Advances in water transparency research: Mechanistic insights and multi-scale monitoring innovations

Water transparency is a critical indicator of water quality and aquatic ecosystem health, governing key ecological processes such as underwater photosynthesis, biodiversity dynamics, and human water security. This review synthesizes advances in the theoretical foundations, influencing factors, measurement techniques, and technological innovations in water transparency research, with a focus on mechanistic insights and multi-paradigm integration. The study elucidates the fundamental mechanisms of light attenuation in water bodies, emphasizing the regulatory roles of suspended particulate matter (SPM), chromophoric dissolved organic matter (CDOM), and algal biomass. These constituents interact to modulate light penetration, influencing ecological functions and water clarity. We critically evaluate conventional measurement methodologies (Secchi disk depth) suffer from observer-dependent variability and spatial-temporal limitations. In contrast, emerging technologies, including advanced optical sensors, hyperspectral remote sensing, and AI-driven analytics, are revolutionizing transparency monitoring by enabling high-precision, real-time, and large-scale assessments. Notably, this work proposes an integrated air-space-ground monitoring framework that synergizes hyperspectral imaging, absorbance spectroscopy, and machine learning for comprehensive water clarity assessment. This multi-scale approach facilitates dynamic tracking of transparency variations across diverse aquatic systems, from inland lakes to coastal waters. This review integrates theoretical advances with cutting-edge technologies to advance water transparency research, enhancing both mechanistic understanding and practical applications.