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Stable isotope analyses at LGL-TPE, at ENSL.

Updated: Oct 31, 2022

Part I. Calcium chemistry in the clean lab

Photo 1. Weighing the samples with the high-precision scale Mettler Toledo XP26 (readability from 0.001 mg).

Photo 2. Leaching the hydroxyapatite and collagen from the cave bear samples with Jeremy and Sebastien, in the clean lab.

Photo 3. Marius performing the X8 protocol, in the clean lab. Eluting the Fe, Mg, Zn, and Sr from our samples.

Photo 4. Photo 4. Leaving the samples on the hot plate overnight.

Bonjour a tous et salutations de Lyon!

Almost 90 bone samples (N = 88) retrieved from the mandibles of cave bears and associated fauna, from the Romanian Carpathians, are being chemically prepared, in the clean lab, for the δ44Ca analyses, scheduled to be performed by the end of October, at Laboratoire de Géologie (Lgl-tpe), Terre Planètes Environnement of the École Normale Supérieure de Lyon (ENSL).

The δ44Ca results that we are about to obtain will help us to better understand the palaeoecology of the cave bears and the other contemporaneous species (deer, brown bears, cave lions, cave hyenas, wolves), from the Late Pleistocene, within the INTEGRATES’s framework.

Theoretically, the δ44Ca analyses and their results indicate a depletion of heavy calcium isotopes in vertebrates, compared to the food sources along each trophic step and therefore, providing us reliable data to understand the puzzling picture of the Late Pleistocene cave bears’ diet. To make it more simple, the high values of δ44Ca are typical for the species with a predominantly vegetarian diet (eg. deer), while the lower values characterize the carnivores (eg. cave lions). For doing this, we have to drain the entire bone of all its constituents but Ca and then analyse the Ca content at the mass spectrometer (MC-ICP-MS: Multicollector-Inductively Coupled Plasma Mass Spectrometer, “The Neptune” or “The Machine” as it is called here).

In theory, it’s quite simple. In the real life, well, things get complex and complicated. First, we have to weigh the samples (between 2-3 mg each), label them, insert them in the database, and assign them new lab numbers.

In order to get rid of all the bone’s constituents - organic (collagen) and anorganic (hydroxyapatite and elements like Fe, Sr, K, Mg, Zn), we have to apply a step-by-step work plan, following at least four protocols (eg. X8, X12, Sr Spec). Each protocol allows running a batch of 22 samples and takes one day of continuous and demanding labour. At the end of the day/protocol, the samples are put on the hot plate (70-80 degrees C), to evaporate overnight (for being able the next day to drain/wash, via another protocol, other elements). Each step of the protocol requires concentration, otherwise, we can either contaminate, mix the samples or add too much acid (acetic, nitric or cloric with various molarities). A simple mistake in the process means a chain reaction and the entire process has to be redone. To make it short, ideally, for 22 cave bear samples, to have the Ca prepared/ready for the Neptune, we need an entire working week (from weighing the samples to collecting the Ca in the teflon beakers). The Neptune requires, again ideally, an additional week to analyze four batches (88 samples) and highly trained operators. So, in theory, for 88 samples five weeks of continuous work is needed. Not to mention that Neptune is a very sensitive machine and capricious sometimes.

More than this, working in a such stimulating environment, apart from learning plenty of things, is helping us to build the research network, one of the goals of our overall endeavour. We couldn’t have done all this work without the help of dr. Jeremy Martin and dr. Sebastien Olive. Many thanks, guys!

Leaving aside the fatigue, we are aware that without certain sacrifices, in research, there will be no real progress to Science. So, fingers crossed and let’s hope for the best!

À tout à l’heure!

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