This comprehensive review explores the escalating challenge of nutrient enrichment in aquatic ecosystems, spotlighting the dire ecological threats posed by harmful algal blooms (HABs) and excessive particulate organic matter (POM). Investigating recent advancements in water treatment technologies and management strategies, the study emphasizes the critical need for a multifaceted approach that incorporates physical, chemical, and biological methods to effectively address these issues. By conducting detailed comparative analyses across diverse aquatic environments, it highlights the complexities of mitigating HABs and underscores the importance of environment-specific strategies. The paper advocates for sustainable, innovative solutions and international cooperation to enhance global water quality and ecosystem health. It calls for ongoing advancement, regular monitoring, and comprehensive research to adapt to emerging challenges, thus ensuring the preservation of aquatic biodiversity and the protection of communities reliant on these vital resources. The necessity of integrating technological innovation, ecological understanding, and global cooperation to safeguard aquatic ecosystems for future generations is paramount.

Freshwater ecosystems face escalating degradation, demanding real-time, scalable, and biodiversity-aware monitoring solutions. This review proposes an integrated framework combining artificial intelligence (AI), geographic information systems (GISs), and environmental DNA (eDNA) to overcome these limitations and support next-generation river health assessment. The AI-GIS-eDNA system was applied to four representative river basins—the Mississippi, Amazon, Yangtze, and Danube—demonstrating enhanced predictive accuracy (up to 94%), spatial pollution mapping precision (85–95%), and species detection sensitivity (+18–30%) compared to conventional methods. Furthermore, the framework reduces operational costs by up to 40%, highlighting its potential for cost-effective deployment in low-resource regions. Despite its strengths, challenges persist in the areas of regulatory acceptance, data standardization, and digital infrastructure. We recommend legal recognition of AI and eDNA indicators, investment in explainable AI (XAI), and global data harmonization initiatives. The integrated AI-GIS-eDNA framework offers a scalable and policy-relevant tool for adaptive freshwater governance in the Anthropocene.

This study investigates the ecological effects of weirs on water quality and phytoplankton communities in the South Han River (SHR) over a two-year period. By focusing on three key weirs—Kangcheon Weir, Yeoju Weir, and Ipo Weir—the research examines how artificial structures influence river hydrodynamics, nutrient cycles, and algal growth patterns. Utilizing water quality measurements, phytoplankton analysis, and environmental factor assessments, the study identifies significant fluctuations in water quality parameters and phytoplankton abundance across the surveyed points. The analysis reveals a direct correlation between environmental conditions such as temperature, flow rates, and nutrient concentrations, particularly nitrogen and phosphorus, and the proliferation of harmful cyanobacteria, notably Microcystis. This research highlights the critical role of comprehensive management strategies that consider hydraulic residence time, nutrient balance, and temperature regulation to mitigate the impacts of weirs on river ecosystems and improve water quality in the SHR.

This paper reviews the evolution and integration of diatom-based water quality assessments with environmental DNA (eDNA) techniques for advancing river ecosystem health evaluations. Traditional methods, relying on microscopy and diatom indices, have significantly contributed to our understanding of aquatic ecosystems but face challenges such as the need for taxonomic expertise and the labor-intensive nature of sample collection. Recent advancements in molecular biology, particularly eDNA analysis, offer opportunities to overcome these limitations, providing more accurate and comprehensive assessments. This study highlights the benefits of combining traditional microscopy with modern molecular techniques, enhancing the precision and efficiency of water quality evaluations. By addressing the challenges of standardizing methods and improving species identification through comprehensive reference libraries and advanced bioinformatics tools, this integrated approach aims to refine and advance the effectiveness of diatom-based strategies in monitoring and managing river health amidst environmental changes.

Plastic pollution has emerged as a pervasive and systemic driver of ecological and biogeochemical disruption in freshwater and marine environments. Unlike natural materials that circulate within closed biogeochemical loops, synthetic polymers predominantly follow unidirectional and irreversible trajectories, a phenomenon we describe as “irreversible plastic transport.” These flows culminate in sedimentary entrapment, where plastics persist as long-term ecological stressors and potential vectors of contaminant transfer. Recent global syntheses indicate that sedimentary microplastic loads can exceed 27,000 particles/kg dry weight in certain river systems, highlighting the urgency of sediment-inclusive risk assessments. This review synthesizes interdisciplinary findings to conceptualize plastics as both pollutants and governance challenges. We highlighted the dominant transport pathways of micro- and nanoplastics and emphasize that sedimentary sinks are critical long-term retention zones. Current monitoring frameworks often underestimate sedimentary burdens by focusing on surface water and overlooking subsurface ecological legacies. We propose an integrated governance approach combining cross-media monitoring, Earth system modeling, and adaptive policies to address these persistent synthetic agents. Embedding plastic dynamics within comprehensive risk assessment frameworks is essential for sustainable water management during the Anthropocene. Our synthesis supports risk-based decision-making and encourages proactive, transdisciplinary global governance strategies that integrate sediment-focused monitoring and long-term ecological risk management.

This study reports two novel species, Gogorevia contracta sp. nov. and G. recticentralis sp. nov., which were isolated from freshwater environments in South Korea. Using an integrative taxonomic approach, we conducted morphological analyses using light microscopy and scanning electron microscopy, along with molecular phylogenetic investigations using SSU rRNA and rbcL gene sequences. Phylogenetic reconstructions highlighted the distinct characteristics of both species, confirming their classification within the genus Gogorevia and elucidating their evolutionary relationships. Morphologically, G. contracta was characterized by a bow-tie-shaped central area and circular depressions in the rapheless valve, whereas G. recticentralis exhibited a rectangular-to-wedge-shaped central area with parallel striae near the center of the raphe valve. Our findings highlighted the ecological significance of Gogorevia species and suggested their potential role as bioindicators of water quality in relatively unpolluted freshwater systems. Over the past decade, our research has focused on the taxonomic and ecological study of diatoms in the Han River system and identified 136 species, including nine newly described taxa. The findings of the present study contribute to a growing understanding of Gogorevia diversity, underscore the importance of region-specific diatom indices, and support the integration of morphological and molecular methods into diatom systematics.