STAR-BULLETIN / MARCH 2008
Snorkelers explore the reef at Hanauma Bay, on the southeast coast of Oahu.
Study links lotion to coral bleaching
Beachgoers slathering on lotions to prevent sunburn could be contributing to coral bleaching, says a study reported in the journal Environmental Health Perspectives.
After experiments in four of the world's coral reef areas, researchers in Italy concluded that "sunscreens, by promoting viral infection, can potentially play an important role in coral bleaching in areas prone to high levels of recreational use by humans."
They estimated that up to 10 percent of the world's coral reefs are at risk for bleaching from swimmers' sunscreens.
"A couple of us have been going back and forth on it (the issue)," said Robert Richmond, professor and principal investigator at the University of Hawaii's Kewalo Marine Lab and a world leader in coral reef conservation.
Coral bleaching can occur for various reasons, such as climate change, heavy rains, freshwater intrusion and pollutants, he pointed out.
"At this point, in terms of issues hurting the coral reef in Hawaii, I wouldn't put sunscreen in the top three."
Richmond lists the top three threats here as "integrated watershed issues (freshwater runoff into the ocean), fishing overharvesting and alien algae."
In a study supported by the European Commission, Roberto Danovaro of the University of Pisa in Italy led experiments with different sunscreen concentrations in sea water surrounding coal reefs in Mexico, Indonesia, Thailand and Egypt.
Sunscreens usually have up to 20 or more chemical compounds, and certain ones triggered viral infections affecting symbiotic algae called zooxanthellae that live within reef-building coral, the researchers said.
Richmond explained, "Bleaching occurs when the relationship between the animal host and resident algae breaks down." Without the algae providing food energy, the coral bleaches, or turns white, and dies.
This can be caused by a number of stressors, including chemicals in water discharge and sunscreens that cause viral infections, Richmond said.
Danovaro's team estimated that 4,000 to 6,000 tons of sunscreen wash off annually in the world's oceans. About 25 percent of sunscreen ingredients on the skin are released in the water within 20 minutes, they said.
Even with low doses, environmental stress occurred within 18 to 48 hours, and complete bleaching of corals occurred within 96 hours, they said.
Dave Gulko, coral reef specialist in the Aquatic Resources Division, state Department of Land and Natural Resources, said there are concerns by interest groups on both sides of the issue.
He said his division is interested in potential effects of sunscreen "relative to places where water motion is limited," such as Hanauma Bay and possible portions of Kaneohe Bay that have a lot of coral and many visitors.
Shallow areas with high coral cover and limited water movement would retain chemicals from lotions or other pollutants for longer periods, he said.
State and federal coral reef managers in Hawaii are increasingly interested in disruptive effects of chemicals on coral fertilization processes and larvae, Gulko said.
He said the division is collecting water samples for some scientists as part of a large global study.