Assessing the additive risks of PSII herbicide exposure to the Great Barrier Reef

► First study to examine risk of herbicide mixtures in the Great Barrier Reef lagoon. ► First study to combine herbicide data from direct water samples and passive samplers. ► Research shows increased area of risk when photosystem inhibition is considered. ► Presents and analyses area of herbicide risk across the Great Barrier Reef lagoon.