Historic Oil Spills

Graphing Changes in Marine Life Abundance

June 4, 2011, 2:29 pm
Source: NOAA Office of Response and Restoration


This activity developed by NOAA will guide you through making a study of the marine life occupying a section, or quadrat, of Mearns Rock (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 zoomed-in photos of that quadrat. Each shows a different year from 1990 to 2009. 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 19 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 bog). They use a frame (generally a 0.25 or 0.5 square meter of rebar or PVC pipe), known as a quadrat (or "quad" for short), 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 quad.


Graphing Changes in Marine Life Abundance Instruction Sheet

Mini Field Guide to recognize the species in your quad, estimate their percent cover, and establish the criteria you'll use to make your observations.

Data Table to record your estimates of percent cover of species in the quad.

Photo Series of the Mearns Rock Quadrat

Timeline Graphs to plot your data.

Related Photo Collections

  • Mearns Rock Time Series: Read our biologists' explanations of the year-to-year changes you see on Mearns Rock. (20 images)
  • Block Island Time Series: Our biologists studied the plants and animals living in this quadrat to see how they recovered after the Exxon Valdez oil spill. (6 images)


Nomack, M. (2011). Graphing Changes in Marine Life Abundance. Retrieved from http://www.eoearth.org/view/exercise/51cbf1507896bb431f6a5124


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