Exploring the Potential of Microscopy Techniques to Study Microplastics and Biofilms in Environmental Samples

José, Silvia; Nogueira, Isabel; Veber, Alexander; Schade, Ulrich; Jordão, Luisa

http://hdl.handle.net/10400.18/7970

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Abstract(s)

Micro and nanoplastic are found worldwide in aquatic ecosystems ranging from highly populated industrialized areas to the most remote regions of the planet being a hot research topic and a concern. Marine waters have been the major research focus. Despite less studied, freshwaters are of crucial importance since life in general and human beings in particular are highly dependent of freshwater for drinking and food production. This fact shows that freshwater could function as a vehicle for MPs toxicity through all levels of the ecosystem. Although it has been suggested that toxicity is driven not only by the plastic forming units (monomers) but also by adsorbed pollutants (such as PAH, pesticides, PCBs) and associated microorganisms little is known about the underlying mechanisms. The lack of validated protocols for isolation and a gold standard technique to identify micro/nanoplastics are important issues. Infrared microscopy (IRM) with diffraction-limited infrared synchrotron radiation sources adds resolution to the traditional fingerprint IR spectra being a potential candidate to a gold standard technique not only for micro/nanoplastic identification but also for adsorbed pollutants. In the present work, IRM allowed us to identify MPs isolated from freshwater samples. Polyethylene (PE) and polystyrene (PS) were among the most common plastic polymers identified. The colonization of environmental samples of MPs by biofilms was monitored by scanning electron microscopy (SEM). Our data suggests that the presence of biofilms on MPs does not interfere with polymer identification by IRM. Biofilm assembly on MPs by microorganisms isolated from water samples in conditions mimic those found in their natural’s habitats was followed over 3 months. Biofilm biomass was accessed by spectrophotometric methods whereas SEM was used to evaluate biofilm distribution on the MPs particles. The results obtained in vitro correlate with those observed in “real samples”. Biofilms assembled by the microbial consortium used were more abundant on the most common plastics detected in the environmental samples (PE and PS).