Plankton are an incredibly diverse group of organisms that can be found in both fresh water and marine environments. There are two types of plankton – phytoplankton, which is the plant form of plankton that makes its own food, and zooplankton, the animal form of plankton that grazes on the phytoplankton.
These microscopic organisms drift atop streams, rivers, lakes and oceans and the presence of plankton can tell you a lot about their environment.

In this activity, we’ll create a net that you can use to catch plankton. Plankton are very small organisms. As you move your net through the water, they will get stuck to the sides.

This activity will take about five minutes of preparation followed by approximately 15 minutes of learning. It is best suited for students in middle school grades.

Materials:

• Recycled (soda, water) bottle with cap
• Nylon pantyhose (cut each leg) or knee highs
• Hole punch
• String
• Wire hanger
• Duct tape
• Scissors
• Jar or Tupperware

Directions:

1. Build your bottle. Start by cutting your bottle into thirds. The first cut should be made about 3-4 inches from the neck, the second about 4-5 inches from the first. Using a hole punch, place three evenly placed holes around one of the ends of the middle piece of the bottle. The bottom portion of the bottle can either be recycled or saved for a later activity. Make sure to keep the bottle lid on the top.

2. Cut your nylon. Cut a small hole in the toe of the nylon stocking and slide the top of the bottle through. Make sure it fits tightly without ripping the nylon, then tape it to make it more secure. Once the top is finished, attach the middle of the bottle (the side without the holes) to the other end of the nylon with tape or glue.
   

3. Create tow line. Measure 3 feet of string, cut and attach string to one of the holes. Repeat until each hole has a string attached, and then tie the strings together.

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4. Use your net. Plankton are not free-swimming organisms, instead they depend on the current to move them. Since phytoplankton are photosynthetic, meaning they depend on the sun to help them create their own food, they are found at the top of bodies of water. There are few ways you can successfully tow for and collect plankton:

• On a boat – The standard way for collecting plankton is from behind a slow moving boat. Carefully lower your net into the water, vertically, until the bottom half of your net is filled with water, pull until the strings are fully extended. Start moving the boat slowly forward for a few minutes and then pull in your net, carefully squeeze the sides of the nylon down toward the bottle cap to collect any plankton. Over a jar or Tupperware, remove the lid to the soda bottle and pour out your sample.
• On a dock or wading – Carefully lower your net into the water, vertically, until the bottom half of your net is filled with water, pull until the strings are fully extended. Start walking slowly forward for a few minutes and then pull in your net. If you are wading, be sure that your net does not drag along the bottom of the waterway. Carefully squeeze the sides of the nylon down toward the bottle cap to collect any plankton. Over a jar or Tupperware, remove the lid to the soda bottle and pour out your sample.

5. Examine what you caught. Since plankton are microscopic, you likely won’t be able to check out their details, like antennae or body shape, without the aid of a microscope. But you probably will find some other microorganisms within your net that you will be able to see easily sans microscope. Use a magnifying glass or your cellphone camera to check out what you’ve found. If you’re up for another build and have a laser pointer lying around, check out this gross science video and build your own microscope before you head out with your net!
   

How to adjust for younger and older learners

Before you go collecting, have younger learners take note of their location, time of day, weather and any characteristics about the body of water you’ve chosen. After collection, as you observe your specimens, encourage your learners to try to find five different types of organism within their net.

Collecting and identifying organisms is fun but monitoring these organisms can help scientists learn a lot about the environments they support. The NOAA Plankton Monitoring Network uses data, in the form of images and numbers, to keep track of plankton populations all over the world. Now that you’ve built your net, older learners can log onto coastalscience.noaa.gov and learn how to become citizen scientists and help researchers. Learn more about this citizen science project here.