|Location:||Thylacine Field In the Otway Basin|
|Position:||South coast offshore Australia
39 14.495' S 142 54.234' E
|Water Temperature:||No data|
|Dates:||22 - 26 May 2006|
|Gas & Oil Company||Woodside Energy|
Dr Adele J Pile, University of Sydney
The science goals for this project are to expand upon the baseline environmental surveys carried out in the area on behalf of Woodside. Detailed ROV megafaunal video surveys will be carried out providing quantitative data on megafaunal ecology; particularly abundance, diversity and distribution in this area. This survey will allow a more detailed and targeted approach to be used for any subsequent surveys. In addition we will deploy bait traps and food arrays within and outside of the drill spoil to determine the effects of the physical disturbance associated with drilling on the diet of benthic fauna.
During the two days of ROV operations we completed six 50 m video transects for megafaunal abundance, diversity and distribution in the area. Transects were conducted randomly away from the port aft leg and extend to 50 m from the drill site. Videos will be analysed for megafaunal diversity and habitat mapping during 2006.
The primary habitat is rock escarpment which serves as substrate for a dense sponge and coral reef. The rock formations are similar to a spur and groove. Grooves are filled with sediment, while spurs have dense communities of sponges, soft corals, bryozoans, and ascidians. Associated with this community are fish assemblages, which include leather jackets, trigger fish, and sea horses. Drill spoil is restricted to a radius of 30-50 m from port aft side, and as in the other sedimentary areas, is settling into the grooves. Ripples in the spoil are indicative of a high energy system. Between the jacket and port leg there is a spoil layer spoil that has covered the escarpment, but the fan, tube and finger sponges rise above the spoil. The sponges all appear healthy with no lesions or bleaching. Fish still inhabit the area of dense spoil sponge communities. There is evidence of worm reworkings in sediment areas 30-50 m from the drilling activity. There are large areas of sediment covered escarpment 45-50 N/NE of the port aft leg that have a much coarser sediment and ripples with a greater wave length indicating that this sedimentary deposition was the result of a past storm.
We deployed baited traps both within and outside of the drill spoil to attract mobile megafauna. Traps were examined after 24 hrs and video taped for 5 minutes. Crabs, cuttlefish and fish were attracted to the bait traps. Initial examination of the data suggests that there is no difference in the diversity of organisms that visit the traps (inside vs outside the drill spoil). Further analysis will elucidate any trends in the data. Behavioural observations at the bait trap revealed the tracks of many of the megafauna and this will be used for the identification of lebenspurren (animal tracks). We videoed food choice arrays deployed within drill spoil both day and night to determine the food preference of benthic fauna. Food choice consisted of six agar blocks: a natural and artificial protein source, a natural and artificial carbohydrate source, a natural lipid source, and agar as a control. Fish were immediately attracted to the blocks during the day and feed primarily on the natural and artificial protein and lipid blocks. Crabs were attracted to the blocks at night but ate from all blocks. Videos will be further analysed for behavioural observations to determine any dietary preferences.
We will prepare a report for Woodside after analysis of all the data. We expect to publish these results in leading peer reviewed journals such as Marine Ecology Progress Series and a portion of this work will comprise the honours thesis of Gareth Andrews.
For further information please contact:
Dr Adele Pile, SERPENT Project, Australia Region, University of Sydney. firstname.lastname@example.org
Thanks as always to our valued project partners