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Stable isotopes Colin MacLeod

Stable isotopes Colin MacLeod

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Stable isotopes Colin MacLeod

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  1. Stable isotopesColin MacLeod

  2. N N N N N N P P P P P P Using Stable Isotopes (SI) To Investigate Ecological Aspects Background (the boring bit) • Nucleus of elements made up of protons and neutrons E.g. Carbon Nucleus 6 Neutrons 6 Protons,

  3. E.g. Carbon 12 N N N N N N P P P P P P 6 Protons, 6 Neutrons Using Stable Isotopes (SI) To Investigate Ecological Aspects Background (the boring bit) • Nucleus of elements made up of protons and neutrons • Some elements have different forms with different numbers of neutrons (but same number of protons)

  4. N N N N N N N P P P P P P Using Stable Isotopes (SI) To Investigate Ecological Aspects Background (the boring bit) • Nucleus of elements made up of protons and neutrons • Some elements have different forms with different numbers of neutrons (but same number of protons) E.g. Carbon 13 6 Protons, 7 Neutrons

  5. N N N N N N N N P P P P P P Using Stable Isotopes (SI) To Investigate Ecological Aspects Background (the boring bit) • Nucleus of elements made up of protons and neutrons • Some elements have different forms with different numbers of neutrons (but same number of protons) E.g. Carbon 14 6 Protons, 8 Neutrons

  6. N N N N N N N N P P P P P P Using Stable Isotopes (SI) To Investigate Ecological Aspects Background (the boring bit) • Nucleus of elements made up of protons and neutrons • Some elements have different forms with different numbers of neutrons (but same number of protons) E.g. Carbon 14 • Number of neutrons does NOT affect chemical reactions but affects weight • Some are radio-active: C14 • Others are stable: C12, C13 6 Protons, 8 Neutrons

  7. N N N N N N N N P P P P P P Using Stable Isotopes (SI) To Investigate Ecological Aspects Background (the boring bit) • Radioactive isotopes used for measuring time e.g. radiocarbon dating (C14) • Stable isotopes used for measuring rates of biological reactions, patterns of energy flow etc. • Usually measured as ratio of two stable isotopes of same element (e.g. C12:C13 or delta C13 or ΔC13 or C13) E.g. Carbon 14 6 Protons, 8 Neutrons

  8. C13 C13 C12 C12 C12 C12 C12 C12 C12 C12 Using Stable Isotopes (SI) To Investigate Ecological Aspects Why Does This Work ? • One neutron = 1·675 × 10-27 kg • Therefore, atoms with more neutrons will be slightly heavier • This affects how they ‘behave’: e.g. CO2 in Solution Air Water (cold) Ratio of C12:C13 1000:12

  9. C13 C13 C12 C12 C12 C12 C12 C12 C12 C12 Using Stable Isotopes (SI) To Investigate Ecological Aspects Why Does This Work ? • One neutron = 1·675 × 10-27 kg • Therefore, atoms with more neutrons will be slightly heavier • This affects how they ‘behave’: e.g. CO2 in Solution Air Water (less cold)

  10. C13 C13 C12 C12 C12 C12 C12 C12 C12 C12 Using Stable Isotopes (SI) To Investigate Ecological Aspects Why Does This Work ? • One neutron = 1·675 × 10-27 kg • Therefore, atoms with more neutrons will be slightly heavier • This affects how they ‘behave’: e.g. CO2 in Solution Air Water (luke warm)

  11. C13 C13 C12 C12 C12 C12 C12 C12 C12 C12 Using Stable Isotopes (SI) To Investigate Ecological Aspects Why Does This Work ? • One neutron = 1·675 × 10-27 kg • Therefore, atoms with more neutrons will be slightly heavier • This affects how they ‘behave’: e.g. CO2 in Solution Air Water (warm)

  12. C13 C13 C12 C12 C12 C12 C12 C12 C12 C12 Using Stable Isotopes (SI) To Investigate Ecological Aspects Why Does This Work ? • One neutron = 1·675 × 10-27 kg • Therefore, atoms with more neutrons will be slightly heavier • This affects how they ‘behave’: e.g. CO2 in Solution Air Water (quite warm)

