Nature Conservancy Seeks Help Tracking Coral Bleaching

‘Tis the season for coral bleaching, and The Nature Conservancy wants to enlist all swimmers, snorkelers and divers to help track coral bleaching in Virgin Islands waters under an initiative known as Bleach Watch VI.

Lisa Terry, a science technician and dive safety officer with The Nature Conservancy, said bleaching is likely to occur as local water temperatures reach their peak during late September and early October.

In general, healthy coral reefs can only tolerate temperatures ranging from about 73 degrees to about 83 degrees. Corals depend on zooxanthellae, symbiotic algae that live within the individual coral animals (known as polyps) to convert sunlight into food which sustains the corals. Zooxanthellae are what give corals their distinctive colors.

When temperatures get higher than 84 degrees, the zooxanthellae abandon their homes within the coral polyps, leaving them weak and more vulnerable to diseases. The corals become pale and eventually turn white, and this is known as coral bleaching.

Terry met with nearly a dozen volunteers on September 9 at the St. John School of the Arts to introduce them to a website ( where divers, snorkelers and swimmers can report sightings of coral bleaching.

Lisa Terry, science technician and dive safety officer with The Nature Conservancy.
Lisa Terry, science technician and dive safety officer with The Nature Conservancy.

“The more eyes we have and the more data we collect, the more we are able to determine the extent and severity of bleaching events,” Terry said. Scientists don’t know how to reverse coral bleaching, but some corals do survive for several weeks in a bleached state and fully recover. “If we can’t make the water cool down, at least we can use the data to determine reef resiliency and inform our conservation efforts,” Terry said.

The website, which can also be downloaded as an app for Androids and iPhones, allows volunteers to report any bleaching events they see on a simple form. The whole process takes less than a minute with a bit of practice.

Those who want to help monitor reefs at a more detailed level can make a report based on a series of samples. Observers can monitor up to five sites during a 15 minute dive or snorkel and report them using waterproof, reusable forms available from the Bleach Watch team. They can also download a sheet from the website or upload the information directly to the site.

A downloadable training presentation is also available on the website which gives basic instruction on how to identify the various categories of corals and the signs of bleaching.

The rise of sea temperatures, a result of global warming, is having a devastating effect on coral reefs around the world. (Click the following link for more details: Global warming and coral reef bleaching.)

The Nature Conservancy’s project is asking for volunteers to submit data gathered from anywhere in the Virgin Islands. These reports are fed into a database also used by the National Park Service, according to Jeff Miller, a fisheries biologist with the Virgin Islands National Park.

Park biologists have been monitoring five sites in detail over the past 20 years, and the information they’ve collected on rising water temperatures confirms the global trend. “During the first ten years of the study, there was only one ‘excursion’ over the bleaching threshold of 84 or 85 degrees,” Miller said. “The water temperature has gone above 84 or 85 degrees eight out of the last ten years, including every year in the past five years.”

This year has already set new records for high temperatures worldwide. (Click this link for the latest data on Rising global temperatures.)

There is one glimmer of hope: some corals—or the zooxanthellae that live within them– may be learning how to adapt. “Some appear to have developed a higher thermal tolerance—corals in mangroves, too, have habituated themselves to higher temperatures,” Miller said.

And though some bleaching events are catastrophic, some corals can recover provided that the bleaching doesn’t happen too often or over too long a period of time. Corals may appear bleached, but if they still look a bit fuzzy, that indicates the polyps are still alive, Terry said.

In the meantime, Terry recommends we all do what we can to maintain healthy oceans: cut down on our carbon footprints; “reduce, reuse and recycle”; support organic agriculture; eat sustainable seafood; choose sunscreens that don’t contain chemicals that are toxic to marine life; and educate ourselves and others to take whatever measures we can to keep our coral reefs healthy.

Photos provided and Amy Roberts.