Figure 1.

Microplastic concentrations in 1972–1987 and 1999–2010. Numerical concentration (no. m⁻³) for (a) 1972–1987 and (b) 1999–2010; microplastic mass concentration (mg m⁻³) for (c) 1972–1987 and (d) 1999–2010. New data from this study include 7205 (asterisks), 7210 (inverted triangles), Southtow 13 (cross symbols), STAR (right-facing triangles), SEAPLEX (triangles) and EX1006 (diamonds). Published data are Wong et al. [7] (crossed circles), Shaw [8] (stars), Day & Shaw [9] (left-facing triangles), Gilfillan et al. [10] (filled circles) and Doyle et al. [11] (filled circles). Gilfillan et al. [10] and Doyle et al. [11] have overlapping stations. Non-peer-reviewed publicly available data from Algalita Marine Research Foundation [19] (plus symbols).