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Stable isotopes Colin MacLeod. Using Stable Isotopes (SI) To Investigate Ecological Aspects Background (the boring bit) Nucleus of elements made up of.

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Presentation on theme: "Stable isotopes Colin MacLeod. Using Stable Isotopes (SI) To Investigate Ecological Aspects Background (the boring bit) Nucleus of elements made up of."— Presentation transcript:

1 Stable isotopes Colin MacLeod

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

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

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

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

6 P P P P P P E.g. Carbon 14 N N N N N N 6 Protons, 8 Neutrons N N Number of neutrons does NOT affect chemical reactions but affects weightNumber of neutrons does NOT affect chemical reactions but affects weight Some are radio-active: C14Some are radio-active: C14 Others are stable: C12, C13Others are stable: C12, C13 Nucleus of elements made up of protons and neutronsNucleus of elements made up of protons and neutrons Some elements have different forms with different numbers of neutrons (but same number of protons)Some elements have different forms with different numbers of neutrons (but same number of protons) Using Stable Isotopes (SI) To Investigate Ecological Aspects Background (the boring bit)

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

8 One neutron = 1·675 × 10 -27 kgOne neutron = 1·675 × 10 -27 kg Therefore, atoms with more neutrons will be slightly heavierTherefore, atoms with more neutrons will be slightly heavier This affects how they behave: e.g. CO 2 in SolutionThis affects how they behave: e.g. CO 2 in Solution C12 C13 C12 C12 C12 C12 C12 C12 C12 C13 Water(cold) Air Ratio of C12:C13 1000:12 Using Stable Isotopes (SI) To Investigate Ecological Aspects Why Does This Work ?

9 Using Stable Isotopes (SI) To Investigate Ecological Aspects Why Does This Work ? C13 C12 C12 C12 C12 C12 C12 C12 C13 Air C12 One neutron = 1·675 × 10 -27 kgOne neutron = 1·675 × 10 -27 kg Therefore, atoms with more neutrons will be slightly heavierTherefore, atoms with more neutrons will be slightly heavier This affects how they behave: e.g. CO 2 in SolutionThis affects how they behave: e.g. CO 2 in Solution Water (less cold)

10 Using Stable Isotopes (SI) To Investigate Ecological Aspects Why Does This Work ? C13 C12 C12 C12 C12 C12 C12 C13 Air C12 C12 One neutron = 1·675 × 10 -27 kgOne neutron = 1·675 × 10 -27 kg Therefore, atoms with more neutrons will be slightly heavierTherefore, atoms with more neutrons will be slightly heavier This affects how they behave: e.g. CO 2 in SolutionThis affects how they behave: e.g. CO 2 in Solution Water (luke warm)

11 Using Stable Isotopes (SI) To Investigate Ecological Aspects Why Does This Work ? C13 C12 C12 C12 C12 C12 C12 C13 Air C12 C12 One neutron = 1·675 × 10 -27 kgOne neutron = 1·675 × 10 -27 kg Therefore, atoms with more neutrons will be slightly heavierTherefore, atoms with more neutrons will be slightly heavier This affects how they behave: e.g. CO 2 in SolutionThis affects how they behave: e.g. CO 2 in Solution Water(warm)

12 Using Stable Isotopes (SI) To Investigate Ecological Aspects Why Does This Work ? C13 C12 C12 C12 C12 C12 C12 C13 Air C12 C12 One neutron = 1·675 × 10 -27 kgOne neutron = 1·675 × 10 -27 kg Therefore, atoms with more neutrons will be slightly heavierTherefore, atoms with more neutrons will be slightly heavier This affects how they behave: e.g. CO 2 in SolutionThis affects how they behave: e.g. CO 2 in Solution Water (quite warm)

13 Using Stable Isotopes (SI) To Investigate Ecological Aspects Why Does This Work ? C13 C12 C12 C12 C12 C12 C12 C13 Air C12 C12 One neutron = 1·675 × 10 -27 kgOne neutron = 1·675 × 10 -27 kg Therefore, atoms with more neutrons will be slightly heavierTherefore, atoms with more neutrons will be slightly heavier This affects how they behave: e.g. CO 2 in SolutionThis affects how they behave: e.g. CO 2 in Solution Water (very warm)

14 Using Stable Isotopes (SI) To Investigate Ecological Aspects Why Does This Work ? C13 C12 C12 C12 C12 C12 C12 C13 Air C12 C12 Ratio of C12:C13 1000:20 One neutron = 1·675 × 10 -27 kgOne neutron = 1·675 × 10 -27 kg Therefore, atoms with more neutrons will be slightly heavierTherefore, atoms with more neutrons will be slightly heavier This affects how they behave: e.g. CO 2 in SolutionThis affects how they behave: e.g. CO 2 in Solution Water(hot)

15 Using Stable Isotopes (SI) To Investigate Ecological Aspects Why Does This Work ? The same happens in animals as they metabolise food they have eatenThe same happens in animals as they metabolise food they have eaten C12 gets preferentially exhaled in C0 2 and animal becomes relatively enriched with the heavier C13C12 gets preferentially exhaled in C0 2 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 N15Similarly, 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 levelThis happens with each trophic level Therefore, the higher up a food-web the greater the enrichment in heavier isotopes of C and NTherefore, 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-webIn addition, in marine environment, warmer waters = greater C13 enrichment at base of food-web

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

17 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 ? Rephrase Question In Terms of Isotopes ?????????????? N14:N15??N14:N15??

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

19 Using Stable Isotopes (SI) To Investigate Ecological Aspects How Can Scientists Use This To Study Ecology ? NH 3 + Seawater Plankton Primary Carnivore Secondary Carnivore Tertiary Carnivore Top Carnivore (N14:N15)1000:3 1000:6 1000:9 1000:12 1000:15 1000:18 1000:141000:14

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 AtlanticUsed 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 hypothesesBut 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 hypothesesUsed stable isotope analysis of bones from stranded animals for testing hypotheses Why bones ? Easy to obtain, reflects long-term diet...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:In total, samples from 150 different individuals collected between 1800 to 2002 obtained from: Museums e.g. National Museums of ScotlandMuseums e.g. National Museums of Scotland Strandings networks e.g. SACStrandings networks e.g. SAC Researchers and naturalistsResearchers and naturalists Represent six different species - all found in North AtlanticRepresent six different species - all found in North Atlantic Primarily sampled inner posterior mandible - least damage to valuable museum specimensPrimarily sampled inner posterior mandible - least damage to valuable museum specimens Samples taken weighed around 0.25gSamples taken weighed around 0.25g Decalcified to remove inorganic carbon (Soak in 0.5N HCl)Decalcified to remove inorganic carbon (Soak in 0.5N HCl) De-lipified to remove fats and lipids (Using Chloroform)De-lipified to remove fats and lipids (Using Chloroform) Actual tissue analysed: Bone collagen (Protein component of bones - makes them flexible)Actual tissue analysed: Bone collagen (Protein component of bones - makes them flexible) Size of samples analysed in mass spec: 0.7mgSize of samples analysed in mass spec: 0.7mg


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