JC36: Geology & biology of the Whittard Canyon


Cruise diary

9 July 2009
Location: Whittard Canyon, 48º 55' N / 11º 09' W

Andy writes:

A couple of days ago, I wrote about creatures living in the mud that we collect on the seafloor. I’m told it wasn’t exciting enough, so this time I’ll write about the mud itself and what we do with it (pause for ironic laughter). First we get our mud from the seafloor using a megacorer, a strange contraption fitted with transparent plastic tubes that sink into the seafloor and fill up with sediment.  This is pretty tedious – you just sit around in the lab watching the corer going down to the seafloor 3.6 km below the ship - and then returning with tubes half full of mud (or not, depending on whether it worked). The whole process takes about 3 hours.

Explaining how we get the tubes off the corer is boring, so let’s skip straight to the next stage – cutting the cores. This is highly technical - you push the core up from the bottom an ‘extruder’ (a stick with a circular thing on the end), slice off sections with a metal plate as they emerge from the top of the core tube, and put them into the bucket. Below is a picture of Paul and Jens doing just that.

Next comes the exciting part. You pour the mud from the bucket onto a sieve and carefully wash away the mud with a fine spray of water from a hose, to leave the animals on the sieve. Apart from sieving gently so that you don’t damage the animals, the important thing is not to turn around quickly and spray the person next to you. Below are some pictures of Teresa and Chris sieving. When you’ve finished you wash the animals off the sieve into a bottle and pour in preservative.

At this point you think you’ve finished the job, but there’s still the washing up to do. The mud from below 15 cm in the core we throw away because few things live that deep.  Then the muddy tubes have to be washed, providing plenty of opportunity to get thoroughly wet rather than just slightly wet. Core cutting and sieving is a bit of a chore, but can actually be quite enjoyable, particularly when the sun is shining and the sea is calm. But it’s not so nice at 4 am when you’ve just crawled out of bed! 

The animals sieved out of the mud are mostly worms and crustaceans between half a millimetre and a centimetre or so in size. They are called macrofauna to distinguish them from the megafauna – the big sea cucumbers, starfish etc that you see on the surface of the sediment. The macrofauna are very important and some people spend their entire working lives studying just one type, for example, the worms.  Well, it has to be done…..!

Corer going down into the sea

Corer coming back out of the sea with tubes
full of sediment from 3.6 km deep

Paul and Jens cutting a core.
Paul is holding, Jens is slicing.

Chris pouring mud from the core
into Teresa’s sieves. Teresa is looking alarmed.

There, that’s better….

This is what you end up with – some muddy
lumps and a few animals on a sieve.

Libby and Jens sending mud back from where
it came from – the bottom of the sea

Lucy doing the washing up.

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