Saturday 5th June 2010

Today is going to be an ROV heavy day. After all, it is our new toy and we are enjoying getting to grips with it. Within ECOMAR and my career as a whole the equipment I have used has been passive. We send landers down on their own to gather data by autonomously and even when using drop down cameras the most input I get is when to take a photograph…..and through 6km of sonar cable the photo is actually taken 10-15seconds later, when the interesting fish is long gone. It’s a lifestyle that breeds patience, or a stomach ulcer. But the ROV is different; we can navigate complex terrain, explore the shear faces of the terraced cliffs that make up the ridge or fly right in and collect a sea urchin no bigger than a golf ball without damaging it. Suddenly we are seeing the parts of the ridge ecosystem that we have had to guess at in the past and we have the means to actively explore it.

 Today focused mainly on ROV transects; 500m representative, yet randomly placed lines on the seabed. As the ROV flies these lines at about 2m from the seabed an array of specialised cameras is manned by the science team. Animals are photographed and quantified, changes in the sediment type can be mapped and if we are lucky we get glimpses into these organisms’ natural behaviour and lifestyle.

The ROV control room

We usually move from one transect to the next as quickly as possible but one path took us up a cliff face and granted us an opportunity to experiment with the ROVs ability to gather swath bathymetry data.

A multibeam head mounted under the ROV sends out a fan of sound beams. These bounce back from the seabed like an echo and the time that passes before each beam returns gives us a single slice of the seabed under the vehicle. Since we know where the ROV is relative to the ship and since we know where the ship is due to GPS we can start putting these slices together. What emerges is a very detailed map of the seabed. In the rough terrain we face on the ridge, this allows us to get resolution far greater than we can from the ship.

The initial, very rough, interpretation of the transit up the cliff face.

Spirits remain high and each day brings something exciting and new. As ever though, time flies when you are having fun. Our time at the NW station is coming to an end and we are eager to get the information we need and leave with no regrets.

Thomas Linley

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