Review of IoT Sensors for Aquatic Biological Indicators

Monitoring aquatic ecosystems is essential for sustaining biodiversity and maintaining water quality. Recent advancements in Internet of Things (IoT) technologies have enabled real-time, high-resolution tracking of key water quality indicators. This systematic review evaluates the application, effectiveness, and challenges of IoT sensors for monitoring biological and physicochemical parameters—such as dissolved oxygen (DO), pH, and turbidity—in freshwater and marine environments. A structured literature search across Google Scholar, Scopus, and Web of Science identified 61 relevant studies published between 2015 and 2025. Findings show increasing adoption of wireless-enabled microcontrollers (ESP32, Arduino) and moderate-cost electrochemical and optical sensors, which dominated usage at 19.67% and 18.03%, respectively. While deployments were largely field-based (65.58%), 26–30% of studies lacked calibration or protocol reporting, highlighting transparency gaps. Biological indicators such as chlorophyll-a were monitored less frequently compared to physical and chemical variables. Key challenges included sensor fouling, calibration complexity, limited methodological reporting, and integration difficulties in low-resource settings. IoT technologies offer transformative potential for aquatic monitoring, but broader adoption requires standardized calibration protocols, affordable hardware, and improved training. Future research should evaluate long-term reliability and policy impact of these systems across diverse aquatic environments.