The Use of Stable Isotopes in Community Ecology

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The Use of Stable Isotopes in Community Ecology

• November 24th, 2009
• Sara Terrebonne

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Stable Isotope Ecology
Theory
Introduction
Case Study 1
Case Study 2
Case Study 3
Conclusion

• Slow beginnings in the 1950s
• Brian Fry (LSU) and Bruce Peterson (Woods Hole)
• Influential biogeochemists
• Peterson, B.J. and B. Fry (1987) Stable Isotopes
  in Ecosystem Studies. Ann. Rev. Ecol. Syst.
  18293-320
• Cited 1,344 times
• Stable Isotope Ecology 2006
• Isotopes for Iso-dopes

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Introduction
Theory
Introduction
Case Study 1
Case Study 2
Case Study 3
Conclusion

• Stable Isotope Analysis
• What is it?
• Hows it work?
• Why use it?
• Use in Community Ecology
• Food Webs
• Case Studies

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Stable Isotope Analysis What is it?
Theory
Introduction
Case Study 1
Case Study 2
Case Study 3
Conclusion

• Stable Isotope Analysis (SIA)
• Analytical tool used to track elemental cycling
  and energy flow pathways
• Useful in food web studies for tracking the flow
  of energy from primary producers to consumers

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How Does It Work?
Theory
Introduction
Case Study 1
Case Study 2
Case Study 3
Conclusion

• Stable Isotopes
• various forms of an element with a different
  number of neutrons in the nucleus that are not
  radioactive.
• Elements commonly used in SIA

(Anderson and Arthur, 1983)
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Measurement
Theory
Introduction
Case Study 1
Case Study 2
Case Study 3
Conclusion

• Its all about the ratios
• How do we get these
• ratios?
• continuous flow Isotope Ratio Mass Spectrometer
  (IRMS)

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pg
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Theory
Introduction
Case Study 1
Case Study 2
Case Study 3
Conclusion
Measurement

• d(RSAMPLE/RSTANDARD)-11000
• R 2H/1H, 13C/12C, 15N/14N, 18O/16O, or 34S/32S
• d values (permil)
• Range in nature from -100 to 50
• Enrichment experiments can artificially increase
  this range

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Theory
Introduction
Case Study 1
Case Study 2
Case Study 3
Conclusion
Food Web Ecologyyou are what you eat
50/50
100
100
Phytoplankton
Benthic Algae
-21 -20 -19 -18 -17 -16
-15 -14
d13C ()
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Theory
Introduction
Case Study 1
Case Study 2
Case Study 3
Conclusion

• Isotope do not behave exactly alike in chemical
  reactions
• Due to subtle differences in behavior and
  differences in element sources, stable isotopes
  can be used as tracers to determine the movement
  of and organic matter through an ecosystem.

• (Fry, 2006 Fig.1.6)

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Enrichment
Theory
Introduction
Case Study 1
Case Study 2
Case Study 3
Conclusion

• More light isotopes are used in chemical
  reactions within the body
• These lighter isotopes are excreted as waste
• More heavy isotopes become incorporated into
  muscle tissues
• The isotope ratio of tissues becomes heavier than
  the prey items.
• d13C is enriched by 1 per trophic level
• d15N is enriched by 3 per trophic level

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Food Web Ecologyyou are what you eat
Theory
Introduction
Case Study 1
Case Study 2
Case Study 3
Conclusion
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Theory
Introduction
Case Study 1
Case Study 2
Case Study 3
Conclusion
Food Web Ecologyyou are what you eat
Phytoplankton
Benthic Algae
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Why Use It?
Theory
Introduction
Case Study 1
Case Study 2
Case Study 3
Conclusion

• Gut Content Analysis
• Cheap to process samples
• Can identify individuals (species)
• Time consuming to process
• Need a very large sample size
• Gives a snapshot of the diet
• Differential digestive rates

• Stable Isotope Analysis
• 8-40/sample if using outside lab
• Only gives d values, no species identification
• Relatively fast and easy processing
• Can use smaller sample sizes
• Gives a long-term view of assimilated diet

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Gut Content Analysis vs. SIA
Theory
Introduction
Case Study 1
Case Study 2
Case Study 3
Conclusion
Day, J.H. 1967. The Biology of Knysna estuary,
South Africa, pp. 397-407. In G.H. Lauff (ed.),
Estuaries.
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Gut Content Analysis vs. SIA
Theory
Introduction
Case Study 1
Case Study 2
Case Study 3
Conclusion
Day, J.H. 1967. The Biology of Knysna estuary,
South Africa, pp. 397-407. In G.H. Lauff (ed.),
Estuaries.
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Detritus Dilemma
Theory
Introduction
Case Study 1
Case Study 2
Case Study 3
Conclusion

• Origin of detritus cannot be determined visually
• Large amounts of terrestrial detritus enters
  estuarine ecosystems and forest streams
• Frequently found in stomach contents
• Eating vs. Assimilating
• SIA useful in determining source and path of
  detritus in food webs

