The Green Lantern

Reefer Sadness

How destructive is snorkeling or diving at a coral reef?

Illustration by Mark Alan Stamaty. Click image to expand.

I’m about to leave for my long-awaited tropical vacation, and now I’ve gotten myself in a tizzy over whether my swimming and snorkeling might contribute to the destruction of coral reefs. How can I be a more responsible ocean visitor? And what about these reports I’ve heard about sunscreen killing corals—is that true? Should I let myself burn to save the reefs?

You’re right to worry. The world’s coral reefs are not in such great shape: According to a comprehensive 2008 report from the Global Coral Reef Monitoring Network, approximately 19 percent of the world’s coral reefs are “effectively lost”—meaning that they’re so degraded or polluted they can no longer support healthy ecosystems or provide other benefits—and another 15 percent are in serious danger of joining that category within the next 10 to 20 years. Reefs are more than just awe-inspiring and gorgeous; they’re also brimming with wildlife. They provide local communities with food and money—both from fishing and from tourism—and help protect coastlines from storms and rough waves.

Vacationing snorkelers and scuba divers aren’t the biggest threat facing coral reefs—that dubious honor belongs to the trifecta of global warming, the fishing industry, and land-based pollution. But tourism is still a major area of concern: In 2002, the United States Coral Reef Task Force identified “recreational overuse” as one of six priority threats facing our country’s coral reefs (PDF). The deleterious effects may be even more pronounced in developing countries, where rapid expansion of the tourism industry isn’t always coupled with well-managed conservation efforts.

Ocean frolickers can damage corals intentionally—by touching them or breaking off branches as souvenirs—and unintentionally, by standing, walking, or dragging their gear over them. Snorkelers and divers can also kick up clouds of sediment with their fins. When that grit lands on a reef, it blocks the sunlight that zooxanthellae—the algae that live in and nourish the corals—need for photosynthesis.

When wading in shallow waters, make sure you’re walking over sand or gravel, particularly if you’re dragging a surfboard. Another way to protect the reefs is to practice swimming before you go—so you’re nimble enough in the water to avoid touching the corals. (Klutzy landlubbers like the Lantern should wear a snorkel vest and make sure to get some training before heading in.) Photographers need to be extra cautious: Your extra gear and desire to get sweet close-up shots make you a special hazard.

Boats that drop their anchors into reefs can also cause a lot of damage, so if you’re planning on taking any kind of boat tour, look for a responsible company that uses mooring buoys instead of anchors. For a list of tour operators around the world that have pledged to follow ocean-friendly practices, check out the Project AWARE Foundation’s ECO Operators program.

Regarding the sunscreen issue: Chances are, you read one of the many alarming news stories on an Italian study published last year  that found that common chemical sunscreen ingredients can trigger viral infections in zooxanthellae, causing the corals to “bleach” and weaken. There’s still considerable debate over the extent to which the study’s findings can be applied in the wild, but in the meantime, it seems prudent to avoid sunscreens that contain the problematic ingredients—namely, oxybenzone, octinoxate, 4-MBC, and the common preservative butylparaben.

Some news reports have recommended zinc oxide or titanium oxide-based sunblocks as “coral-friendly” alternatives. * But the Lantern is a bit wary of that claim: So far, she hasn’t seen any data that prove these sunblocks are coral-safe, just a lack of data showing that they’re dangerous. As she noted in her previous column about sunscreens, there’s still a lot we don’t know about the fate of these products in the environment. Luckily, there’s an easy, lotion-free way to stay protected while snorkeling: a long-sleeved T-shirt and leggings.

All of this said, the tourism industry has the potential to be a net positive for our oceans. Swimmers and divers who’ve experienced the spiny majesty of a coral reef firsthand are more likely to press hotels and tour operators to adopt more sustainable practices. Meanwhile, vendors who want to keep tourists happy have a strong economic incentive to maintain beautiful, healthy reefs.

So before you get in the water—and before you even leave home—do your part by supporting businesses with established conservation policies. Choose hotels that properly treat their wastewater and sewage: If these polluting effluents wind up in the ocean, they encourage algae blooms that can overwhelm coral reefs. When planning your beach excursions, try to patronize marine protected areas, which are managed in ways that promote long-term ecosystem health.

Finally, to really green up your vacation, consider donating some of that leisure time to conservation-oriented activities, like the Reef Environmental Education Foundation’s Volunteer Survey Project. If your trip is taking you anywhere within REEF’s monitoring areas, you can sign up to collect data on the fish you see on your dives. Your data will get fed into much larger data sets that scientists can use to study population trends. Sun, sand, and citizen science—what could be better?

Is there an environmental quandary that’s been keeping you up at night? Send it to, and check this space every Tuesday.

* Correction, Aug. 18, 2009: The original sentence stated that zinc oxide and titanium dioxide physically reflect UV rays, rather than absorbing them as chemical sunscreens do. In fact, zinc oxide and titanium dioxide both reflect and absorb UV rays. (Return to the corrected sentence.)