Plastics are
considered to be one of the major environmental challenges of our
time. They are highly durable synthetic polymers, around 30% of which
are produced for short-life purposes, such as disposable packaging,
and are discarded within a year of being manufactured. Despite the
large number of plastic items being manufactured and then thrown
away, and visible evidence of plastic debris in ecosystems from pole
to pole, environmental scientists for a long time struggled to find
evidence of plastic accumulation (rather than presence) in natural
ecosystems, until they began to examine microplastic particles (tiny
plastic fragments, generally formed from the break-down of larger
items) in sediments and ocean waters, where a steady build-up of
plastics over time has been confirmed. However even these studies
have failed to account for the amount of plastic thought likely to be
present in the environment, leading scientists to suspect that a
large amount of plastic is present but unaccounted for somewhere in
the natural environment.
In a paper
published in the journal Royal Society Open Science on 17 December 2014,
Lucy Woodall of the Department of Life Sciences at The Natural History Museum, Anna Sanchez-Vidal and Miquel Canals of the
Departament d’ Estratigrafia, Paleontologia i Geociències Marines
at the Universitat de Barcelona, Gordon Paterson, also of the
Department of Life Sciences at The Natural History Museum, Rachel
Coppock and Victoria Sleight of the Marine Biology and Ecology Research Centre at Plymouth University, Antonio Calafat, also of the
Departament d’ Estratigrafia, Paleontologia i Geociències Marines
at the Universitat de Barcelona, Alex Rogers of the Department of Zoology at the University of Oxford, Bhavani Narayanaswamy of the
Scottish Association for Marine Science and Richard Thompson, again
of the Marine Biology and Ecology
Research Centre at Plymouth University,
discus the presence of microplastic particles in deep-marine sediment
samples collected from a series of sites in the North Atlantic,
Mediterranean and southern Indian Ocean.
The samples
examined were taken from the upper portions of cores gathered for
other studies by the Universitat de Barcelona and the Natural History
Museum over a twelve year period. Because of this the samples were
gathered following different procedures, limiting the amount of
comparison that can be made between the samples. Nevertheless it was
possible to establish the presence of plastics in areas not
previously sampled, and compare the proportions of different plastics
within individual samples.
Locations
of sampling sites of bottom sediment and deep-water coral where
content of microplasticswas investigated. Sample depth ranged down to
3500 m, for details see table 1. Sediment was collected by the
University of Barcelona (circles) and the Natural History Museum
(filled squares), and deep-water corals were collected by the Natural
History Museum (open squares). Bathymetry corresponds to ETOPO1Global Relief Model. Woodall et al. (2014).
The areas
sampled included open slopes in the subpolar North Atlantic, the
northeast Atlantic and the Mediterranean, canyons in the northeast
Atlantic and Mediterranean, basins in the Mediterranean and Corals
from seamounts in the southwest Indian Ocean.
All of the
samples were found to contain microplastics in the form of fibres 2-3
mm in length and ~0.1 mm in width. The most abundant fibre was rayon,
which is not strictly speaking a plastic (it is made from dissolved and resolidified cellulose from wood-pulp, rather than hydrocarbons) and which comprised
56.9% of all the fibres found in the study; this is comparable to
results for rayon in previous studies of synthetic fibres ingested by
Fish (where 57.8% of all fibres were rayon) and in ice cores (where
54% of all fibres were rayon). Of actual plastics sampled 53.4% were
polyester, 34.1% were 'other plastics (including polyamides and
acetate) and 12.4% were acrylic.
Plastics
were found at comparable levels to those seen in intertidal and
shallow-marine sediments, and at a rate roughly a thousand times
higher than found in surface waters. Given the vast areas covered by
the deep ocean floor, this is likely to account for a substantial
proportion of the 'missing' plastic predicted to be present in the
natural environment.
All of the
plastics found were heavier than water. At first sight this is what
would be expected as such plastics should sink whereas plastics
lighter than water should not, however for microplastics the
situation is more complex, as such plastics will tend to be held at
the surface by surface-tension, only sinking after becoming colonized
by marine organisms, adhered to phytoplankton and the aggregated with
organic debris and small particles in the form of marine snow.
The impact
of microplastics on deep-sea ecosystems is unclear. In surface and
shallow-marine organisms such plastics have been shown to have
adverse effects both due to their physical and toxicological
properties, and this is likely to be the case also with deep-marine
organisms, but this cannot be asserted confidently without further
study.
See also...
Counting floating plastics in the world’s oceans. Floating plastic is considered to be a major pollutant in the world’s
oceans. It enters the oceans in large quantities from shipping, coastal
communities...
Marine litter on the European seafloor. Manmade rubbish (litter) is known to be extremely harmful to aquatic
lifeforms, both as a direct physical hazard (such as nets which continue
to trap and kill Fish long after they have become detached from fishing
vessels or plastic items which resemble food and...
Plastic contamination in Lake Garda, Italy. Plastic contaminants are known to present a threat in many ecosystems,
with particular concern being raised about the oceans, where large
accumulations of plastic are known to be found on ocean gyres (large
rotating currents) and where damage to wildlife from plastic ingestion
is well documented. The effect of plastic contamination on freshwater
ecosystems is less well documented, though studies of...
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