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The adverse effect of chemical additives leaching from microplastics (MPs) on Daphnia magna populations is not fully understood. In this study, D. magna populations were exposed to polyethylene (PE) MP fragments (5.0 mg/L), PE MP fragments containing the ultraviolet stabilizer benzophenone-3 (MP/BP-3 fragments, 5.0 mg/L), and BP-3 leachate (79 ± 10 µg/L) from PE MP/BP-3 fragments. The test duration was 42 days to observe the population dynamics of D. magna. BP-3 leachate delayed the development and somatic growth of D. magna, resulting in a significantly lower (p < 0.05) population size (number of organisms) compared with the control group. For instance, the population size was 7.7 ± 8.1 and 115 ± 3.5 (n = 3), respectively, at 18 d. However, both MP and MP/BP-3 fragments did not significantly decrease (p > 0.05) the population size of D. magna until day 18. These findings suggest that chemical additive leachates from MPs may have a distinct adverse effect on aquatic organisms, requiring further comprehensive investigation., Competing Interests: Declarations. Conflict of Interest: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2024. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.)

The increase in the usage of biodegradable microplastics (MPs) as an alternative to conventional plastics has necessitated comprehensive ecotoxicity assessments of biodegradable MPs alongside conventional MPs. This study aimed to assess ecotoxicity of biodegradable polylactic acid (PLA) MPs at concentration of 1 and 5 mgL -1 including a genetic analysis of Daphnia magna, and compared to effects of conventional polyethylene terephthalate (PET) MPs. The survival rate for D. magna exposed to 5 mg L -1 of PLA-MPs declined to 52.4 %, signifying a higher rate of mortality when contrasted with PET-MPs, which exhibited 85.7 % survival rate. Chronic exposure to 1 and 5 mgL -1 PLA-MPs resulted in a decrease of offspring, while increasing the sex ratio and deformed embryo. Interestingly, down-regulation of the SOD and AK genes was observed in D. magna after exposure to 5 mgL -1 of PLA-MPs, while 1 mgL -1 of PLA-MPs up-regulated. These results means that 5 mgL -1 PLA-MP could not produce energy and cope with oxidative stress, resulting in high mortality, and 1 mgL -1 of MP was maintained survival due to energy production and antioxidant action. This study contributes to our understanding of biodegradable microplastics (BMPs) toxic effects on D. magna which could be similar to conventional MPs and provide the importance of ecotoxicological data for risk assessment of BMPs in aquatic organisms., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier B.V. All rights reserved.)

Plastic additives may accelerate adverse effects of microplastics (MPs). This study aimed to identify the role of benzophenone-3 (BP-3) additive (10.82 ± 1.20% w/w) in chronic toxicity of polyethylene MP fragments to Daphnia magna (D. magna). MP fragments with and without BP-3 (48.37 ± 6.26 and 44.39 ± 11.16 μm, respectively) were synthesized and 4 d-old D. magna were exposed for 17 d. Daphnids exposed to MP/BP-3 fragments (98%) showed higher survival than those exposed to MP fragments (62%), which can be explained by a significantly low (p < 0.0001) bioconcentration of MP/BP-3 fragments. BP-3 leachate induced significantly low (p < 0.05) phototactic behavior of D. magna, likely leading to the low bioconcentration of MP/BP-3 fragments. Unlike MP fragments, both MP/BP-3 fragments and BP-3 additive inhibited embryonic development and offspring growth in a similar manner. Additionally, only BP-3 additive significantly induced (p < 0.05) higher lipid peroxidation in D. magna. This study suggests the critical role of plastic additives in MPs chronic toxicity to aquatic organisms, which should be further identified for other environmentally relevant plastic additives., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2021 Elsevier B.V. All rights reserved.)

Biodegradable plastics (BPs) are widely used as alternatives to non-BPs due to their inherent ability to undergo facile degradation. However, the ecotoxicological impact of biodegradable microplastics (MPs) rarely remains scientific documented especially to aquatic ecosystem and organisms compared to conventional microplastics. Therefore, this study aimed to investigate the ecotoxicity of biodegradable polylactic acid (PLA) MPs to Daphnia magna with that of conventional polyethylene (PE) MPs with and without ultraviolet (UV) treatment (4 weeks). The acute toxicity (48 h) of PLA MPs was significantly higher than that of PE MPs, potentially attributable to their elevated bioconcentration resulting from their higher density. UV treatment notably reduced the particle size of PLA MPs and induced new hydrophilic functional groups containing oxygen. Thus, the acute lethal toxicity of PLA MPs exhibited noteworthy increase, compared to before UV treatment after UV treatment, which was greater than that of UV-PE MPs. In addition, UV-PLA MPs showed markedly elevated reactive oxygen species concentration in D. magna compared to positive control. However, there was no significant increase in the level of lipid peroxidation, possibly due to successful defense by antioxidant enzymes (superoxide dismutase and catalase). These findings highlight the ecotoxicological risks of biodegradable MPs to aquatic organisms, which require comprehensive long-term studies. [Display omitted] • PLA MPs showed higher bioconcentration and acute toxicity in D. magna than PE MPs. • UV treatments degraded PLA MPs and produced hydrophilic functional groups on their surface. • UV-PLA MPs showed higher acute lethal and sublethal toxicity than that of PLA before UV treatments. [ABSTRACT FROM AUTHOR]

