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Crozet Cruise 13/12/2005

For those of you who having been following the D300 Crozet blog, you may have detected a note of frustration over the past few days. Well that has largely evaporated today and changed to mild euphoria. All because of a two buckets full of sea cucumbers and some nice fish pics!

The day started with the recovery of a bottom trawl fished overnight at 4200 metres water depth. Such trawls require a lot of skill to do; because of their depth, they need 11.2 km of trawl cable out from the ship. As you can imagine, setting the trawl on the sea floor, keeping it there and then recovering is not easy. Luckily Ben is a trawling expert and despite the fact that the trawl got snagged and was damaged, we got an excellent catch. Although it is very early in the day, it seems that the catch, particularly that of invertebrate detritovores was dominated by holothrians (sea cucumbers), and seems very diverse for such an abyssal site. This is an important result, of which more later!
Just some (five) of the species found at Crozet site M5
Just some (five) of the species found at Crozet site M5

ROBIO was recovered following its deployment yesterday and, as promised, has come up with some great photos of fish feeding at the sea floor. The dominant species is Coryphaenoides armatus, the abyssal grenadier, which also turned up in the trawl. The fish arrived at the bait after about 25 minutes and in some numbers as you can see. The photographs also show the remains of phytoplankton (known as "phytodetritus") at the sea floor.

Coryphaenoides armatus arrive to feed on bait (mackerel) set by ROBIO
Coryphaenoides armatus arrive to feed on bait (mackerel) set by ROBIO. Note the green material (phytodetritus) at the bottom of the photograph

And one we caught in earlier!
And one we caught in earlier!

The “phytodetritus” is the key to the Crozet project. We hypothesized that its presence or absence is an important driver for the diversity of the deep-sea community below the bloom site (see blog 4-5/12/2005) our site M5. Where there is no bloom and presumably not much if any phytodetritus (M6) we predict that we will see a very different community. A long way to go, but the first piece of the jigsaw puzzle is in place!

Last updated 4/02/08