Understanding hazards of nanoplastics using Daphnia magna

Abstract: This thesis presents the results of studies focused on effects caused by nano-sized particles using freshwater filter feeder Daphnia magna. I showed that both positively and negatively surface charged PS NPs induced significant mortality in D. magna after a life-time (103 days) of exposure at low concentrations. Previously, it was shown that negatively surface charged PS NPs are acutely not toxic toward D. magna.Secondly, I analyzed metabolic responses in D. magna after 37 days of exposure to low concentrations of PS NPs. The observed results revealed that levels of free amino acids were affected at PS NPs concentrations as low as 3.2 μg/L, which is lower than various NPs concentrations quantified in nature. Nanomaterials, including PS NPs, adsorb biomolecules on their surfaces and form corona. Therefore, I identified proteins that bind to differently surface charged PS NPs. The results showed that the profiles of bound proteins are different depending on the particle size and charge, which can partly explain differences in acute toxicity.PLA is recognized as an alternative to synthetic plastics, therefore recently has received a lot of attention. I evaluated the effects of PLA breakdown nanoplastics and PLA NPs on D. magna after acute exposure. The observed results showed that neither PLA NPs nor PLA nanoplastics induced adverse effects on D. magna. Contrarily, PLA plastic cup nanoplastics significantly extended the survival of D. magna compared to a control group.