Over 85% of the marine plants and animals in Southern Australian waters are found nowhere else on earth.
To create an artificial reef is to sink a man-made object in the sea, and then allow it to become part of the ocean ecosystem. Marine life has been quick to adapt to artificial reefs. In fact, barracuda have been known to stake out their territory on an artificial reef moments after a vessel has been scuttled.
Turning trash into treasures is the philosophy behind artificial reefing. Large artificial reefs are created from obsolete ships or aircraft obtained from sources such as navies, merchant marine companies and airlines. Once meticulously cleaned, decontaminated and deployed in the ocean, these shipwrecks, previously useless structures, become positive additions to the local ecology. Once under water, an artificial reef attracts a staggering array of marine life. It provides protection from predators, shelter from ocean currents, breeding opportunities and a supply of rich food sources.
Encrusting and reef building organisms such as algae, sponges, gorgonians, and other benthic organisms, require solid substrate to incorporate a reef community. Surface area is the limiting factor.
Within days of being placed, algae begins to grow, encrusting organisms, drifting as planktonic larvae in the water column, secure themselves to every available surface. Small fish come to the reef to feed and lay their eggs, while larger fish migrate to the area to feed on the smaller fish and so the food chain evolves.
Sea life finds temporary sanctuary amongst protective overhangs, and pelagic fish soon associate to the vertical relief. The subsequent colonisation into a functioning reef evolves over time, attracting numerous permanent finfish and invertebrate species, as well as larger pelagic and transient species such as shark, barracuda, kingfish, stingrays, etc. Over time the biodiversity becomes larger and more complex attracting more marine life, scuba divers and fisherman.
Artificial reef structure provides two primary services critical to the survival of most marine organisms — protection from predation and an ample forage source. Symbiotic relationships, such as the cleansing of parasites, are an additional benefit that attracts organisms to reef communities. The presence of complex benthic habitats, typical of artificial reefs, provides many interstitial areas for juvenile organisms to hide, reducing the potential for predation. It has been proven that this increased survivability of pre-recruits, in a particular species, will eventually increase the future spawning stock biomass, and thus the fishery.
The establishment of a reef community produces large communities of diverse benthic organisms such as sponges, gorgonians, hydroids, anthozoans, bryozoans, crustaceans, and algae. This abundance of benthic species creates an ample food supply for recreationally and commercially important marine species such as crabs, snapper, crayfish, flounder etc. Furthermore, species such as these may supplement the diet of larger piscivores, which have been noted in copious quantities on many artificial reefs. This abundance of prey attracts numerous species to artificial reefs, helping to establish a successful and thriving community.
Marine Research Opportunities
The ex HMAS Canberra Reef presents many valuable marine research opportunities. It will provide us with a way to better understand how life takes hold beneath the sea. VARS hopes that once the ex HMAS Canberra has been scuttled, local researchers will be able to partner with divers to document its metamorphosis from warship to ecosystem.