Fossil Biodiversity Distribution as a Habitat Mapping Tool

Erin Arnold

Antarctic CRC/IASOS

Introduction

• Quantifying and qualifying variability in the pelagic ocean, though space and time

• Exploring biodiversity of Recent fossil planktonic foraminifera: both global distribution and temporal patterns

• Advantages of foraminifera– Widely distributed, global taxonomy, well

preserved in the sedimentary records

Diversity• Indices describe how individuals in a

sample are distributed among the species

• 3 diversity measurements– Species richness (S, simple number of species)– 2 diversity indices (Shannon Index, Evenness)

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Diversity

• Advantages of method:– Species independent – Describe and compare between both ancient

and modern systems– Describe and compare between different

taxonomic groups

Spatial Patterns

• Diversity of fossil forams from coretop records calculated for points distributed over world’s oceans

• Exploring the response of community structure (dominance and evenness) to habitat change

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Distribution of species number

Species Number

< 00-55-1010-1515-2020-25>25adapted from Rutherford et al. 1999

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Distribution of Shannon Index

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Shannon Index

Arnold 2002

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Distribution of Equitability

Equitability

<00-0.20.2-0.40.4-0.60.6-0.80.8-1>1

Arnold 2002

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annual average SST

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Temporal Variability

• Exploring the temporal variability of the pelagic habitat over a timescale of a half million years

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Subantarctic Front

Polar Front

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Temporal Variability

• Rates of change in diversity calculated to determine periods of high variability

• d Diversity/ d time

• Absolute values show total magnitude of change

• The relation between biodiversity and habitat change through time was explored by comparing rates of diversity and oxygen isotope ratios

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Oxygen Isotope Ratios

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Plot title for analysis

80% level coherency CI

Data files: E4918_18.series, E4918_H.series

Non-zero coherency (80%)

E4918 -O18

E4918 H'

Coherency

FreqPeriod

Bandwidth for 100 lags on 244 values at ²t = 2.000

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.000 .0100 .0200 .0300 .0400 .0500 .0600 .0700 .0800 .0900 .1000100.0 50.00 33.33 25.00 20.00 16.67 14.29 12.50 11.11 10.00

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80% level CI

Frequency vs Phase Angle Data files: E4918_18.series, E4918_H.series

FreqPer

Bandwidth for 100 lags on 244 values at ²t = 2.000

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Conclusions

• Planktonic habitat sensitive to rapid climate change

• Rapidly fluctuating diversity during orbitally driven transition periods

• Diversity is sensitive to habitat, as defined by SST• Diversity as a habitat mapping tool can be applied

to modern and ancient ecosystems, and to different plankton groups