Characterization of microbial community, ecological functions and antibiotic resistance in estuarine plastisphere.

The plastisphere is a new ecological niche. Compared to the surrounding water, microbial community composition associated with the plastisphere is known to differ with functional consequences. Here, this study characterized the bacterial and fungal communities associated with four types of plastisphere (polyethylene, polystyrene, polypropylene and polyvinyl chloride) in an estuarine habitat; assessed ecological functions including carbon, nitrogen, phosphorus and sulfur cycling, and determined the presence of antibiotic resistance genes (ARGs) and human pathogens. Stochastic processes dominated the community assembly of microorganisms on the plastisphere. Several functional genera related to nutrient cycling were enriched in the plastisphere. Compared to surrounding water and other plastisphere, the abundances of carbon, nitrogen and phosphorus cycling genes (cdaR, nosZ and chpy etc.) and ARGs (aadA2-1, cfa and catB8 etc.) were significantly increased in polyvinyl chloride plastisphere. In contrast, the polystyrene plastisphere was the preferred substrate for several pathogens being enriched with for example, Giardia lamblia 18S rRNA, Klebsiella pneumoniae phoE and Legionella spp. 23S rRNA. Overall, this study showed that different plastisphere had different effects on ecological functions and health risk in estuaries and emphasizes the importance of controlling plastic pollution in estuaries. Data from this study support global policy drivers that seek to reduce plastic pollution and offer insights into ecological functions in a new ecological niche of the Anthropocene.

Long-term effects of chlorothalonil on microbial denitrification and N2O emission in a tea field soil.

Pesticide chlorothalonil is widely applied in tea agroecosystem, potentially disturbing soil microbial-mediated nitrogen cycle. The underlying toxicity mechanism, however, is not well explored. Here, we investigated the long-term effects of chlorothalonil on soil microbial denitrification and N2O emission pattern in a tea field after 40 days of exposure. Results showed that chlorothalonil inhibited denitrification process but remarkably promoted N2O emission by 380-830%. Chlorothalonil significantly inhibited N2O reductase activity but did not affected nosZ abundance. Our results further revealed that chlorothalonil influenced soil denitrification by directly suppressing microbial electron transport system activity, and decreasing electron donor nicotinamide adenine dinucleotide (NADH) and energy source adenosine triphosphate (ATP) levels. Additionally, chlorothalonil also downregulated denitrifying functional genes (narG, nirS, and norB) and declined the relative abundances of potential denitrifiers (i.e., Pseudomonas and Streptomyces). Stepwise regression and path modeling suggested that nitrate reductase was the most significant factor in explaining denitrification rate under chlorothalonil applications. This study provides important information for revealing the chronic impacts of pesticide on tea soil denitrification and N2O emission on the basis of electron transport mechanism. Most significantly, N2O emission is underestimated in chlorothalonil-treated soils, which suggests that future estimations of N2O emission from agricultural lands should take account of pesticide dependency conditions.

Thermal Structure-Induced Biochemical Parameters Stratification in a Subtropical Dam Reservoir.

Although stratification in deep lakes is well-discussed, few studies pay attention to thermal structure as well as its influences on stratification of biochemical parameters in subtropical lakes in mountainous cities. Here, we studied the depth profile of temperature and biochemical parameters in Longjing Lake, a subtropical reservoir in a mountainous city. Thermal stratification became strong during summer. Biochemical parameters were strongly associated with thermal structure. Stratification started at 2~6 m depth with a substantial decrease in dissolved oxygen, biochemical oxygen demand (BOD5), chlorophyll a, and pH, corresponding to an increase in total nitrogen, ammonium (), nitrite (), total inorganic nitrogen (TIN), total phosphorus, and soluble reactive phosphorus (SRP) with depth; the majority of biochemical parameters showed slight variations from 12 m downward. Our results indicated the stratification of Longjing Lake was stronger and more stable than the stratification of tropical and temperate lakes in lowland cities.