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Factors Driving Mercury Concentrations in Snapping Turtles

Factors Driving Mercury Concentrations in Snapping Turtles. Madeline Turnquist , Charles Driscoll, Martin Schlaepfer, & Kim Schulz July 14, 2010. Why Study Turtles for Mercury?. High in trophic position Long life span Small home range Sedentary life style

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Factors Driving Mercury Concentrations in Snapping Turtles

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  1. Factors Driving Mercury Concentrations in Snapping Turtles Madeline Turnquist, Charles Driscoll, Martin Schlaepfer, & Kim Schulz July 14, 2010

  2. Why Study Turtles for Mercury? • High in trophic position • Long life span • Small home range • Sedentary life style • Unique biophysical characteristics • At times, consumed by humans

  3. Snapping Turtle Natural History • Chelydra serpentina • Description • Largest turtle in NY • Omnivores • Hibernate in winter • Females lay eggs in June • Reach sexual maturity late in life (~14yrs or 20cm) • High tolerance of pollutants • Habitat • Mainly freshwater • Bottom-dwellers Gibbs et al. 2007

  4. Objectives • Determine the driving factors for mercury concentrations in snapping turtles • Examine the correlation between body size and mercury levels • I hypothesize similar factors driving fish mercury levels are also driving the levels of mercury in snapping turtles.

  5. Objectives •   Measure a correlation between tissue mercury levels and scute mercury levels in snapping turtles. • I hypothesize a linear increase in shell mercury concentrations as mercury tissue concentrations increase.

  6. Methods and Data Collection • Lake selection

  7. Non-Lethal Tissue Sampling • Hoop nets set with bait for 12-48 hours

  8. Non-Lethal Sampling Methods • Weigh and Measure Turtle • Age Turtle • Take Shell Sample • 3rd Pleural scute • Take Muscle Sample from Tail and Legs

  9. Additional Data Collected • Water samples – pH, ANC, DOC, Total Phosphorus • Major Anions • GIS Data • Lake Area • Watershed Area • % Wetlands • % Forests – NLCD • Mercury Deposition

  10. Sample Analysis • Clean and crush shell samples • Total Hg - Milestone – DMA 80 • Paired t-test, Two-sample t-test • Pearson’s correlation coefficient (r) • One-way ANOVA

  11. Results • Muscle – 0.041 – 1.50 µg g-1 • Shell – 0 .47 – 7.43 µg g-1 • Shell 12 times GREATER than muscle • Methyl Mercury – 94% • 8 subsamples • US EPA Action Limit – 0.3 µg g-1

  12. Results – Muscle • Leg and Tail mercury levels significantly different

  13. No correlation with Size or Sex

  14. Male vs. Female Mercury levels • Collectively – muscle mercury levels not significantly different • P-value = 0.746 • Shell length and weight significantly different

  15. Water Chemistry Correlations

  16. Landscape Correlations

  17. Average Muscle Hg n = 4 n = 2 n = 3 n = 8 n = 5 n = 1 n = 3 n = 7 EPA Action Limit (0.3 µg g-1) n = 1 n = 8 A B B AB AB AB B A B A

  18. Average Shell Hg n = 8 n =9 n = 5 n = 3 n = 5 n = 4 n = 2 n = 3 n = 8 n = 1 EPA Action Limit (0.3 µg g-1)

  19. Shell Correlated with Muscle r = 0.386 p-value = 0.012

  20. Final Thoughts • Female turtles were smaller than males • Eggs/young potential way to remove Hg • Shell as possible mechanism to eliminate mercury • Useful indicator of Hg level – potential to resample • ~38% above EPA action limit • Would not recommend consuming turtles

  21. Future Directions • Sample toe nails for Hg levels – less invasive • Skin samples to test Hg levels • Growth relationship between shell Hg • Mercury in lake sediments • Compare to fish levels • Possibly compare to loon levels

  22. Acknowledgements • Edna Bailey Sussman Foundation • Maggie Schultz • Martin Schlaepfer • Charles Driscoll • Kim Schulz • NYS Parks and Campsites • Eric Paul and Ben Durie • Ed Mason • Mario Montesdeoca • Bradley Blackwell

  23. Questions, Comments, Suggestions

  24. Environmental Factors controlling Hg • Water Chemistry • Low pH <6.0 • Low productivity – Total phosphorus < 30 µg/L • Dissolved Organic Carbon (DOC) > 4 mg/L • Acid-neutralizing capacity (ANC) < 100 µequiv./L • Landscape Characteristics • Presence of wetlands • Forest cover • Large watershed relative to lake size • Mercury deposition Driscoll et al. 2007

  25. High concentrations in their brains • Birth defects • Decreased neurological ability of hatchling turtles • Lowered population survival • Damage to kidneys and renal failure (nephrotoxic)

  26. Snapping Turtle Natural History • Natural History • Omnivore • Plants, Invertebrates • Fish, Birds, Carrion • Active foraging • Ambush predator • Hibernate in winter • Females lay eggs in June • High tolerance for polluted waters • Threats • High egg and hatchling mortality • Adults vulnerable to road mortality • Human persecution Gibbs et al. 2007

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