Lab 18
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Lab 18
Plastics in the Ocean
Description of the Lab
Students explore the fate of plastics in the ocean and the issues that must be considered
when sampling for something in a large, three dimensional environment. The density of
Laboratory Materials and Equipment for Student Use
Materials and Equipment
Per
Student
Per Pair of
Students
Per Lab
Group
Per
Room
500 mL beaker
1
1
Refractometer
1
transfer pipette
1
1
Selection of 1 cm plastic samples
from each of the 7 categories (small
1
Compound Microscope with ocular
micrometer
1
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Stir bar
1
Top Loading Balance (g)
2
7.5 cm aquarium dip net with
coarse mesh (approx. 2 mm)
1
Seawater (35 0/00, 20°C)
Approx
16 L
Distilled water
200 mL
7.5 cm aquarium dip net with fine
mesh (approx. 100 µm)
1
different types of plastic cut into
pieces of different
15 g
filled with 15 L of seawater (35
Weigh boat
1
Top-loading balance
1
Paper towels
1 roll
Microscope slides and coverslips
1
Hot plate/stirplate
1
Hotpads
1
Goggles
1
Outline of Investigation
Exercise 1 – Does it Float?
Materials needed:
• 1 beaker 500 mL
Note: The approximate density of seawater of this salinity and temperature is 1.025
g/cm3, use a density, salinity, temperature chart or an online density calculator, e.g.,
http://www.es.flinders.edu.au/~mattom/Utilities/density.html to adjust for differences in
temperature, salinity or location, if it is not possible to read specific gravity from
Exercise 2 – Microplastics
Materials needed:
• 20 g Clean & Clear Daily pore cleanser (Johnson & Johnson)
• Microscope slides and coverslips
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Note: Many personal hygiene products will contain small beads of plastic. If you
substitute another product there can be other small abrasive particles such as mica.
Exercise 3 – How Much is Really There?
Materials needed:
• 7.5 cm aquarium dip net with coarse mesh (approx. 2 mm)
Note: Make sure sample contains different pieces of different sizes and plastics of
different densities, since plastic breaks down in the environment to pieces of smaller and
smaller sizes-you could have the students cut up and crush the samples they brought in, if
Answers to Questions for Lab 18
Exercise 1 – Does it Float?
a) Were you able to predict the behavior of the plastic item in the seawater based on
its recycling symbol?
Answers will vary, but in general yes. Plastics with a density greater than the
b) Based on your observations how do you think type of plastic will affect the fate of
an item in the ocean?
Answers will vary. But in general, some plastic will sink (depending on
Exercise 2 – Microplastics
1. What was the size of the microplastic beads found in the facial scrub?
2. Are these beads in the size range that would be taken in by filter feeding
organisms?
3. Certain kinds of plastic preferentially adsorb toxins such as PCB’s. Certain kinds
of plastics also provide a substrate for attachment for bacteria and other
microorganisms. What questions might a scientist ask about the effects of
microplastics both positive and negative based on this information?
Exercise 3 – How Much is Really There?
a) How does the estimate of the plastic density compare to the known density
compare using the two different types of nets?
b) Were there any other variables that affected how effective the sampling method
was at estimating the amount of plastic in the system?
How the net was held may matter. The size and the nature (e.g., resin type)
c) Neuston (surface-dwelling organisms) sampling nets are typically 333 µm mesh.
How does this compare to the size of the microplastic beads found in the body
wash. Do you think we have a good estimate of the plastics in our oceans?
d) What is the effect of sampling method on our estimate of the amount of plastic in
the tank? Do you think this would be relevant in sampling marine
environments? Why or why not?
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e) Comment on sources of error in your sampling method.
Questions
1. Using the Internet, define the “Pacific Garbage Patch.”
An area in the central North Pacific approximately between 135° W-155° W and
2. What are some of the known issues related to plastics in the marine environment?
Answers will vary but include: Marine animals mistake plastic items for food,
3. Read the commentaries posted on the issue of the Pacific Garbage patch at the three
sites listed below and answer the following questions.
a) Is there any controversy related to the size of the garbage patch? Explain.
Yes, research cruise data is not in agreement with the popular press. The
b) Is there any controversy related to the importance of plastic pollution in the
marine environment? Explain.
Yes, the effect that small pieces of plastic in the marine environment will
3. What are the options for recycling different kinds of plastic where you live?
4. Survey the body care products in your home or in the facial cleanser aisle of a grocery
or drug store for the presence of microplastic beads. Look particularly at ‘scrubs’ or
exfoliating cleansers. List the items that contain an ingredient called polyethylene
(just polyethylene not polyethylene glycol) contain small spheres of plastic.
5. Metric system review:
Optional Activity
Mass of plastic generated in 1 week ______ g x 52 weeks/year = ______ plastic per year.
2 kg per person/day x 0.12 x 365 days = ___87.6 kg ________ average amount of plastic
per year
How do your results compare to annual plastic consumption in the US and can
you think of ways to reduce this waste stream?