Microbes on a Bottle: Substrate, Season and Geography Influence Community Composition of Microbes Colonizing Marine Plastic Debris

Abstract

Plastic debris pervades in our oceans and freshwater systems and the potential ecosystem-level impacts of this anthropogenic litter require urgent evaluation. Microbes readily colonize aquatic plastic debris and members of these biofilm communities are speculated to include pathogenic, toxic, invasive or plastic degrading-species. The influence of plastic-colonizing microorganisms on the fate of plastic debris is largely unknown, as is the role of plastic in selecting for unique microbial communities. This work aimed to characterize microbial biofilm communities colonizing single-use poly(ethylene terephthalate) (PET) drinking bottles, determine their plastic-specificity in contrast with seawater and glass-colonizing communities, and identify seasonal and geographical influences on the communities. A substrate recruitment experiment was established in which PET bottles were deployed for 5–6 weeks at three stations in the North Sea in three different seasons. The structure and composition of the PET-colonizing bacterial/archaeal and eukaryotic communities varied with season and station. Abundant PET-colonizing taxa belonged to the phylum Bacteroidetes (e.g. Flavobacteriaceae, Cryomorphaceae, Saprospiraceae—all known to degrade complex carbon substrates) and diatoms (e.g. Coscinodiscophytina, Bacillariophytina). The PET-colonizing microbial communities differed significantly from free-living communities, but from particle-associated (>3 μm) communities or those inhabiting glass substrates. These data suggest that microbial community assembly on plastics is driven by conventional marine biofilm processes, with the plastic surface serving as raft for attachment, rather than selecting for recruitment of plastic-specific microbial colonizers. A small proportion of taxa, notably, members of the Cryomorphaceae and Alcanivoraceae, were significantly discriminant of PET but not glass surfaces, conjuring the possibility that these groups may directly interact with the PET substrate. Future research is required to investigate microscale functional interactions at the plastic surface.

A catchment‐scale perspective of plastic pollution

“…Within urban river systems, plastics have been identified as a unique and important substrate for the colonization of aquatic microbial biofilms (McCormick, Hoellein, Mason, Schluep, & Kelly, ). Similar findings have been presented within marine systems, with diatoms, phytoplankton and cyanobacteria colonizing plastic particles suspended within the water column (Oberbeckmann, Osborn, & Duhaime, ; Reisser et al, ; Zettler, Mincer, & Amaral‐Zettler, ). While in some instances, the microbial communities on these plastic particles maintained comparable species richness and evenness to communities present on natural substrates (Zettler et al, ), other studies (e.g.…”

Evidence for selective bacterial community structuring on microplastics

“…Using a controlled experiment with microplastics and other substrates, we showed that bacterial assemblages developing on microplastics differ significantly from those on non‐plastic microparticles when exposed to the same source community. Biofilms from the tested microplastics were characterized by an overrepresentation of OTUs associated with hydrocarbonoclastic bacteria, which – in line with previous studies (Zettler et al ., ; De Tender et al ., ; Oberbeckmann et al ., ) – is suggestive of substrate carbon utilization. Moreover, differences in biofilm community structure were found to be strongly related to the variation in substrate hydrophobicity.…”

“…Zettler et al . () reported that bacteria growing on polyethylene and polypropylene debris from the Sargasso Sea mainly belonged to the classes Alpha‐ and Gammaproteobacteria, similar to reports from other marine areas (Oberbeckmann et al ., , ; De Tender et al ., ). By contrast, in our study, Gammaproteobacteria and Flavobacteriia were generally rare, including the plastics‐associated biofilms, which is not surprising, because these bacteria are normally found in truly marine areas and not brackish systems, such as the Baltic Sea.…”

Microplastics alter composition of fungal communities in aquatic ecosystems

“…Previously, Oberbeckmann et al . () examined the presence of prokaryotic and eukaryotic microorganisms on PET bottles in the North Sea, and reported only 24 fungal OTUs assigned to Ascomycota, Basidiomycota and Chytridiomycota. In our study, the observed fungal richness and diversity were significantly higher with up to 136 OTUs per sample, mostly assigned to Chytridiomycota and Cryptomycota, and to a lesser extend to Ascomycota and Basidiomycota.…”

“…In addition, fungi are of special interest for potential plastic decomposition in the environment, due to their vast metabolic potential and ability to degrade recalcitrant structures (Krueger et al ., ; Grossart and Rojas‐Jimenez, ). However, to date, a single study has reported on the presence of fungi on plastic bottles made of polyethylene terephthalate (PET), but insights into fungal diversity and their ecological meaning remained peripheral (Oberbeckmann et al ., ).…”