Diamondback terrapins are turtles that inhabit estuaries along the east and Gulf coasts of the United States. They range from Cape Cod, Massachusetts to northern Mexico. Terrapins were harvested in the late 1800’s through the early 1900’s as a food source with a high demand leading to reductions in their populations across their range. In the 1930’s, terrapins became less desirable food sources and populations increased in areas with good habitat, but not much is known about populations in certain areas. What make terrapins so interesting are their markings, which are highly variable and prominent. Reasons for the variation include genetic diversity and some variations in their patterns could be linked to environmental conditions.
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Soil Matters for Nesting Diamondback Terrapins!
A Lesson to be used for
High School
Earth Science
or STEM programs
developed by
Cynthia Gui,
Gabby Ignacio
Danny Schreiber
Marine Academy of Technology and Environmental Science
195 Cedar Bridge Road
Manahawkin, New Jersey 08050
projectterrapin@gmail.com
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Soil Matters for Nesting Diamondback Terrapins!
Background:
The temperature of the soil plays a key role in the outcome of Northern Diamondback
Terrapin hatchlings (Malaclemys terrapin terrapin). Not only does warmer soil lead to faster
hatchings, the temperature of the soil impacts the gender of a hatchling (Tang, 2016).
Temperature-dependent sex determination (TSD), which is common for vertebrates classified
under the reptile class, is a type of environmental sex determination through which, during
embryonic development, temperature determines the sex of the offspring (“Temperature-
dependent,” 2014). In terrapins, a higher nest temperature produces more females, while a lower
nest temperature produces more males (“Basic Facts,” 2012). Typically, a nest temperature
below 28°C, or 82°F, will produce males and temperatures above 30°C, or 86��F, will produce
females (Alderton, 1988).
In this lab, soil types, with different expected soil fractions, will be tested to determine if
a relationship exists between the percent sand of a soil and its change in temperature. Because in
New Jersey, there are daily soil temperature variations between 2 to 12°C, this lab will resemble
the temperature change during a simulated two-day period (Alderton, 1988). Through the
conduction of this lab, a greater understanding will be obtained on soil fractions and their effect
on soil temperature. This information can then be applied to hypothesize the majority sex of a
nest of Northern Diamondback Terrapin hatchlings depending on its location.
Objective:
To determine a possible trend between varying soil types and the temperature of the soils
through the conduction of a lab, and by extension, the effect of soil type on the sex of a Northern
Diamondback Terrapin hatchling.
Materials:
● Soil samples (three from three
different locations)
● Vernier software*
● 3 Vernier temperature probes*
● Vernier computer interface*
● Logger Pro*
● Tape
● Bowl
● Heat lamp
● Ruler
● Plastic milk jugs
● Computer
● Ice
*In place of Vernier System, you can use a Celsius thermometer. Vernier or compatible equipment
is for more advanced versions of this lab.
Prelab:
1. Prepare a plastic milk jug for the soil simulation (Figure 1).
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2. Cut the top off the milk jug. NOTE: Make sure to leave at least 10 cm of the milk jug.
3. Create vertical 3 holes, approximately the same circumference as the Temperature
Probes, at 1 cm, 3 cm, and 7 cm. below the soil surface.
Procedure:
1. Collect three different soil types with different expected soil fractions.
- Soil was collected from areas that were close to bodies of water, such as the
Barnegat Bay.
2. The class should be split into three groups each of which consisting of approximately 10
students. Each group will be assigned to collect data (sand fractions and temperature
readings) for one of the three soil types.
3. In order to determine percentage sand composition of the soil sample, first add 15 mL of
the sample into the soil tube along with 1 mL of dispersant.
4. Add 30 mL of water to the tube, and invert it several times to ensure all of the soil is in
solution, and that the dispersant has been evenly incorporated.
5. Once the soil has been thoroughly mixed, let it sit for 30 seconds, undisturbed.
6. After 30 seconds, take a reading of where the sand has settled out of solution and
separated with the liquid. This number is the fraction of sand out of 15 mL for the
sample.
7. After percent sand composition for the soil sample has been determined, experimentation
may begin.
8. Connect three Temperature Probes to Channels 1-3 of the Vernier computer interface.
9. Prepare the computer for data collection by opening the file “09 Soil Temperature” from
the Earth Science with Vernier folder.
