Occurrence and Influencing Factors of Antibiotics and Antibiotic Resistance Genes in Sediments of the Largest Multi-habitat Lakes in Northern China

Baiyangdian Lake is a typical and largest multi-habitat lake in the North plain of China. To understand the generation and transmission of antibiotics resistance genes (ARGs) in multi-habitat lakes, the contents of nutrients (TC, TOC, TN, TP and TS), heavy metals (Zn, Cr, Ni, Cu, Pb, As, Cd and Hg), 22 antibiotics, 16S-rRNA(16S), Class I integron (intI1) and 20 ARGs were determined. Samples were taken from the Fuhe river, river estuaries, reed marshes, living area, fish poods and open water of Baiyangdian Lake. The results showed that quinolones (QNs) were the main pollutants, and the content range was ND-104.94 ng/g. Thereinto, aac (6') -IB, blaTEM-1, ermF, qnrA, qnrD, tetG, sul1, sul2 and tetM were detected in 100%. The absolute abundance of sul1 was the highest (5.25×105copies/g-6.21×107 copies/g), which was the dominant ARGs. In these different habitats, the abundance of antibiotics and ARGs in river estuary was the highest, and that in reed marshes was the lowest. There was a significant positive correlation between the abundance of heavy metals (Cu, Pb, Zn, Ni, Cd, Hg) and the absolute abundance of 11 ARGs (P<0.01). Redundancy analysis showed that Cu, Zn, intI1, TP and macrolides (MLs) were the important factors affecting the distribution of ARGs. Our findings provides a more likely driving and influencing factor for the transmission of ARGs in lakes with complex and diverse habitats.

Jeotgalibacillus Auranticolor sp. nov., Isolated from Freshwater Collected from Baiyangdian Lake Lake, China

A novel Gram-positive, strictly aerobic, rod-shaped, orange-pigmented bacterial strain, designated R-1-5s-1T, was isolated from Baiyangdian Lake, China. Strain R-1-5s-1T grew at 15-37℃ (optimum 37℃) and pH 7-11 (optimum pH 8) in Luria-Bertani medium. Based on 16S rRNA gene sequence analysis, strain R-1-5s-1T was assigned to the genus Jeotgalibacillus and showed the closest relationships with Jeotgalibacillus salarius ASL-1T (97.69%), Jeotgalibacillus alkaliphilus JC303T (97.29%), Jeotgalibacillus marinus DSM 1297T (97.15%), Jeotgalibacillus campisalis SF-57T (97.01%), and Jeotgalibacillus spp. (≤ 97%). The predominant polar lipids were phosphatidylglycerol and diphosphatidylglycerol; the major cellular fatty acids were iso-C15:0, anteiso-C15:0, iso-C17:0, and anteiso-C17:0; and the major respiratory quinones were MK-7 and MK-8. The peptidoglycan type of the cell wall was A1a linked via L-lysine as the diamino acid. The G+C content was 43.6%, and the draft genome size of strain R-1-5s-1T was 3.4 Mbp. Between strain R-1-5s-1T and the related strain J. salarius ASL-1T, the ANI and dDDH relatedness values were 78.9% and 20.8%, respectively. Phylogenetic, chemotaxonomic, and genotypic analyses revealed that strain R-1-5s-1T is a novel species in the genus Jeotgalibacillus, for which the name Jeotgalibacillus auranticolor sp. nov. is proposed. The type strain is R-1-5s-1T (=CGMCC 1.13567T=KCTC 43038T).

Abundance and distribution of microplastics in water and sediment of Baiyangdian Lake, Northern China

Microplastics (MPs) have been found in all environment matrices and have become an issue of concern worldwide. In this study, Baiyangdian Lake in Northern China was investigated for the presence of MPs (0.45 µm–5 mm) in sediment and at different water depths. MPs were found at 1,000–20,000 pieces/m3 (average 9,595) in water and at 400–2,200 pieces/kg (average 1,023) in sediment. Since the implementation of pollution abatement measures, visible MPs have been nearly eliminated; the MPs found in this study were mainly in the micrometer range, with no more than 3–5 pieces greater than 1 mm per sample. The main forms of MPs were fibrous and fragmented, and the main components were polyamide, polyethylene, and polypropylene. MPs found in water near a garbage transfer station showed the following abundance of MPs: surface water < middle water < bottom water. The sediment contained a higher amount of MP fragments, indicating that the historical transfer and disposal of garbage was a main source of plastic deposition in this area. There was a high content of fibrous MPs in surface water, while the abundance of fragmented MPs increased with the depth of water. The main sources of MPs in the study area were residential activities, local plastic factories, and the treated effluent from a sewage treatment plant.

