Coral reefs are often called the “rainforests of the sea”.
They are one of the most diverse ecosystems in the world.
Reefs are made up of corals or marine invertebrates held together by calcium carbonate.
They protect coastlines from storms and erosion, they support fishing and tourism industries,
they provide shelter for marine organisms and they are a source of new medicines to treat cancer,
arthritis, Alzheimer’s, etc. About 25% of the ocean’s fish depend on healthy coral reefs.
Unfortunately, coral reefs are under constant threat from pollution, excess nutrients like
nitrogen and phosphorus, overfishing, rising ocean temperatures, climate change, increased carbon
dioxide levels and ocean acidification. When corals are stressed, they eject algae that live
inside them, lose their color, become bleached and eventually die. From 2014-2017 unusually warm
waters affected 70% of coral reef ecosystems worldwide. 33% of coral cover was disrupted
in the Great Barrier Reef in Australia and 60% of coral cover was killed in the Maldives.
In the past, humans have dropped old subway cars, tugboats, tanks and barges into the ocean
to stimulate coral reef growth. They removed glass windows, paint and any toxic materials
before dumping them. Just like with shipwrecks, these have proven to be very effective. Fish,
mussels, shrimp, crabs, lobsters, and algae quickly create habitats for themselves
in these structures. However, large subway cars don’t allow microstructural developments
so there’s no potential for developing a more abundant and varied marine life.
Humans have also dumped tires, PVC pipes and plastic tubs in the ocean under the guise of
creating new coral reefs. Predictably, these leached toxic chemicals and hurt the growth of
corals. Also tires and pipes are light-weight and not anchored down to the ocean floor. When ocean
currents move them around they destroy fragile habitats and eventually wash up on shorelines.
Humans have also dumped small cinder blocks in the ocean hoping to grow coral reefs.
However, a storm or monsoon would scatter them across the ocean floor or
bury them in the sand, disrupting any existing coral fragments.
Scientists are also using underwater coral nurseries to restore damaged reefs. Small,
broken fragments of corals are hung on secured PVC pipes and allowed to grow for several months.
Then, they are transplanted to degraded reefs in the hope that they bring them back to life.
Now we come to the next generation of artificial coral reefs - 3D printed concrete ones. XtreeE,
a French 3D printing company has teamed up with Seaboost, a marine life restoration company.
They are developing biomimetic designs - which means that they understand and copy elements
of nature to solve human problems. They use 3D scanners to scan existing coral reefs and
create digital versions of them. Their complex structures and twisting valleys attract algae
and marine life. Their nooks and crannies are ideal nesting or hiding spots from predators.
Using this knowledge, a 3D model is created of an artificial coral reef with similar niches.
Xtreee then prints this structure using a mix of concrete, local sand and local seawater
so that flora and fauna will recognize the structure and be attracted to it.
There are many advantages of using 3D printed concrete to create artificial reefs. We can design
intricate, porous forms that mimic local reefs. We can create modular structures that can be handled
by single divers with no extra help. These modular structures can be attached to one another to form
large, heavy artificial reefs that don’t move. We can also use concrete that is resistant to
chemical attack and doesn’t disintegrate in the salty ocean waters. These artificial reefs don’t
have any steel reinforcement that will rust over time. Instead of concrete, we can also use natural
materials for these 3D printed reefs so they don’t further damage underwater flora and fauna.
Xtree and Seaboost’s first project was at Calanques National Park in France in 2017.
This structure mimicked the Coralligenous, one of the richest natural habitats in the
Mediterranean Sea. It shelters thousands of species including fish, crustaceans,
algae, molluscs etc. The 3d printed coral reef was approximately 1 cubic meter or 35 cubic feet. Each
module weighed 900 kg or 2000lbs. The module was taken into the Sea on a barge. It was bolted in
place so that it wouldn’t move. The narrow, complex crevices allow marine life to find
enclosed spaces while maintaining contact with the open environment. This 3D printed artificial reef
has been quite successful. Many rare lobsters have created homes in the structure.
The second project was in Monaco in 2018. 5 artificial reefs were bolted to the Mediterranean
Sea floor. The parametric design of the reef was catered to the Grouper fish whose presence ensures
a biological balance. Each unit measured 3 cubic meters or 100 cubic feet and weighed 1000kg or
2200 lbs. This design has also been successful. The third installation was in 2019 at Cap D’Agde,
also in France by the Mediterranean Sea. These are similar to the first reef, but have smaller
gaps and crevices. They also have a large, heavy base to make sure that they don’t move around.
Another concrete block at the top of the makes it easier to lift it with a crane. Each reef weighs
around 3,200 lbs or 1,400 kg. Just a year later, all 32 units were covered in marine life.
Obviously, if ocean temperatures continue to rise and waters get more acidic, no amount of 3D
printing is going to save our coral reefs. We need to address the cause and not just the effect.
However, 3D printers are a tool to safely explore the possibility of restoring damaged reefs.
It has allowed biologists to create intricate structures out of clay, calcium carbonate and
artificial stone. These experiments have helped scientists identify heat-tolerant corals and
algae that thrive in warm waters and may be able to adapt to climate change. There are also groups
starting large-scale coral farms. The tricky thing is that we’re dealing with Mother Nature,
who is fickle, difficult to understand and varies in every region. There is no universal solution
to coral restoration. Every project is site specific. But continued research and creative
3D printed approaches give us a glimmer of hope in the face of global threats that have already
destroyed much of the world’s coral ecosystems. Do you think 3D printed coral reefs have a future?
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