Microplastics Stress Alters Microorganism Community Structure and Reduces the Production of Biogenic Dimethylated Sulfur Compounds

Dimethylsulfoniopropionate (DMSP) is a plentiful organic sulfur metabolite and the primary precursor for dimethyl sulfide (DMS), which plays a crucial role in global sulfur cycling, the formation of clouds, and cooling the warming earth. The origin and fate of DMSP are intricately linked to marine microorganisms, making the variation of the microorganism community crucial for DMSP dynamics. Nonetheless, the impact of pervasive marine microplastics on microorganisms and processes related to DMSP synthesis and degradation remains insufficiently investigated. To bridge this gap, the present study aimed to investigate the influences of microplastic pollution on microorganic community structure and the synthesis and degradation of DMS and DMSP. A 14-day deck-based microcosm experiment was conducted, revealing that exposure to microplastics led to significant alterations in the diversity and structure of microorganism communities and had detrimental effects on the productions of DMS and DMSP. Furthermore, multivariate analysis indicated that variations both in environmental variables, such as Si, Chl-a, and microorganism communities caused by microplastics were forcing factors influencing the synthesis and degradation of DMS and DMSP. Additionally, the predicted function of the bacterial community showed a significant reduction in the presence of dddP and dmdA genes when exposed to microplastics, which directly disrupted both the demethylation and cleavage pathways of DMSP. These results indicate that the release of DMS and DMSP in marine ecosystems can be significantly affected by microplastics through influencing microorganisms. Under the influence of environmental pollution, the sea-air exchange flux of DMS in coastal areas may undergo substantial modifications, consequently impacting regional and even global climate patterns. Thus, it is imperative to conduct research on controlling the synthesis and degradation of DMSP in the ocean, particularly in response to these environmental pollution issues. Such research can help discern new patterns from specific phenomena and identify crucial processes.