Relative Influence of Plastic Debris Size and Shape, Chemical Composition and Phytoplankton-Bacteria Interactions in Driving Seawater Plastisphere Abundance, Diversity and Activity

Abstract

The thin film of life that inhabits all plastics in the oceans, so-called “plastisphere,” has multiple effects on the fate and impacts of plastic in the marine environment. Here, we aimed to evaluate the relative influence of the plastic size, shape, chemical composition, and environmental changes such as a phytoplankton bloom in shaping the plastisphere abundance, diversity and activity. Polyethylene (PE) and polylactide acid (PLA) together with glass controls in the forms of meso-debris (18 mm diameter) and large-microplastics (LMP; 3 mm diameter), as well as small-microplastics (SMP) of 100 μm diameter with spherical or irregular shapes were immerged in seawater during 2 months. Results of bacterial abundance (confocal microscopy) and diversity (16S rRNA Illumina sequencing) indicated that the three classical biofilm colonization phases (primo-colonization after 3 days; growing phase after 10 days; maturation phase after 30 days) were not influenced by the size and the shape of the materials, even when a diatom bloom (Pseudo-nitzschia sp.) occurred after the first month of incubation. However, plastic size and shape had an effect on bacterial activity (3H leucine incorporation). Bacterial communities associated with the material of 100 μm size fraction showed the highest activity compared to all other material sizes. A mature biofilm developed within 30 days on all material types, with higher bacterial abundance on the plastics compared to glass, and distinct bacterial assemblages were detected on each material type. The diatom bloom event had a great impact on the plastisphere of all materials, resulting in a drastic change in diversity and activity. Our results showed that the plastic size and shape had relatively low influence on the plastisphere abundance, diversity, and activity, as compared to the plastic composition or the presence of a phytoplankton bloom.

Bacterial Abundance, Diversity and Activity During Long-Term Colonization of Non-biodegradable and Biodegradable Plastics in Seawater

“…Such dissimilarities were not found during the primo-colonization (day 3) and the growth of the biofilm (day 10) that showed distinct but close communities whatever the plastic type. Primocolonizers (day 3) together with bacteria on the growth phase of the biofilm (day 10) belonged to Gammaproteobacteria (mainly Alteromonadaceae, Oceanospirillaceae, and Alcanivoracaceae), which is in accordance with previous studies (Dussud et al, 2018a;Cheng et al, 2021). Under our conditions, significant dissimilarities were observed after 31 days, which corresponds to the maturity of biofilms for non-biodegradable materials on the one hand, and to the continuous growth with high extra-and intracellular activities for biodegradable materials on the other hand.…”

“…The description of these colonization phases has been done on several conventional plastic types, including on PE-based plastic bags ( Lobelle and Cunliffe, 2011 ; Harrison et al, 2014 ), polyethylene terephthalate (PET)-based plastic bottles ( Oberbeckmann et al, 2014 ), polyvinyl chloride (PVC) ( Dang et al, 2008 ), PS coupons ( Briand et al, 2012 ), and in comparisons between PE, PP, PET, and polycarbonate (PC) materials ( Webb et al, 2009 ; De Tender et al, 2017 ). Fewer studies have compared conventional to biodegradable plastics (including PLA, PHBV, and OXO) in terms of community composition and dynamics ( Eich et al, 2015 ; Dussud et al, 2018a ; Cheng et al, 2021 ), with different experimental conditions and microbial parameters that made more challenging comparison between these studies.…”

Biogeography rather than substrate type determines bacterial colonization dynamics of marine plastics

“…Common community members include bacteria that prefer a surface-attached lifestyle, i.e., Flavobacteriaceae ( Zheng et al, 2018 ) and Saprospiraceae ( McIlroy & Nielsen, 2014 ), opportunistic colonizers (Rhodobacteriaceae; Dang & Lovell, 2016 ), and biofilm formers (Hyphomonodaceae; Abraham & Rohde, 2014 ), which made up 11.66%, 2.64%, 8.80%, and 1.62% of the median bacterial community composition in this study, respectively. Other recurring members of proteobacterial biofilms on plastics, such as the orders Alteromonadales ( Zettler, Mincer & Amaral-Zettler, 2013 ), Oceanospirillales ( Roager & Sonnenschein, 2019 ), and Cellvibronaceae ( Oberbeckmann & Labrenz, 2020 ; Cheng et al, 2021 ) represented 2.20%, 2.67%, and 0.60% of the median relative community structure, respectively. Micavibrionaceae (0.54%) was recently described as a PA-specific community member ( Di Pippo et al., 2020 ), while Miao et al (2019) associated Cyclobacteriaceae (2.51%) with PE and PP.…”

Microbial biofilm composition and polymer degradation of compostable and non-compostable plastics immersed in the marine environment

“…In our study, no genus is specific of a polymer. As it was showed in other studies, the plastic serves as an attachment surface for the bacteria in biofilms with no specific selection for their degradation capabilities (Pinto et al, 2019;Oberbeckmann et al, 2016;Cheng et al, 2020). Concerning the PLA, previous study showed that no evidence of bacterial degradation was observed in seawater after 10 weeks (Karamanlioglu et al, 2017).…”