Abstract
Plastic is incredibly abundant in marine environments but little is known about its effects on benthic microbiota and biogeochemical cycling. This study reports the shotgun metagenomic sequencing of biofilms fouling plastic and bioplastic microcosms staged at the sediment–water interface of a coastal lagoon. Community composition analysis revealed that plastic biofilms were indistinguishable in comparison to a ceramic biofilm control. By contrast, bioplastic biofilms were distinct and dominated by sulfate-reducing microorganisms (SRM). Analysis of bioplastic gene pools revealed the enrichment of esterases, depolymerases, adenylyl sulfate reductases (aprBA), and dissimilatory sulfite reductases (dsrAB). The nearly 20-fold enrichment of a phylogenetically diverse polyhydroxybutyrate (PHB) depolymerase suggests this gene was distributed across a mixed microbial assemblage. The metagenomic reconstruction of genomes identified novel species of Desulfovibrio, Desulfobacteraceae, and Desulfobulbaceae among the abundant SRM, and these genomes contained genes integral to both bioplastic degradation and sulfate reduction. Findings indicate that bioplastic promoted a rapid and significant shift in benthic microbial diversity and gene pools, selecting for microbes that participate in bioplastic degradation and sulfate reduction. If plastic pollution is traded for bioplastic pollution and sedimentary inputs are large, the microbial response could unintentionally affect benthic biogeochemical activities through the stimulation of sulfate reducers.
Highlights
Microorganisms rapidly colonize and form biofilms on biotic and abiotic surfaces in marine environments (Dang and Lovell, 2016)
Numerous studies have characterized microbe-plastic interactions in pelagic systems, yet the effects of plastic pollution on benthic microbiota and biogeochemical cycling remain unclear. To address this knowledge gap, we conducted an in situ microcosm designed to ask how the benthic microbial community responds to plastic and bioplastic in coastal marine sediments
Coastal sediments are especially vulnerable to plastic loading due to their proximity to population centers and urban environments (Barnes et al, 2009), and the majority of plastic debris entering the oceans accumulates in coastal zones (Barnes et al, 2009; Thompson et al, 2009)
Summary
Microorganisms rapidly colonize and form biofilms on biotic and abiotic surfaces in marine environments (Dang and Lovell, 2016). Marine microbial communities are commonly distinguished as free-living or particle-associated (DeLong et al, 1993; Crump et al, 1999; Hollibaugh et al, 2000). A recent global assessment of all mass-produced plastics estimated that 4.9 billion tons of plastic waste was discarded in landfills or natural environments (Geyer et al, 2017). It is clear that marine microorganisms colonize and form biofilms on floating plastic debris and it is clear that plastic-associated microbial communities are distinct compared to free-living communities (Bryant et al, 2016; Oberbeckmann et al, 2016)
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