Wednesday, 27 August 2008

First station teething problems

I guess any first station is likely to have a few teething problems; this one certainly did!
We neglected to check how the display of the CTD software was prepared for the cast - we wanted to have fluorescence (a measure of the amount of chlorophyll a, and therefore phytoplankton [microscopic plants], in the water) displayed so we could trigger bottles at particular depths, depending on the fluorescence readings. Unfortunately, we couldn't see the downcast (measurements as the instrument descends) data either, so we couldn't estimate fMax from that either; we opted to trigger the bottles at fairly standard depths (3,000, 2500, 1750, 1250, 1050, 850, 500, 300, 211 100, 50 and at the surface). We've fixed the display for the next station, of course!

That wasn't the only problem; quite a few of the Niskin bottles on the CTD mafunctioned in one way or another. The one triggered at the deepest depth we can reach with the wire available (3,000m) failed to trigger at all. The third bottle from 1,750m had a length of string on it that was somehow too short and didn't close properly. The 10th bottle, triggered at 100m had a leaky tap on it and the 11th bottle out of 12 had a tap missing by the time we saw it on deck again. This meant that we couldn't really take samples from 4 of the bottles, as there would have been contamination of the water samples, rendering them useless.

We hope the ship's crew can fix the niggles with the bottles, or swap them out for others, as it's rather important that we can effectively sample throughout the water column!

This had knock-on effects for 3 components of the science I'm partly responsible for, namely taking nutrient samples (4 depths unavailable), chlorophyll a sampling and phytoplankton collection. (I'll cover what those entail later in the cruise when we're more into the swing of things and I have a chance to take photos of someone else doing it, instead of me being too involved in doing the work to mess about with photography!).

Yes, the time on this post is correct, I am up and about and still working at after 4am (having not been to bed yet)!
CTD deployment photo courtesy Bradley Flynn

Comments:
Well, its been an interesting first few days, steaming to the first station into strong north-easterly winds on the nose; finally settled down now. Having access to email onboard has its pros and cons - you can stay in touch with family and friends, but the land-based work continues!

Just spent half an hour vainly looking for dinoflagellates under the microscope - its pretty barren out here although Bradley picked up quite a bit of plankton in the multinet sample from the upper layers. Its been useful to see how the CTD is used and how the water samples are processed - being an East coast fisheries biologist I haven`t been exposed to much of this.... trawls are much anticpated!
 
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