  13. C13 C13 C12 C12 C12 C12 C12 C12 C12 C12 Using Stable Isotopes (SI) To Investigate Ecological Aspects Why Does This Work ? • One neutron = 1·675 × 10-27 kg • Therefore, atoms with more neutrons will be slightly heavier • This affects how they ‘behave’: e.g. CO2 in Solution Air Water (very warm)

  14. C13 C13 C12 C12 C12 C12 C12 C12 C12 C12 Using Stable Isotopes (SI) To Investigate Ecological Aspects Why Does This Work ? • One neutron = 1·675 × 10-27 kg • Therefore, atoms with more neutrons will be slightly heavier • This affects how they ‘behave’: e.g. CO2 in Solution Air Water (hot) Ratio of C12:C13 1000:20

  15. Using Stable Isotopes (SI) To Investigate Ecological Aspects Why Does This Work ? • The same happens in animals as they metabolise food they have eaten • C12 gets preferentially exhaled in C02 and animal becomes relatively enriched with the heavier C13 • Similarly, with isotopes of nitrogen, N14 gets preferentially excreted in urea etc. and animal becomes relatively enriched with the heavier N15 • This happens with each trophic level • Therefore, the higher up a food-web the greater the enrichment in heavier isotopes of C and N • In addition, in marine environment, warmer waters = greater C13 enrichment at base of food-web

  16. NH3+ NH3+ NH3+ NH3+ Primary Carnivore Secondary Carnivore Plankton Seawater Top Carnivore Tertiary Carnivore Using Stable Isotopes (SI) To Investigate Ecological Aspects What Happens in Nature ? (N14:N15) 1000:6 1000:9 1000:12 1000:3 +3‰ +3‰ +3‰ +3‰ +3‰ 1000:15 1000:18

  17. Rephrase Question In Terms of Isotopes ??????? N14:N15?? Using Stable Isotopes (SI) To Investigate Ecological Aspects How Can Scientists Use This To Study Ecology ? What Trophic Level Does a Species Feed At ? What is the Ratio of Nitrogen Isotopes in its Tissues ?

  18. Blender Blender N14:N15? PREPARATION Decalcification Delipification Dehydration Mass Spectrometer (measures weights all atoms of specific elements in sample) ON ON OFF OFF Using Stable Isotopes (SI) To Investigate Ecological Aspects How Can Scientists Use This To Study Ecology ? Ratio of different isotopes e.g. 1000:14 N14:N15 (reflects trophic level of animal)

  19. (N14:N15) 1000:12 1000:3 1000:6 1000:9 NH3+ NH3+ NH3+ NH3+ Primary Carnivore Secondary Carnivore Plankton Seawater Top Carnivore 1000:14 Tertiary Carnivore 1000:15 1000:18 Using Stable Isotopes (SI) To Investigate Ecological Aspects How Can Scientists Use This To Study Ecology ?

  20. Using Stable Isotopes To Investigate Beaked Whale Ecology (the interesting bit!!) • Used data from stranded animals to develop hypotheses on beaked whale ecology in the North Atlantic • But Strandings data subject to an number of unquantifiable biases - therefore need independent testing of hypotheses • Used stable isotope analysis of bones from stranded animals for testing hypotheses • Why bones ? Easy to obtain, reflects long-term diet... • ...And hard to get a whole whale into a blender!

  21. Using Stable Isotopes To Investigate Beaked Whale Ecology (the interesting bit!!) • In total, samples from 150 different individuals collected between 1800 to 2002 obtained from: • Museums e.g. National Museums of Scotland • Strandings networks e.g. SAC • Researchers and naturalists • Represent six different species - all found in North Atlantic • Primarily sampled inner posterior mandible - least damage to valuable museum specimens • Samples taken weighed around 0.25g • Decalcified to remove inorganic carbon (Soak in 0.5N HCl) • De-lipified to remove fats and lipids (Using Chloroform) • Actual tissue analysed: Bone collagen (Protein component of bones - makes them flexible) • Size of samples analysed in mass spec: 0.7mg