A laser-induced fluorescence microscopic sensor for in-situ detection of microbial particle dynamics in aquatic environments

Marine microorganisms play a fundamental role in the biogeochemical cycling of matter and energy within ocean ecosystems. However, in-situ observations remain limited by the lack of advanced instrumentation, restricting our understanding of microbial dynamics in natural waters. To address this gap, we developed a deep-ultraviolet (DUV) laser-induced fluorescence (LIF) microscopy imaging sensor designed for long-term, in-situ monitoring of microbial particle concentration dynamics. The system integrates DUV fluorescence spectroscopy, microscopic imaging, and environmental sensing components such as Conductivity–Temperature–Depth (CTD). Laboratory calibration revealed a linear correlation between fluorescence intensity and particle concentration (R² > 0.95, RSD < 2%), with a detection limit under ~10⁵ cells/mL. Field deployment during a flood tide in the Xinzhou section of the Pearl River estuary showed a significant increase in fluorescence intensity, indicating elevated concentrations of micro-biological particles. DUV microscopic imaging further confirmed the alignment between fluorescence signals and particle dynamics. This sensing platform demonstrates high suitability for complex aquatic environments and provides a practical tool for characterizing tidally modulated changes in micro-biological particles concentrations. • Integrated DUV LIF and DUV microscopy for in situ particulate flux monitoring. • Sub-minute resolution reveals microscale particle distribution dynamics. • Robust linear calibration between fluorescence intensity and particle concentration. • Field validation confirms stability and multimodal synergy in estuarine waters.