For the last six weeks or so I’ve been working on a small scale project to attempt to find out if stable isotopes in modern terrestrial snail shell carbonate can provide reliable climate records in southern Cyprus. This is a pilot study for an archaeologist (interdisciplinary or what?) who hopes to use shells excavated from ancient settlements to see to what extent changes in human behaviour (e.g. migration) can be linked to climate change. The period she is interested in is during the mid-Holocene, around the time of Sapropel one, when there are well documented changes between more arid and more humid climate regimes. However these records tend to be from marine and lake cores (my corals also showed evidence of a cool and wet period around this time (Royle et al., 2015)) and so it is hard to directly relate them to distal changes in human behaviour due to uncertainty in dating techniques and the effects of local microclimates. Therefore getting climate data from the sites themselves would be pretty handy.
Snails are good for this as they are a common find on archaeological sites with most just being bagged, tagged and stored away; so there is plenty of material to work on and recent work has been promising (e.g. Prendergast et al., 2015a, 2015b). However, some species are burrowers and so could be later intruders into the deposits meaning careful species identification is necessary.
This has meant that the 3 days a week I’m not working at the climbing wall I’ve been back in the Stable Isotope Laboratory with the painstaking task of identifying, cleaning, crushing, weighing and analysing a fuck-tonne (well a few smuggled Tupperware boxes worth) of modern snail shells to see if they give consistent results.
Annoyingly, not being associated with the Environmental Sciences labs in any official capacity (somehow working under the strange umbrella of the ‘Art, Media and American Studies’, seriously, what the fuck???) or have ANY research budget, means I have been completely reliant on friendly technicians to let me into labs, donate leftover (highly toxic and corrosive) chemicals and borrow equipment, which has meant a lot of wandering around the maze of ENV looking for people with the necessary access rights, begging and bartering.
I was given a few hundred snail shells that had been collected (supposedly all already dead with no bits of snail inside them…) from various localities around Cyprus to sort through and pick out the best for analysis. Unsurprisingly, the helix of a snail shell is not very easy to clean, although my re-appropriated bouldering brush did a good job of getting the shallower dirt out.
|So many snails to clean...|
After a day of repeatedly washing and rinsing and fishing globules of rotten snail carcass from deep inside the shells the whole lab, my hands and clothes stank of rancid mollusc, and they still needed a night in bleach and another morning’s cleaning to get them properly clean. One had had a maggot living deep inside it which took a lot of dislodging, while another wasn’t actually dead, just aestivating (snail hibernation) and so was released into the shrubbery…
After they’d all been cleaned and oven dried, each shell had to be individually ground into a VERY fine powder with a pestle and mortar until completely homogenised. This took a surprising amount of time and effort with my right arm suffering from some major pump – pretty sure those few days’ work did more for my climbing endurance than the whole winter’s training!
70 micrograms (that’s 0.000070g) of each powdered shell then had to be weighed out ready for analysis, that’s not a lot of shell, it’s really quite fiddly using a really tiny spatula which is actually just a bit of wire with a flattened end.
Surprisingly for the three runs necessary for the analysis the mass spectrometer worked perfectly (read previous blogs to see what a rarity this is) and from a first going over the data all looks pretty good and sensible (which, again, is a rarity). There might even be a short paper in it, so I can’t divulge too much here. But we’ll see, there are some rather big sciencey things going on here right now, that are taking up most of my time, but more on that in a future blog…