Earth Science Week Classroom Activities

Monitoring Life in the Rocky Intertidal Ecosystem

National Oceanic and Atmospheric Administration

Activity Source:

NOAA National Marine Sanctuary Program and Farallones Marine Sanctuary Association, 2006. Adapted with permission.


The five national marine sanctuaries along the West Coast monitor the health of the rocky intertidal ecosystem. One way of doing this is to collect data on the relative abundance of the organisms living in that ecosystem. Since this is such a big task, the national marine sanctuaries are training students in how to follow standardized protocols to help with the monitoring. The information collected is added to an online database that the sanctuaries use to collect baseline data and track long-term changes in the environment. This activity will allow you to learn the sampling techniques used in the field by these citizen scientists who participate in LiMPETS.


For a group of three to four:

  • Photos of the rocky intertidal zone
  • 6 photo quadrats printed on 8.5" x 11" paper
  • Photo quadrat data sheets
  • Photo quadrat answer sheet
  • Animal and algae ID cards
  • Ruler


  1. Look at the photos of the rocky intertidal ecosystem. What are the characteristics of this environment? Why do you think that monitoring the abundance of organisms in this ecosystem is important? How could this information be used? Discuss with your group.
  2. You will need two photo quadrats and two ID cards. On each photo quadrat, draw six equal-sized boxes (4" x 4.5").
  3. You will monitor the abundance of algae and animals in each quadrat using two methods. For the larger invertebrates, you will record a total count of the number of individuals on the data sheet (under “individuals”). For algae and the more abundant animals, record the number of squares out of six with any portion of the algae or animal under “count and record” on your data sheet. The organism is counted if it is attached in that square.
  4. Fill out the photo quadrat sheet by looking to see if each species listed on the data sheet is present in the quadrat.
  5. First with your group, and later as a class, discuss which organisms were hard to identify and how this might be different in the field. What are some problems you think you might have in using this method in measuring relative abundance of organisms in the field? Why do you think it is important to monitor the health of the rocky intertidal ecosystem? What can this information tell scientists and resource managers?

This activity was adapted from the LiMPETS Rocky Intertidal classroom kit developed by Dr. John Pearse and Dawn Osborn, University of California Santa Cruz.