Introduction
Diary
	19 July
	16 July
	15 July
	14 July
	13 July
	12 July
	11 July
	10 July
	9 July
Participants

 

R/V Pelagia Cruise BIOSYS
Thursday, 20 July 2006	The sidescanwinch: "Ron, Veit and Tim busy with the winch for the side scan"
For me the day usually starts at 10:30 or 11 in the morning. After having a shower, I get myself a cup of tea and sneak into the lab to watch the biologists' underwater camera runs or have a look at the different species of animals or types of muddy stuff they bring up on deck with their sampling devices. This is very important for me as a geologist, because the biologists' work is ground-truthing what I have been seeing during my night shifts.
Together with a colleague, I start working soon after dinner, around 8 PM until about 4 AM. We operate a sidescan sonar, a fish-like instrument that is being towed behind the ship. This sonar sends out pulses of sound toward the seabed. Depending on the seabed morphology and sediment type, different amounts of sound are scattered back to the sonar vehicle. This returning sound is then converted into grey scales and continuously displayed as a kind of aerial photograph as the survey profile continues. All the profiles together make an acoustic map of the seafloor in a fast and economic way (which is also a reason why we work during the night). On these maps we can then distinguish areas of living cold-water corals, dead coral framework and background sediment (mostly mud), as well as all other types of sediment and bedrock geology exposed on the seabed. Operating the sonar can be quite demanding as we 'fly' the sonar only about 10-20m above the seafloor. The only control of 'flying' is by hauling in or paying out cable from the winch to which the sonar is attached. Since some coral reef structures sit on top of mounds several tens of meters high, one has to have a constant look at the multibeam to know when the seabed rises in order to avoid hitting the ground. The ship speed also has to be watched all the time, because, for example, when the ship slows down the cable sinks to the bottom and the sonar height has to be compensated by hauling in cable. Anyway, enough of the technicalities. My day continues with a culinary delight created by John, the chef de cuisine. Other people call it just lunch, but it is more than that. One has to be here to taste and enjoy it. After lunch I prepare for the coming night shift. First I have a chat with Conny and Andy, setting the frame for the new survey, then we calculate new survey track lines and hand them to the bridge. After this I have time off: drink more tea, eat biscuits and try to enjoy the Scottish summer until John serves another one of his masterpieces on a plate (dinner). And after dinner, we get ready again on deck to deploy the sidescan sonar for another exciting watch into the unknown. even if it is all absolutely flat terrain and boring muddy seafloor for hours without change, not many people have experienced and seen this before on the seabed in the area, apart from us. It is exactly this circumstance that makes the sidescan survey so exciting, as you never really know what is down there to be seen and found.   Veit Huehnerbach National Oceanography Centre, Southampton, UK