Plastics counteract the ability of Antarctic krill to promote the blue carbon pathway in the deep ocean.

The Antarctic krill (Euphausia superba) play a critical role in promoting the so-called "blue carbon pathway" by producing a large amount of fast-sinking faecal pellets (FPs) which facilitate the transport of CO through the water column. Here we assess how exposure to negatively (PS-COOH) and positively (PS-NH) charged polystyrene nanoparticles, impacts degradation of krill FPs (i.e. change in peritrophic membrane state, Carbon concentration and Carbon/Nitrogen ratio). Our findings suggest that exposure of nanoplastics, particularly negatively charged particles, increases krill FP degradation. This can result in a potential loss of FP-sequestrated C of up to 27 %, equivalent to up 5.5 Mt. C per productive season (Spring-early Autumn). This study provides new insights into how increasing levels of plastic pollution could affect the natural capital provided by krill FPs. The effect of this emerging anthropogenic contaminant should be considered by international policies focused on climate change mitigation and adaptation.