Polystyrene microplastics exposure modulated the content and the profile of fatty acids in the Cladoceran Daphnia magna

Microplastics originated from Plasmix-based materials caused biochemical and behavioral adverse effects on Daphnia magna

The implementation of advanced recycling techniques represents a key strategy for mitigating the mismanagement and the environmental impact of plastic waste. A limited array of plastic polymers can be efficiently recycled, while a notable portion of plastic waste remains unrecyclable. In Italy, this residual, heterogeneous fraction is referred to as Plasmix. Because of its complexity and non-homogeneous composition, Plasmix is primarily directed towards low-value applications. However, recent developments in laboratory-scale mechanical recycling have enabled the creation of new plastic materials from Plasmix. Prior to their application, these materials must undergo rigorous eco-safety evaluation. The present study aims to assess the potential toxicity of microplastics (MPs) from Plasmix-based materials on the freshwater crustacean Daphnia magna. Specifically, this study investigated sub-individual and individual effects induced by a 21-day exposure to different concentrations of MPs generated from the grinding of naïve and Additivated Plasmix-based materials (hereafter referred to as Px-MPs and APx-MPs, respectively). Sub-individual endpoints focused on changes in oxidative status, including the modulation of antioxidant and detoxifying enzyme activities, as well as oxidative damage, such as lipid peroxidation. Individual level endpoints included alterations in survival and reproduction. Microscopy analyses confirmed the ingestion of both Px-MPs and APx-MPs by D. magna individuals. An oxidative stress condition raised in organisms exposed to Px-MPs, whereas no effect was observed in individuals exposed to APx-MPs. Although survival was not affected, a significant impairment in reproductive output was detected at the end of exposure to all the concentrations of both MP types. These findings suggest that even low concentrations of Px-MPs and APx-MPs could negatively affect the health status of D. magna, underscoring the need for further research to complete the risk assessment of Plasmix-based materials prior to their use in consumer products.

Sublethal effects of microplastic and oil co-exposure on biological rates and lipid profiles of keystone Arctic copepods

Microplastics (MPs) and petroleum hydrocarbons are contaminants of emerging concern in the Arctic, but little is known about their co-exposure effects. In this study, we present the first assessment of the sublethal impacts resulting from combined exposure to microplastics and oil in three key Arctic copepod species. Specifically, we investigated the effects of a 5-day exposure to oil alone (1 μL L-1) and in combination with MPs (polyethylene microspheres, 20 μm, 20 MP mL-1) and dispersant (Corexit 9500, 0.05 μL L-1) on the biological functions and lipid profiles of the planktonic copepods Metridia longa, Calanus finmarchicus, and Calanus glacialis. Exposure to oil alone caused a significant reduction (34-58%) in fecal pellet production, but neither microplastics nor dispersant increased the negative effect of oil on fecal pellet production. C. glacialis and C. finmarchicus exposed to the studied pollutants for 5 days produced eggs with delayed hatching and lower hatching success. The highest hatching inhibition (50%) was observed in eggs of C. glacialis exposed to oil plus MPs and dispersant for five days. This indicates that maternal transfer of oil components to eggs negatively affects embryonic development and hatching. Lipid content and fatty acids profiles varied among the studied copepod species but were not affected by the tested pollutants after five days of exposure. By microscopical observation of fecal pellets, ingestion of small oil droplets and MPs was confirmed in all species, but the estimated ingestion of MPs was low (<25 MPs cop-1 d-1, <0.2% of total offered MPs) suggesting avoidance of MP consumption in copepods. Our results indicate that virgin MPs did not increase the toxicity of oil to the studied Arctic copepods under co-exposure conditions, and dispersants can slightly increase certain adverse effects of oil (hatching). However, environmentally relevant concentrations of oil alone can negatively impact Arctic keystone copepods and potentially the biological carbon pump. These findings emphasize the need to reduce petrogenic pollution and the risk of oil spills in the sensitive Arctic ecosystem.

