The Marine Life of the ex-HMAS Adelaide, 5 years post sinking.

The marine life of the ex-HMAS Adelaide is expected to develop quickly once the ship is sunk off Avoca Beach, near Terrigal Beach on the New South Wales Central Coast. The ex-HMAS Adelaide will become a haven for recreational scuba divers who will be able to experience the various stages of marine life development on the wreck.

The ex-HMAS Brisbane was sunk off the Sunshine Coast on the 31st July 2005 and recent videos by the acclaimed underwater photographer Ian Banks has demonstrated that the wreck has an incredible array of marine life and in particular soft coral. Soft coral like this one below are likely to colonise the wreck of the ex-HMAS Adelaide.

Southern Soft Coral

Southern Soft Coral (Dendronephthya australis). Shelly Beach, Manly, NSW courtesy R. Ling flickr

Ian Banks has taken some incredible footage of the marine life of the ex-HMAS Brisbane 5 year post-scuttling and the marine life of the ex-HMAS Adelaide is expected to develop over time into a spectacular scuba dive site on the NSW Central Coast.

Apart from soft coral, the ex-HMAS Brisbane has an incredible variety of fish colonising the wreck and Ian banks has another video titled “A day in the life on the ex-HMAS Brisbane” which was taken on the 25th April 2010 which is nearly 5 years post scuttling which shows the marine life diversity.

The Queensland Museum undertook a study of the colonisation of the ex-HMAS Brisbane wreck by marine life (benthos and fish assemblages). The report, BIOLOGICAL MONITORING OF THE EX-HMAS BRISBANE ARTIFICIAL REEF: PHASE II – HABITAT VALUES by Monika A. Schlacher-Hoenlinger and other authors  indicated that after 3 years post sinking:

