Refuge at Hurricane Hole

 

 

In the red mangroves of Hurricane Hole, St. John, corals are finding refuge from 

climate change. Climate change is causing a rise in threats including warming ocean 

temperatures, increased ocean acidity, and solar radiation. 

Red mangroves have prop roots that make them appear to be walking on water, 

so they are sometimes called the “walking trees”. These prop roots reach down to the 

seafloor allowing corals grow on and under them. Eckerd College along with scientists 

from the U.S. Geological Survey recently published research on the discovery of the 

refuge at Hurricane Hole where over 30 coral species are living. 

One way that mangroves protect corals is by providing them with shade that 

partially shields them from solar radiation. The tropical environment where corals are 

found make them more susceptible to solar radiation. Firstly because the transparency 

of the water allows solar radiation to penetrate deeper into the water column. Secondly 

because the ozone layer, which absorbs UV radiation is thinner above the tropics. 

Rises in temperature can kill corals because it can result in coral bleaching. Coral 

bleaching is where symbiotic algae, often zooxanthellae abandon the coral tissues 

during times of stress causing the corals to appear bleached. These symbiotic algae not 

only provide the striking color in corals, but also the oxygen and other necessary 

materials needed for their survival.

 

In addition to shade, the chemical, physical and biological conditions found 

around mangroves work to lower the water acidity. High acidity caused by an increase 

in carbon dioxide hinders coral’s ability to absorb the calcium carbonate they use to 

build their skeletons.Researchers found that some species, such as the boulder brain corals were thriving in mangrove areas, yet unhealthy and bleaching in the unshaded areas outside of the mangroves.