Amid widespread coral bleaching, this reef is thriving
7 min
Editor’s note: This week Conservation International’s first virtual reality film, “Valen’s Reef,” debuted at the Cannes Lions International Festival of Creativity; watch the film here. Its spectacular setting — eastern Indonesia’s Bird’s Head region — contains some of the most species-rich waters on Earth; it could also hold clues for how to help our oceans adapt to climate change. Conservation International marine scientist Mark Erdmann explains.
Indeed, many coral scientists are lamenting that coral-dominated reef systems as we know them will cease to exist within the next few decades — a shift that could spell the end for a number of fisheries and marine tourism industries and cause significant economic hardship and food security problems for tropical countries around the globe.
While bleaching has been severe in other parts of Indonesia, Raja’s reefs are healthy and thriving. What’s their secret?
What we’ve learned is rather incredible: Reefs across Raja Ampat experience temperatures fluctuating between 19 and 36 degrees Celsius (66–96 degrees Fahrenheit), with many individual reefs exposed to a whopping 6–12 C variation within a single 24-hour period! According to most marine biology textbooks, such variation should easily kill these corals, yet they are thriving.
Examples of the data retrieved from temperature loggers placed at 1-meter (3.3-foot) depth (above) and 40-meter (131-foot) depth (below) on the reef at Cape Kri in Indonesia’s Raja Ampat archipelago. While these loggers are both in areas of healthy coral and are only separated by a distance of around 200 meters (656 feet), they are exposed to vastly different temperature regimes.
Key to this insight was the prior discovery that these zooxanthellae (once believed to be a single species) are actually quite genetically diverse, and that different species have different thermal tolerances. Baker, Palumbi and colleagues have shown that reefs exposed to warmer waters tend to have more heat-tolerant zooxanthellae in their tissue.
Further reading
What does this mean in a super diverse reef system like Raja Ampat, where there is such large variability in temperatures? Well, we assume that, like the corals themselves, the symbiotic algae in Raja Ampat are likely very diverse – with some strains performing best in cooler waters and others quite tolerant to super-heated reef flat waters. This means that Raja Ampat’s reefs are not only resilient and able to readily bounce back from any bleaching that might happen, but also that these reefs are likely to be increasingly important in the future as a genetic repository for heat-tolerant zooxanthellae — potentially serving as watery “seed banks” for restoration efforts on other reefs that succumb fully to coral bleaching.
Knowing how special and important Raja Ampat’s reefs are, CI has worked with local communities and the government to give priority protection to reef areas that are exposed to either cold-water upwellings or regular high temperatures. These reefs have been placed in strict “no-take” zones within Raja Ampat’s network of seven large marine parks, to ensure that they are given the highest possible protection to safeguard them from other disturbances (including overfishing) that might compromise their resilience.
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