  1. Species richness of invertebrates and algae on the wreck had clearly increased and species composition had considerably changed due to colonisation by new animal groups (eg. corals) which were not present in the 2006 survey. The wreck of the ex-HMAS Adelaide will develop a variety of marina fauna over time and it will be fascinating to follow this development.
  2. Community structure of invertebrates and algae varied over several spatial scales on the wreck. 87 species were recorded from the external superstructure; 25 species from the decks; 49 species in internal areas; 49 species from upper hull areas; and 36 species from the lower hull near the seafloor. Which means that the complex architecture of the wreck resulted in great species diversity.
    Horizontal surfaces supported fewer species with substantialy reduced cover. The colonisation of the decks with various species of hard and soft corals underlines the predominance of spatial heterogeneity in community structure. Hence the great video by Ian Banks which showcases the soft corals.
  3. For some invertebrate groups the fauna colonizing the wreck is broadly representative of that on adjacent natural reefs of the Inner Gneering Shoals. Conversely, the dominant species of sponges, corals, and sea squirts on the wreck are not proportionally representative of the surrounding natural reef. Will the marine life of the ex-HMAS Adelaide be representative of the surrounding reefs? Only measuring and monitoring will tell.
  4. Overall, the diversity of benthic invertebrate assemblages was higher on the natural reef sites than found on the wreck. The wreck supported 79 species of sessile invertebrates and algae after one year and 120 species after three years, lower than the 173 species on the natural reef. Trajectories in species richness varied greatly between taxonomic groups, most notably for corals which took more than one year to colonize the ship. Maybe with more time the ex-HMAS Brisbane will mirror the diversity of the natural surrounding reefs. It will be interesting to see how quickly the ex-HMAS Adelaide gets colonised by marine life.
  5. The wreck continues to support a high fish biomass relative to that found during previous surveys on the site, and to that on nearby natural reefs. Trends in abundance levels have generally been steady, or have had moderate deviations up or down. Some piscivores increased, omnivores recorded both increases and declines, while planktivores and herbivores mostly registered modest declines. If this trend is any indication of the ex-HMAS Adelaide, then high fish numbers are likely to be high at Avoca Beach and the fishing exclusion zone will ensure number will increase rapidly.
  6. The wreck continues to attract additional species of fishes, with 192 species now recorded cumulatively between 2006 and 2008. However net resident species totals have remained relatively constant, with surveys in July 2006 recording 133 species, followed by 111 in November 2006, and 139 during the most recent in November 2008. It will be interesting to see what factors influence fish diversity on the ex-HMAS Adelaide, will major storm events play a role?
  7. Composition of the fauna continues to evolve, most likely according to competitive pressures between fishes and changes in available food and habitat led by the development of invertebrate communities over time. Documenting and photographing the changes on marine fauna on the ex-HMAS Adelaide by recreational scuba divers and researchers will help with attracting divers from around the world.
  8. Since 2006 new colonizers were outnumbered by emigrants, indicating fish communities may be approaching a more mature phase. In the most recent survey, 40 of the 139 species had not been recorded in 2006, but 52 of those found during 2006 were not recorded in 2008. Changing fish populations and diversity indicates that diving the ex-HMAS Adelaide will be a different experience every time.
  9. Species new to the wreck included several serranids (rock cods and basslets), pempherids (bullseyes), labrids (wrasses) and gobiids (gobies), while those now absent include priacanthids (bigeyes), some carangids (trevallies and scads), several pomacentrids (damselfishes), an acanthurid (surgeonfish) and most monacanthids (leatherjackets). Will the same trends occur with the fishes of the ex-HMAS Adelaide? Good information gathered by recreational divers and researchers will prove to be an interesting bank of knowledge.
  10. The deck area remains the most favoured habitat for fishes on the wreck, with 69 percent (or 133 species) of all species found in this area. The sector that had the least diversity overall was the internal areas, with only 40 percent of the fauna, or 76 species. The internal areas did, however, support a greater diversity of chaetodontids (butterflyfishes) than other sectors. By 2008, differences in diversity of the top six families between the superstructure, internal areas, and lower hull had become less pronounced than previously. The deck area of the ex-HMAS Adelaide will be accessible in 20m of water, which is a dive that can be made by even inexperienced divers.
  11. Evidence of recruitment and maturation on the wreck has been observed for two common serranid fishes, Purple Rock Cod, Epinephelus cyanopodus and Maori Rock Cod, E. undulostriatus. Recruitment of small juveniles was observed in the early stages of the wreck, followed by apparent site fidelity and retention of adults up to the present. This indicates the wreck has acted as a selfgenerating system and is not merely encouraging migration of adults to the wreck at the expense of nearby natural reef areas. The population of Snapper, Pagrus auratus on the site has also experienced progression in size classes. Large adults were previously lacking around the site, but are now present in significant numbers, along with the juveniles and subadult stages previously noted. The ex-HMAS Brisbane is becoming its own ecosystem. Will it take 5, 10 or 15 years for the ex-HMAS Adelaide to become part of the ecosystem with self sustaining populations of marine life?
  12. Surveys on natural reefs adjacent to the ex-HMAS Brisbane wreck in summer/early autumn 2009 recorded 193 species of 40 families, versus 192 species of 47 families found cumulatively on the wreck from 2006 to 2008.
    However,resident species recorded on the reef outstrip those found at any one time on the wreck by a large margin (39-74 percent). Of the larger families, chaetodontids (butterflyfishes), pomacentrids (damselfishes) and labrids (wrasses) were much more diverse on the reefs, carangids (trevallies and scads) and lutjanids (tropical snappers and fusiliers) were much more diverse on the wreck, while serranids (rock cods and basslets) had similar numbers of species in both areas.
    If these trends are the same on the ex-HMAS Adelaide, then visitors should not only dive the ex-HMAS Adelaide wreck, but also the surrounding reefs to get a full appreciation of the marine life of the Central Coast.
  13. Biomass on the wreck was significantly greater than that in similar-sized areas on the natural reef, being composed of greater numbers of generally larger fish. Overall, large piscivores, molluscivores, omnivores and planktivores were more abundant on the wreck, while groups with species more specialised on benthic invertebrates (especially corals) were clearly more common on the reef environments. Maybe we will see very large fish numbers on the ex-HMAS Adelaide wreck?
  14. Physical habitat features (e.g. depth, aspect) are important in determining the rate of colonisation by encrusting assemblages (‘fouling communities’). In 2006, we found that there was very little difference in the coverage of sessile fauna between the starboard (exposed) and port (sheltered) sides of the wreck. In 2008, the composition of epifaunal assemblages differed between the starboard and port sides of the wreck at both 12 and 18 m depth. The difference between depths was due largely to the reduced coverage of the bryozoan, Celleporaria sp. 1, and increased coverage of the sponge, Batzella sp. 4217.  Spending time examining the different aspects of the ex-HMAS Adelaide should result in viewing a greater amount of marine diversity, and the diversity will change as the marine fauna develops over time. Looks like lots of visits to the wreck are in order.
  15. In 2006 and 2008, we compared vertical surfaces on the port and starboard sides of the wreck with horizontal surfaces on the main and upper decks. The vertical sides were settled by more species at significantly higher densities than the horizontal surfaces. This might be explained by smothering by sediment which settles at greater rates on horizontal surfaces. However, the relative dominance of particular species in 2006 had changed overtime, with barnacles, bivalves and bryozoans dominating assemblages in 2006, and bryozoans and sponges dominating in 2008. Don’t forget to examine surfaces of different orientation on the ex-HMAS Adelaide dive wreck when it is finally scuttled, to see the greatest array of diversity.
  16. There are indications of continual community change on the wreck, with a trend towards greater similarity between natural and artificial reef communities over time. Nevertheless, three years after the scuttling, the structure of epifaunal assemblages on the artificial reef remains quite different from that found on adjacent natural reefs. Will the marine life on the ex-HMAS Adelaide ever mirror the marine life of the surrounding reefs?

The development and study of marine fauna will be a fascinating subject of study at the scuba dive site of the ex-HMAS Adelaide off Avoca Beach on the New South Wales Central Coast. One of the key findings of the stdy into the marine life of the ex-HMAS Brisbane was “The wreck is visited by a large number of divers, but awareness of its ecological value appears to be limited outside the diving community.” So, the great challenge for all scuba divers is to get the message out there that the ex-HMAS Adelaide dive wreck will become a fantastic area to view marine life and that frequent visits will allow a changing view of the marine life.

A great resource to read is the report written by Monika A. Schlacher-Hoenlinger, Simon J. Walker, Jeffrey W. Johnson, Thomas A. Schlacher, John N.A. Hooper, Merrick Ekins, Ian Banks, and Patricia R. Sutcliffe, BIOLOGICAL MONITORING OF THE EX-HMAS BRISBANE ARTIFICIAL REEF: PHASE II – HABITAT VALUES, published by the Queensland EPA.

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