Are the primary characteristics of polystyrene nanoplastics responsible for toxicity and ad/absorption in the marine diatom Phaeodactylum tricornutum?

Abstract

Nowadays, the occurrence of a large volume of plastic litter in oceanic and coastal zones has increased concern about its impacts on marine organisms. The degradation of plastic polymers leads to the formation of smaller fragments at both micro and nano scale (<5 mm and <1 µm respectively). Nanoplastics (NPs), due to their smaller size and high specific surface area can establish colloidal interactions with marine microalgae, therefore potential toxicity can be led. . To assess this hypothesis, the aim of the present study is to examine the behaviour of polystyrene nanoparticles (PS NPs) of different sizes (50 and 100 nm) in marine water and their possible effects at different physiological and cellular levels in the marine diatom Phaeodactylum tricornutum. Different biomarkers and stress responses in P. tricornutum were analysed when organisms were exposed to environmentally relevant PS NPs concentrations between 0.1-50 mg•L -1 . Our results showed significant differences between controls and exposure microalgae, indicating toxicity. After 24h, an increase in oxidative stress biomarkers, damage to the photosynthetic apparatus, DNA damage and depolarization of mitochondrial and cell membrane from 5 mg•L -1 were observed. Further after 72 h the inhibition of population growth and chlorophyll content were observed. Examining effects the effects related to PS NPs size, the smallest (50 nm) induced greater effects at 24 h while bigger PS NPs (100 nm) at72 h. This bigger particles (100nm) showed more stability (in size distribution and spherical form) in the different culture media assayed, when compared with the rest of particles used. Strong adsorption and/or internalization of PS NPs was confirmed through changes in cell complexity and cell size as well as the fluorescence of 100 nm fluoresbrite PS NPs after washing cell surface.

Behavior and Bio-Interactions of Anthropogenic Particles in Marine Environment for a More Realistic Ecological Risk Assessment

“…Interestingly, most of the studies reported no or limited effect on microalgal growth after exposure to increasing concentrations of plain PS and PS-COOH NPs (Bergami et al, 2017;Yi et al, 2019) up to 250 µg ml −1 (Sjollema et al, 2016), while many sub-lethal physiological alterations have been observed, such as a strong adsorption of nanoplastic agglomerates on microalgal surface (Bergami et al, 2017;Sendra et al, 2019b;Yi et al, 2019), a decrease in photosynthesis efficiency and lipid content, as well as the production of reactive oxygen species (ROS) (González-Fernández et al, 2019;Sendra et al, 2019b;Seoane et al, 2019). Moreover, a significant increase in the DNA damage as well as depolarization of mitochondrial and cell membrane were found in the benthic diatom Phaeodactylum tricornutum exposed to increasing concentrations (in the range 0.1-50 µg ml −1 ) of plain PS NPs, although toxicity was not affected by their nominal sizes of 50 and 100 nm (Sendra et al, 2019b). Recent findings also underline how PS-COOH (50 nm) adhesion onto a diatom's surface causes a reduction in their chain length with potential ecological implications as, for instance, changes in diatom's chain buoyancy as well as the formation and sinking of aggregates (Bellingeri et al, 2020).…”

Rapid fragmentation of microplastics by the freshwater amphipod Gammarus duebeni (Lillj.)

“…Furthermore, the finding that species such as G. duebeni can also produce numbers of nanoplastics suggests a new pathway for the environmental presence of nanosized plastics, which are of high concern as they can potentially pass through cell wall barriers and produce adverse effects. Adverse effects of nanoplastics have already been reported in microalgae [60][61][62] , aquatic 63 and terrestrial 64,65 plants, daphnids 60,66 or blue mussel larvae 67 . Moreover, the findings presented here can also be highly relevant for plastic modelling studies as biological fragmentation is currently not considered in the fate of plastics in the environment 68 .…”

A Meta‐analysis of Ecotoxicological Hazard Data for Nanoplastics in Marine and Freshwater Systems

“…The results of the present study are therefore in contradiction to the expectation that nanoplastics are more hazardous than microplastics (Lehner et al 2019). Indeed, some studies have shown that smaller sized nanoplastics exhibited higher toxicity than larger particles (Fadare et al 2019; Li et al 2020), yet some other studies have also shown no size‐dependent effect or even shown that larger particles were more toxic (Sendra et al 2019; Choi et al 2020). To further understand the effect of size on nanoplastic ecotoxicity, we conducted a statistical analysis based on 21 ecotoxicity data for D. magna and found no statistically significant effect of size on ecotoxicity of nanoplastics for the mass‐based NOECs.…”