The Oregon Coast Education Program

Tidepool Diversity

(Adapted from OCEP teacher Kristy Morrow, Willamette High School Zoology)

Summary: This activity uses common data collection methods to introduce students to how scientists study highly dense and diverse rocky intertidal populations. Written for a site near Cape Perpetua, the concepts are highly adaptable to any intertidal area, or even a habitat nearby school. Students can compare data to long term data sets collected along the Central California coast in the LiMPETS program and explore the broader context of their data collection.

Concepts to Teach: Population ecology, rocky intertidal communities, vertical zonation, data collection & monitoring

Goals: Students will use standard field monitoring techniques to understand and describe the community of species that live in a rocky intertidal habitat.

Standards: H.2L.2, H.3S.2, H.3S.3

Specific Objectives:

Students will be able to:

Understand and explain why diversity is important and why long term data sets can help us monitor changes over time due ecological changes
Conduct a simple population survey along a transect of a rocky intertidal habitat
Identify and describe the dominant organisms in the rocky intertidal ecosystem and where they occur
Students will understand classic vertical zonation patterns in the rocky intertidal
Students will use critical thinking skills to determine whether their data are consistent with published data.

Required Materials:

You will need to acquire or construct the following items:

A low tide that allows for data collection in all tidal zones, ideally one that is lower that 0.5 – 1 foot at your site; data collection takes about 1.5 hours depending on the site

Transect line – one per group, use either a long meter tape (10m+) or purchase sturdy rope and have students mark 1meter increments

Quadrat – one per group, use the instructions from South Slough’s TIDES curriculum to build a pvc quadrat The one described in this document is smaller; a standard size quadrat measures 0.5 x 0.5 or 0.25m2

Field notebook – write in the rain paper works best, but a sheet of paper and a small writing surface works well

Copies of Student Directions for Diversity Survey

Clothing and sturdy shoes appropriate for the site and current weather

Optional:

Field guides

Cones or markers to identify places for groups to start their 0m mark for their quadrat.

Camera to document quadrats; have students practice using macro settings in the classroom, smart phones have increasingly good cameras for this, just be careful not to drop them!

Small buckets/containers to conduct the optional hermit crab inquiry

Background

Utilize the topic guide and resources in “Tidepool Inquiry” found in this module to study the habitat and species that call this place home. Additionally “Rocky Shore Survivors” in the middle school level of this module is an interactive way to familiarize students with species.

LiMPETS ( has numerous teacher and student resources including “The Rocky Intertidal: Fact Sheet” and “Field Sampling Techniques: Fact Sheet” to further prepare students for the activity.

Prerequisites/Preparation

The directions written out below follow a high tide – low tide transect so each group surveys in the different tidal zones at Cape Perpetua. This site has a broad volcanic basalt shelf with little to no cobbles in the intertidal zone. Rocky intertidal areas along Oregon’s coast vary drastically. It is especially important that you do a pre-site visit or do your homework with local connections to be prepared to collect data in the small window of low tide.
Students will need to have good knowledge of species they might find in the habitat. Use ocean introduction lessons from this module (especially “Tidepool Inquiry”) and look into the middle school module for “Rocky Shore Survivors”, tap into field guides, and look to online resources provided by Oregon State Parks and enthusiastic naturalists with hobby websites.
Students should be oriented to the field site prior to arrival. By showing students where the site is relative to their watershed they will have an idea how both ecosystems are connected. This allows for a richer experience in this diverse ecosystem by way of making comparisons and integrating additional field exercises.
Before going into the field have students prepare their field kit and data collection tables. Have students review directions and practice the techniquesusing posters, large images, props of rocky intertidal areas; set up a transect in the classroom or on school grounds so that field time can be used right away for exploring and collecting data

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Directions for Biodiversity Survey at Cape Perpetua

Introductions and Safety Rules (from OCEP Tidepool Inquiry)
Safety introduction (5 minutes)

