Along with planting soft coral, TRACC also has been building artificial reefs for the hard coral. Hard coral grows at much slower rate than it’s soft cousin, so it needs a more stable structure to mature.
They use what are called bottle reefs which are made of rectangular cement blocks that have glass bottles attached to the bottom to build artificial reefs. The blocks also have round cutouts on the top for coral biscuit placement (I’ll explain more about that later).
They use the sand from the surrounding beach to make the cement for the blocks. This sand is basically Parrotfish poo, which is digested coral. Using this sand means the cement blocks will have a similar make up to the coral itself which in turn will make for an easier transplant and better growth.
They also use glass bottles for the reefs because glass is also made of sand and a more natural material. And of course the labels are removed from the bottles before they are used.
Once these blocks have hardened, they are then loaded into the boat and dropped near the designated location for placement.
I’m sure you are wondering…..How do we move the cement blocks into place underwater?
TRACC designed lift bags for us to use underwater and move the bottle reefs into place.
The lift bags have a rubber inner tube with adjustable cording attached to each end. The cording is placed around the bottle reef and adjusted tight. Then one of the two volunteers working with the lift bag will use their alternate reg and fill the tube just enough to raise the bottle reef off the ground.
This allows us to easily move it into place.
Once we get the bottle reef to the appropriate location, we will flip the cement block so the bottles are pointed down and let the air out of the lift bag. Then we push the bottles into the rubble to try and secure the cement blocks.
The bottle reefs not only provide a solid structure for the coral to grow, but they also act as a barrier to stop the dead coral rubble from sliding down the slope.
The actual designs of the reefs are still a work in progress, but the scientists and interns working at TRACC have been coming up with new ideas to make the artificial reefs more efficient.
While we were doing maintenance on one of the bottle reefs that had been laid down a long time ago, we were actually able to see how the reef was really working. This one particular area was having a lot of issues with the rubble sliding down its steep slope.
So TRACC installed what they call the “Ribbon Reef” to help create a barrier. There were a few problems though. The blocks themselves would get pushed by turtles or other forces breaking the barrier, so TRACC came up with the idea to put stray pieces of hard coral in-between the bottle reefs in the hopes that it would attach to both sides binding the cement blocks together.
Well, it worked! There are now several areas being held together by coral!!!
Soft coral is important to have in a reef system in laying ground work, but hard corals makes up the hearty structures of a reef and creates more biodiversity. Think of it like soft coral being the shrubs of a forest and hard coral being the trees.
TRACC began collecting hard coral pieces from areas nearby that were still being bombed. These corals are considered “corals of opportunity” because their death would have been imminent had they been left in their original location.
Now they have a fighting change of survival.
Once they had collected enough coral fragments, TRACC placed the pieces into small cement rounds called coral biscuits. Like the bottle reefs, the biscuits are also made of local sand to mimic the corals natural makeup.
These biscuits are then taken to the coral nursery on the northern tip of Pom Pom Island and left to mature for a long period of time. Like I said before, hard coral grows at a very slow rate.
Every once and a while we would tend to the nursery and make sure all the biscuits were upright and getting plenty of sunlight. Biscuit flipping might have been one of my favorite chores. It was almost therapeutic. I could have done it for hours if my air supply would have let me.
After the biscuits have matured for long enough, we then would gather up a few dozen and take them to the various bottle reefs for placement.
I was part of building one of the new step bottle reefs when I first arrived. Even in just 6 weeks, I saw a good amount of change.
Fish had moved into the artificial reef, and algae had completely covered the surface. It’s a slow process, but I do believe in a year, it will be a bustling habitat filled with beautiful coral and full of fish as well as some macro.
TRACC has plans to build many more artificial reefs around Pom Pom Island. Hopefully I will be able to go back in the future and see what progress has been made.
If you would like to help support TRACC or sign up to volunteer and help rebuild the coral reef, you can find more information on TRACC’s website.