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NSW Crown Land

Science

About “Artificial Reefs”

The Ex-HMAS Adelaide was purpose prepared and sunk to create an artificial dive reef.

An artificial reef is a structure placed on the sea bottom to attract new marine life to an area. Artificial structures have been purposely placed in marine environments across the world to enhance fishing opportunities, to serve as dive sites, to assist in coastal protection, deter trawling activity and to reverse habitat loss.

The reef develops over time and experiences different stages of marine growth and occupation, to eventually become the kind of dive site with marine life which make sites like the SS Yongala in Townsville, Truk Lagoon in Micronesia and the S.S. President Coolidge in Vanuatu world renowned.

HMAS Adelaide 

More about artificial reefs

When a 'new' structure is introduced to the marine environment, tiny organisms like microscopic algae present in ocean waters land on the structure’s surface creating a first layer of “slime”. Layer upon layer of more micro organisms slowly settle on these surfaces, creating a food source for many more permanent and visiting organisms and eventually a more prominent community develops on the surface of the structure. The layer upon layer of marine organisms is what is called a “reef” and provides the structure for marine organisms to create a true habitat in and around. There is nothing “artificial” about the marine community that develops, this term simply refers to providing the new structure for organisms to settle upon.

The many fish located at any reef, natural or artificial, each start out as eggs drifting in the ocean’s waters. The eggs hatch into either drifting or actively swimming “larvae” before further development leads to transformation into a juvenile fish, and later an adult fish. A combination of different factors determine what fish we see in any marine habitat. Factors such as natural predators and competition for space and food will determine whether a young larval fish will take up residence at any new site. The location of both near and far away habitats which are home to a fish’s parent population will also influence what fish species make up a developing marine community. Providing a new space to settle, in addition to meeting the other biological and environmental requirements of the organisms making up the marine community, leads to the development of a new marine community at an artificial reef site.

See the technical environmental monitoring reports that detail the development of the reef community below.

HMAS Adelaide 

Environmental Considerations

Australian Law regulates the creation of artificial reefs under the Environment Protection (Sea Dumping) Act 1981.

A Sea Dumping Permit ensures that appropriate sites are selected, materials are suitable and appropriately prepared, that there are no significant adverse impacts on the marine environment and that the reef does not pose a danger to marine users. A permit was issued following the compilation of a comprehensive environmental assessment. View the Ex-HMAS Adelaide environmental assessment report.

The Administrative Appeals Tribunal also considered the comprehensive range of environmental issues in reviewing the Permit issued by the Commonwealth, and allowed the scuttling to proceed. Read the decision on the AAT website, or alternatively go to the plain English summary of the decision.

Strict permit conditions regulated the preparation of the Ex-HMAS Adelaide. These preparations included:

  • Removing all fuels, oils and greases
  • Identifying and removing all hazardous materials, including Polychlorinated Biphenyls (PCBs), asbestos, heavy metals, batteries, chemicals, plastics etc.
  • Removing items that could break loose during the scuttling process or be a diver hazard
  • Preparing a safe and interesting dive site to suit different levels of expertise, including cutting diver access holes, removing items that could be a safety hazard (including cabling, non-structural partitions, hatches/doors) and sealing some areas to prevent access for safety reasons
  • Designing the scuttling process to ensure the vessel would settle to the seabed with its structural integrity maintained, in an upright position in the correct location, depth and orientation
  • Towing to the scuttling site, undertaking final on-site preparations, and scuttling the ship
  • Post-scuttling activities, including retrieving debris, clearance dive, and repairing any damage from the scuttling process
  • Installing navigation markers and mooring buoys for operation as a dive site

In choosing the specific location to scuttle the vessel, desirable site characteristics included:

  • Sand at least 2-5 metres deep to enable the ship to settle in the sand and remain stable and upright
  • Water depth of 30-35 metres
  • Suitable coastal and oceanographic characteristics (currents, wave characteristics and clarity)
  • No navigation safety hazards
  • The ability to attract marine life to colonise the artificial reef
  • No impact on threatened species
  • Minimal impact on commercial fisheries
  • Proximity to on-shore infrastructure for dive operators

An on-going condition of the Sea Dumping Permit is that the Department of Primary Industries – Catchments and Lands, must carry out a Long Term Monitoring and Management Plan (LTMMP). All monitoring reports are available to download.

