May 18 2008
May 18 2008
Hi, it’s Kate again! Although you hear from me quite a lot - I’m the one whose been writing most of the “anonymous” blogs and captions you see with the photos everyday – I thought I’d write a bit about what I’m doing here on board. When I’m not writing blogs, of course!
I did my PhD at the University of Oxford (UK) investigating, along with some other things, the chemistry of diatoms. Diatoms are a type of phytoplankton (algae) that make their shells from opal (amorphous silica, a bit like glass). Why did I want to look at diatoms? Well, when paleoceanographers want to look back in time at past ocean temperatures and chemical properties, they usually use the relationship between water properties and the chemistry of calcium carbonate grown by a different type of algae, foraminifera. In other words, foram shells can be “proxies” for past ocean conditions. However, in the Southern Ocean, which is a really important region to study in terms of climate change over a range of timescales, calcium carbonate is poorly preserved in marine sediments, the source of fossil algae. Opal, on the other hand, is preserved really well and could provide a wealth of information. Most studies have focused on forams, and there’s a lot to be done to show that opal proxies work in the modern ocean before they can be used back in time.
My postdoc in Oxford is mostly involved with continuing my studies of diatom chemistry. However, on this cruise I’m carrying out a “little” side project looking at the chemistry of deep sea sponges. Most species of sponges make their skeletons out of opal too but, unlike diatoms, they only live on the seafloor and so their skeletal chemistry records deep water rather than surface conditions. This means that fossil sponge skeletons should record past deep waters, which, together with diatoms, means that we could potentially have information about the whole ocean! This is great, but even more work needs to be done to figure out sponge as even less is known about them than diatoms! This is where I come in: my project is to investigate different species of sponges from a variety of depths in the Southern Ocean to see if they really do reflect the surroundings in their skeletal chemistry. The sampling fits in really neatly with the rest of the cruise: whilst the others look for corals, I can just pick up any sponges that get brought to the surface in trawl and dredges. In fact, I’ve been really lucky because sponges seem to be brought up pretty much every time!
Sponges are very much harder to identify than diatoms (and can only be done by looking at the tiny pieces of skeleton under a microscope!), but I’m really lucky to have the help of taxonomist Laura Schejter from the Benthos Laboratory in the National Institute for Fisheries Research and Development (INIDEP) in Argentina. So, thanks Laura!
It’s been great fun being on board, and I’m really grateful to Laura Robinson and Rhian Waller for having me along!
Kate
Josef Kuehnast and Zim Zimmerman set another full box dredge on deck.
Daniel Wagner helps to make another mesh bag for inside the dredge, to help catch small pieces of coral.
Someone (possibly Daniel Wagner) gets friendly with the dredge bag... and possibly needs more rest...
Laura Schejter and Kate Hendry sort through some sponges that came up with the dredge.
A delicate stylasterid coral survives the dredging process.
Delicate sponge spicules, made of amorphous silica (or opal), under the microscope.
The bright moon shining over the Palmer tonight, shot by Dann Blackwood with a short exposure.
The same shot with a long exposure – the colours of the sky and sea change to a deep blue.