What are nudibranchs? Any of various shell-less gastropods of the order Nudibranchia, having a colorful body with fringe- like projections. They are beautiful, graceful, unreal-looking creatures. They eat plankton.

Plankton are plant and animal organisms, generally micro- scopic, having little or no power of locomotion, that float or drift in great numbers in fresh or salt water. The plant forms include diatoms and dinoflagellates; the animals include protozoans, small crustaceans, jellyfish, and fish eggs and larvae. In the ocean, plankton is the source of food, either directly or indirectly through the food chain, for all marine animals.

They must be very nutritious little critters; immense basking sharks cruise around with their mouths open, eating plankton and who knows what else is dumb enough to swim into that maw. Those are about the biggest sharks that exist, and they got that big by eating plankton. Whale sharks also subsist mainly on plankton.

You can construct a net to collect small organisms such as plankton. To do this, use string to lace the opening of a nylon stocking to an embroidery hoop or looped coat hanger wire. Place a small open bottle in the toe of the stocking, and, using rubber bands, secure it in place with the mouth toward the hoop. Attach a towing string or nylon cord to the hoop. Tow the net through the water, or let a current flow
through it.

After the net has been in the water for several minutes, pull it out, and remove the small bottle. Examine its contents under a microscope. Don't eat that stuff! Yuck!

Also collect samples from other locations. If green material -- algae -- is collected, place some in a baby food jar. Label the jars of algae to show where the samples were obtained. The jars can be arranged according to the amount of green material each contains. (Generally, the greater the amount of algae, the more nutrients there are in the
water.)