisms (mobile species, size range: 40-1,000 µm) on floating plastics, that can influence the extension of their geographical range. Portion of plastic debris maybe from overseas which may introduce non-indigenous or invasive species to an ecosystem. We examined a total of 23 debris objects including ropes, plastic bags, containers, expanded polystyrene buoys and bottles collected at the major MPD hotspots in Korea during March-April in 2021. The surface of MPD was washed with high-pressure spray to physically remove the hitch-hikers and preserved for microscopic analysis using ethanol and formalin. Some MPDs were selected for extra incubation to observe possible organisms that may have not been physically removed. We identified 30 taxa from 9 phyla, and the dominant taxa included harpacticoids, bivalve larvae and nematodes. Our findings suggest that MPD may act as a vector for dispersal of hitchhikers and that further studies are need to understand impact on the ecosystem.