BOOK OF ABSTRACTS 237 IHSS&IWA26 / BRNO / CZECHIA / 23–28 August 2026 Hall A Poster Session / Environment, Agriculture, and Forestry P4.13 Difference in the Growth of Ecologically Relevant Green Algae (Raphidocelis Subcapitata and Chlorella Vulgaris) in Response to Microplastic Leachates Christoph Steinbach1, Katerina Novotna1, Michaela Prokopova1, Lenka Cermakova1, Martin Pivokonsky1, Sidika Sakalli1 1 Institute of Hydrology of the Czech Academy of Sciences, Pod Patankou 30/5, 160 00 Prague 6, Czech Republic, steinbach@ih.cas.cz Microplastic (MP) contains additives, including organic matter, that can leach into aquatic environments. Given the ubiquitous presence of MPs, anthropogenic organic matter derived from microplastic leachates (MPL) may contribute significantly to the dissolved organic matter [1]. In the present study, polyvinyl chloride (PVC) and polyisocyanurate (PIR), two common plastic materials with a high potential to release harmful leachates, were selected. PVC contains additives, such as stabilizers, plasticizers, and pigments, which can leach into aquatic environments and exert toxic effects [2]. PIR foams are treated with a mixture of compounds, including toxic flame retardants such as tris(1-chloro-2-propyl) phosphate (TCPP) [3]. However, there is currently a lack of literature that describes the effects of MPL compared to those of MP. Plastic additives are considered to cause adverse effects on aquatic biota. Possible adverse effects on algae the primary producers are of particular concern, potentially affecting ecosystem functions. Furthermore, changes in the composition of natural organic matter (NOM) could also affect drinking water treatment processes. Therefore, the present study aimed to investigate the effects of polyvinyl chloride (PVC) and polyisocyanurate (PIR) leachates on two ecologically important freshwater microalgae, Chlorella vulgaris and Raphidocelis subcapitata. Both species were exposed to leachates at concentrations corresponding to 1, 2, 5 and 15 g/L of PVC or PIR for 14 days. Growth inhibition was observed in R. subcapitata exposed to the PVC leachate, while the 72 and 96 h EC50 values were estimated at 7.2 g/L. No growth inhibition was observed in the other treatments. The effects of the leachates on chlorophyll a, b, total chlorophyll and carotenoids levels were determined, as well as the chlorophyll a/b and carotenoids/total chlorophyll ratios. In both algal species exposed to PVC leachate, photopigments exhibited patterns of stress response. Furthermore, the activity of antioxidant enzymes (catalase, superoxide dismutase, glutathione S-transferases, and glutathione reductase) and oxidative stress (lipid peroxidation) were significantly affected in algae exposed to both PVC and PIR leachates. Based
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