(2017) estimated microplastic particles in the order of 100,000 km – 2 through the entire water column at sample sites closest to Antarctica. (2019) estimated a mean microplastic concentration in oceanic surface waters of 1794 km – 2 relative to the estimated density range for over 70% of the world’s oceans of 1000–100,000 particles km – 2, whilst Isobe et al. Reports of microplastics range from an absence ( Kuklinskia et al., 2019) to dense concentrations comparable to concentrations observed in the Northern Hemisphere oceans. Consequently, determining the concentration of plastic pollution in the region remains challenging ( Cincinelli et al., 2017 Isobe et al., 2017 Lacerda et al., 2019 Jones-Williams et al., 2020 Suaria et al., 2020). Even concerning the better studied microplastic, there is a paucity of data in the Southern Ocean with studies specifically dedicated to microplastic investigation emerging only from 2017 ( Tirelli et al., 2020). Whilst the technical challenges of determining exactly how much nanoscale plastic exists in the natural environment have thus far limited the detection of nanoplastic in the Southern Ocean, nanoplastic is predicted to be as pervasive as microplastic ( Alimi et al., 2017). (2019), referring to a nanoplastic size criterion of <1 micron (μm) to conform to existing definitions for nanomaterials. Here, we use the definition provided by Hartmann et al. Oceanic plastic exists in a continuum of sizes, from the macro to nanoscale ( Ter Halle et al., 2017), though size classifications are still evolving. In the Southern Ocean, plastic debris has been detected from surface waters (e.g., Jones-Williams et al., 2020 Suaria et al., 2020) to the sea-floor (e.g., Munari et al., 2017 Reed et al., 2018), and across a range of Antarctic biota such as pelagic amphipods ( Jones-Williams et al., 2020), pelagic and demersal fishes ( Cannon et al., 2016), and benthic invertebrates ( Sfriso et al., 2020). Since the biological thresholds to any stressors can be altered by the presence of additional stressors, we propose that future nanoplastic ecotoxicology studies should consider the changing global ocean under future climate scenarios for assessments of their impact and highlight that determining the behaviour of nanoplastic particles used in incubation studies is critical to determining their toxicity. Further, we found that the proportion of embryos developing through the early stages to reach at least the limb bud stage was highest in the control treatment (21.84%) and lowest in the multi-stressor treatment (13.17%). We observed that negatively charged nanoplastic particles suspended in seawater from the Scotia Sea aggregated to sizes exceeding the nanoscale after 24 h (1054.13 ± 53.49 nm).
Produced eggs were incubated at 0.5 ☌ in four treatments (control, nanoplastic, ocean acidification and the multi-stressor scenario of nanoplastic presence, and ocean acidification) and their embryonic development after 6 days, at the incubation endpoint, was determined. Gravid female krill were collected in the Atlantic sector of the Southern Ocean (North Scotia Sea). Here, we investigate the behaviour of nanoplastic in Antarctic seawater and explore the single and combined effects of nanoplastic (160 nm radius, at a concentration of 2.5 μg ml – 1) and ocean acidification (pCO 2 ∼900, pH T 7.7) on the embryonic development of Antarctic krill. Furthermore, Antarctic krill may be especially vulnerable to plastic pollution due to their close association with sea-ice, a known plastic sink. Ocean acidification and plastic pollution have been acknowledged to hinder Antarctic krill development and physiology in singularity, however potential multi-stressor effects of plastic particulates coupled with ocean acidification are unexplored. Within the Southern Ocean, Antarctic krill ( Euphausia Superba) support many marine predators and play a key role in the biogeochemical cycle. In aquatic environments, plastic pollution occurs concomitantly with anthropogenic climate stressors such as ocean acidification. 3Plymouth Marine Laboratory, Plymouth, United Kingdom.2College of Life and Environmental Sciences, University of Exeter, Exeter, United Kingdom.1British Antarctic Survey, Cambridge, United Kingdom.Emily Rowlands 1,2*, Tamara Galloway 2, Matthew Cole 3, Ceri Lewis 2, Victoria Peck 1, Sally Thorpe 1 and Clara Manno 1*
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