10. A plastic milk jug had already been prepared with soil (refer to figures). One one side,
you should find three small holes, at 1 cm, 3 cm, and 7 cm below the soil surface.
a. Insert Probe 1 (Probe in Channel 1) into the hole that is 1 cm below the soil
surface. Push the probe in far enough so that the tip of the probe is in the center of
the jug.
b. Insert Probe 2 the same distance into the hole that is 3 cm below the soil surface.
c. Insert Probe 3 the same distance into the hole that is 7 cm below the soil surface.
11. The Temperature Probes must be parallel to the table during data collection. Secure them
in this position by taping them to a ruler as shown in Figure 2.
12. Position the lamp so that the bulb is between 5 and 10 cm from the soil surface. Do NOT
turn it on yet. Once it is in position, move it slightly off to the side to make room for the
bowl of ice to be placed on the soil. Later, when you are instructed to turn on the lamp,
move it back over the soil.
13. Fill the bowl with ice.
14. When everything is ready, place the bowl of ice on the surface of the soil as shown in
Figure 3 and click “Collect” to begin data collection.
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Figure 1
15. Once every five minutes, you will need to change the setup. These changes will simulate
the temperature changes over a two-day period. Watch the time in the meter.
16. Data collection will stop after 40 minutes.
17. Autoscale your graph by clicking the Autoscale button on the toolbar.
18. Analyze your data to determine the temperature changes.
a. Click the Statistics button and select all three Temperature Probes.
b. Click “OK”
c. Find the minimum and maximum temperatures for each sensor and record them in
the data table. NOTE: You may need to move the Statistics boxes around so that
they are visible and it is clear which one is associated with which line.
d. Subtract to find the change in temperature for each sensor and record time in your
data table.
19. Compile the data collected into Microsoft Excel.
20. Using the Data Analysis ToolPak, compare the temperature change of each soil sample
with the percent sand composition of the sample using a regression test.
21. Using the Data Analysis ToolPak once again, compare the temperature of each sample
and the depth at which the temperatures were recorded using an ANOVA test.
Simulation:
Time (minutes) Change to Setup
Time of Day (simulated)
0
Place bowl of ice on soil
Nighttime
5
Remove ice and position lamp above soil (do
not turn lamp on)
Morning
10
Turn on lamp
Daytime
15
Turn off lamp and move it aside
Evening
20
Place bowl of ice on soil
Nighttime
Figure 3
4
25
Remove ice and position lamp above soil (do
not turn lamp on)
Morning
30
Turn on lamp
Daytime
35
Turn off lamp and move it aside
Evening
40
Data collection will stop
Data Table:
Sand Fraction
(mL/15 mL)
1 cm Depth
3 cm Depth
7 cm Depth
Soil Type #1
Maximum Temperature (°C)
Minimum Temperature (°C)
Change in Temperature (°C)
Soil Type #2
Maximum Temperature (°C)
Minimum Temperature (°C)
Change in Temperature (°C)
Soil Type #3
Maximum Temperature (°C)
Minimum Temperature (°C)
Change in Temperature (°C)
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Further Questions:
1. Did the rising and falling temperatures reach their peaks and valleys at the same time?
2. How long after the light was turned off did the 1 cm line reach its first temperature peak?
3. How long after the 1 cm line reached its first peak did the 3 cm line reach its peak?
4. Looking at the graphs, was there a correlation between temperature change and the
percentage of sand in the soil sample?
5. How would the introduction of precipitation (rain, snow, sleet, etc…) affect the moisture
within a soil type and impact the temperature change of that soil?
References:
Alderton, D. (1988). Turtles & Tortoises of the World. New York, NY: Facts on File
Publications.
Basic Facts About Diamondback Terrapins. (2012). Retrieved April 19, 2016, from
http://www.defenders.org/diamondback-terrapin/basic-facts
Soil Temperature. (n.d.). Retrieved April 19, 2016, from
http://www2.vernier.com/sample_labs/ESV-09-COMP-soil_temperature.pdf
Tang, B. (2016). New Jersey Endangered and Threatened Species Field Guide. Retrieved April
19, 2016, from http://www.conservewildlifenj.org/species/fieldguide/view/Malaclemys
terrapin terrapin/
Temperature-dependent sex determination. (2014). Retrieved April 19, 2016, from
http://research.omicsgroup.org/index.php/Temperature-dependent_sex_determination