Block a burn bleach a reef? |

Block a burn bleach a reef?

Photo by: Bradley Cornelius Groot

The bleaching of the world’s coral reefs has been an increasingly concerning mystery in recent years.  Healthy corals harbor a host of zooxanthelae, colorful algae that live symbiotically within the coral tissue providing energy to the coral.  The coral in turn provides shelter, plenty of carbon dioxide for photosynthesis, nutrients, and protection.  When the corals are “bleached” these necessary algae are expelled leaving only the shell of the coral, its white, bleached skeleton.  Scientists for years have struggled trying to identify a cause for this. Climate change is still a major contender but National Geographic just came out with an article that suggests something else, sunscreen.

“Four commonly found sunscreen ingredients can awaken dormant viruses in the symbiotic algae called zooxanthellae that live inside reef-building coral species.

The chemicals cause the viruses to replicate until their algae hosts explode, spilling viruses into the surrounding seawater, where they can infect neighboring coral communities. “

Those four ingredients are as follows:

  1. Parabens
  2. Cinnamate
  3. Benzophenone
  4. “A camphor derivative” (likely methylbenzylidene camphor)

Photo by: Breno PeckParabens in particular are in all sorts of other products, even our food.  If they are the culprits in this fiasco we have a lot more to worry about other than just sunscreens. With growing concern around them I suggest reading all of your product labels and seeking out companies that are paraben-free. Even some main stream companies are transitioning over to paraben-free now so it should be getting easier in the near future.

The study is not the end all be all, it is just a step in the direction of possibly understanding this phenomena. It isn’t that hard to find a sunscreen that is made with physical sunblock rather than chemical sunblocks. Look for titanium dioxide or zinc oxide on the ingredient list and avoid the ingredients listed above.  If all else fails put on a long sleeved white shirt and a giant hat.. you may look silly but you won’t get burned and you just might make a difference.

10 Responses

  1. Nick Says:

    very useful comment Jimbo. The actual concentration of sunscreen in these areas is not enough to make an impact.

    by the way the fish in the pic is not healthy it looks half starved.

    the bleaching of the reefs is more likely caused by polution water temperatures and storms. If one of many things is not correct they will bleach.

  2. Carlos Says:

    I raise coral, I dive, and I love the beach.

    Owning a reef tank and successfully growing corals from all regions and types (soft corals, LPS, SPS) I have come to many conclusions about the abilities and limitations of corals, and have come to appreciate that they are capabable of withstanding dramatic temperature swings and varying conditions.

    Sunscreen, however, causing wide spread reef bleaching is absurd.

    “Bleaching” is as vague a sympton as someone sneezing or having a fever. It is a very broad response to any number of factors — there is no magic bullet to bleaching, and these articles need to stop suggesting that one thing causes it.

    It really pisses me off.

  3. Arcturus Kirwin Says:

    And what about for people, such as myself, who need high-strength chemical sunscreens?

    I’m an extremely pale-skinned redhead and as such, even a few minutes of sun on a hot summers day leads to burns without sunscreen.

    And wearing clothing to block the sun just leads to overheating and heavy sweating.

  4. Aquahobbyist Says:

    This doesn’t make sense to me and here is why: those of you who have home reef aquariums know that you are feeding your corals phytoplankton, cyclopese, brine, and all kinds of stuff. These are food sources that *surprise* often contain paraben. The dosage levels received in a small tank would be much larger than in the wild. Why aren’t reef keepers experiencing large reef die-offs if parabens are really to blame?

  5. maew Says:

    Long sleeved t-shirt and big floppy hat great idea kinda makes it hard for swimming tho…

  6. RickS Says:


    There is increasing validity to the issue posed in this article. This year, there have also been studies out of Italy that corroborate this story. I certainly don’t think that sunscreens are the chief cause, but definitely are contributory. If you read the whole article, it talks about 4-6,000 metric TONS of this stuff washing off swimmers. It’s estimated that 27,000 metric tons of sunscreen are used annually. SOMETHING happens to this huge amount when it washes off. Just ask the dive boat captains that work popular dive and snorkel spots about the sunscreen slick on the water at the end of busy days.

    Arcturus, this month’s green guide ( has an article about this and lists three sunscreens that are actually safe for the reefs, yet still provide excellent protection for your skin. I prefer Soléo Organics All Natural Sunscreen (

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