Microbial methanogenesis in sediment plays a crucial role in CH₄ emission from freshwater lake ecosystems. However, knowledge of the layer-depth-related changes of methanogen community structure and activities in freshwater lake sediment is still limited. The present study was conducted to characterize the methanogenesis potential in different sediment-layer depths and the vertical distribution of microbial communities in two freshwater lakes of different trophic status on the Yunnan Plateau (China). Incubation experiments and inhibitor studies were carried out to determine the methanogenesis potential and pathways. 16S rRNA and mcrA genes were used to investigate the abundance and structure of methanogen and archaeal communities, respectively. Hydrogenotrophic methanogenesis was mainly responsible for methane production in sediments of both freshwater lakes. The layer-depth-related changes of methanogenesis potential and the abundance and community structure of methanogens were observed in both Dianchi Lake and Erhai Lake. Archaeal 16S rRNA and mcrA genes displayed a similar abundance change pattern in both lakes, and the relative abundance of methanogens decreased with increasing sediment-layer depth. Archaeal communities differed considerably in Dianchi Lake and Erhai Lake, but methanogen communities showed a slight difference between these two lakes. However, methanogen communities illustrated a remarkable layer-depth-related change. Order Methanomicrobiales was the dominant methanogen group in all sediments, while Methanobacteriales showed a high proportion only in upper layer sediments. The trophic status of the lake might have a notable influence on the depth-related change pattern of methanogenesis activity, while the methanogen community structure was mainly influenced by sediment depth.

Effective monitoring for stream habitat health is essential for sustainable restoration and management to conserve ecosystem services. Traditional in situ surveying with multi-metric indices is widely used by state and federal agencies but is often labor-intensive and spatially limited. To address these challenges, this study introduces a suite of cost-effective drone-based monitoring toolkits that integrate automated flight-route design, Structure-from-Motion (SfM) image reconstruction, and multi-metric index (MMI) computation. The toolkits form an end-to-end workflow for quantitative habitat evaluation, enabling centimeter-scale mapping and standardized MMI scoring based on Wisconsin DNR and EPA guidelines. The toolkits were examined at Black Earth Creek, Wisconsin, where high- and low-elevation drone images were collected and processed to generate high-resolution (< 1 cm) ortho-photos and terrain maps. The reconstructed terrain achieved horizontal and vertical accuracies of 0.04 m and 0.17 m, respectively, and the UAV-derived MMI results showed strong agreement with field measurements. The entire process—from flight planning to assessment—can be completed by one operator within three hours using an off-the-shelf drone (< USD 1000) and standard photogrammetry software. Beyond improving efficiency, the integrated toolkits provide spatially continuous, repeatable assessments that capture habitat variability and degradation hotspots often missed by conventional transect-based methods. By significantly reducing labor and costs associated with data collection, processing, and assessment, these UAV-based toolkits offer a cost-effective, scalable, and reproducible solution for routine stream habitat monitoring and long-term conservation planning.

Pollution remains a major global challenge, impacting air, water, and soil while posing risks to human health and ecosystems. This study aims to provide a comprehensive overview of global pollution research through a large-scale bibliometric analysis. Using 735,138 publications indexed in the Web of Science Core Collection from 1990 to 2024, we examined four key aspects: (1) overall research trends, (2) geographical distribution of studies, (3) topic patterns across environmental media, pollution problems, pollutant sources, and pollution mitigation strategies, and (4) current research gaps and policy-relevant recommendations. Results reveal a rapid rise in pollution research, with strong collaboration among developed countries and between developed and emerging economies. However, notable disparities persist: low-income regions remain underrepresented, and cross-media interactions—especially between air and other systems—are insufficiently explored. Sentiment analysis shows topic- and region-specific variation and suggests increasing concern over emerging issues such as microplastics. Additionally, scientific and technological solutions dominate pollution research, while economic policies and education receive far less attention—an imbalance that should be addressed to better translate research into practical solutions. Addressing these gaps requires interdisciplinary research, equitable global collaboration, and broader integration of social and behavioral dimensions into pollution mitigation strategies.