Investigating the composition and distribution of microplastics surface biofilms in coral areas

In recent years, global climate change and pollution of the marine environment have caused large-scale coral deaths and severe damages to coral reef ecosystems. Numerous studies have shown that coral diseases are closely related to microorganisms. And microplastics (MPs) are a potential threat to corals. In marine ecosystems, MPs are an emerging contaminant. MPs have a strong adsorption effect on pollutants in the water environment, and they are very easily colonized by microorganisms to form biofilms. Biofilms may accumulate many pathogens, increasing the probability of coral disease. However, there is no report about the composition of biofilms on the surface of microplastics in coral growth areas. In this study, nine kinds of MPs were chosen in the experiments, which are commonly found in the ocean. Four stakeout points were selected in the coral area. Biofilms were cultivated in natural environment. The composition and distribution of biofilms on the surface of the MPs were analyzed by 16 S rRNA sequencing. The characteristics of biofilms were observed by scanning electron microscopy (SEM). The experimental results show that the species composition and abundance distribution of the biofilm on the MP surface are significantly different from the surrounding seawater. The type of MPs and the stake out point are important factors affecting the structure of the biofilm bacterial community. Compared to seawater samples, MPs are enriched with certain dominant bacteria such as Vibrionaceae, Rhodobacteraceae, Flavobacteraceae, Microtrichaceae and Sphingomonadaceae. Among them, Vibrionaceae, Rhodobacteraceae and Flavobacteraceae are closely related to the tissue damage of stony corals, and Vibrios are also the main pathogens of coral albinism. In addition, Pseudomonas and Bbellvibrio cholerae are also detected on the MPs biofilm. SEM graphs of the MPs after culture could clearly observe rod-shaped bacteria and Streptococci. This study can provide a new direction for the study of coral toxicology by MPs and provide basic data for the toxicology research of MPs.