According to the National Ocean Service, more than half of the United States Caribbean coral reefs were lost in 2005 due to thermal stress; more thermal stress than the past 20 years combined. In 2010, cold water temperatures, possibly due to changes in the jet stream and melting ice caps, bleached coral in the Florida Keys. The extreme susceptibility of these habitats to damage, to the extent that the Australian government prohibits even touching the Great Barrier Reef, makes it all the more important to be aware of reef health. An abundance of marine species rely on the reefs and could be lost forever if conservation warnings are not heeded. It’s for this reason that we’re taking to the skies to better monitor the state of our reefs.
Coral reefs undergo a phenomenon called bleaching when exposed to extreme stress, usually from higher than normal water temperatures, but also from cold water temperatures and water acidification. Bleaching is exactly what it sounds like: an absence of all pigmentation in the coral, leaving them bone white. During bleaching, the symbiotic organisms that give coral its color, zooxanthellae, are expelled by the coral’s polyps, leaving it without a food source and unable to sustain life or undergo calcification.
While bleaching is extremely harmful, it’s not permanent and can be reversed before lasting damage is done. Unfortunately, reversing this process means slowing global warming, a feat that has proven to be deeply political and slow moving.
Beacons of Hope
Fortunately for the coral, scientists are utilizing satellite technology to keep a keen eye on our reef systems. In a topic that can sometimes appear grim, the technology is proving extremely interesting, and even inspiring hope.
Satellites are being used to monitor the reflectance of different portions of coral reefs, with their reactions to specific light wavelengths telling us something about their health. Not to be confused with fluorescent pigments, which are produced by the coral themselves, the relevant pigments in this case lay within the zooxanthellae. According to a report published in the Advances in Marine Biology journal, peridinin, a pigment making up 39 percent of zooxanthellae’s total pigmentation, can be used to differentiate bleached from unbleached coral.
(For more about light spectrums and absorption see our article Coral Pigments and the Light Wavelengths That Stimulate Them).
Peridinin has a peak light absorption rate of 475nm. As light wavelengths near the range between 500-560 nm, unbleached corals will show a more drastic change in reflectance because of peridinin’s presence. Bleached corals, or those that have lost their zooxanthellae, will show a very gradual increase in reflectance.
The extreme gradient change for unbleached coral (think a sharp upward moving line) between 500-560 nm tells us that zooxanthellae is present. Bleached coral shows a much gentler gradient, because white reflects all colors, and therefore doesn’t produce such a drastic change in reflection.
Beyond light reflection and searching for already bleached coral, our satellites are also able to monitor water temperatures, alerting us to potentially dangerous conditions for our coral reefs. The National Oceanic and Atmospheric Administration (NOAA), keep records derived from satellite readings that detail Sea Surface Temperature (SST) and something called Degree Heating Weeks, which monitor temperature in relation to the coral bleaching threshold, among other readings. The combination of these readings gives us the Coral Reef Watch plan, alerting to upcoming detrimental reef conditions and giving scientists the ability to demonstrate measurable results to politicians.
The ways in which we already utilize technology to monitor reef health are fairly spectacular. Two generations ago, these feats would have been written off as nothing more than sci-fi fantasy. But today, this satellite application is giving us very real information on how to save the world’s coral reef systems.
For more information about coral reefs, talk to one of our experts. We would be happy to go into further detail about coral reefs, or just give you our own opinions on the matter. We can also get you set up with a coral ecosystem of your own.