Ecosub technology helps restore Sound's seabed meadows
The submersible vehicle labours slowly and methodically in the marine environment of Success Bank off Coogee, south of Fremantle.
A Murdoch seagrass researcher in the 'living laboratory' While its purpose is not immediately apparent, the submersible Ecosub 1 is the central piece of equipment in what is regarded as the world's most comprehensive seagrass rehabilitation programme.
The revolutionary project to save this important marine resource is an integral part of Cockburn Cement Limited's wide-ranging Environmental Management Programme (EMP) for its shellsand dredging operations on Success Bank.
The shellsand is used in the manufacture of quicklime, an essential product for the state's mineral processing industry, but the dredging causes the loss of some of the seagrass beds growing above the shellsand resource.
The EMP's aims are to determine the ecological significance of seagrasses in the area, the development of a rehabilitation strategy to replace lost seagrass, to ensure dredging will not adversely affect the wave climate and its effects on the shoreline, and the feasibility of using shellsand of lower quality from other sources.
The three-tonne Ecosub 1 was developed by Murdoch University researchers in conjunction with underwater engineers (Ocean Industries Pty Ltd) and a commercial diving team (Diver I/Diver II Co.) as a means to extract, transport and transplant sods of seagrass from dredging sites to the barer sites of Success Bank.
Over the approximate 100 days suitable for diving over a year, the team operates the submersible, which works like a large underwater turf cutter.
The sods, a quarter of a square metre in area and up to half a metre deep, are cut and picked up by a cutting head and stored in a large hopper on the back of the submersible for transportation and transplantation at the recipient site.
The leader of Murdoch's Seagrass Rehabilitation Programme, Dr Eric Paling, from Environmental Science, said seagrass was considered ecologically important for a number of reasons.
"Seagrass is believed to act as a nursery for young fish and crustacea some of which are of commercial importance, it may trap and stabilise sediment, it forms the basis of the food chain, cycles nutrients in the environment and baffles currents," he said.
Dr Paling is assisted in the study by Research Officer Cathy Walker, Research Assistant Mike van Keulen and a team of underwater engineers and commercial drivers.
Dr Paling said the aim of the project was to demonstrate new techniques for successful seagrass rehabilitation in Australia and the world.
"If we can establish viable techniques for seagrass rehabilitation they may become standard practice for marine developments that affect seagrass meadows."
The team's research flies in the face of the popular belief that transplanted seagrasses do not regrow or spread.
Transplantation began six months ago; most sods have survived for that amount of time, and are showing signs of spreading.
Dr Paling is optimistic that the project can meet its first set of performance criteria. The team must revegetate 1000 square metres of area on Success Bank, and the revegetated seagrasses must then survive for at least three years.
To meet its second set of performance criteria, returning one hectare or more with a survival time of at least one year, the team has started designing new machines with a greater transplant capacity.