Recent global plastic pollution models predict that two-thirds of the plastic mass released from land into the ocean since the 1950s is likely to have stranded around the world’s shoreline. Yet, our knowledge about the degradation, burial and transportation of beached marine plastic debris (MPD) remains limited and little is known about the exact capacity of beaches to store and retain MPD. The beaches of Hawaii accumulate high amounts of MPD given their location and proximity to the North Pacific Subtropical Gyre, in which the floating plastic accumulation is known as the Garbage Patch. However, research on beached MPD has focused mostly on sampling at the surface and near surface of the beach (<10 cm depth). Here, we present the first objective of the STORAGE project: “predicting the fate of plaSTic On beaches by theiR 3D-distribution and weAtherinG processes”, which aims to fill in current knowledge gaps in the global monitoring of MPD in coastal environments and with a particular focus on the role of beaches in the fate of MPD (transportation, storing, and transformation). We sample MPD (with sizes > 0.5 mm) for each 10 cm layer of sand (in 60x60 cm quadrats), down to 1 meter depth, which are categorized, measured and counted through the use of an image segmentation model. A random subset of sampled MPD is analysed further under Infrared Spectroscopy for polymer identification. For the different 10 cm layers we observe a range of concentrations at the different depths with the number of MPD particles ranging from 0 to over 1000 particles per 10 cm layer (36 litre of sand) and observe significant differences in MPD distribution in the sand column between the three selected beaches. To aid our understanding of the role of beaches in the fate of MPD, we are also monitoring the beach dynamics by assessing the sand accretion and erosion rates through long-term timelapse imaging.

Primary Presenter: Astrid Delorme, Center for Marine Debris Research, Hawai'i Pacific University, The Ocean Cleanup Foundation, Université Clermont Auvergne, CNRS, Clermont Auvergne INP, ICCF (astrid.delorme@sigma-clermont.fr)

Authors:

Olivier Poirion, The Jackson Laboratory, Connecticut, USA  ()

Florence Delor-Jestin, Université Clermont Auvergne, CNRS, Clermont Auvergne INP, ICCF  ()

Laurent Lebreton, The Ocean Cleanup Foundation, The Modelling House Limited  ()

Sarah-Jeanne Royer, Center for Marine Debris Research, Hawai'i Pacific University, The Ocean Cleanup Foundation  ()