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Lab 9
Macroalgae
Description of the Lab
An introduction to the diversity of macroalgae in the lab with an optional field
exercise. Students will look at basic anatomy and investigate the different pigments found
in the major groups using paper chromatography. Students can then investigate the
distribution of different species of algae at a field site. Alternatively students can use
internet to look at algae monitoring sites.
Laboratory Materials and Equipment for Student Use
Materials and Equipment
Per
Student
Per Pair of
Students
Per Lab
Group
Per
Room
Compound microscope
1
Hand lens
1
Mortar and pestle
Goggles
1
Funnel
Filter paper
4
Capillary tubes
4
specimens of Green, Brown and Red
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Algae or photographs
group
Chromatography paper
4 strips
Erlenmeyer flasks
4
Optional Field Supplies
0.5 m2 quadrat
1
100 m horizontal transect rope
1
50 m vertical transect rope
1
Clipboards
1
GPS (optional)
1
keys (set)
Fresh Live Materials Needed
Green algae Chlorophyta
10 g
Brown algae Phaeophyta
10 g
Fresh spinach leaves (or other dark
10 g
of chromatography solution
Colored pencils
Grease pencil
1
Scissors
1
Internet access
1
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Reagents
20% ethanol/80% acetone solution
50-75
mL
Preparation of Laboratory Materials and Reagents
Reagents
Note: Preparation of all reagents and filling of chromatography tubes with
20% Ethanol/80% acetone solution for pigment extraction (1L)
1. Measure 200 mL of 95% ethanol into reagent bottle.
Chromatography solution (10% acetone/90% petroleum ether) 0.5L
1. Measure 50 mL of acetone into a reagent bottle
Mix gently and cap.
3. Store in flammables cabinet until ready for use.
chromatography solvent
40-50
mL
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Outline of Investigation
Exercise 1 – Diversity in Macroalgae Structure
Materials needed:
• assorted examples of green, red, and brown algae; fresh specimens, preserved or
dried herbarium specimens or photographs can be used
Exercise 2 – Identifying an Unknown Algal Sample using Paper Chromatography
Materials needed:
• mortar and pestle
• goggles and gloves
• funnel
• filter paper (coffee filters work just fine)
• beaker of appropriate size to balance funnel
• chromatography solvent (NOTE this contains ether-do NOT leave uncapped at
any time)
Note: If access to a field site to collect algae samples is limited, tissue can be collected
and frozen for use later. If algae is collected and begins to deteriorate the pigments will
begin to breakdown and students will see those breakdown products in their paper
Chromatography solution contains petroleum ether, make sure that tubes remain capped
except when chromatography paper is being attached. Make sure ventilation in room is
adequate. Prepare solution and fill tubes in a fume hood.
Exercise 3 – Macroalgae Identification
Materials needed:
• 0.5 m2 quadrat
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• reference charts and identification keys
Exercise 4 – Macroalgae Monitoring
Materials needed:
Answers to Questions for Lab 9
1. How are the basic algal structures (e.g., blade, stipe, holdfast) different from the
leaves, stems and roots of land plants? What are the functions of those structures?
Most terrestrial plants have vascular tissue that is specialized to conduct water
a. pneumatocyst: filled with gas, helps thallus to stay upright and to absorb
sunlight.
2. How were you able to identify the type of algae that was the source of the unknown
pigment extract?
Banding pattern of pigments. If the unknown was brown algae there should be a
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3. Why do green algae and terrestrial plants share so many of the same photosynthetic
pigments?
4. What is the purpose of accessory pigments?
To increase the energy available for photosynthesis by increasing the range of
5. How are the different pigments found in different types of algae related to the depth
at which each algae is found?
In general, the pigments found in red algae allow it to harvest the wavelengths of
6. Why is it necessary for biologists to monitor the algae growth on the coastline?
The growth of algae gives us information about the clarity of water, pollution
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7. Other than food sources for ocean communities, what are other ways these different
forms of algae are used in our society?
a. Source of iodine to prevent enlarged thyroid (Goiter)
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8. Use your text and other resources to fill in the table below as a review exercise
Main
Pigments
Accessory
Pigments
Chemicals
Making
Up
Cell Walls
Evolutionary
Ancestors
Ocean Zone
in which
They Are
Found
Chlorophyll
a and b
carotenoids
(different
xanthophylls and
carotenes)
Cellulose
Some
species
calcium
carbonate
plastid
bearing
ancestor that
arose through
primary
endosymbiosis
generally
shallow
intertidal for
the
macroforms,
many
planktonic
microalgae