“…Although there remains considerable controversy concerning the missing oceanic sink (Weiss et al, 2021), a large amount of plastics have been recovered from seafloor sediments (Kane et al, 2020), which infers the deep ocean is an ultimate sink for plastics (Woodall et al, 2014;Cózar et al, 2017). Freshwater sediment has also been considered as a transient or terminal sink for MPs (Leiser et al, 2021;Yang et al, 2021). Several hypotheses are proposed to explain the removal of MPs from surface waters (Michels et al, 2018;Foekema et al, 2013;Cole et al, 2016;Reisser et al, 2015;El Hadri et al, 2020), whereas the sinking of MPs caused by a density increase after biofouling (i.e., rapidly colonization of submerged MP surfaces by microorganisms) is considered to be an important pathway for the downward transport of MPs in the ocean and freshwaters (Fazey and Ryan, 2016;Kooi et al, 2017;Kaiser et al, 2017;Amaral-Zettler et al, 2021;Semcesen and Wells, 2021).…”