Zooplankton grazing of microplastic can accelerate global loss of ocean oxygen

K Kvale,A Landolfi,A Oschlies,A E F Prowe,C.-T Chien

doi:10.1038/s41467-021-22554-w

Abstract

Global warming has driven a loss of dissolved oxygen in the ocean in recent decades. We demonstrate the potential for an additional anthropogenic driver of deoxygenation, in which zooplankton consumption of microplastic reduces the grazing on primary producers. In regions where primary production is not limited by macronutrient availability, the reduction of grazing pressure on primary producers causes export production to increase. Consequently, organic particle remineralisation in these regions increases. Employing a comprehensive Earth system model of intermediate complexity, we estimate this additional remineralisation could decrease water column oxygen inventory by as much as 10% in the North Pacific and accelerate global oxygen inventory loss by an extra 0.2–0.5% relative to 1960 values by the year 2020. Although significant uncertainty accompanies these estimates, the potential for physical pollution to have a globally significant biogeochemical signal that exacerbates the consequences of climate warming is a novel feedback not yet considered in climate research.

Highlights

Global warming has driven a loss of dissolved oxygen in the ocean in recent decades
This result demonstrates that a physical effect of plastic pollution might presently have a disruptive influence on global ocean oxygenation equivalent of up to half that of climate warming, and it suggests a missing mechanism in Earth system models, which typically underestimate 21st century ocean deoxygenation[2]
Biological uptake has the potential to profoundly shape microplastic particle distributions in the global ocean[7], concentrating particles in biologically-active surface regions as well as in gyres, and transporting particles to the deep ocean

Summary

Introduction

Global warming has driven a loss of dissolved oxygen in the ocean in recent decades. We demonstrate the potential for an additional anthropogenic driver of deoxygenation, in which zooplankton consumption of microplastic reduces the grazing on primary producers. A growing body of work shows zooplankton consume the smaller size fractions of plastic[4,5] These small particles (the microplastics, typically defined as having a length between 0.1 μm and 5 mm) replace food in the zooplankton’s diet and reduce their consumption (and subsequent export) of particle-bound organic carbon[6]. We report that the zooplankton ingestion of microplastic in those same simulations affects ocean biological rates relevant to dissolved oxygen This result demonstrates that a physical effect of plastic pollution might presently have a disruptive influence on global ocean oxygenation equivalent of up to half that of climate warming, and it suggests a missing mechanism in Earth system models, which typically underestimate 21st century ocean deoxygenation[2]

Methods

Results

Conclusion