Mangrove ecosystems as natural barriers against waterborne pathogens: A case study from Shenzhen, China

This study investigates the capacity of mangroves in Shenzhen, a highly urbanized and polluted coastal area of China, to remove pathogenic bacteria and their virulence factors (VFs). Using high-throughput sequencing, qPCR, and culturing methods, we assessed pathogen and VF removal across a subtropical mangrove ecosystem. Results show that mangroves significantly reduced the abundance of key pathogens: Escherichia coli (up to 99.89 %), Salmonella spp. (93.40 %), Vibrio spp. (56.03 %), and Enterococcus spp. (97.04 %). Concurrently, the number of detected VFs decreased by 26.8 %, and total VF gene abundance declined by 36.8 % in long-term settings. Removal efficiency improved with longer water retention time, indicating a time-dependent purification effect. Critically, this removal was independent of nutrient variations (e.g., NO₃^-, NH₄⁺), suggesting primary mechanisms such as particulate trapping and antibacterial phytochemicals. This study uniquely integrates VF abundance to assess functional health risks posed by microbial communities, providing new insights into mangroves' capacity to mitigate not only pathogen abundance but also disease-causing potential. Shenzhen serves as a critical case study due to its high levels of anthropogenic pressure, demonstrating the scalability and effectiveness in reducing health risks of mangroves in polluted coastal regions. By addressing key knowledge gaps in pathogen removal mechanisms and dynamics, these findings emphasize the importance of mangrove conservation and restoration as a nature-based solution to enhance water quality and public health, which may in turn contribute to reducing potential public health risks in polluted coastal regions.