The role of microbes in the fate of plastics in marine sediments: a case study from the Dutch Wadden Sea

Plastic pollution has risen exponentially since its introduction in the 1950s, with major impacts across ecosystems, particularly in the marine environment where plastics tend to accumulate. The fate of plastic in ocean sediments remains poorly understood, especially regarding the succession of microbial communities on plastic debris in sediments, their potential biodegradation by microorganisms and the associated kinetics. To address this knowledge gap, we conducted an experiment using 13C-labeled polyethylene (PE) and polyethylene terephthalate (PET) in anoxic microcosms containing sediments from two depths (0-5 cm and 25-30 cm) of the Dutch Wadden Sea. Degradation processes were monitored through headspace analysis with Gas Chromatography (GC) and Isotope Ratio Mass Spectrometry (IRMS), Dissolved Inorganic Carbon (DIC) measurements and prokaryotic community profiling via 16S rRNA amplicon sequencing using Illumina next-generation sequencing (NGS). A second experiment investigated microbial succession on PE, PET, nylon and a bioplastic bag incubated in sea water and surface sediments (0-5 cm). Finally, polymer degradation was assessed with Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy (ATR-FTIR). These experiments provide new insights into the microbial interactions with traditional and biobased polymers in marine sediments and contribute to understanding their potential degradation pathways.