Quadrat Sampling

In this Hands-On Activity, you'll learn how scientists study nature using a method called quadrat sampling. A quadrat is just a square frame that helps you look closely at a small part of an ecosystem, like the intertidal zone at the coast. You'll place the square on the ground and count the different plants or animals you see inside it. This helps scientists understand how many living things are in an area and how they are spread out. If you can visit the coast, great! But you can also try this activity in a park, field, or even your backyard.

Materials:

• Clipboard
• Paper
• Pencil
• Quadrat, or length of string or rope
• Intertidal Species guide (optional)
• Magnifying glass (optional)

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Introduction:

The intertidal zone is the area of shoreline between high and low tide. It’s a popular place for scientists to study because it is dynamic, meaning it’s always changing, shifting from underwater to exposed over the course of a day. To study such an environment, scientists use a method called quadrat sampling. A quadrat is a square frame that defines a small sampling area, allowing scientists to count and observe species in one section instead of the entire beach, which would take days.

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In this activity, we’ll ask focus questions, form hypotheses, make observations, and use the quadrat method to study the intertidal zone. In our quadrat, we’ll find both moving and non-moving organisms. Animals that can move, like crabs, shrimp, and snails, are called mobile species. Those that cannot, like seaweed, barnacles, mussels, and algae, are sessile species. We’ll count individuals for mobile species. For sessile species, we will estimate the percentage of the quadrat that is covered by the species, this is called percent cover.

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Procedure:

1. Review what the intertidal zone is and why it’s a unique and important environment.
2. If possible, visit a nearby beach with tide pools or an exposed rocky shore. Always go with an adult and keep safety as your top priority.
3. Before starting, create a focus question about what you want to learn (for example: Do more sessile species live on rocks or sand?). Then, make a hypothesis predicting what you think you’ll find.
4. Choose a section of the intertidal zone to study. To create your quadrat, use a square frame, or a 6-foot length of rope or string tied into a loop and shape it into a square over your sampling area. If you don’t have rope, you can imagine a square boundary instead.
5. Observe what’s inside your quadrat or study area. What is the sand or rock like? What animals or plants do you see? Count how many mobile species and sessile species you can find.
6. (Optional) Record your findings using the Quadrat Sampling SC Activity Sheet.

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Accommodations:

Quadrat sampling is used by scientists to sample all sorts of ecosystems. If you don't live near the coast, you can sample any kind of environment with this method -- give it a try in a forest, lakeside, or even your backyard!