Before entering the tidepools, gather the group to talk about safety issues. It is a good idea to do this is at the top of a trailhead usually in front of a Rules and Regulations sign away from the beach and water to minimize distraction. Regulations vary from site to site, please advise all posted rules.
Review safetyrules and tidepool etiquette slowly and thoroughly
Watch where you step. If it’s green, it’s slippery. If it’s brown, it’s slippery. If it’s grey or black, it’s slippery.
Gentle giants! It’s okay to touch, but only use one or two fingers.
If you pry, it will die! It’s okay to pick things up, but if you have to pull to get it off a rock, it will die. So if it’s stuck, leave it there and use your eyes and fingers to learn.
Stay low and slow. The rocks are slippery. Take your time when climbing on the rocks and use your hands.
Please, turn over rocks, there’s lots of cool stuff underneath, but remember to turn it back over. Things that live on the top can survive on the bottom and vice versa.
We’ll use the two hand rule: “If both of your hands do not entirely cover the rock it is too big to turn over”
If you take something out of a tidepool, make sure you return it to where you found it: how would you feel if someone plucked you off the couch in your living room and put you in some strangers home a mile away? Or worse, didn’t return you at all, which leads to…
Don’t take anything home. Leave things there so the next people can enjoy them just like you did!
Allow students a set period of time to explore the site and make observations. This allows for any last minute prep to set up transect lines as well.
After students have completed and documented their transect have them explore the site safely and compare data with other groups.

Student Directions for Biodiversity Survey at Cape Perpetua

You will be surveying the change in biodiversity from the high tide zone to the low tide zone using a transect line & quadrats.

Set up a transect line that is perpendicular to the water and runs from the high tide zone to the low tide zone.
Use a tape measure or pre-measured string
Begin the transect line where you start to see animals of the splash zone – barnacles and limpets
End the transect line as close to the water as you reasonably can while still maintaining a safe distance from the incoming waves.
Starting at the high end of your transect line, complete 1 quadrat count every ___ meter(s) beginning with 0 meters
You may survey along the left or right side of your transect line, but be consistent throughout the survey.
Name your first quadrat with the transect line measurement and your group letter “ 0A, 3A, etc.”.
For each quadrat, note the ground cover of the area: rocky, tidepool, etc. Identify and name (or describe) all the different species that you can find inside the quadrat area. Record the density (number of individuals) or percent-cover for the five most dominant animal and alga species. Also record any additional information that you observe in this area; such as seaweeds, rock/shell material on ground, debris, other exceptional animals that you see outside of your quadrat, etc.
In your field notebook, create a data table for this information. Example:

Quadrat Name: ______

Species Name / Density or Percent-Cover

Additional Notes:

Now move another ___ meter(s) closer to the ocean along your transect line. Complete another quadrat and record this data in you field notebook the same way.
Again move ___ meter(s) closer to the ocean along your transect line. Complete a third quadrat and record this data in you field notebook the same way.
Continue this process until you have reached a close, but safe distance from the water’s edge.

When to use percent-cover instead of density (number of individuals):

Organisms that should be quantified using percent-cover include some species that are sessile (fixed to the rock) and can’t be easily counted as individuals (sponges are a good example). Other examples include surfgrasses and algae/seaweeds (using where they attach to the rock). To help you estimate the percent-cover, remember that each corner (1/4) of the quadrat represents 25% of the total sample area. Half of that would be 12.5% and so on.

25%

Organisms that should be quantified using density include mobile animals (sea stars, urchins, etc.) AND sessile organisms that can be easily identified as individuals (barnacles, mussels, anemones, etc.).

When counting sessile fixed organisms it is acceptable to count the number of species in a smaller area of your quadrat and use that value to determine the total number of individuals in your entire quadrat. A common sample size is 10cm x 10cm or about the size of the back of your hand when making a fist. In a .5m x .5m quadrat this makes for quick math.

Optional inquiry:

Determining the species of hermit crab:

There are three different species of hermit crabs that you may encounter:

Blue-handed Hermit – has a blue stripe on legs

Hairy Hermit – white stripe on legs

Grainyhand Hermit – no distinct stripe, splotchy legs

Collect hermit crabs (and all other crabs) from your quadrat area before counting anything else.
Place them into your bin.
Then, one at a time, hold them in your hand until their legs come out.
Look for striping and record species.
Return crabs to exactly where you found them.
Determine if you can find a pattern in their distribution.

Back in the classroom

Summarizing data:

Have students summarize their data into clean data tables. They might have species that were unidentified, but documented they want to look up. Students should download and label photos if they took any.

Students should identify 4 dominant species that occur most frequently along the transect. From there make 4 line graphs that shows the vertical zonation patterns of these species. Make a graph for each individual species on the same sheet. The x-axis should be the quadrat location along the transect (0m or high intertidal to __meters or low intertidal), where the y-axis is the abundance of these species (#/m2) for those species that were counted individually or % cover (10x10 cm squares/0.25m2)

Students can look for and identify patterns and causes of high density of a species within their transect then compare with other student groups.

Use the LiMPETS Unit 4 Analyze and Interpret activity setup for comparing student data to scientific evidence.

Evaluation:

Conduct a pre-post survey that analyzes student anticipation and expectations similar to that of LiMPETS Unit 2: Reflections on Rocky Intertidal Monitoring