Contribution of stochastic processes to the microbial community assembly on field‐collected microplastics

Abstract

Summary A growing body of evidence suggests that microplastics may be colonized with a unique microbiome, termed ‘plastisphere’, in aquatic environments. However, the deep mechanisms (deterministic and/or stochastic processes) underlying the community assembly on microplastics are still poorly understood. Here, we took the estuary of Hangzhou Bay (Zhejiang, China) as an example and examined the assembly mechanisms of bacterial communities in water and microplastic samples. Results from high‐throughput sequencing showed that Proteobacteria, Firmicutes, and Actinobacteria were the dominant phyla across all samples. Additionally, microorganisms from plastisphere and planktonic communities exhibited contrasting taxonomic compositions, with greater within‐group variation for microplastic samples. The null model analysis indicated the plastisphere bacterial communities were dominantly driven by the stochastic process of drift (58.34%) and dispersal limitation (23.41%). The normalized stochasticity ratio (NST) also showed that the community assembly on microplastics was more stochastic (NST > 50%). Based on the Sloan neutral community model, the migration rate for plastisphere communities (0.015) was significantly lower than that for planktonic communities (0.936), potentially suggesting that it is the stochastic balance between loss and gain of bacteria (e.g., stochastic births and deaths) critically shaping the community assembly on microplastics and generating the specific niches. This study greatly enhanced our understanding of the ecological patterns of microplastic‐associated microbial communities in aquatic environments.

The Succession of Bacterial Community Attached on Biodegradable Plastic Mulches During the Degradation in Soil

“…To date, studies have explored the dynamics of microbial communities inherited from conventional non-degradable plastics in aqueous environments by means of null modeling-based or neutral theory-based approaches. Most studies demonstrated the dominant role of stochastic processes in plastisphere microbiota ( Sun et al, 2021 ; Zhang et al, 2021 ; Zhu et al, 2021 ), and a few suggested a higher influence of deterministic ecological processes ( Hou et al, 2021 ; Li et al, 2021a ). None of previous studies presented the microbial assembly of BDMs in soils.…”

“…A smaller selective role may imply that the plastisphere microbial community was more resistant to changes in plastic components and environmental factors. Many previous studies have found that properties of plastics and environmental factors largely affected the composition and assembly mechanism of microbial communities ( Li et al, 2021a ; Sun et al, 2021 ). One of the possible explanations for the lower selection observed in our study is that the samples were only collected in our potted soils.…”

“…The scale of sampling may influence the importance of stochastic and deterministic processes in shaping microbial communities ( Chase, 2014 ; Zhou and Ning, 2017 ). It was reported that narrow scales tended to maintain a lower level of environmental heterogeneity, which may reduce the impact of selection and increase the role of stochastic processes ( Garzon-Lopez et al, 2014 ; Wang et al, 2020b ; Sun et al, 2021 ). These studies corroborated with our findings on BDMs.…”

“…Thereafter, the selection stress on PE mulch consistently increased over time ( Figure 5 ). This was possibly attributed to the microbial preferential colonization and selection effects that emerged in PE as a non-degradable stable plastic, resulting in enhanced selection ( Wang et al, 2020a ; Li et al, 2021a ; Sun et al, 2021 ). In contrast, with the continuous degradation and fragmentation of BDMs over time, the trend of the microbial survival space (colonized area provided by the substrate) and proportion of selection process were consistently decreasing ( Sander, 2019 ; Sintim et al, 2020 ).…”

“…However, the true degradation rate and state of different types of BDMs debris in soil after harvest and their potential ecological risk in comparison with classic plastic mulches have always been controversial ( Sintim and Flury, 2017 ; Bandopadhyay et al, 2018 ; Sridharan et al, 2021 ). Meanwhile, it has always been a key issue of concern that microorganisms preferentially adhered to the debris surface may affect the assembly processes of biofilms and lead to a series of ecological heterogeneity ( Hou et al, 2021 ; Sun et al, 2021 ).…”