What are the most important animals in the ocean? Whales? Sharks? Giant squids? Think smaller. Arguably, the most important animals in the ocean are found at the bottom of the food chain—the tiny creatures called plankton.
Plankton are microscopic animals that are found all over the world in large bodies of water. They have many different shapes and sizes because they’re not grouped together by how they look, but by their place in the food chain (the bottom). Becoming a planktologist—a scientist who studies plankton—is simple; all you need is a special net.
The plankton nets found in stores are very expensive, often more than $50! Luckily, though, they can be easily made from household items for less than $10.
This is a bonus experiment (the supplies for this project aren’t in the main shopping list), so you’ll find the the supply list of materials you’ll need (below).
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First, gather your materials. Here’s what you will need:
- A cheap pair of nylon stockings (if you use a used pair, be sure to ask the owner first).
- A wire hanger.
- Pliers.
- A plastic bottle.
- A strong rubber-band.
- Strong string (like fishing line, or kite string).
- A washer or plastic ring.
- A Stapler.
- A tray with a dark bottom.
Got all of that? Great! Here’s how to make it:
- Unwind the hanger (ask for help) using the pliers.
- Make a 6-10 inch (15-20 cm) ring with the hanger.
- Cut stocking near the foot. Fit the open end over the wire ring and then staple it on.
- Cut a hole the size of the mouth of the bottle in the toe, and fit it over the bottle.
- Secure the stocking to the bottle with the rubber band. Make sure that it’s on tight.
- Attach three pieces of string (2 feet (60 cm) each) to the wire ring. Space them evenly.
- Attach the other ends of the string to a washer or plastic ring.
- Attach a long piece of string to the washer or plastic ring. This is the towing string.
Let’s collect some plankton!
On a boat: Attach the towing string to the boat away from the propeller. Go slowly for 15 minutes. Pour the contents of the bottle into the tray.
On a dock: Throw the net into the water and drag it back a couple times. The more you do it the more plankton you will get.
Now, observe your plankton!
You should be able to see your plankton swimming around with your naked eye, but for a detailed look it’s best to look through a magnifying glass or a microscope. Sketch out a couple of them in a notebook and look at their different body types. Are there any that seem to be moving themselves? Are there any that seem to just be drifting? Although refrigeration helps preserve them, it’s best to observe the plankton as soon as possible.
Why this works: The net works by pushing plankton and water into the bottle and only letting water out. As the net moves through the water, it funnels water and plankton into the mouth of the bottle. However, when water and plankton go in, water and plankton also go out. The net makes sure that the plankton that comes out of the mouth of the bottle goes back in.
Troubleshooting: Not catching any plankton? The plankton may be escaping before they reach the bottle. Are there any large holes in the stocking? Is the bottle securely attached to the net? Remember, the plankton are tiny—any holes larger than those found in a normal nylon stocking will allow the critters to escape.
Another problem may be that the net is not facing forward. Make sure that the string is evenly spaced around the ring. If the ring isn’t facing forward when you pull it forward you may be filtering the plankton from the bottle! If you’re unsure, you can test it in a bathtub before taking it to the ocean, lake, or pond.
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