Microplastics, microfibers and associated microbiota biofilm analysis in seawater, a case study from the Vesuvian Coast, southern Italy

The growing concerns regarding pollution from microplastics (MPs) and microfibers (MFs) have driven the scientific community to develop new solutions for monitoring ecosystems. However, many of the proposed technologies still include protocols for treating environmental samples that may alter plastic materials, leading to inaccurate results both in observation and in counting. For this reason, we are refining a protocol, based on optical microscopy without the use of pretreatments, applicable to different environmental matrices, which allows not only counting but also a complete morphological characterization of MPs and MFs. Previously, the protocol has successfully been tested on marine sediments from the Vesuvian area of the Gulf of Naples (Italy) with good results. In the present study, we tested the protocol on MPs and MFs in seawater samples collected from the same geographical area to provide a comprehensive overview of their distribution in the marine environments. The protocol enabled not only the morphological characterization of MPs and MFs but also the collection of information on the colonies of microorganisms present on the microparticles. Next Generation Sequencing (NGS) metagenomic technologies enabled us to characterize the microbiota composition of the sampled MPs, the so-called Plastisphere. The analytical approach allowed the characterization of several potentially pathogenic bacteria, which represent a potential threat to the environment and human health. In fact, they may exploit their ability to form biofilms on plastics to proliferate in marine ecosystems.