Microplastic (MP) pollution poses a growing concern in freshwater ecosystems, which are further threatened by global warming. Thus, this study investigated the effect of elevated temperature (25 °C) on acute toxicity of polyethylene MP fragments to Daphnia magna over a 48 h period. At the reference temperature (20 °C), MP fragments (41.88 ± 5.71 µm) induced over 70 times higher lethal toxicity than that induced by MP beads (44.50 ± 2.50 µm), with median effective concentrations (EC 50) of 3.89 and 275.89 mg L−1, respectively. Elevated temperature significantly increased (p < 0.05) the lethal (EC 50 = 1.88 mg L−1) and sublethal (lipid peroxidation and total antioxidant capacity) toxicity in D. magna exposed to MP fragments compared to those at the reference temperature. Additionally, the elevated temperature led to a significant increase (p < 0.05) in the bioconcentration of MP fragments in D. magna. Overall, the present study increases understanding for the ecological risk assessment of microplastics under global warming, highlights that elevated temperature can be seriously increased bioconcentration of MP fragments, leading to increased acute toxicity in D. magna. [Display omitted] • Elevated temperature increased bioconcentration of microplastics in Daphnia magna. • Elevated temperature enhanced acute immobilization of microplastics to Daphnia magna. • Elevated temperature enhanced acute oxidative stress of microplastics to Daphnia magna. • Increased bioconcentration of microplastics induced enhanced acute toxicity. [ABSTRACT FROM AUTHOR]

• Synthesized microplastic fragments with known amounts of benzophenone‐3 (BP-3). • Synergistic toxicity of microplastic fragments and BP-3 in D. magna was assessed. • Effect of microplastic fragments on bioconcentrations of BP-3 was evaluated. The interactive effect of polyethylene microplastic (MP) fragments and benzophenone‐3 (BP-3) additives on Daphnia magna was assessed in the present study. The 48 h median effective concentration (EC 50) revealed that MP fragments (37.24 ± 11.76 μm; 3.90 mg L−1) were over 80 times more acutely toxic than polyethylene microbeads (37.05 ± 3.96 μm; 323 mg L−1), possibly because of their irregular shape and high specific surface area. Moreover, the addition of BP-3 (10.27 ± 0.40 % w/w) to MP fragments (MP + BP-3) resulted in greater acute toxicity to D. magna (EC 50 = 0.99 mg L−1) compared to MP fragments (EC 50 = 3.90 mg L−1) or BP-3 (EC 50 = 2.29 mg L−1) alone. Additionally, MP + BP-3 exposure induced a synergistic increase in reactive oxygen species, total antioxidant capacity, and lipid peroxidation in D. magna. These synergistic effects can be attributed to enhanced bioconcentrations of BP-3 in D. magna caused by MP fragments. These findings suggest that MP fragments containing chemical additives represent a synergistic ecological risk and have the potential to harm aquatic organisms. [ABSTRACT FROM AUTHOR]

Fragmented microplastics (MPs) are emerging contaminants in freshwater environments; however, long-term assessment of their toxicity remains limited. This study aimed to evaluate and compare the chronic toxicity (21 d) of synthesized polyethylene MP fragments and commercial polyethylene MP beads to Daphnia magna. Ingestion of small- and large-sized MP fragments (17.23 ± 3.43 and 34.43 ± 13.09 μm, respectively) by D. magna was significantly (p < 0.05) higher, by 8.3 and 5.2 times, respectively, than that of MP beads (39.54 ± 9.74 μm). The survival of D. magna exposed to small- and large-sized MP fragments (20 and 60%, respectively) was significantly (p < 0.05) lower than that of individuals exposed to MP beads (90%). In particular, small-sized MP fragments significantly (p < 0.05) reduced algal feeding (from 95% to 76%), body length (from 4.20 mm to 3.98 mm), and the number of offspring (from 109 to 74) in D. magna , when compared with MP beads, likely due to their longer retention time and greater interference in the digestive tract. These findings suggest that fragmentation of MPs into μm-scale particles can pose a significant ecological risk to aquatic organisms; moreover, further studies are required to identify the underlying toxicity mechanism. [Display omitted] • Accumulation of microplastic (MP) fragments was higher than that of MP beads. • This likely resulted in higher mortality in Daphnia magna for MP fragments. • MP fragments decreased the carbohydrate and protein reserves of D. magna. • Inhibition of feeding in D. magna depended on the size of MP fragments. • This may lead to size-dependent reduction in growth and reproduction of D. magna. [ABSTRACT FROM AUTHOR]