The effects of polystyrene microplastics on feeding, growth, and trophic upgrading of protozoan grazers

Microplastics have become ubiquitous in the global marine environment, posing substantial influences on marine organism health, food web function and marine ecosystem structure. Protozoan grazers are known for their ability to improve the biochemical constituents of poor-quality algae for subsequent use by higher trophic levels. However, the effects of microplastics on the trophic upgrading of protozoan grazers remain unknown. To address this knowledge gap, the ciliate Euplotes vannus and the heterotrophic dinoflagellate Oxyrrhis marina were exposed to microplastic particles (5 μm) for four days with various concentrations (1-20 mg/L). Both O. marina and E. vannus ingested microplastics. At the exposure level of 20 mg/L, the ingestion rate, growth rate, biovolume, and carbon biomass of E. vannus were significantly decreased by 28.18 %, 32.01 %, 30.46 %, and 82.27 %, respectively, while such effects were not observed for O. marina. The contents of highly unsaturated fatty acids in O. marina and E. vannus on a mixed diet of microplastic particles and green algae significantly reduced by 8.66 % and 41.49 % relative to feeding only on green algae, respectively. Besides, we also observed an increase in the composition of C18:3 (ω-3) and C20:3 (ω-3) concurrence with a significant decrease in C16:0 and C18:0 in E. vannus after 96 h exposure at 20 mg/L. These results indicate that microplastics can weaken trophic upgrading of the nutritional quality by protozoan grazers, which may consequently alter the function of food webs.

Multi-level toxicity assessment of polylactic acid (PLA) microplastics on the cladoceran Daphnia magna

The accumulation of plastics waste in the environment has raised a worrisome concern, moving the society to seek out for sustainable solutions, such as the transition from the use of fossil-based, conventional plastics to bioplastics (BPs). However, once in the environment bioplastics have the same probability to accumulate and experience weathering processes than conventional plastics, leading to the formation of microplastics (MPs). However, to date the information on the potential toxicity of MPs originated from the weathering of bioplastics is limited. Thus, this study aimed at investigating the adverse effects induced by the exposure to MPs made of a bioplastic polymer, the polylactic acid (PLA), towards the freshwater cladoceran Daphnia magna. Organisms were exposed for 21 days to three concentrations (0.125 µg/mL, 1.25 µg/mL and 12.5 µg/mL) of PLA microplastics (hereafter PLA-MPs). A multi-level approach was performed to investigate the potential effects through the biological hierarchy, starting from the sub-individual up to the individual level. At the sub-individual level, changes in the oxidative status (i.e., the amount of reactive oxygen species and the activity of antioxidant and detoxifying enzymes) and oxidative damage (i.e., lipid peroxidation) were explored. Moreover, the total caloric content as well as the content of protein, carbohydrate and lipid content assess were used to investigate the effects on energy reserves. At individual level the changes in swimming activity (i.e., distance moved and swimming speed) were assessed. Our results showed that the exposure to PLA-MPs induced a slight modulation in the oxidative status and energy reserves, leading to an increase in swimming behavior of treated individuals compared to control conspecifics. These results suggest that the exposure to MPs made of a bioplastic polymer can induce adverse effects similar to those caused by conventional polymers.

Changes in Flavor-Related Biomarkers in Pacific Oysters (Crassostrea gigas) Following Microplastic Exposure

Microplastics have been an emerging threat to filtering species and the ingestion and impacts of microplastics on oysters are a cause for concern. However, much remains unknown about the effects of microplastics on flavor-related biomarkers in oysters. Herein, a laboratory microplastic exposure with concentrations of 1, 10, and 100 mg/L for 15 days was performed to investigate the impacts of microplastics on the flavor parameters of oysters. Exposure to microplastics changed the odor characteristics of oysters. Microplastic exposure had minor effects on the fatty acid composition; however, significant alterations in free amino acids and nucleotides were observed under the 1 and 10 mg/L exposure groups, respectively. The overall results indicated 10 mg/L of microplastic exposure significantly increased the equivalent umami value of oysters. These findings stressed the effects of microplastics on oysters and would be an important reference for the assessment of the potential risks associated with microplastics in marine edible species.