The geographical and seasonal variations in the microbiome composition of marine microplastic - the case study of Israel and Portugal

Floating microplastic debris (<5 mm) have been found in almost all marine environments around the world. Due to their high durability at sea, floating plastic polymers such as polyethylene, polypropylene and polystyrene serve as stable substrates for the colonization of diverse communities of marine organisms.

In this study we aimed to characterize and compare the marine microplastic and its microbiome in contrasting seasons (Winter and Summer) between two separate marine environments – near the Yarkon estuary in the Israeli coastal water of the Mediterranean Sea, and near the Sado estuary in the Portuguese coastal water of the Atlantic Ocean (PT). At both locations microplastics and surrounding water were sampled in every season for the two years of the study. State-of-the art DNA metabarcoding methodology was used for the characterization of the microplastic microbiome. Additionally, the physical environmental parameters, including the microplastic itself were analyzed and compared using the same methods for both locations.

In similar to previous studies, our results suggest that the geographical location is the strongest source of microplastic microbiome variation followed by the season. While few reoccurring bacteria have been identified in the samples from the two marine environments, most genera were significantly enriched in either one of them. The overall plastisphere microbial composition of the samples from the two environments was different and showed different seasonal effects. These results suggest that the plastisphere is composed of multiple different ecosystems that are defined by multiple environmental factors of their specific geographical locations.