# Prince William's Oily Mess - A Story of Recovery

## Graphing Changes in Marine Life Abundance

Want to try your hand at some marine biology? Then grab your raingear and follow steps 1, 2, 3 & 4 above to make a study of the marine life occupying a quadrat of Mearns Rock. A quadrat is a small sampling plot or area that is designed to represent a larger area that is being studied. Mearns Rock is a boulder in Prince William Sound, Alaska, that was oiled in 1989 by the Exxon Valdez oil spill. For your study, you'll use a series of close-up photos of the quadrat, each showing a different year from 1990 to 2004. Your goal will be to see how the percent cover of mussels, barnacles, and Fucus gardneri (a kind of seaweed, also called rockweed) in this study area has changed during those 15 years.

As you complete this project, you'll be using the same method used by real marine biologists. To study how marine life abundance changes from one year to the next, marine biologists sometimes section off a small plot of land that's representative of the particular habitat they're studying (for example, a rocky shoreline or a beach). They use a frame (generally a 0.25 or 0.5 square meter of PVC pipe), known as a quadrat, which they place on the ground to mark an area to study in depth. Each year, the biologists return to count the organisms or plants that occupy the area inside the quadrat. In most studies, many quadrat samples are necessary to adequately represent the whole area. In the photo at the left, a NOAA marine biologist is using a quadrat in his studies of the Mearns Rock site. He's trying to find out how the abundance of Fucus, barnacles, mussels, and other organisms has changed since the year before.

Proceed to Step 1b: Learn the Organisms

Glossary Express

Abundance—the total number of individuals of a species present in an area.

Barnacles
—marine crustaceans with feathery appendages for gathering food that are free-swimming as larvae but permanently fixed (to rocks, boat hulls or whales) as adults.

Boulder—a mass of rock greater than 256 millimeters in diameter.

Marine—relating to the seas and oceans.

Mussels—a bivalve mollusk usually having a dark elongated shell.

Percent Cover—the proportion (in percent) of a certain species or group of species that is occupying a surface such as the ground, a rock, etc.

Quadrat—a small plot or sample of land that is representative of the particular habitat that is being studied. Often the plot of land is demarcated using a frame made of PVC pipe or other material.

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