![](media/image1.wmf){width="2.3361111111111112in"
height="2.2604166666666665in"}

**Objectives:** To demonstrate use of plankton net. To show diversity of
organisms living as plankton.

**Methods:** Students will use plankton net to gather organisms off a
floating dock. Observations will be made using microscopes.

**Background:** A variety of organisms float around the ocean and
estuaries. These drifters are called plankton. Plankton form the basis
for the marine food chain. Plant plankton is referred to as
phytoplankton. Their position and importance in marine ecosystems is
equivalent to that of frass, shrubs and trees in terrestrial ecosystems.
Because they carry on photosynthesis, they need to float near the
surface to catch sunlight. Air bubbles and spines aid them. Scientists
estimate that 80% of the oxygen we breathe comes from phytoplankton.
Their shells have piled up on the ocean floor for millions of years,
forming what is called diatomaceous earth. Diatomaceous earth is used as
a natural pesticide, for filters in swimming pools, and as a cleaning
agent in toothpaste.![](media/image2.wmf){width="1.5256944444444445in"
height="1.5368055555555555in"}

But that\'s only part of the picture. The animal plankton, called
zooplankton, feed upon phytoplankton and each other. Zooplankton also
have adaptations to help them stay afloat. Jellyfish and comb jellies
are almost all sea water and therefore naturally buoyant. Others, like
the Portuguese man-o\'-war, have gas-filled spaces. Weak swimming
ability and hair-like structures to increase surface area are also
utilized. Some zooplankton feed whales and other filter feeders. Others
become more familiar organisms such as fish and crabs - critters that
humans like to eat. This is another connection to the plankton. One day,
we may not wait for these plankton to become the familiar seafood.
Studies are being conducted to investigate the possibility of plankton
as a human food source. Plankton patties, here we come!

**Procedure:**

\- Discuss plankton with the students. Explain that they will have a
chance to collect and then examine the microscopic organisms they swim
with at the beach.

\- Walk students to the floating dock. Emphasize safety!

\- Explain the use of the plankton net. It consists of a net with a
collecting tube attached to a holder by rope. The tiny mesh lets water
out but catches the plankton and concentrates them in the tube at the
bottom. To use the net, unwind the rope and gently drop the net in the
water. Drag the net along one complete side of the dock. At the end,
swish the net up and down to wash any plankton down into the collecting
tube. Empty the tube into a collecting jar. Hand the net to another
student.

\- After collecting is completed, return to the lab to examine your
plankton. The zooplankton move to one side toward the top if the sample
is placed near a bright light. The phytoplankton settle to the bottom
because there is no current to help keep them afloat. Be sure to take
samples from both
areas.![](media/image3.wmf){width="2.0243055555555554in"
height="1.7861111111111112in"}

-Have students make a slide by taking a dropperful of sample water and
placing a few drops on a slide. Gently slide a coverslip along the slide
until the water touches it, then drop the coverslip. This should entrap
plankton but not air bubbles. Examine the slides under the microscopes.

\- As students discover this world, have them tell characteristics of
the plankton they see.

**Evaluation:** Have students define plankton. What two types of
plankton are there? Why is plankton important?