Slow biological microplastics removal under ocean pollution phase-out trajectories
File(s)
Published version
Author(s)
Azimrayat Andrews, Zhenna
Kvale, Karin
Hunt, Claire
Type
Journal Article
Abstract
Microplastics are ubiquitous in marine environments and can be incorporated into biological aggregates including marine snows and faecal pellets. These aggregates are suspected to be a major removal mechanism for microplastics from the surface ocean, transporting them to deeper levels and the seafloor as they sink and remineralise. However, simple budget calculations, observations, and model parameter testing suggest that aggregation might also lead to retention of microplastics in the upper ocean, sustaining contamination in biologically-productive environments. The ability of the biological microplastic sink to reduce water column contamination has relevance to the setting of ocean plastics pollution reduction targets, as are currently under negotiation by the International Negotiating Committee of the United Nations Environment Assembly (UNEA). Here we apply eight idealised global pollution reduction trajectories, from 1%–100% per year, starting from the year 2026 and ending in the year 2100 to an Earth System Climate Model with a representation of ocean microplastics and their aggregation in biological particles. We find that the global ocean microplastic inventory and surface concentrations stabilize within this century for reduction rates exceeding 5% per year but the inventory does not substantially decrease under any trajectory. Furthermore, microplastics are retained by marine biology in the surface ocean, where concentrations stabilise to a non-zero value over decades. Lastly we find that irrespective of scenario, contamination of deeper ocean layers continues to increase for the duration of our simulations via the export of microplastics by biological aggregates. These results suggest that ambitious targets for pollution reduction exceeding 5% per year will be required to progress the resolution of the UNEA to 'end plastic pollution' in this century, and that ongoing microplastic contamination of the marine food web may be unavoidable.
Date Issued
2024-06
Date Acceptance
2024-05-03
Citation
Environmental Research Letters, 2024, 19 (6)
ISSN
1748-9326
Publisher
IOP Publishing
Journal / Book Title
Environmental Research Letters
Volume
19
Issue
6
Copyright Statement
© 2024 The Author(s). Published by IOP Publishing Ltd Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 license. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.
License URL
Identifier
http://dx.doi.org/10.1088/1748-9326/ad472c
Publication Status
Published
Article Number
064029
Date Publish Online
2024-05-24