Long term monitoring of photosystem II herbicides - Correlation with remotely sensed freshwater extent to monitor changes in the quality of water entering the Great Barrier Reef, Australia

► Photosystem II herbicides routinely monitored on Great Barrier Reef over 5 years. ► Photosystem II activity dominated by diuron contributing 89% on average. ► Diuron is the most consistently detected PSII herbicide. ► Photosystem II herbicides present at concentrations which affect corals, diatoms and seagrass. ► Concentrations correlate with remotely sensed CDOM a proxy for freshwater extent.