Name
Marine Biology—Mr. Nelson
"The Wanderers"-- PLANKTON LAB
Objectives:
1.
2.
3.
4.
Identify several types of plankton.
What are plankton and what are their roles in ecosystems?
What are some morphological characteristics of phyto & zooplankton?
What adaptations do plankton have to a pelagic life?
Materials:
prepared plankton slides
compound microscope
pipette and beaker of water
living marine plankton
cottonballs
cover slips
Background:
Plankton are free floating organisms found in fresh water or salt water.
The term plankton is Greek for "wanderers," and these organisms are usually
found drifting with the currents. They generally are found floating in the top 200
meters of the ocean, but some can migrate vertically to deeper depths. They are
mostly small organisms-- unicellular in size,
although they can grow to several thousand
pounds like the Mola sunfish.
Plankton are extremely important in the
first two trophic levels of the food pyramid.
Phytoplankton (plant plankton), are the
primary producers of the ocean and produce
most of the world's oxygen. Zooplankton
(animal plankton), are the primary consumers
and eat the phytoplankton.
In general, plankton are pelagic
organisms (organisms in the water column)
that are unable to swim against a current for an
extended period of time. Pelagic animals
capable of swimming are called nekton.
Plankton may be classified in a number of
ways. They can be grouped into phytoplankton
(plant organisms) or zooplankton (animal
organisms). They may also be classified by
habitat, such as oceanic (offshore), neritic (near shore),
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epipelagic (surface to 100-200 meters), or mesopelagic (200-1000 meters).
Sometimes special terms are used for plankton occupying specific habitats.
The name neuston refers to organisms that live at the surface film of the water.
Some plankton, the holoplankton, exist as such throughout life, whereas
meroplankton are planktonic for only a portion of their life cycle, as are clams at
the juvenile stage or fish at the larval stage.. Pelagic animals capable of
swimming are called nekton.
During this lab you may notice that some of the plant organisms, or
phytoplankton, are capable of movement. For example, many of the flagellates
(phytoplankton with whiplike tails) exhibit motion and, if your sample contains
dinoflagellates (meaning "horrible whips"), you may see them spiraling through the
water. Even some of the diatoms move! Generally speaking, there are two main types
of diatoms; the round ones are called centric diatoms, and the elongated ones pennate
or raphate diatoms. The elongated diatoms seem to glide along the bottom of the
sample. They do so by creating waves of their cell membrane in a groove (the raphe)
that runs between their two valves. Of the zooplankton, many of the ciliate protozoans
(microorganisms with hairlike processes, or cilia, extending from the cell surface) tend
to glide along, and the tintinids (ciliates with a vase like shell) may dart around. Other
small animal organisms that you may see are rotifers, or wheel animalcules; ostracods,
which are crustaceans that appear to have a clam like shell around them; cladocerans,
another crustacean; and numerous forms of benthic and nektonic organisms that may
be illustrated in the plankton guides available in class.
Some larger zooplankton that you might see include copepods, mysids, shrimp,
chaetognaths (glass or arrow worms), salps, and medussa. The copepods are common
in most seawater samples, and it is interesting to note how they use their antennae to
swim: in fact, the word copepod means "oar foot". If chaetognaths are present you will
probably find that they are eating other organisms. You should also see some microand nannoplankton. If smaller plankton are present, they may appear to be moving
rapidly and you will need to add cotton ore gelatin to slow them down.
Finally, plankton can be classified according to size, as in the following list:
macroplankton = Over 2000 micrometers
mesoplankton = 200 - 2000 micrometers
microplankton = 20 - 200 micrometers
nannoplankton = 2-20 micrometers
ultranannoplankton = smaller than 2 micrometers
In this lab you will be examining a sample of plankton taken by a standard
mesh net that was pulled by a ship in the ocean. Just think, these are very
important organisms in the ocean and we can't even see most of them.
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Procedure:
1. Obtain a preserved zooplankton slide from the lab cart.
2. Use low power to scan your slide and observe the different types of plankton.
3. Accurately sketch 3 different zooplankton organisms under the highest power
possible in which you still see the whole organism.
4. Remember our rules for microscope sketches. The total magnification should be
recorded below the sketch. In addition, indicate the size of the plankton organism on
line #3 of each sketch.
For consistency use the following:
Low power diameter = 5000 um.
Medium power diameter = 2000 um.
High power diameter = 500 um
5. Use colored pencils to indicate any color which will improve the accuracy of your
drawing.
6. Use the plankton keys, text, etc., to help you identify each of the three plankton.
First, determine if it is a zooplankton or a phytoplankton and add this to your sketch on
line #1.
7. On line #2, write the name of the organism. Depending on the the key, this could be
the a scientific name, a genus name, a family name, etc. Try to avoid the use of common
names.
8. On line #4, classify the plankton based on its size (macroplankton through
ultranannoplankton in the background information on the first page of this lab).
9. Obtain a prepared slide of diatoms from the lab cart. Sketch 2 different diatoms
following the same rules:
a. Total magnification below the sketch
b. Zooplankton or Phytoplankton on line 1
c. Name of organism on line 2
d. Size of the organism on line 3
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e. Classification based on size on line 4
10. Now you will observe a saltwater sample with unpreserved living plankton. Use
your depression slide and obtain a living plankton sample from your teacher. Try
focusing at different powers. At high magnifications, be prepared for rapid movement
of the plankton. You may notice that many organisms become more active the longer
you look at them under the microscope. The microscope light is heating the water,
causing them to move faster. You can slow them down by adding cotton fibers to the
water. Other chemical methods for slowing plankton movement should be avoided
because they tend to kill the organism.
11. Identify 4 different living plankton organisms (under the highest power in which
you can see the entire organism). Can you determine which organisms are eating
which? Try to obtain different organisms than your preserved plankton and sketch
each. For the 4 living plankton sketches, include all the information from procedures 48.
Analysis Questions:
1. Planktonic organisms have special adaptations that enable them to remain and or
move within their pelagic environment . Name a specific example of planktonic
adaptation that you see in your sketches of the plankton. Give the name of the
organism, describe the structure, and specify its function.
Organism Name:
Describe structure:
How does this structure help this organism remain in or move within the Pelagic
Zone?
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2. The oxygen your breathing, right now, probably was produced by the
phytoplankton. According to Wikipedia, oceanic autotrophs (phytoplankton) account
for only about 0.2% of the total biomass. However, phytoplankton account for over
50% of oxygen production. Why does more photosynthesis take place on Earth in the
oceans than on the land?
3. Many species of Zooplankton display "vertical migration". What is vertical
migration and how is it beneficial to plankton?
4. Based on your previous answer, would you expect to find both zooplankton and
phytoplankton at the same vertical depth or at different vertical depths of the ocean?
Support your answer.
5. Describe one physical/structural difference you can observe between zooplankton
and phyto plankton. Describe why they have this difference.
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6.
Why are the plankton so important to marine ecosystems?
7. Use a resource to research "red tide". In a few sentences summarize what red tide is,
name a group of plankton responsible, and tell me why red tide blooms cause us to
close clam beds.
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