Largest Continuous Coral System Found

After two decades of exploration, scientists have discovered the largest continuous coral system surrounding the Hawaiian Islands.  Aside from the popular reefs found on the shallow, they also discovered more incredible reefs in mesophotic zone.  Also known as “twilight zone” with depths of 30 to 150 meters (100 to 500 feet) and is almost totally dark, they did not expect to see a higher cover percentage. "What is unique about this study is how vast and dense the coral cover is" according to Richard Pyle, lead researcher from Bishop Museum in Honolulu.

The biggest challenge that they have encountered was logistics. The twilight zone was too deep to reach using traditional scuba gear and too shallow to rationalize the cost for an unmanned submersible which cost $30,000 to $40,000.  Instead, the international team of researchers which is comprised of geologists, biologists, and botanists had to make use of advanced diving equipment such as rebreathers, drop cameras, data recorders and remote operated vehicles when they are able to afford them.  “We can do things that submarines can’t, like collect fish specimens and lift rocks and go inside caves” says Richard Pyle.  Despite of the challenges that the researchers faced, they have managed to explore 2,590 kms of the Hawaiian archipelago.

Coral Reef found on the twilight zone.  Photo taken from Science Alert

The scientists were able to do interesting experiments, one of which was using a lift dome. They would place a dome on top of a coral and staining it to monitor its growth.  They have also discovered that aside from the 17% of endemic fish species found on the shallow, there are more found on the deep which increases the percentage to 50%.  According to Pyle “there were some spots, particularly in Kure, down at 300 feet, where literally every fish on every survey is a species known only from the Hawaiian Islands.”

The researchers suspect that the reef found on the twilight zone maybe ancient and the condition on that depths remain constant.  Compared to the shallow reefs which is easily affected by rising temperatures, pollution and especially the sea level fluctuation that occurs every 100,000 years or so, “That’s due to ice ages,” Pyle says.  “So every time we have an ice age, a lot of the world’s water is locked up in glaciers, and as a consequence the sea level drops by about 300 feet”.  It is possible that the deeper reefs serve as a refuge to the species that could retreat at those depths. 

This discovery is truly remarkable and further study would help answer their questions.