Distribution of Surface Plastic Debris in the Eastern Pacific Ocean from an 11-Year Data Set

TLDR

The authors conducted a comprehensive survey of floating plastic debris in the eastern North and South Pacific using over 2,500 plankton net tows from 2001 to 2012. The survey sampled the eastern Pacific (17.4°S–61.0°N, 85.0°W–180.0°W) via plankton net tows to quantify surface microplastic distribution. The data revealed a North Pacific subtropical gyre accumulation zone (25–41°N, 130–180°W) with peak concentrations exceeding 10^6 pieces km^−2, a median of zero outside the gyre, no clear temporal trend, and large spatiotemporal variability that produced order‑of‑magnitude differences in short‑term statistics, while estimating a minimum of 21,290 t of floating microplastic across the eastern Pacific.

Abstract

We present an extensive survey of floating plastic debris in the eastern North and South Pacific Oceans from more than 2500 plankton net tows conducted between 2001 and 2012. From these data we defined an accumulation zone (25 to 41 °N, 130 to 180 °W) in the North Pacific subtropical gyre that closely corresponds to centers of accumulation resulting from the convergence of ocean surface currents predicted by several oceanographic numerical models. Maximum plastic concentrations from individual surface net tows exceeded 10(6) pieces km(-2), with concentrations decreasing with increasing distance from the predicted center of accumulation. Outside the North Pacific subtropical gyre the median plastic concentration was 0 pieces km(-2). We were unable to detect a robust temporal trend in the data set, perhaps because of confounded spatial and temporal variability. Large spatiotemporal variability in plastic concentration causes order of magnitude differences in summary statistics calculated over short time periods or in limited geographic areas. Utilizing all available plankton net data collected in the eastern Pacific Ocean (17.4 °S to 61.0 °N; 85.0 to 180.0 °W) since 1999, we estimated a minimum of 21,290 t of floating microplastic.