A bioindicator system for water quality on inshore coral reefs of the Great Barrier Reef

► We determined how reef biota change consistently along five water quality gradients. ► We then identified a bioindicator system for changing water quality in coral reefs. ► Benthic cover, coral recruitment, Porites and FORAM index are parts of this system. ► Turbidity strongly alters coral reefs and should be monitored directly where feasible. ► Complementary, our bioindicator system may be used to assess changes in water quality.