Coral Reefs of the Seychelles—Mysterious, Vital, and Vulnerable
Coral Reefs of the Seychelles—Mysterious, Vital, and Vulnerable
/ Categories: Ocean Health, All

Coral Reefs of the Seychelles—Mysterious, Vital, and Vulnerable

Coral reefs support more marine life than any other ocean ecosystem and are, not surprisingly, a favorite pursuit for many divers. But as well as being physically and biologically spectacular, coral reefs also support the livelihoods of over half a billion people.

What is more, this number is expected to double in coming decades while the area of high-quality reef is expected to halve. In combination with the very real threat of climate change, which could lead to increased seawater temperatures and ocean acidification, we start to arrive at some quite frightening scenarios.

Scientists are putting much effort into increasing understanding of how reefs of the future may look and function. Functionality in this sense also refers to the quality of services reefs may provide to dependent communities, such as supporting fisheries and protecting coastlines against wave action and erosion.

For the past five years, members of the Coral Reef Research Unit in the Seychelles have joined forces with Earthwatch. Many enthusiastic and dedicated volunteers have examined the health and diversity of coral reefs of these islands.


Over five years of study we have comprehensively surveyed three atolls and islands of the Seychelles. Our research goals were quite simple—to determine the conservation status of reefs in the region, to identify the key threats to them, and, most importantly, to identify conservation management actions that could be implemented to best protect this incredibly important resource for future generations.

One of the greatest threats that reefs face, apart from overfishing of certain key species that are important to their function, is the impact of environmental conditions that are significantly beyond the norm. The best known of these environmental anomalies is El Niño, a cyclical climatic phenomenon that in some parts of the world can significantly increase seawater temperatures and light intensities. In 1998, the biggest El Niño ever recorded hit the western Indian Ocean, and seawater temperatures rose by 2° to 3°C for a period of a few months. In the Seychelles up to 90 percent of the coral reefs died as a result of this relatively small temperature rise.

Increases in temperature coupled with increases in light intensity cause coral bleaching. However, coral bleaching simply refers to loss of coral color and is not always associated with dramatic climatic events. Many species of coral go through seasonal changes in color, and such changes are due to normal processes they undergo to fine-tune their physiology to best suit environmental conditions.


So arguably, far from being sensitive, corals that partially bleach or change their color but do not die could be among the most tolerant rather than the most vulnerable species, as they may be better equipped to adapt to environmental stress.

However, when environmental conditions change as rapidly and dramatically as they did during the 1998 El Niño event, many coral colonies are so affected that a bleached coral rapidly becomes a dead one.

The questions that our team of researchers and volunteers in the Seychelles are now addressing are:

  • Which species are most tolerant and which are most sensitive to sea   temperature rise?
  • Is the sensitivity of the most vulnerable species altered by the normal conditions in which they grow—or, put another way, are there any natural environments or sites that protect corals from the impacts of dramatic environmental change?

Our research team has carried out many hundreds of dives in the Seychelles region. We have demonstrated that some coral colonies containing certain species are much older than the 13 years that have elapsed since the 1998 El Niño event, whereas other corals, particularly the numerous branching species, are all much younger and have established themselves in the system since 1998.

Clearly corals display a range of tolerance to environmental change. The next phase of our research took our teams to crystal-clear waters, deeper reef systems, granitic boulder reefs, and eerie turbid lagoons. Perhaps surprisingly, it was in the low-visibility lagoons where we first found examples of “old” colonies of the most sensitive species.

When fragments of these colonies were exposed to altered environmental conditions, as in previous experiments, they appeared to be tolerant rather than sensitive. This was one of those rare and exciting Eureka moments in science—we had found that under the right environmental conditions, corals that are otherwise very susceptible to changes in climate can increase their ability to resist environmental change.


Well, we can utilize these areas that afford protection to the corals to establish ecological refuge environments that could enable us to protect the most sensitive species from future environmental change. This is the direction that conservation research surely has to take. Much effort has been put into understanding species biology and climate change, but how do we now use this vast knowledge to protect the Earth’s natural systems?

Thanks to the dedicated team of diving Earthwatch volunteers and the support from our sponsors, we are now starting to ensure that we at least give these incredibly beautiful and important but vulnerable systems the best chance to survive.

If you have good dive skills, a passion for the natural world, an interest in conserving coral reefs for future generations, and are happy to put up with the tough job of living on a tropical island, join us on Coral Communities in the Seychelles.

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