Investigating the Top of the Water Column

Organisms that live at or near the water surface--at the top of the water column--are especially vulnerable to oil spills, because these creatures come into contact with oil slicks on the water surface (like the slick escaping from the tanker in the photo at right).

This presentation explains how to visit a coastal location to observe the organisms that live near the water surface. In this presentation, we talk mainly about ocean organisms, but you could use the same basic methods to learn about organisms living near the surface of a big lake or river.

Making Your Investigation

1. Prepare your tool set. Collect the following tools:

• One or two glass or clear plastic containers for collecting samples. You'll use these to take a closer look at some of the things you'll find. Flat-sided containers are best, but jars are fine, too.
• A magnifying glass or hand lens.
• A plankton net. (We've written some instructions for making your own net. See the link at the bottom of the page.)
• A small notebook for keeping notes on your observations.
• A pad or tarp, so you can comfortably kneel or lie on your stomach to get a good look down into the water.
• One or more field guides to the marine or seashore life in your region, so you can identify the things you see (there are many good guides to marine life; ask your librarian for help selecting some).
• You also may want to bring a camera and/or sketchpad.

2. Travel to a coastal location where you can get down to the water surface. A public boat or fishing dock is an especially handy place to look, as long as the dock floats right on the water surface instead of being high on pilings.

3. Once you're at your location, start by just taking a careful look around. Focus your attention on the water just below the surface. It's often easiest to see down into the water in areas that are shaded by buildings or moored boats. You may see things like schools of juvenile fish, barnacles, and other organisms that live on pilings or on the underside of docks, as well as clouds of plankton, or small jellyfish if you're visiting during a jellyfish "bloom." You'll see different things at different times of the year.

Depending on the rules where you are, you may be able to gently capture interesting organisms and place them, along with plenty of water, in a container so that you can take a good look at them with your magnifier or photograph them. If you decide to do this, keep organisms in the jar for no more than a few minutes, and be careful not to leave the jar in bright sunlight so that it heats up: many small organisms can be hurt or killed by changes in water temperature. Once you've finished your observations, gently and slowly submerge the jar back into the water, tipping it so that the organism can swim or crawl away.

4. Sample some plankton. Plankton are the most important organisms you'll see, because all the other organisms depend on them for survival, one way or another. You'll need your net to collect your sample.

Use a hand lens or magnifying glass to get a close look at the plankton you've sampled. It's easiest to view plankton if you put them in a clear, flat-sided container, but a jar will also work fine.

For more information

Safety Tips Please follow our safety tips as you work!

How To Make A Plankton Net Instructions for making a sturdy plankton net to use in your investigations.

How to Take a Plankton Sample Instructions for sampling plankton.

Related image galleries

Edmonds Dock Tour Some things that you might see during your investigation of the water's surface. (10 images)

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Oil Spills at the Water Surface