● The maximum coliforms concentration increased by 2 Logs during rainfall. ● Culturable bacterial concentrations had a delayed increase during precipitation. ● DOC concentration was the main impact factor for the microbial characteristics. ● Culturable bacteria concentrations in waters could recover to pre-rainfall levels.
Climate change leads to an increase in both the frequency and intensity of extreme precipitation. Surface runoff generated by extreme precipitation has a significant impact on water. However, the impact of persistent precipitation on surface water quality is easy to neglect, due to its prolonged duration and lower-intensity rainfall. This study established eight sampling points within selected surface waters to observe the variation of microbial characteristics in a typical persistence precipitation event. The primary difference between Furong Lake (FL) and Chengqian Reservoir (CR) was: the concentrations of dissolved organic carbon (DOC) were 21.3 ± 0.7 and 8.3 ± 1.5 mg/L in FL and CR, respectively. The concentrations of R2A culturable bacteria and coliforms were 104.57 and 101.58 colony-forming units (CFU)/mL in FL, and were 105.46 and 102.64 CFU/mL in CR, respectively. During precipitation, the maximum increase concentrations of R2A, NA culturable bacteria, and coliforms were 100.75, 101.30, and 102.27 CFU/mL in FL, respectively. Furthermore, microbial concentration and rainfall did not increase simultaneously, and a delay phenomenon was observed in the increasing microbial concentrations. Through analyzing the concentration change trends and correlation of various water quality indicators during persistent precipitation, the significant correlation between the DOC concentration and the changes in the dominant species of microbial community structure was found in this study (p < 0.05). For example, as the DOC concentration declined, the abundance of hgcl_clade and CL500-29_marine_group increased. Consequently, although persistent precipitation might not obviously alter the water quality visibly, it could still pose potential microbial risks.
● The highest absolute abundance of ARGs in seawater reached 2.3 × 104 copies/mL. ● Multidrug resistance genes were major ARGs in seawater of many sites. ● Insertion sequences were the dominant MGEs in seawater. ● Prochlorococcus _MIT9313 and Clade_la were the predominant genus in seawater. ● Anthropogenic activities had important effect on ARGs and MGEs.
Antibiotic resistance genes (ARGs) might have great effect on ecological security and human health. Oceans are important reservoirs that receive tremendous amounts of pollutants globally. However, information on the proliferation of ARGs in seawater is still limited. This study performed field sampling to investigate the occurrence and distribution of ARGs in seawater of the South China Sea, which is the deepest and largest sea in China. The results showed that the total absolute abundances of ARGs in seawater samples ranged from 2.1 × 103 to 2.3 × 104 copies/mL, with an of 5.0 × 103 copies/mL and a range of 2.2 × 103–1.8 × 104 copies/mL for those with mobile genetic elements (MGEs). Genes resistant to multidrug, aminoglycoside, tetracycline, and fluoroquinolone antibiotics accounted for 77.3%–88.6% of total ARGs in seawater. Proteobacteria and Cyanobacteria represented 32.1%–56.2% and 30.4%–49.5% of microbial community, respectively. Prochlorococcus_MIT9313 and Clade_la were the prevalent genera in seawater of the South China Sea. Complex co-occurrence relationship existed among ARGs, MGEs, and bacteria. Anthropogenic activities had critical influence on ARGs and MGEs. Hospital wastewater, wastewater treatment plant effluent, sewage, aquaculture tailwater, and runoff were determined as the important sources of ARGs in seawater of the South China Sea based on positive matrix factorization analysis.
● A continuous wastewater-based monitoring of SARS-CoV-2 was conducted. ● Positive correlation between RNA concentrations and reported cases was observed. ● Similar genetic diversity patterns in wastewater and patient source were observed. ● Wastewater-based surveillance aided the early warning of the COVID-19 pandemic. ● Wastewater-based surveillance in the post-pandemic era was evaluated.
Wastewater-based surveillance serves as a supplementary approach to clinical surveillance of COVID-19 during the epidemic. This study aimed to track the prevalence of the disease and the viral genetic variability through wastewater-based surveillance in the post-epidemic era. Between January to December 2023, samples were collected from the influent lines of two wastewater treatment plants (WWTPs), concentrated using PEG8000, and subjected to detection of the target genes ORF 1ab and N of SARS-CoV-2 via reverse transcriptional quantitative PCR (RT-qPCR). For next-generation sequencing (NGS), high-quality samples from both wastewater and clinical patients were selected. Weekly analysis were performed using R software to evaluate the correlation between the SARS-CoV-2 RNA concentrations in wastewater and positive rate of reported cases, indicating a positive correlation. Genetic diversity patterns of SARS-CoV-2 in wastewater resembled those in the patient source based on Principal Coordinates Analysis (PCoA) with three clusters for different stages. The rise of RNA concentration in wastewater indicates the growth of cases and the emergence of new variants, serving as an early warning of potential viral mutations, disease outbreaks even possible epidemics. Furthermore, the genomic surveillance of wastewater could help identify new variants that may not be captured through population monitoring, especially when sample sizes are insufficient. Consequently, surveillance of SARS-CoV-2 in municipal wastewater has emerged as a reliable, early-warning monitoring system for COVID-19 in the post-epidemic era.