Environmental Benefits and Considerations

The HMAS Canverra Environmental Benefits and Considerations

Artificial reef construction and research were initially centred in Japan and the United States. However, many other countries such as Australia, Canada, United Kingdom and New Zealand are now implementing their own artificial reefing initiatives.

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 colonization 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.

The first artificial reefs in the United States were constructed in the mid-1800's. The Japanese had begun constructing artificial reefs several hundred years earlier. The United States utilises the reefs primarily to enhance sea-life for fishing and more recently as diver attractions. Reefs in Japan were mainly constructed to enhance commercial fishing.

In 1976, Japan began a 6 year program with $250 million for artificial reef projects. Of this $65 million was used for research alone. In 1982, the Japanese government started another 6 year plan with approximately $500 million to be spent on artificial reef implementation.

Artificial reefs have been a tremendous help in coastal Alabama to both the commercial and sport fishing industry. Catches of reef fish species, such as red snapper and grey triggerfish, probably exceed all other coastal areas in the United States. The Alabama Marine Resources Division along with a great many private fishers has been intensely active in constructing artificial reefs. Other states are following the example set by Alabama and are planning or already have in place their own special reef-building zones.

Canada and the State of Florida, USA, have completed hundreds of artificial reefs using decommissioned ships, concrete type constructions and more recently sinking retired drilling platforms into deeper water. Retired ships continue to be a significant source of material for artificial reefs in these regions and once sunk, quickly become a significant source of marine life.

Such artificial reefs form valuable breeding grounds and are a significant complement to existing Marine Parks. A five year environmental study conducted on the HMAS Swan after sinking in Western Australia has confirmed this value within the Australian context.

In the resource consent application to sink the HMNZS Waikato a specialist marine ecologist observed that the experience of the HMNZS Tui and Rainbow Warrior demonstrated that such vessels provide a range of ecological opportunities, which have been fully exploited by marine life. A diverse fish community has colonised both vessels and sessile marine life such as sea squirts, sponges and small algae have attached over much of their hulls. Giant snapper are often seen within the vessel with schools around its upper structure.

The Rainbow Warrior, HMNZS Tui and HMNZS Waikato projects received the support of the community, consent agencies, Greenpeace, NZ Navy and NZ Government. They have proven to be an environmentally sustainable and beneficial activity.

Recent artificial reefs created in Australia (HMAS Hobart and HMAS Brisbane) have shown the same propensity to attract marine life and rapidly become fully functioning ecosystems. Within Victoria, there are a large number of artificial reefs that were created either by the accidental or deliberate sinking of vessels between 70 and 100 years ago. All of these sites are now highly regarded for the biomass they support.

There are environmental considerations associated with the sinking man-made object such as a ship.

There is a need to ensure that there is no negative impact on the local environment. Consequently, the ship must be well prepared with careful removal of any potential contaminants such as heavy metals, asbestos, and oils. Further, the site must be carefully chosen to minimise any initial damage to existing natural reefs and sea grasses. Additionally, it is very important to ensure that the new reef does not simply become an attraction device that aggregates local fish populations making them more prone to exploitation and over-fishing.

All of these concerns can be successfully dealt with.

Clean up Concerns

Ships have been a part of the underwater landscape for thousands of years. Since the advent of civilization hundreds of thousands of ships have sunk to the bottom of the world's oceans for many different reasons. Most of these ships were not cleaned of any of the fuel, oil or cargo that they contained as they went down. Despite this, many of these ships have become magical underwater ecosystems. The idea to intentionally deploy fully decontaminated, obsolete ships as marine habitat, research platforms, educational opportunities or recreational destinations is a relatively new one in human history. The primary concern is that all projects are protective of the public health and the environment. Obsolete ships that are tied to a pier or anchored in some forgotten bay are considered environmental liabilities. The artificial reefing process safely turns these unwanted ships into wonderful assets for coastal communities.

Human beings have been altering their environment since the time of the hunter-gatherers. For the most part, this activity has been undertaken for the purpose of making the world safer and to provide easier access to food. The idea of altering the environment to make it better for the environment's sake is a brand new one in terms of human history.

Site Selection Concerns

There are many criteria to be considered when selecting a site for a new artificial reef. Consideration must be given to local navigation requirements and safety, diver safety, accessibility, protection of the asset over the longer term and protection of the existing environment.

To ensure maximum protection of the existing environment, sites should be selected to minimise impact on existing natural reefs and seagrasses. The ideal site will consist of a bare, sandy bottom into which the new structure will easily settle. The vast majority of the ocean floor in fact consists of such a substrate.

Fish Population Concerns

It is well established that fish are readily attracted to artificial reefs and are soon present in large numbers. Indeed the rationale for the establishment of many artificial reefs has been to enhance or even re-establish fish populations.

However, there is concern that artificial reefs may simply act as aggregating devices that bring together fish individuals and make it easier for fishermen to exploit them. As such the fish species are in a worse position and may become over-fished in a short period of time. For this reason, a number of authorities have banned the creation of new artificial reefs within their jurisdictions.

Unfortunately, this view has been formed from only a very limited set of scientific data. There are a number of other studies that have been conducted that have demonstrated a contrary view. That is, artificial reefs act as nurseries for fish populations and, if managed properly, increase the viability of a species within a locality.

Studies that have been conducted on reefs where fishing is prohibited strongly support this view. In such cases local fish (and other marine species) populations have increased. In these localities, local communities have expressed strong support for the continuation of the "no-take" policy on the artificial reef realising quickly that fishing opportunities are enhanced in a sustainable fashion as a result.

[ Visit the ex HMAS Canberra web site ] [ Subscribe to our Newsletter ] [ Tell A Friend | Top ]