Seafloor microplastic hotspots controlled by deep-sea circulation

While 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 of up to 1.9 million pieces m^2. This is the highest reported value for any seafloor setting, globally. Previous studies propose that microplastics are transported to the seafloor by vertical settling from surface accumulations; instead we demonstrate that the spatial distribution and ultimate fate of microplastics is 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.

Methods
EMODNET Bathymetry is available from this link:

https://portal.emodnet-bathymetry.eu/

P90 bed shear stress, near bed velocity and velocity vectors used to create all graphs in the manuscript are named BSS (.tfw, .tif. and .xml), speed (.tfw, .tif, .xml) and velocity vectors (.dbf, .prj, .sbn, .sbx, .shp, .xml,.shx) respectively.

FTIR data are here recorded in csv and sp files. Microplastic samples were randomly chosen from the confirmed plastics recorded in the samples; this is not intended as a complete data set or analysis, rather just a snapshot of plastic types in the samples.

Grain Size data were established using laser diffraction analysis at the Univeristy of Manchester. Pdf files 1-8

Microplastic counts and colours are listed here: 'MP data' excel spreadsheet

The artistic block diagram is included here and should be referred to appropriately, using the citation (Kane et al.) and doi.