Author(s): Chai Beibei; Zhuo Tianyu; Li Yumei; Yu Kehong; Chen Bin

Linked Author(s):

Keywords: Microplastics; Metagenomics; Microbial community structure; Functional genes; Freshwater environment; Elemental cycling

Abstract: Microplastics (MPs) are recalcitrant to degradation in the environment, causing combined and persistent organic pollution. Aquatic ecosystems are being increasingly polluted by microplastics (MPs), which calls for an understanding of how MPs affect microbially driven biogenic element cycling in water environments. However, the effects of various MPs on microbially driven biogenic element cycling in water environments have been insufficiently investigated at the gene level. In the present study, natural water samples were collected from a freshwater lake in northern China and incubated with three popular types of MPs in a simulated experimental device. The following questions were raised and solved based on metagenomics: (1) How did various MPs affect microbial species abundance, community composition, and potential function in carbon, nitrogen, phosphorus, and sulfur cycling? (2) Which MP type had the greatest effect on microbial community structure and specific functions in biogenic element transformation? (3) What effects could various MPs have on microbially driven biogenic element cycling at the functional gene level? A 28-day incubation experiment was conducted using freshwater lake water added with three polymer types of MPs (i. e., polyethylene, polypropylene, polystyrene) separately or in combination at a concentration of 1 items/m3. Metagenome DNA extraction and shotgun sequencing (metagenomics) were used to study the effects of various MPs on microbial communities and functional genes related to carbon, nitrogen, phosphorus, and sulfur cycling. Results showed that Sphingomonas and Novosphingobium, which were indicator taxa (genus level) in the polyethylene treatment group, made the largest functional contribution to biogenic element cycling. Following the addition of MPs, the relative abundances of genes related to methane oxidation (e. g., hdrD, frhB, accAB) and denitrification (napABC, nirK, norB) increased. These changes were accompanied by increased relative abundances of genes involved in organic phosphorus mineralization (e. g., phoAD) and sulfate reduction (cysHIJ), as well as decreased relative abundances of genes involved in phosphate transport (phnCDE) and the SOX system. Findings of this study underscore that MPs, especially polyethylene, increase the risk of greenhouse gas emissions (CO2, N2O) and water pollution (PO43–, H2S) in freshwater lakes at the functional gene level.

DOI: https://doi.org/10.3850/iahr-hic2483430201-50

Year: 2024