Sunblock Kills Coral because it Kills Algae
Yep. They're called zooxanthellae. Sunblock kills the algae which kills the coral and sunblock might even be killing people, too. It all has to do with three chemical compounds that absorb UV rays and some oil...
Chemical compounds found in sun screen, well, block the sun. This sorta kills animals who generate food energy through photosynthesis.
Coral's situation gets complicated. The chemicals in the sunscreen also happen to trigger a virus that lies dormant in the DNA of zooxanthellae algae - and that's who's dinner on the coral reef. The algae live right alongside of the coral polyps inside of their exoskeleton and they provide up to 80% of coral polyps' nutrition.
So, anyway, this virus just goes crazy and replicates until the algae cell bursts! Now all kinds of virus has been dispersed out into the water column, headed to a coral reef near you; the algae's all dead, and the stationary coral polyps just lost 80% of their food. Not good.
Oils are used to keep waterproof sunblock chemicals adhered to the skin, but the sun block still comes off gradually in the water. This oily residue carries trace amounts of toxic chemicals and settles as a film over the entire coral reef. Really not good.
After all the algae leave, this creates what is called a bleaching event. This sunscreen scenario described above is only one of the reasons bleaching occurs but it is probably more prevalent than is documented. Right now, the main thing cited as a cause is global warming.
But, hey, you don't have to give up the beach over skin cancer just yet! Mineral-based sun screens that promote the reflection of UV rays work great without jeopardizing the coral cornerstone of the marine environment.
And, hey, the sunblock might just be the reason people are getting skin cancer, anyway.
Most types of sun protection absorb UV rays - right into your skin!!
The biological integrity of about 60% of the world's coral reefs is under assault, and the percentage of threatened reefs is expected to continue rising. Coral bleaching, which indicates the death of colored symbiotic algae that provide nutrients to coral, is a visible sign of this damage.
New suspects in the bleaching process include four commonly used sunscreen ingredients that routinely wash off into water, according to a team of Italian researchers who published their study online January 3 in Environmental Health Perspectives (2008, DOI 10.1289/ehp.10966). The ingredients killed the algae within just 4 days at very low levels, at or below what would be observed with typical usage by swimmers worldwide. The team says this is the first evidence linking sunscreens to coral bleaching.The problematic ingredients included a paraben preservative and three types of UV filters—a cinnamate, a benzophenone, and a camphor derivative. The researchers conclude that these compounds likely kill algae by stimulating latent viruses that have been found in almost all classes of coral-inhabiting algae. The number of viruses in seawater surrounding coral samples exposed to the ingredients increased as much as 15-fold, and viruslike particles were found in and around the algae. All sunscreen brands, sun-protection factors, and concentrations tested bleached the coral.The researchers used field and laboratory analyses to evaluate more than half a dozen coral species from sites in the Red Sea, the Caribbean Sea, the Andaman Sea in the Indian Ocean, and the Celebes Sea in Indonesia. They calculate that approximately 10% of the world's coral reefs are potentially threatened by about 4000–6000 metric tons of sunscreen that annually wash off swimmers in these and other reef waters.
According to the Environmental Working Group's Skin Deep database (skindeep.ewg.org), the reef-damaging ingredients are also linked to cancer, allergic reactions, endocrine disruption, neurotoxicity and reproductive harm in humans.
Read about the scientific study here: http://www.ehponline.org/members/2008/10966/10966.html
It's still beautiful but this scallop is surrounded by a number of species of dead and dying coral.
http://www.cleanairgardening.com/sunscreenbaby.html
Choose Biodegradable Sunscreen to Save Coral Reefs
Transexualizing Fish with Sunscreen (or) How About Some Soybeans With That Tan? http://www.treehugger.com/files/2006/01/transexualizing_1.php
National Geographic Magazine article
http://news.nationalgeographic.com/news/2008/01/080129-sunscreen-coral_2.html
Photographs courtesy of Maurice F., all rights reserved