We compiled data on OSL plastic abundance and distribution from published literature and unpublished sources, totaling 11,777 stations used in this trend analysis (Fig 1 ; S1 Dataset and on GitHub https://github.com/wincowgerDEV/ocean_plastic_modeling ). Data were aggregated primarily from peer-reviewed manuscripts and previously unpublished data from 5 Gyres Institute expeditions. The data were collected with multiple methods of sea-surface sampling: manta trawl [8 (link), 16 (link)], AVANI trawl [17 (link)], or a rectangular neuston net [7 (link), 18 (link)]. We filtered the data to include samples with a lower mesh size range between 53μm and 505μm. Of the 11,777 samples in this study, 0.2% of samples were collected with a 53μm mesh (n = 27), 2.5% used 200μm (n = 303), 2.5% used 500–505μm (n = 293), and 94.7% used a 320–350μm (n = 11,154). The upper range of net openings was between 0.5m and 1m (S1 Table ).
Although there was some variability in the methodology for each dataset, the methods typically were as follows: with the aid of a dissecting microscope, microplastics were manually separated from natural debris after being sorted through sieves [19 (link), 20 (link)], then counted individually, before all microplastics from each size category were weighed together. To compute count data (in pieces km-2) we divided the total count of plastics collected by the surface area of water that the trawl went through. If this metric was not provided, we computed it using trawl dimensions and distance sampled as reported in the corresponding literature. If only the month and year were provided for the date, we used the 15th of the month specified as the day. Mass was estimated with a common conversion rate reported in the literature (1.36 x 10−2 g particle-1) by Morét-Ferguson et al. [21 (link)].
Although there was some variability in the methodology for each dataset, the methods typically were as follows: with the aid of a dissecting microscope, microplastics were manually separated from natural debris after being sorted through sieves [19 (link), 20 (link)], then counted individually, before all microplastics from each size category were weighed together. To compute count data (in pieces km-2) we divided the total count of plastics collected by the surface area of water that the trawl went through. If this metric was not provided, we computed it using trawl dimensions and distance sampled as reported in the corresponding literature. If only the month and year were provided for the date, we used the 15th of the month specified as the day. Mass was estimated with a common conversion rate reported in the literature (1.36 x 10−2 g particle-1) by Morét-Ferguson et al. [21 (link)].
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