Analysis of bacterial biodiversity and ecological risk evaluation of organophosphorus in Lianhuan Lake

PLOS One | https://doi.org/10.1371/journal.pone.0332712 September 26, 2025 2 / 20 use of pesticides and fertilizers has increased, alongside the growing discharge of residential sewage, resulting in significant water pollution [3]. Eutrophication of lakes has become a major global environmental issue [4]. Extensive research has been conducted on this topic. For example, Zhu et al. examined the water quality and phytoplankton dynamics in Chaohu Lake, finding it to be moderately eutrophic [5]. Similarly, Suresh et al. highlighted that eutrophication is characterized by elevated nitrogen (N) and phosphorus (P) levels in water bodies, which promote the growth of harmful algae and phytoplankton biomass [6]. Zhou et al. demonstrated that biolog- ical treatment is a widely adopted method for mitigating eutrophication [7]. Recent years have seen some improvement in the management of lake eutrophication. Lianhuan Lake, located in Dulbert Mongolian Autonomous County, Daqing City, Heilongjiang Province, China, is a large shallow lake situated on the Songnen Plain. The lake consists of 18 smaller bodies of water, including Habuta Pao, Talahong Pao, Xihulu Pao, Hongyuan Pao, and East Lake, covering a total area of over 840 square kilometers. Each year, Lianhuan Lake receives 120 million cubic meters of water from the Nenjiang River. It serves as a crucial water source for towns, agriculture, fish- eries, and wetland ecosystems in Daqing City. Despite its significance, research on the biodiversity and ecological security of Lianhuan Lake has been limited in recent years.

To gain a comprehensive understanding of the biological condition of lakes and provide a scientific foundation for their management and conservation, various assessment methodologies, such as the WQI and the TLI, have been employed [8]. WQI is a metric used to assess the overall water quality by evaluating specific water quality parameters [9], and it is a common tool for analyzing pollution levels and identifying patterns in water quality [10]. El-Serehy et al. review notes that the WQI “reduces big amounts of data to a single number in a simple reproducible manner,” making it useful to managers and policymakers [11]. However, it is important to note that there is no universally accepted method for calculating the WQI [12]. Each index has its own advantages and limitations, which may constrain its applicability and ease of use. To enhance the assessment of water contamination risks in Lianhuan Lake, we applied the innovative IWQI (Improved Water Quality Index) methodol- ogy [13]. Fu et al. proposed an improved IWQI that considers both lower and upper thresholds for water quality parameters, which was applied to the assessment of the Tuojiang River Basin in Sichuan Province [14]. TLI is used to assess the trophic sta- tus of lakes and predict future trends under environmental changes [15]. Biodiversity analysis typically relies on high-throughput sequencing techniques, which offer rapid detection and high precision [16]. For example, Buccheri et al. used high-throughput sequencing of 16S and 18S rRNA genes to investigate the Mediterranean tourist site

of Aci Castello [17]. Zhao et al. highlighted that high-throughput sequencing enables swift and precise identification of harmful microorganisms in aquatic systems, over- coming the challenges posed by complex environmental samples and low concen- trations [18]. High-throughput sequencing is increasingly used to identify intricate community structures and biodiversity [19,20]. Water Resources and Water Environment grant numbers ES202217 and Basic Research Business Fees for Provincial Higher Education Institutions in Heilongjiang Province grant numbers 2023-KYYWF-1495. The funders had no role in the study design, data collection, analysis, decision to publish, or manuscript preparation. Competing interests: The authors have declared that no competing interests exist.