A remarkable difference in the way that coral reefs recover from stress has been revealed by a comparative study involving reefs in the Caribbean and the Indo-Pacific region, including the Great Barrier Reef. A study by Dr. George Roff and Professor Peter Mumby from the ARC Centre of Excellence for Coral Reef Studies and The University of Queensland has shown that Caribbean reefs are more vulnerable than those found in the Indo-Pacific.
Addressing delegates attending the 12th International Coral Reef Symposium in the Australian city of Cairns, Dr. Roff explained “The main reason that Indo-Pacific reefs are more resilient is they have less seaweed than those in the Caribbean Sea. Seaweed and corals are age-old competitors in the battle for space.
Impact of Seaweed
“When seaweed growth rates are lower, such as the Indo-Pacific region, the reefs recover faster from setbacks. This provides coral with a competitive advantage over seaweed, and our study suggests that these reefs would have to be heavily degraded for seaweeds to take over.
According to Dr. Roff: “This doesn’t mean that we can be complacent – reefs around the world are still heavily threatened by climate change and human activities. What it indicates is Indo-Pacific reefs will respond better to protection, and steps we take to keep them healthy have a better chance of succeeding.”
Seaweed in the Caribbean blooms up to four times faster. “We’re not sure why this happens, but a plausible theory is that Caribbean waters are highly enriched in iron,” say the researchers. “For thousands of years, the Caribbean Sea has received dusts that blow across the Atlantic from the Sahara, and the dust contains iron – an essential element for algae to grow.
“This suggests that the difference between the Indo-Pacific and Caribbean oceans and their coral reefs is fundamental, and occurs at a very large scale.
The Significance of Reef Fish
“Another factor that protects these reefs is the abundance of herbivorous fish, such as surgeon and parrotfish that treat seaweed as a delicacy. The Indo-Pacific region has a lot of these fishes. For instance, the Indo-Pacific region has 70 species and six genera of parrotfish, while the Caribbean only has 13 species and two genera of the fish.”
The scientists are keen to stress that this is not to suggest that conservation measures are less significant in the Indo-Pacific region. “All reefs face an uncertain future, particularly in places with lots of human activities,” they point out. “We still need to curb the overfishing of herbivorous fish, as they are very sought-after in the Pacific. We also need to control the level of nutrients in the water and prevent runoff when necessary.
“The good news is that our Indo-Pacific reefs are tougher than we thought – we just need to make sure that our actions won’t destroy their natural resilience.”