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| RESEARCH VOYAGES | |
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MAPPING SEABED HABITATS OFF wEST AUSTRALIA SS07/05 Jul 05 [Introduction] [The Voyage] [The Voyagers] [Ship to shore] Ship to shoreDays 2 and 3 - Sophisticated Lady
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Date: 23 July 2005 |
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LAT |
S 21º 57' |
LONG |
E 113º 47' |
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The Southern Surveyor has become a sophisticated ship, since I last sailed on her 10 years ago. Our quest continues to explore more and more of the deep ocean and to bring back images and biological material, so that others may join in our discoveries. This places increasing demands on our sampling equipment and operators.
I've just counted 27 computer monitors in the 'operations room' alone, which does not include computers used elsewhere, for the video system, personal computers, etc. or the array of technology actually used to run the ship.
The backbone of our sampling equipment is the swath mapper that uses reflected sound to produce high resolution topographic maps of the seafloor that we pass over. When we reach an area that we are interested in (at the moment we are off Ningaloo Reef) we set up a survey box and then survey up and down this box producing contiguous mapped strips of seascape ("mowing the lawn"). Each strip is 5 times as wide as the water depth, so we get great coverage at our deepest survey areas (1000 m deep ) but less at our shallowest (100 m deep). Joined together by the computer, these strips provide a complete topographic map of the area so that we can see the underwater sediment flats, canyons, escarpments, sink holes, slumps and many other geological features.
After a while the biologists can't be held off any longer -- we just have to sample something and see what lives down there. On this trip we are sampling the sediments for live animals, the distinctive shells of dead animals, porosity, and stable isotopes of carbon to determine the origin of the primary production (did it all come from the ocean or did some come from shoreline macrophytes).
We'll be back in November, with a different team of specialists, to sample the larger animals with sleds and a beam trawl. So once we have identified an area of softer sediments from the swath map, over goes the sediment grab down to the seafloor, hundreds of meters below. It brings back a good bucket of interesting mud. Well, it's interesting to the scientists, once they can work it up and identify and measure everything back on dry land.
But, topographic maps and buckets of mud and bottles of water take us only so far -- to really see what is going on we need a camera. And we have brand new one bristling with technology. So we all wait for the deepwater towed camera system to go over the side.
Suspended by a fibre optic cable up to a kilometer or more behind the ship and an equal distance below it, the camera system is towed behind the ship beaming back real time video images to the camera pilot, who flies it (hopefully) just above the seabed. This can be tricky in rough terrain.
This is when you want everything to go well, so it was a bit of a shock when a circuit breaker blew on the winch just as we were hauling up over a particularly interesting (but treacherous) section of seafloor off Ningaloo. With power to the winch gone, the camera settled to the bottom and became a very sophisticated anchor. Power was restored quickly and the towed video system retrieved, but minus its stabilizing tail fin. Time to go into repair mode and do some more swathing while we wait.
Sometimes it's nice to forget all this sophistication and just go up on deck to enjoy the sea itself. We have a good swell running from the south which adds a bit of interest, but otherwise its sunny and pleasant. And really good viewing conditions for whales. When I've been up on deck there have usually been one or more whales spouting in the distance. Occasionally they come a little closer and we turn off the TOPAZ sub-bottom acoustic profiler. There's no point in risking upsetting our nearest neighbours.
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voyage reportsUpdated: 29/03/07
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