HMAS Adelaide 

Environmental Monitoring

Environmental and structural integrity monitoring has been carried out for the Ex-HMAS Adelaide in accordance with the requirements of the Long Term Monitoring and Management Plan - a condition of the Commonwealth Sea Dumping Permit.

The monitoring was carried out by Worley Parsons who were commissioned to carry out the work by NSW Crown Lands. Copies of all the reports can be accessed below.

The reports below detail the following:

  • Increasing abundances and diversity of fish and organisms associated with the artificial reef over time.
  • No appreciable differences in the concentrations in a suite of heavy metals observed from marine sediments around the Ex-HMAS Adelaide or from the control sites within Bulbararing Bay.
  • Results from bioaccumulation studies are in conclusive due to adverse weather causing control samples to be lost along with site marker buoys.

Post Scuttling Report April 2011

This report confirms the date and time of placement, position, water depth, inspection dives and position of navigation markers.

Learn about the development of the reef for the first 3 years

Reef Community and Sediment Movement

The survey at six months found that “... the majority of the ship’s surface had changed from being virtually bare to completely covered in encrusting organisms including serpulid polychaetes, barnacles, ascidians, encrusting algae, bryozoans and hydroids.” and that “... fish abundance and diversity observed around the Ex-HMAS Adelaide have also increased substantially.”

Reef Community Survey 2, some ten months after the ship was scuttled, found that the thickness of the encrusting assemblage appeared to have increased.  A spatial analysis of photoquadrats found the assemblage was significantly different in the February 2012 survey compared to the prior October 2011 survey although the effect of time was not consistent among parts on the ship.

Reef Community Survey 1 at six months post scuttling found that “... the majority of the ship’s surface had changed from being virtually bare to completely covered in encrusting organisms including serpulid polychaetes, barnacles, ascidians, encrusting algae, bryozoans and hydroids.” and that “... fish abundance and diversity observed around the Ex-HMAS Adelaide have also increased substantially.”

Reef Community Survey 2, some ten months after the ship was scuttled, found that the thickness of the encrusting assemblage appeared to have increased.

Reef Community Survey 4, 15 months post scuttling, the thickness of the encrusting assemblage has continued to increase and a transition observed from an assemblage numerically dominated by an encrusting serpulid matrix to that dominated by barnacles and ascidians. Fish abundance and species richness observed around the Ex-HMAS Adelaide had also generally increased over the previous year.

HMAS Adelaide 

Sediment Sampling

Sediment quality and movement have been measured via sampling the seabed to examine how metal corrosion and degradation of protective paint layers could potentially influence the surrounding environment, and to understand sediment movement patterns around the vessel, accumulation rates and scour depths.

Each monitoring report is available to download below.

The first report details the initial sampling of sediments at one month post-scuttling. No appreciable differences in the concentrations in a suite of heavy metals from marine sediments around the Ex-HMAS Adelaide and from control sites within Bulbararing Bay were detected.

The second report on sampling some six months post-scuttling concludes “…  no appreciable increase in the concentrations of the metals tested in marine sediments adjacent to the ship” and that  “testing of sediments which have accumulated within the hull of the ship did not indicate significant lead contamination.”  The report therefore concluded that “impact to the marine environment and associated benthic biota as a result of metal corrosion and/or degradation of paint layers from the Ex-HMAS Adelaide is considered unlikely.”

HMAS Adelaide 

Bioaccumulation Studies

Bioaccumulation monitoring is required as a condition of the permit, to determine whether resident marine species are likely to be affected by zinc chromate paint, which may have been used originally on the aluminium alloy of the vessel as an anti corrosive application.

Each monitoring report is available to download below.

Attempts at bioaccumulation monitoring in accordance with the Long Term Monitoring and Management Plan have been compromised as a consequence of adverse weather impacts over the periods when samples have been deployed, resulting in the loss of control samples.  Without data from controls the results are confounded.

A further round of sampling is planned to coincide with the next reef community survey.

 HMAS Adelaide
 HMAS Adelaide
 HMAS Adelaide
 HMAS Adelaide

Photographs by Justin Gilligan