The Effects of Combined Ocean Acidification and Nanoplastic Exposures on the Embryonic Development of Antarctic Krill

Abstract

In aquatic environments, plastic pollution occurs concomitantly with anthropogenic climate stressors such as ocean acidification. Within the Southern Ocean, Antarctic krill (Euphausia Superba) support many marine predators and play a key role in the biogeochemical cycle. 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. Furthermore, Antarctic krill may be especially vulnerable to plastic pollution due to their close association with sea-ice, a known plastic sink. Here, we investigate the behaviour of nanoplastic [spherical, aminated (NH2), and yellow-green fluorescent polystyrene nanoparticles] 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 (pCO2 ∼900, pHT 7.7) on the embryonic development of Antarctic krill. Gravid female krill were collected in the Atlantic sector of the Southern Ocean (North Scotia Sea). Produced eggs were incubated at 0.5 °C 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. 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). 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%). 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.

Nanoplastic Toxicity: Insights and Challenges from Experimental Model Systems

“…pointed out that the “protein corona” formed on the particle surface is highly dependent on the surface chemistry of the particles. [ 55 ] In addition to the “protein corona” which is formed around the particles when entering a physiological environment like an organism or cell culture media, particles can be encapsulated by dissolved organic molecules building a so called “eco‐corona.” [ 99,100 ] In contrast to carboxylated particles which agglomerate within seawater due to the loss of stability, positively charged particles are less vulnerable and mostly maintain their nanoparticle characteristics. [ 101,102 ]…”

“…[55] In addition to the "protein corona" which is formed around the particles when entering a physiological environment like an organism or cell culture media, particles can be encapsulated by dissolved organic molecules building a so called "eco-corona." [99,100] In contrast to carboxylated particles which agglomerate within seawater due to the loss of stability, positively charged particles are less vulnerable and mostly maintain their nanoparticle characteristics. [101,102] In summary, there are several studies indicating that a variety of parameters may influence the uptake as well as the effect of PS NPs to cells, including their particle size and shape, their surface modification, and external factors like suspension medium used during exposure.…”

Status, Change, and Futures of Zooplankton in the Southern Ocean

“…We also only considered the potential impacts of each driver in isolation and recognize that the additive, synergistic, or antagonistic impacts of multiple drivers on these taxa will be important and warrants further attention. Although we did not assess the impacts of some other global drivers, such as ocean deoxygenation, increased ultraviolet radiation, or recovery of the ozone hole over Antarctica and the Southern Ocean, or local drivers, such as pollution (e.g., microplastics), invasive species, parasites, or pathogens (see Grant et al, 2021), existing and emerging research suggests that these may also elicit future changes in zooplankton (Flores et al, 2012a;Rowlands et al, 2021). All of these will have important implications for the dynamics of zooplankton population dynamics and their spatial connectivity.…”

Macro- and Microplastics in the Antarctic Environment: Ongoing Assessment and Perspectives

“…However, possible effects cannot be ruled out for larval Antarctic krill, which throughout furcilia stages lives in close association with sea ice (i.e., an important plastic sink) and is concomitantly exposed to climate stressors, such as ocean warming and acidification. Rowland et al [117] investigated the combined effects of different nanoplastics and ocean acidification on the embryonic development of Antarctic krill and observed a lower proportion of developing embryos in the multi-stressor treatment. As calcifying organisms, pteropods are certainly exposed to ocean acidification.…”