Algal blooms accelerate plastic weathering, potentially fueling microplastic formation

Algal blooms have been identified as a catalyst for the accelerated weathering of discarded plastics, potentially increasing the rate of microplastic formation, according to a study conducted by researchers at Korea Advanced Institute of Science and Technology (KAIST). The findings, based on experiments using water samples from KAIST’s Duck Pond, reveal that the presence of algal blooms alters the microbial environment on the surface of low-density polyethylene (LDPE), a type of plastic commonly used in plastic bags. This alteration leads to faster oxidation and the development of microscopic cracks, making the plastic more vulnerable to breakdown. The research was carried out by a team led by Professor Jaewook Myung from the Department of Civil and Environmental Engineering. Through a controlled microcosm experiment, the team recreated eutrophic conditions by manipulating light exposure and nutrient levels to simulate algal blooms. They observed how these conditions influenced the microbial communities that develop on plastic surfaces. Over a period of six weeks, the researchers monitored the growth of biofilms, the evolution of microbial populations, and shifts in genetic expression patterns related to plastic degradation. The study revealed that under eutrophic conditions, cyanobacteria, photosynthetic bacteria, alongside a range of other bacterial species, formed a denser biofilm on the plastic surface. This biofilm was composed largely of microorganisms capable of producing extracellular polymeric substances (EPS), a viscous, glue-like material that aids in microbial adhesion and cohesion. The increase in EPS-producing microbes contributed to the thickening of the biofilm, which in turn altered the chemical and structural properties of the plastic. Further examination using advanced analytical techniques, including Fourier-transform infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM), confirmed that the plastic underwent visible changes. The surface of the LDPE developed oxygen-rich functional groups, such as carbonyl and hydroxyl groups, indicative of oxidation. Additionally, the plastic exhibited fine, hairline cracks, suggesting a heightened susceptibility to mechanical stress and subsequent fragmentation. These changes were attributed not to a single microbial species but to the collective activity of a diverse microbial community encompassing both photosynthetic and non-photosynthetic bacteria. The implications of these findings highlight a previously unrecognized interaction between water pollution and plastic pollution. As algal blooms become more prevalent due to climate change, the risk of accelerated plastic degradation, and thus microplastic generation, may rise significantly. This underscores the importance of integrating strategies for managing both types of pollution, rather than treating them as distinct issues. Professor Myung emphasized that the study provides critical insights into the complex relationship between environmental factors and plastic behavior. He noted that understanding these interactions is essential for developing effective mitigation strategies. The research also contributes to broader discussions on the global challenge of microplastic contamination, offering a new perspective on how human-induced environmental changes can exacerbate existing pollution problems. The next steps for the research team include expanding the scope of their studies to different aquatic environments and exploring potential interventions to mitigate the effects of algal blooms on plastic degradation.