Community Structure and Function of Epiphytic Bacteria Associated With Myriophyllum spicatum in Baiyangdian Lake, China

Epiphytic bacteria on the surfaces of submerged macrophytes play important roles in the growth of the host plant, nutrient cycling, and the conversion of pollutants in aquatic systems. A knowledge of the epiphytic bacterial community structure could help us to understand these roles. In this study, the abundance, diversity, and functions of the epiphytic bacterial community of Myriophyllum spicatum collected from Baiyangdian Lake in June, August, and October 2019 were studied using quantitative PCR (qPCR), high-throughput sequencing, and the prediction of functions. An analysis using qPCR showed that the epiphytic bacteria were the most abundant in October and the least abundant in August. High-throughput sequencing revealed that Proteobacteria, Gammaproteobacteria, and Aeromonas were the dominant phylum, class, and genus in all the samples. The common analyses of operational taxonomic units (OTUs), NMDS, and LDA showed that the epiphytic bacterial communities were clustered together based on the seasons. The results of a canonical correlation analysis (CCA) showed that the key water quality index that affected the changes of epiphytic bacterial community of M. spicatum was the total phosphorus (TP). The changes in abundance of Gammaproteobacteria negatively correlated with the TP. Predictive results from FAPROTAX showed that the predominant biogeochemical cycle functions of the epiphytic bacterial community were chemoheterotrophy, nitrate reduction, and fermentation. These results suggest that the epiphytic bacterial community of M. spicatum from Baiyangdian Lake varies substantially with the seasons and environmental conditions.

The Spatial Variations of Water Quality and Effects of Water Landscape in Baiyangdian Lake, North China

Baiyangdian Lake (BYD), a large shallow lake in North China, has complex water landscape patterns that are underlies spatial variations in water quality. In this study, we collected 61 water samples from three water landscapes (reed littoral zones, fish ponds and open water) and analyzed them for water quality parameters, such as dissolved organic carbon (DOC), total nitrogen (TN), and total phosphorus (TP). Water landscape distribution (determined using remote sensing imagery) was then used to assess correlations between water quality parameters and water landscape proportion in differently scaled buffer zones. There was substantial variation across all subareas, with TN and TP concentrations ranging from 0.90–4.10 mg/L and 0.06–0.18 mg/L, respectively. Spatial variations in water quality were mainly caused by water landscape distribution and external nutrient inputs. There were negative correlations between DOC, TN, and TP concentrations and the area proportion of reed littoral zones in the 300 and 500 m buffers. In contrast, DOC, TN and TP concentrations were significantly positively correlated with the area proportion of fish ponds in the 100 m buffer. Furthermore, compared with reed littoral zones, a lower nitrogen to phosphorus ratio and a higher proportion of dissolved organic nitrogen and tyrosine-like proteins were found in fish ponds. These effects were mainly attributed to development of internal sediment loadings due to nutrient exchange between sediment and overlying water. Therefore, dredging-based sediment removal from fish ponds should be considered to suppress internal phosphorus loading and accelerate recovery of the BYD ecosystem.

Remote Sensing-Based Analysis of Spatial and Temporal Water Colour Variations in Baiyangdian Lake after the Establishment of the Xiong’an New Area

The Forel-Ule Index (FUI) is an important parameter that can be calculated from optical remote sensing data to assess water quality based on water colour. Using Sentinel-2 images from April to November within the 2016–2020 period coupled with the Google Earth Engine Platform, we calculated FUI to analyse the spatial distribution, seasonal variations, and inter-annual variations of water colour in Baiyangdian Lake in the Xiong’an New Area established on 1 April 2017. The lake was divided into seven sub-regions, A–G; subsequently, high and low FUI values were observed in the south and north, respectively. Additionally, the mean FUI values of G and F zones in the south were 11.9 and 12.7, respectively, whereas those for the A, B, C, D, and E zones in the north were 10.5, 9.8, 10.4, 11.1, 11.2, respectively. The seasonal variations in the Baiyangdian Lake and seven sub-regions were consistent, with turbid water in spring and autumn, and clear water in summer. Inter-annual variations analyses for 2016–2020 indicated that the zone of A became progressively turbid, whereas the B, C, D, E, F, and G zones exhibited slow and gradually decreasing trends. Our findings suggest that the overall water quality of Baiyangdian Lake may be better, which may be related to the governance policies of the region.