PhD defence: Microbial colonization, biodegradation, and photodegradation of marine plastics in (sub)tropical waters:

Plastic pollution in our oceans is a critical issue affecting marine life, human health, and economies dependent on coastal tourism and fisheries. Plastics, primarily derived from petrochemicals, are omnipresent due to their versatility and durability. The surge in plastic demand has led to a significant increase in waste, especially of common polymers like polyethylene (PE), polypropylene (PP), and polystyrene (PS). These materials often end up as marine debris, originating from both land and sea activities. 

Marine plastic debris (MPD) not only litters the surface but also sinks to the ocean floor, posing a long-term environmental challenge. Biofouling, the process where microorganisms colonize plastic surfaces, facilitates this sinking. The interaction between plastics and microbial communities is complex, with some microbes potentially capable of degrading plastics, though this process is not fully understood.

A study focusing on subtropical coastal waters in the Caribbean and Mediterranean Sea investigated the factors influencing plastic degradation. We found that the type of plastic and environmental conditions significantly affect microbial colonization and degradation. We used advanced techniques like 16S rRNA gene sequencing and stable isotope tracing to track microbial activity and plastic-derived carbon assimilation.

Results showed that while microbial communities vary initially based on polymer type, environmental factors like location and habitat have a more substantial impact over time. Additionally, photodegradation through UV radiation plays a crucial role in breaking down floating plastics, highlighting the need for further research to understand its ecological impacts.

Overall, this research emphasizes the importance of environmental context in plastic degradation processes and the potential of isotope tracing to quantify microbial activity. It underscores the complexity of tackling plastic pollution and the need for comprehensive strategies that consider both biotic and abiotic degradation pathways.