Quantifying microplastic pollution in marine organisms from a coastal lagoon: an ecological perspective using laser...

Fish is widely recognized as a valuable source of high-quality proteins, omega-3 fatty acids, and essential micronutrients. However, these nutritional benefits are increasingly compromised by marine pollution, particularly plastics and microplastics (MPs), particles smaller than 5 mm that enter the food chain after ingestion by marine organisms. These emerging pollutants represent a growing threat to both marine ecosystems and human health. In this study, laser direct infrared microscopy (LDIR) was used, an innovative technique based on a mid-infrared quantum cascade laser that enables precise and sensitive characterization of MPs. Samples from multiple species inhabiting the Mar Menor lagoon (Spain) were analysed, including muscle tissue, liver, and gastrointestinal contents. The muscle and liver samples were treated using acid digestion, while the gut contents were processed using oxidative digestion combined with density flotation. The results showed a predominance of particles between 50 and 100 μm (over 70%), primarily rounded in morphology. Polyethylene was the most frequently detected polymer, representing more than 45% of particles in all the samples. Statistical analyses demonstrated trend toward MP accumulation in gut contents, with no significant differences among marine species. Additionally, a cytotoxicity assay using marine fish cells (SAF-1 cell line) revealed a decrease in cell viability in response to polyamide MP, highlighting the urgent need for monitoring their environmental and food safety implications.