Chemical-Based Sunscreen Bleaches Reefs.
How Sunscreen Contrubites to Bleaching
Coral bleaching occurs when the water temperature exceeds a threshold, causing cells on the coral to be released. These cells are what give coral their bright colors. Without them, the coral turns white, hence the name bleaching. Bleaching is not only an aesthetic change. It can cause the coral to die. Compounds found in chemical-based sunscreens have been found to decrease the temperature required to cause bleaching, making bleaching much more likely to occur. These studies must be spread to pass additional legislation banning the use of chemical-based sunscreens, especially in areas near coral reefs.
How varying concentrations of benzophenone-3 effect coral
These graphs show how coral is affected by different concentrations of benzophenone-3, an active ingredient in many chemical-based sunscreens. The percent of coral that died had a direct correlation with increased concentration. These findings are particularly concerning after viewing the concentrations that can be found where many tourists swim. It was found that "Coral reef contamination of oxybenzone in the U.S. Virgin Islands ranged from 75 µg/L to 1.4 mg/L, whereas Hawaiian sites were contaminated between 0.8 and 19.2 µg/L."(DiNardo Et. all, para. 1)
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On the left are images from the article Toxicopathological Effects of the Sunscreen UV Filter, Oxybenzone (Benzophenone-3), on Coral Planulae and Cultured Primary Cells and Its Environmental Contamination in Hawaii and the U.S. Virgin Islands. Image A is a planula from the control group. Notice its elongated shape and number of zooxanthella cells (brown dots). When exposed to benzophenone-3 the planulae develop a deformed shape and release many of their zooxanthella cells, causing the coral to lose its color. This study provides evidence showing a direct cause-effect relationship between active ingredients from chemical-based sunscreen and the bleaching and deformation of coral reefs.