Short summary is that beaches where sunblock is used a lot show much higher concentrations of the relevant chemical compared to beaches where sunscreen is less common or beaches that saw fewer swimmers, and that heightened levels of these chemicals can be observed up to 600 meters out from these beaches. The observed correlation between high concentrations of these chemicals in the water and the lack of coral growths is very strong.
Short summary is that beaches where sunblock is used a lot show much higher concentrations of the relevant chemical compared to beaches where sunscreen is less common or beaches that saw fewer swimmers, and that heightened levels of these chemicals can be observed up to 600 meters out from these beaches. The observed correlation between high concentrations of these chemicals in the water and the lack of coral growths is very strong.