LAB 4A: CLIMATE ANALYSIS USING PLANKTONIC FORAMINIFERA
Background: You have been given a series of samples containing planktonic
foraminifera representing time from the present to 150,000 years ago. You are
processing the samples to look at the climatic signal they reveal in Earth’s recent
history. You are aware that two particular species of foraminifera, Ammonia beccarii and
Elphidium excavatum, are excellent recorders of water temperature through geologic
time. Both species live in the shallow water, near-shore environment. When the Earth
experiences periods of relatively cold temperatures, ocean waters are cooler and can
retain more dissolved oxygen. These conditions favor the species Elphidium
excavatum. Alternatively, during periods of relatively warm climatic periods, ocean
waters heat up and are unable to retain as much dissolved oxygen. These conditions
favor the species Ammonia beccarii. Therefore, you have separated each species from
your samples to determine their A/E Index (Ammonia beccarii/Elphidium excavatum
Index). Comparing the number of the two species found in each sample will provide the
A/E Index by using the following formula:
A/E Index = [#A/(#A+#E)] x 100
where # = number of each species in the sample
As ocean waters heat up, the A/E Index goes up; alternately, as ocean temperatures go
down, so does the A/E Index.
1) You will need graph paper or use online graphing software to construct the graph for
2) For each time period sample you have counted the number of each species. Your
data is recorded in Table 1. Your next step is to calculate the A/E Index for each
sample. Complete the worksheet in Table 1 by using the equation provided. The first
sample has been done for you.
3) Use graph paper to plot your results. On the vertical axis you should plot the age of
the samples with "0" at the top and "-150,000" at the bottom. On the horizontal axis, plot
the A/E Index. You should now have a graph representing the climatic signal derived
from the comparison of Ammonia beccarii to Elphidium excavatum populations.
4) After completing your calculations and plotting your results, answer questions #4 and
#5 found on the next several pages.
A/E Index =
[#A/(#A+#E)] x 100
4) Analyze your graph and make an interpretation of the climatic history on our planet
during the last 150,000 years. Describe this history below (use words to explain what
is displayed on your graph).
Don’t forget the question on the next page...
5) Search the Internet for a graph of Earth’s temperature history over the past 150,000
years. Copy and paste that graph below. Compare it with your graph. Note and explain
any similarities or differences.
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