Comparative Toxicity of Biodegradable Plastic Fragments, Leachates, and Degradation Products on the Marine Microalgae, Skeletonema pseudocostatum = 생분해성 플라스틱의 입자, 침출수 그리고 분해산물이 해양 미세조류 Skeletonema pseudocostatum에 미치는 독성 비교

다국어 초록 (Multilingual Abstract)

This study evaluated the ecotoxicological effects of marine biodegradable plastics on the marine microalgae Skeletonema pseudocostatum by distinguishing between physical and chemical exposure pathways. Toxicity was assessed under three environmentally relevant exposure scenarios: degradation products generated during marine degradation, mechanically produced microplastic fragments, and plastic leachates. Degradation products obtained after more than 90 days of marine biodegradation did not induce significant growth inhibition in S. pseudocostatum for any tested polymer. Nylon 6,6 showed no toxic effects under any exposure condition. In contrast, microplastic fragment exposure revealed polymer- and size-dependent responses. Polyhydroxyalkanoate (PHA) induced growth inhibition only at the highest concentration in the ≤500 μm fragment group. Polybutylene succinate (PBS) and poly(butylene adipate-co-butylene succinate-co-ethylene adipate-co-ethylene succinate) (PBEAS) exhibited clearer toxic responses, with concentration-dependent growth inhibition observed in fragment exposures. Leachate tests demonstrated pronounced differences depending on polymer type, size, and leaching duration. Petroleum-based PBS and PBEAS leachates induced strong growth inhibition, particularly from powdered materials and with increasing leaching time from 24 hours to one week, whereas bio-based polymers generally showed lower toxicity. Increased toxicity was associated with longer leaching durations and greater surface area, suggesting the importance of additives release. Overall, these results indicate that the toxicity of biodegradable polymers cannot be determined solely by their biodegradability. This study represents the first ecotoxicological evaluation of marine biodegradable plastic degradation products conducted in accordance with ISO 5430 using microalgae and provides fundamental data for improving environmental risk assessment frameworks for marine biodegradable plastics.

목차 (Table of Contents)

• Abstract i
• Table of Contents iii
• List of Tables v
• List of Figures vi
• Chapter 1. Introduction 1
• 1.1. Background 1
• 1.1.1. Environmental issues of conventional plastics 1
• 1.1.2. Emergence of biodegradable plastics and limitations in toxicity
• research 2
• 1.1.3. Test organism selection 5
• 1.1.4. Research needs and rationale for experimental design 5
• Chapter 2. Materials and Methods 12
• 2.1. Test materials 12
• 2.2. Test organism and cultivation 15
• 2.2.1. Preparation of preculture and inoculum 15
• 2.3. Exposure test of degradation products from marine biodegradable plastic
• materials 18
• 2.3.1. Biodegradation test 18
• 2.3.2. Pretreatment of the degradation products 21
• 2.3.3. Exposure of microalgae to degradation products 21
• 2.4. Microplastic fragments exposure test 23
• iv
• 2.4.1. Preparation of microplastic fragments 23
• 2.4.2. Toxicity assessment of TWEEN20 as a dispersant 23
• 2.4.3. Preparation of microplastic suspensions 26
• 2.4.4. Exposure of microalgae to microplastic suspensions 26
• 2.5. Leachate exposure test 27
• 2.5.1. Review of literature on leachate preparation methods 27
• 2.5.2. Preparation of leachate 27
• 2.5.3. Exposure of microalgae to leachate 31
• 2.6. Measurement of cell density and calculation of specific growth rate 31
• 2.7. Statistical analysis 34
• Chapter 3. Results 35
• 3.1. Effects of degradation products on microalgae 35
• 3.2. Effects of microplastic fragments on microalgae 38
• 3.3. Effects of leachate on microalgae 45
• Chapter 4. Discussion 55
• Chapter 5. Conclusion 64
• Acknowledgements 66
• Reference 67
• 국문초록 73
• v