Artificial reefs have been around, surprisingly, for thousands of years. In ancient times they were built by Persians to prevent pirates from entering the mouth of the Tigris River, and the Romans boldly constructed a reef to trap enemy ships inside the mouth of Sicily’s Carthaginian harbor. In Japan, artificial reefs have been used since the 17th century, both to improve fish yields and to grow easily accessible kelp beds. In the United States, fishing communities have built artificial reefs since around the 1830’s, interlacing logs, and tossing all kinds of junk ranging from old shopping carts to outdated vending machines into the water, all in the name of creating habitat. During the past few decades, as diving has gained popularity, boats and ships have been scuttled, too; both to create habitat and to serve as dive sites. Some of the most interesting artificial reef structures are harder to identify though; let’s take a closer look at reef balls, biorock, and more.
Why Provide Artificial Reefs?
In areas where reefs are healthy and complete, rushing water slows as it strikes the reef’s surface, and its energy is diffused; in some places, artificial reefs were first set in place to slow erosion. As scientific knowledge regarding marine life increased over the centuries, people discovered that adding structures to otherwise barren underwater environments greatly increased fish populations, making life easier and more convenient for those who relied on the ocean for food. Today, with reef health declining in many places, artificial reefs provide essential habitat; without them, marine life would be much less likely to flourish. In addition, artificial reefs help to boost game fish populations, creating areas where fish can thrive in large numbers.
Reef Balls and Other Structures
While an artificial reef can be constructed of concrete blocks, old cement culverts, and other materials commonly associated with the building industry, there are some intriguing objects that have been developed specifically to serve as artificial reefs.
•Steel Pyramids – Designed to allow water to flow through, and to prevent sand from covering their structures, steel pyramids have heavy concrete bases and provide basic shelter for fish, crustaceans and more. Economical and easy to deploy, these reefs are a favorite with artificial reef societies. One drawback is that these reefs are designed to last for only 30 to 50 years.
•Reef Balls – Often used to restore coral reefs, and sometimes simply used on their own to create new habitat, reef balls come in a variety of sizes and are designed to act like condos for fish and other creatures. They are usually dome shaped, with lots of holes for water circulation and for easy access to shelter.
•Eternal Reefs – Sometimes shaped just like reef balls, and sometimes taking on the shape of stone lions or other monuments, Eternal Reefs are created using cremated remains mixed with concrete to form an underwater memorial with a purpose. One of the best known eternal reefs is the Neptune Memorial Reef located off the coast of Miami, Florida.
•Coliseums – Often used for aquaculture, and particularly popular with oyster farmers, coliseums are circular shaped artificial reef structures that are reminiscent of Rome’s Coliseum; they have openings in the sides and a completely open top, providing shelter to marine life, yet allowing water to flow through. These can be made from stacked concrete blocks or other materials, and are usually between three and seven feet across.
•A-Jacks – Like gigantic versions of the jacks you might have played with when you were a child, these concrete structures are usually bundled together in groups of eight or more. Suitable for use in channels and in open water, they create a jumbled environment that fish and other creatures seem to enjoy.
•Underwater Sculptures – Form and function – what could be better? Usually situated in shallow water, and sometimes built along existing reefs, underwater sculptures such as Christ of the Abyss and installations by Jason deCaires Taylor provide habitat for marine life as well as incredible photo opps for divers. Some sculptures stand alone; others have been installed as underwater museums.
Artificial reef programs are usually powered by volunteers – divers help to install artificial reefs, plus they monitor growth and watch for damage. They catalogue fish and other marine life living in artificial reef systems, and they help to promote awareness. If you live in an area where artificial reefs are being installed, consider volunteering your time. You’ll be playing an important role in helping the ocean return to health.