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Stable isotopes as tracers of organic matter
input and transfer in benthic food webs A
reviewPeterson, 1999
Theory
Introduction
Case Study 1
Case Study 2
Case Study 3
Conclusion
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Stable isotope evidence for the foodweb
consequences of speciesinvasions in lakes
Vander Zanden et al. 1999
Theory
Introduction
Case Study 1
Case Study 2
Case Study 3
Conclusion

• Looked at consequences of invasion of food webs
• Invaders Micropterusdolomieu (smallmouth bass)
  and Ambloplitesrupestris(rock bass)
• Native Salvelinusnamaycush(lake trout)
• The pattern Less littoral prey-fish in invaded
  lakes (abundance and richness)
• Test Using 13C and 15N SIA, determine if this
  change in community structure is consistent with
  changes in the food web

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Theory
Introduction
Case Study 1
Case Study 2
Case Study 3
Conclusion
Results of Vander Zanden et al. 1999
d15N
d13C
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Theory
Introduction
Case Study 1
Case Study 2
Case Study 3
Conclusion
Results of Vander Zanden et al. 1999

• Discovered that the top predator of the system,
  previously considered a pelagic-feeder, was
  actually more dependent on littoral prey-fish in
  lakes not invaded
• Invasive, bottom-feeding basses are able to
  outcompete native trout for littoral prey-fish,
  forcing them to rely more heavily on zooplankton
• The change in community structure that occurred
  with the invasion was consistent with trophic
  shifts that were observed and quantified using
  stable isotope analysis

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Other uses of SIA in Community Ecology
Theory
Introduction
Case Study 1
Case Study 2
Case Study 3
Conclusion

• Distribution of species (Rubenstein and Hobson
  2004)
• Niche breadth (Bearhop et al. 2004)
• Otolith SIA (contaminants)-nursery ground stock
  marker (Spencer et al. 2000)

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Conclusions
Theory
Introduction
Case Study 1
Case Study 2
Case Study 3
Conclusion

• Stable isotopes are really cool
• SIA is a useful method for tracing the flow of
  organic matter through an ecosystem
• SIA is a means for determining the long-term diet
  of organisms and food web structure
• When used in combination with gut content
  analysis and/or other observations, SIA can
  answer important ecological questions

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References

• Anderson, T. F. and M. A. Arthur (1983). Stable
  isotopes of oxygen and carbon and their
  application to sedimentologic and
  paleaoenvironmental problems. Stable Isotope
  Ecology. New York, Springer Science Business
  Media, LLC. 9.
• Bearhop, S., C. E. Adams, et al. (2004).
  "Determining trophic niche width a novel
  approach using stable isotope analysis." Journal
  of Animal Ecology 73(5) 1007-1012.
• Behringer, D. C. and M. J. Butler (2006). "Stable
  isotope analysis of production and trophic
  relationships in a tropical marine hard-bottom
  community." Oecologia 148(2) 334-341.
• Day, J.H. 1967. The Biology of Knysna estuary,
  South Africa, pp. 397-407. In G.H. Lauff (ed.),
  Estuaries.
• Fry, B., D. M. Baltz, et al. (2003). "Stable
  isotope indicators of movement and residency for
  brown shrimp (Farfantepenaeus aztecus) in
  coastal Louisiana marshscapes." Estuaries 26(1)
  82-97.
• Fry, B. (2006). Stable Isotope Ecology. New York,
  Springer Science Business Media, LLC. 308 pp.
• Newsome, S. D., C. Martinez del Rio, et al.
  (2007). "A niche for isotopic ecology." Front
  Ecol Environ 5(8) 429-436.
• Peterson, B. J. and B. Fry (1987). "Stable
  Isotopes In Ecosystem Studies." Annual Review of
  Ecology and Systematics18 293-320.
• Peterson, B. J. (1999). "Stable isotopes as
  tracers of organic matter input and transfer in
  benthic food webs A review."
  ActaOecologica-International Journal of Ecology
  20(4) 479-487.
• Post, D. M. (2002). "Using stable isotopes to
  estimate trophic position models, methods, and
  assumptions." Ecology 83(3) 703-718.
• Spencer, K., D. J. Shafer, et al. (2000). "Stable
  lead isotope ratios from distinct anthropogenic
  sources in fish otoliths a potential nursery
  ground stock marker." Comparative Biochemistry
  and Physiology a-Molecular and Integrative
  Physiology 127(3) 273-284.
• Rubenstein, D. R. and K. A. Hobson (2004). "From
  birds to butterflies animal movement patterns
  and stable isotopes." Trends in Ecology
  Evolution 19(5) 256-263.
• Vander Zanden, M. J., J. M. Casselman, et al.
  (1999). "Stable isotope evidence for the food web
  consequences of species invasions in lakes."
  Nature 401 464-467.
• Winemiller, K. O., S. Akin, et al. (2007).
  "Production sources and food web structure of a
  temperate tidal estuary integration of dietary
  and stable isotope data." Marine Ecology-Progress
  Series343 63-76.

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Questions?