Page 11 - Shimadzu Journal vol.7 Issue1

Environmental Analysis

Table 2 Results of the FTIR analysis on fiber material across six Pacific hadal trenches: Japan (JT), Izu-Bonin (IBT), Mariana (MT), New Hebrides (NHT), Kermadec (KT)
and Peru- Chile (PCT).
Trench Depth(m) Material Description
JT 7703 Lyocell Blue fibre
IBT 9316 Polyester reinforced cotton; Rayon Twisted blue fibre
IBT 9316 Polyethylene Degraded fibre, red
MT 10890 Low density polyethylene film with inorganic filler Dark/black fibre
MT 10890 Ramie Blue fibre
MT 10890 Ramie Blue fibre
NHT 6948 Unidentified polyvinyl Dark/blue fibre
NHT 6948 Polyamide with inorganic filler Dark/black fibre
KT 7014 Lyocell Black fibre
KT 9908 Unidentified plastic Black fibre
KT 7884 Unidentified plastic, but very close to PVAL or PVC with inorganic filler Dark/blue fragment
KT 9908 Ramie Blue fibre
KT 9053 Nylon 12 Black/dark fibre
PCT 7050 Polyester core with Polyethylene coating Black fibre
PCT 7050 Polyethylene with inorganic filler Black fibre

Discussion
The salient finding of this study is that man-made microfibers and the stomachs of vertically migrating pelagic organisms and marine
fragments, including microplastics, were found in the hindguts of carrion [32, 46] . The temporal mismatch among sampling the trenches is
amphipods from six of the deepest parts of the Earth's oceans, a confounding factor when explaining why there are differences in
including within the deepest area of the Mariana Trench, at observed numbers of microparticles in the amphipod stomachs. The
Challenger Deep. Plastic has been present at hadal depths for the differences may be related to the duration of time that plastics have
last couple of decades [16] but, as far as we are aware, this is the first accumulated in the area rather than whether areas accumulate more
record of microplastics being ingested by hadal organisms. plastic in the surface or deep water and if there are regional
Therefore, microplastics are bioavailable in the hadal zone and differences in the mechanisms that transport plastics to the deep
ingested by one of the most important and dominant scavenging sea. However, given our sampling occurred from 2008 onwards, it
fauna in the deep sea at a similar frequency (72%) to crustaceans in indicates that microplastics were ingested by amphipods for at least
coastal water habitats [29, 30] . the past decade, providing an important baseline to monitor
Previous studies have found microplastics ingested by deep-sea subsequent change.
[9]
invertebrates down to 2200 m in the North Atlantic , 611 m in the
[8]
equatorial mid-Atlantic and 1062 m in southwest Indian Ocean . The crude colour-based categorisation is consistent with findings in
[8]
The species ingesting microplastics include: the echinoderms surface waters where fibres dominate and account for a high
Ophiomusium lymani, Hymenaster pellucidus (North Atlantic) [9] and proportion of microplastics [59] . The source and mechanism by which
an unknown species of holothurian (southwest Indian Ocean) ; a these microplastics are released into the marine environment is
[8]
crustacean (unknown hermit crab) from the southwest Indian varied and includes airborne transport, terrestrial sources, e.g.
Ocean ; and a mollusc (Colus jeffreysianus) from the North Atlantic synthetic fibres from washing clothes which enters the marine
[8]
[9] . As with the amphipods in this study, these species are all deposit environment through sewage [60-63] , direct release of fibres through
feeders or are predatory [8, 9] . It is not clear whether these trophic maritime activities, e.g. fishing [22] and fragmentation of larger plastic
guilds are more susceptible to microplastic ingestion in the deep sea debris. Blue fibres were the most prevalent microparticles ingested in
than filter feeders or whether there are toxicological implications the Pacific hadal amphipods which is consistent with other studies [45,
[8]
as microplastics breakdown [38] . This can only be tested with a wider 59] . Furthermore, in Pacific subsurface water black, red and purple
range of species from different trophic guilds with accompanying fibres [59] are also prevalent; all of these colours were found ingested
microplastic concentrations from sediments and water column. in Pacific hadal amphipods in this study. However, it is clear from the
The six trenches are bathymetrically and geographically isolated by FTIR analysis and previous works that the colour-based
large distances. The distance between the Japan Trench, in the categorisation is not an adequate method to identify whether a
northern hemisphere, and the Kermadec Trench, in the southern microparticle is indeed of plastic origin [64] . The range of plastic found
hemisphere, is approximately 8640 km, and between the Peru-Chile in the hindguts of the amphipods included PE, PA, and polyvinyls
Trench in the Southeast Pacific and the trenches in the northwest resembling PVAL or PVC but we also found other synthetic polymers
Pacific is over 15,000 km. The distances highlight the geographical that are not plastics (e.g. ramie, lyocell). PE, PA and polyester have
extent in the distribution of microplastics and synthetic particles that all been identified in the guts of other deep-sea organisms albeit at
are ingested at full ocean depths. It is difficult to ascertain why the much shallower depths [8, 9] .
amphipods have different numbers of microparticles in their The presence of microplastics in the hindgut of amphipods indicates
hindguts among these six trenches. The mechanisms transporting the possibility of trophic transfer to higher trophic levels within the
microplastics and synthetic fibres to the deep sea are likely to be hadal environment. Trophic transfer of microplastics are known from
similar at all the locations. These include sinking of large plastics (>5 other marine organisms including from Mytilus edulis to Carcinus
mm) from the surface waters and subsequent fragmentation at maenas [23] and between mesozooplankton to higher level
depth [7, 13, 16, 49] ; direct sinking of microplastic that are not adhered to macrozooplankton [24] . These studies were conducted under
other particles; sinking of microplastics in association with marine experimental conditions using high concentrations of microplastics
snow [19, 49] ; and the downward transport of large and microplastics in but their results indicate the possibility of microplastics transferring

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