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Effects of Ocean Acidification on Large Benthic Foraminiferal Stable Isotope Composition Paul O. Knorr, Ph.D., Bureau of Ocean Energy Management Lisa L. Robbins, Ph.D., U.S. Geological Survey Jonathan Wynn, Ph.D., University of South Florida Pamela Hallock, Ph.D., University of South Florida Peter J. Harries, Ph.D., North Carolina State University Article submitted to ICES-JMS 1 of 1
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Effects of Ocean Acidification on Large Benthic Foraminiferal Stable Isotope Composition Paul O. Knorr, Ph.D., Bureau of Ocean Energy Management Lisa L.

Jan 18, 2016

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Page 1: Effects of Ocean Acidification on Large Benthic Foraminiferal Stable Isotope Composition Paul O. Knorr, Ph.D., Bureau of Ocean Energy Management Lisa L.

Effects of Ocean Acidification on Large Benthic Foraminiferal Stable Isotope Composition

Paul O. Knorr, Ph.D., Bureau of Ocean Energy ManagementLisa L. Robbins, Ph.D., U.S. Geological Survey

Jonathan Wynn, Ph.D., University of South FloridaPamela Hallock, Ph.D., University of South Florida

Peter J. Harries, Ph.D., North Carolina State University

Article submitted to ICES-JMS

1 of 1

Page 2: Effects of Ocean Acidification on Large Benthic Foraminiferal Stable Isotope Composition Paul O. Knorr, Ph.D., Bureau of Ocean Energy Management Lisa L.

2

vs pCO2

2

Ωcalcite

2.0

4700 1300 3000

4.4

8.0

pCO2 (µatm)

Saturation   state  = Ω calcite=[Ca 2+][ CO3 2− ])K sp (𝑐𝑎𝑙𝑐𝑖𝑡𝑒)

Control (pH 8.0, Alkalinity is 10% CO32-, ~2025)

Treatment (pH 7.6, 4% CO32-, ~2140)

Page 3: Effects of Ocean Acidification on Large Benthic Foraminiferal Stable Isotope Composition Paul O. Knorr, Ph.D., Bureau of Ocean Energy Management Lisa L.

3

Large Benthic Forams

3

Miliolid (Miliolida) Rotalid (Rotaliida)

Porcelaneous Hyaline

Imperforate Perforate

High-Mg calcite Low-Mg calcite

2 mm 2 mm

Archaias angulatus Amphistegina gibbosa

Page 4: Effects of Ocean Acidification on Large Benthic Foraminiferal Stable Isotope Composition Paul O. Knorr, Ph.D., Bureau of Ocean Energy Management Lisa L.

4

Miliolid Calcification

4 Modified after Ter Kuile et al. (1989) and Cotey and Hallock (1988)

Page 5: Effects of Ocean Acidification on Large Benthic Foraminiferal Stable Isotope Composition Paul O. Knorr, Ph.D., Bureau of Ocean Energy Management Lisa L.

5

Rotalid Calcification

5Modified after ter Kuile et al. (1989) and De Nooijer et al. (2014)

Page 6: Effects of Ocean Acidification on Large Benthic Foraminiferal Stable Isotope Composition Paul O. Knorr, Ph.D., Bureau of Ocean Energy Management Lisa L.

6

Sample Location

6

Miliolid

Rotalid

Page 7: Effects of Ocean Acidification on Large Benthic Foraminiferal Stable Isotope Composition Paul O. Knorr, Ph.D., Bureau of Ocean Energy Management Lisa L.

7

Apparatus

7

pH and Alkalinity analysis using Ocean Optics spectrophotometers

Stable isotope analysis using Thermo Delta V IRMS w/ Gasbench II, 2σ < 0.1 ‰

Referenced Guide to best practices for OA research and data reporting (2010)

Page 8: Effects of Ocean Acidification on Large Benthic Foraminiferal Stable Isotope Composition Paul O. Knorr, Ph.D., Bureau of Ocean Energy Management Lisa L.

8

Tank Chemistry

8

Page 9: Effects of Ocean Acidification on Large Benthic Foraminiferal Stable Isotope Composition Paul O. Knorr, Ph.D., Bureau of Ocean Energy Management Lisa L.

9

Results

9

n = 30

Page 10: Effects of Ocean Acidification on Large Benthic Foraminiferal Stable Isotope Composition Paul O. Knorr, Ph.D., Bureau of Ocean Energy Management Lisa L.

10

Results

10

-2 -1 0 1

-2

-1

0

1

2

δ13C

δ18O

Rotalid pH 8.0

Miliolid pH 8.0

Rotalid pH 7.6

Miliolid pH 7.6

Page 11: Effects of Ocean Acidification on Large Benthic Foraminiferal Stable Isotope Composition Paul O. Knorr, Ph.D., Bureau of Ocean Energy Management Lisa L.

11

Significance

Miliolid Rotalidδ18O p < 0.005 p < 0.005

δ13C NS (p = 0.25) p < 0.001

11

Tukey’s pairwise method

Page 12: Effects of Ocean Acidification on Large Benthic Foraminiferal Stable Isotope Composition Paul O. Knorr, Ph.D., Bureau of Ocean Energy Management Lisa L.

12

Interpretation

12

Miliolid

δ18O fractionation dependent on carbon speciation: HCO3

- 16‰ > CO32-

(Less CO32- at low pH)

δ13C not correlated to carbon speciation, no vital effect on carbon pool

Rotalid

δ18O fractionation dependent on carbon speciation

δ13C consequence of vital effect on internal carbon pool; diatom endosymbionts may benefit from increased CO2