[OANNES Foro] Deep-ocean seafloor islands of plastics

[Mario Cabrejos]

Science  05 Jun 2020:
Vol. 368, Issue 6495, pp. 1055
DOI: 10.1126/science.abc1510 
Deep-ocean seafloor islands of plastics
David Mohrig
Summary
One of the most striking images of ocean pollution are the patches or
islands of floating plastic debris, concentrated in open-ocean gyres (1) and
large enough to be seen from space. These concentrations of plastics on the
ocean surface were first recognized in the early 1970s (2). Even with the
impressive size of these patches, mass-balance estimates for ocean-borne
plastics pointed toward a sink. That sink has recently been shown to be
deposition on the deep seafloor (3). On page 1140 of this issue, Kane et al.
document the occurrence of enriched zones or islands of plastic debris that
accumulate on the seafloor of the deep ocean (4).
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Science  05 Jun 2020:
Vol. 368, Issue 6495, pp. 1140-1145
DOI: 10.1126/science.aba5899 
Seafloor microplastic hotspots controlled by deep-sea circulation
Ian A. Kane1
<https://science.sciencemag.org/content/368/6495/1140?utm_campaign=toc_sci-m
ag_2020-06-04&et_rid=34815706&et_cid=3352260> ,*
<https://science.sciencemag.org/content/368/6495/1140?utm_campaign=toc_sci-m
ag_2020-06-04&et_rid=34815706&et_cid=3352260> , Michael A. Clare2
<https://science.sciencemag.org/content/368/6495/1140?utm_campaign=toc_sci-m
ag_2020-06-04&et_rid=34815706&et_cid=3352260> , Elda Miramontes3
<https://science.sciencemag.org/content/368/6495/1140?utm_campaign=toc_sci-m
ag_2020-06-04&et_rid=34815706&et_cid=3352260> ,4
<https://science.sciencemag.org/content/368/6495/1140?utm_campaign=toc_sci-m
ag_2020-06-04&et_rid=34815706&et_cid=3352260> , Roy Wogelius1
<https://science.sciencemag.org/content/368/6495/1140?utm_campaign=toc_sci-m
ag_2020-06-04&et_rid=34815706&et_cid=3352260> , James J. Rothwell5
<https://science.sciencemag.org/content/368/6495/1140?utm_campaign=toc_sci-m
ag_2020-06-04&et_rid=34815706&et_cid=3352260> , Pierre Garreau6
<https://science.sciencemag.org/content/368/6495/1140?utm_campaign=toc_sci-m
ag_2020-06-04&et_rid=34815706&et_cid=3352260> , Florian Pohl7
<https://science.sciencemag.org/content/368/6495/1140?utm_campaign=toc_sci-m
ag_2020-06-04&et_rid=34815706&et_cid=3352260>  
Not just settling
What controls the distribution of microplastics on the deep seafloor? Kane
et al. show that the answer to that question is more complicated than
particles simply settling from where they are found on the sea surface (see
the Perspective by Mohrig). Using data that they collected off the coast of
Corsica, the authors show that thermohaline-driven currents can control the
distribution of microplastics by creating hotspots of accumulation,
analogous to their role in causing focused areas of seafloor sediment
deposition. Such currents also supply oxygen and nutrients to deep-sea
benthos, so deepsea biodiversity hotspots are also likely to be microplastic
hotspots.
Abstract
Although microplastics are known to pervade the global seafloor, the
processes that control their dispersal and concentration in the deep sea
remain largely unknown. Here, we show that thermohaline-driven currents,
which build extensive seafloor sediment accumulations, can control the
distribution of microplastics and create hotspots with the highest
concentrations reported for any seafloor setting (190 pieces per 50 grams).
Previous studies propose that microplastics are transported to the seafloor
by vertical settling from surface accumulations; here, we demonstrate that
the spatial distribution and ultimate fate of microplastics are strongly
controlled by near-bed thermohaline currents (bottom currents). These
currents are known to supply oxygen and nutrients to deep-sea benthos,
suggesting that deep-sea biodiversity hotspots are also likely to be
microplastic hotspots.



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