Microbial pioneers of plastic colonisation in coastal seawaters

Plastics, when entering the environment, are immediately colonised by microorganisms. This modifies their physico-chemical properties as well as their transport and fate in natural ecosystems, but whom pioneers this colonisation in marine ecosystems? Previous studies have focused on microbial communities that develop on plastics after relatively long incubation periods (i.e., days to months), but very little data is available regarding the earliest stages of colonisation on buoyant plastics in marine waters (i.e., minutes or hours). We conducted a preliminary study where the earliest hours of microbial colonisation on buoyant plastics in marine coastal waters were investigated by field incubations and amplicon sequencing of the prokaryotic and eukaryotic communities. Our results show that members of the Bacteroidetes group pioneer microbial attachment to plastics but, over time, their presence is masked by other groups - Gammaproteobacteria at first and later by Alphaproteobacteria. Interestingly, the eukaryotic community on plastics exposed to sunlight became dominated by phototrophic organisms from the phylum Ochrophyta, diatoms at the start and brown algae towards the end of the three-day incubations. This study defines the pioneering microbial community that colonises plastics immediately when entering coastal marine environments and that may set the seeding Plastisphere of plastics in the oceans. [Abstract copyright: Copyright © 2022 The Authors. Published by Elsevier Ltd.. All rights reserved.

Pili allow dominant marine cyanobacteria to avoid sinking and evade predation

How oligotrophic marine cyanobacteria position themselves in the water column is currently unknown. The current paradigm is that these organisms avoid sinking due to their reduced size and passive drift within currents. Here, we show that one in four picocyanobacteria encode a type IV pilus which allows these organisms to increase drag and remain suspended at optimal positions in the water column, as well as evade predation by grazers. The evolution of this sophisticated floatation mechanism in these purely planktonic streamlined microorganisms has important implications for our current understanding of microbial distribution in the oceans and predator–prey interactions which ultimately will need incorporating into future models of marine carbon flux dynamics

Marine Plastic Debris: A New Surface for Microbial Colonization

Plastics become rapidly colonized by microbes when released into marine environments. This microbial community-the Plastisphere-has recently sparked a multitude of scientific inquiries and generated a breadth of knowledge, which we bring together in this review. Besides providing a better understanding of community composition and biofilm development in marine ecosystems, we critically discuss current research on plastic biodegradation and the identification of potentially pathogenic "hitchhikers" in the Plastisphere. The Plastisphere is at the interface between the plastic and its surrounding milieu, and thus drives every interaction that this synthetic material has with its environment, from ecotoxicity and new links in marine food webs to the fate of the plastics in the water column. We conclude that research so far has not shown Plastisphere communities to starkly differ from microbial communities on other inert surfaces, which is particularly true for mature biofilm assemblages. Furthermore, despite progress that has been made in this field, we recognize that it is time to take research on plastic-Plastisphere-environment interactions a step further by identifying present gaps in our knowledge and offering our perspective on key aspects to be addressed by future studies: (I) better physical characterization of marine biofilms, (II) inclusion of relevant controls, (III) study of different successional stages, (IV) use of environmentally relevant concentrations of biofouled microplastics, and (V) prioritization of gaining a mechanistic and functional understanding of Plastisphere communities

Marine Plastic Debris: A New Surface for Microbial Colonization

Plastics become rapidly colonized by microbes when released into marine environments. This microbial community—the Plastisphere—has recently sparked a multitude of scientific inquiries and generated a breadth of knowledge, which we bring together in this review. Besides providing a better understanding of community composition and biofilm development in marine ecosystems, we critically discuss current research on plastic biodegradation and the identification of potentially pathogenic “hitchhikers” in the Plastisphere. The Plastisphere is at the interface between the plastic and its surrounding milieu, and thus drives every interaction that this synthetic material has with its environment, from ecotoxicity and new links in marine food webs to the fate of the plastics in the water column. We conclude that research so far has not shown Plastisphere communities to starkly differ from microbial communities on other inert surfaces, which is particularly true for mature biofilm assemblages. Furthermore, despite progress that has been made in this field, we recognize that it is time to take research on plastic–Plastisphere–environment interactions a step further by identifying present gaps in our knowledge and offering our perspective on key aspects to be addressed by future studies: (I) better physical characterization of marine biofilms, (II) inclusion of relevant controls, (III) study of different successional stages, (IV) use of environmentally relevant concentrations of biofouled microplastics, and (V) prioritization of gaining a mechanistic and functional understanding of Plastisphere communities.R.J.W. was supported by an MIBTP PhD scholarship (BB/M01116X/1) and Waitrose & Partners as part of the Association of Commonwealth Universities Blue Charter Programme. G.E.-C. was supported by a NERC CENTA PhD scholarship. V.Z. was supported by CONICYT-BECAS CHILE/Doctorado Becas Chile en el Extranjero, Folio 72160583 and NERC research project NE/S005501/1. M.L. was supported by an MIBTP PhD scholarship (BB/M01116X/1). J.C.-O. was supported by the NERC Independent Research Fellowship NE/K009044/1, Ramón y Cajal contract RYC-2017-22452 (funded by the Ministry of Science, Innovation and Universities, the National Agency of Research, and the European Social Fund) and MINECO project PID2019-109509RB-I00 (FEDER cofunding)

Carbon dioxide and methane exchange of a perennial grassland on a boreal mineral soil

Cultivation of perennial crops can be an option to sequester carbon in agricultural soils. To determine the carbon budget of a perennial cropping system under the boreal climate, we studied carbon dioxide (CO2) and methane (CH4) exchange of timothy and meadow fescue mixture (TIM) on a boreal mineral soil. Based on the mean annual net ecosystem CO2 exchange (NEE), TIM was a sink for both CO2 (–1000 g CO2 m–2) and CH4 (–140 mg CH4 m–2). In comparison, soil without vegetation (BARE) was a source of CO2 (1300 g CO2 m–2). Based on the literature review, the net CO2 uptake of TIM was similar to the perennial cropping systems in northern Finland but higher than that of the annual cropping systems in this region. Our multi-year study shows that the perennial cultivation system based on TIM is an environmentally sustainable land-use option to mitigate agricultural CO2 emissions in regions with short growing seasons.202