What are Artificial Reefs?

The world’s coral reef ecosystems are under threat from climate change, pollution, and human activity. Rising sea temperatures and ocean acidification are accelerating coral bleaching, threatening the delicate balance of marine ecosystems. Over half of the world’s coral reefs have already been lost, and without intervention, 90% could disappear by 2050.

More than just colourful tourist destinations, coral reefs are called the ‘rainforests of the sea’ due to their tremendous biodiversity value. While covering just 1% of the seafloor, coral reefs support 25% of all marine life, providing shelter, breeding grounds, and food sources. 

Artificial reefs have emerged as a solution to restore marine biodiversity and protect ocean life – and the safety, coastal protection, well-being, food and economic security of coastal communities who depend on them. 

But what is an artificial reef, how do artificial reefs work, and how are artificial reefs made? 

Artificial reefs are man-made underwater structures created to mimic the characteristics of natural reefs. Artificial reefs provide habitats for marine life, enhancing biodiversity in areas where natural reefs may have been lost or degraded.

Pollution, overfishing, and climate change have severely impacted coral reefs and marine ecosystems. To counteract the decline, artificial reefs, made from durable materials like concrete and steel, are installed on the seafloor to restore marine habitats, support fisheries, and protect coastlines.

By mimicking the functions of natural reefs, artificial reefs provide shelter, food, and breeding grounds for a wide range of marine species, helping to restore ecological balance in underwater ecosystems.

Artificial reefs work just like a natural coral reef, but – instead of the seafloor – marine organisms attach themselves to an intentionally-placed man-made structure, from simple modules of concrete blocks and steel to recycled materials or even sunken ships.

Once installed, artificial reefs quickly become colonised by algae, coral, and small organisms, forming the foundation of a thriving ecosystem that supports fish, crustaceans, and other marine species.

How are artificial reefs made?

Constructing an artificial reef is a carefully planned process that considers location, materials, environmental impact, and sustainability. Below is an overview of the key steps involved in their creation:

• Site selection

The artificial reef must support marine life without disrupting existing ecosystems, so choosing the right location is critical. Factors considered when determining site location include water depth, seabed composition, ocean currents, and proximity to natural reefs or sensitive habitats – as well as the intended purpose of the reef (e.g., marine habitat restoration, fisheries enhancement, or coastal protection).

• Planning and permits

Before proceeding with reef construction, approvals are required from environmental agencies and local authorities to ensure compliance with regulations, and safeguard against unintended ecological damage. Stakeholders including scientists and conservationists are often involved in the planning phase. 

• Design and material selection

The design of an artificial reef depends on its purpose, whether for habitat restoration, fisheries support, or coastal protection. Common materials include concrete, steel, reef balls, or repurposed structures like ships and train carriages. These materials must be durable, non-toxic, and safe for marine life to attach to. 

• Construction and deployment

Once materials are prepared, the artificial reef is transported to its designated site. Deployment methods vary based on the structure’s size and weight; some are carefully placed on the seafloor, while others, like ships, are sunk in a controlled manner to prevent toppling and damage to surrounding ecosystems. 

• Monitoring and maintenance

After deployment, artificial reefs require ongoing monitoring to track marine life colonisation, coral growth, and structural integrity. Regular assessments help identify potential hazards or necessary maintenance, to ensure the reef continues to support biodiversity and ecosystem health.

Various types and designs of artificial reefs are used in coastal environments across the world, each serving different purposes and offering unique benefits to marine ecosystems. Here are some examples of types of artificial reef structures and how they work:

Concrete modules

Concrete blocks or structures designed to provide attachment surfaces for marine life. CyBe Construction, for example, uses 3D concrete printing to create modules that mimic the design of natural coral structures.

Sunken ships and vessels

Retired ships and vessels intentionally sunk to provide complex habitats for marine life. The ships (such as the retired warship, HMAS Brisbane) create intricate environments that support a diverse range of marine life, boosting fish populations and creating recreational diving opportunities.

Reef balls

Specially designed spherical concrete structures, reef balls incorporate hollow spaces that encourage coral growth and provide protection for marine organisms. Their design allows water circulation, making them ideal for long-term habitat restoration.

Fishing Aggregating Devices (FADs)

Man-made objects, such as floating buoys, rafts or artificial logs placed in the ocean to attract fish. They provide a focal point for fish to gather, making it easier for fishermen to locate and catch them.

Oil rigs-to-reefs

Decommissioned offshore oil platforms converted into artificial reefs support marine life at multiple depths. These structures act as vertical reefs, enhancing biodiversity from the seabed to the surface.

Rock piles and boulders

Natural or quarried rocks placed on the seabed to create artificial reef-like environments, offering shelter for fish and crustaceans while stabilising the seafloor.

BioRock reefs

An advanced reef restoration technique using low-voltage electrical currents to promote mineral accretion, stimulating coral growth and increasing reef resilience.

Artificial reefs provide a variety of advantages to marine ecosystems, coastal areas, and the environment. Here are some specific benefits of artificial reefs:  

• Habitat restoration

Artificial reefs help restore damaged marine habitats by providing new homes for coral, fish, and other marine life to colonise. They compensate for habitat loss caused by climate change, pollution, and coastal development.

• Biodiversity support

By mimicking natural reef formations, artificial reefs encourage the growth of diverse marine species, from small invertebrates to larger predatory fish, improving ecological balance and fostering a thriving underwater ecosystem.

• Fisheries enhancement

By serving as breeding and feeding grounds, artificial reefs boost fish populations, supporting sustainable fisheries by improving fish stocks and benefiting local economies. Recognising this, the Tasmanian government partnered with the University of Tasmania to install two artificial reefs to enhance recreational fishing and aquaculture opportunities for local fishers.

READ MORE: What is aquaculture?

• Coastal protection

Strategically located artificial reefs act as natural barriers, reducing wave energy and preventing coastal erosion caused by storms and rising sea levels.

• Recreational and economic opportunities

Artificial reefs create new sites for diving, snorkelling, and fishing, attracting tourists and boosting marine tourism.

Restoring marine ecosystems through artificial reefs

As governments, researchers, and communities increase their focus on marine ecosystems, artificial reefs are emerging as a key solution for restoring habitats, enhancing fisheries, protecting coastlines, and driving new economic opportunities

With thoughtful design and strategic placement, artificial reefs have the potential to shape the future of ocean conservation, and create lasting benefits for both marine life and coastal communities.