Pacific Rim National Park | Tidepools & Beachcombing
Can you identify all of these creatures? Clicking each image opens up a larger (800x600) version. These pictures were taken at Terrace Beach / He-Tin-Kis Park in Ucluelet, and at Half Moon Bay in Pacific Rim National Park.
Simone's Tidepool Adventure
The intertidal life in Pacific Rim National Park is the most diverse and abundant in the world. After reading this, I hope you will appreciate the diversity of the intertidal life in PRNP and want to protect it. Take a look through this page and you will learn to name some adaptations these creatures use to live in the intertidal zone, understand the basic causes of tides and the implication tides have on the intertidal zone, and how you can help with conservation of the intertidal zone.
Hi, welcome to our little virtual adventure into the intertidal zone. Don't take this as a substitute for the real thing though, it's more of a guide to the things you should do when you get here.
If you really want to see everything, plan on spending a couple hours out on the beach. This can be a 'rain or shine' kind of adventure if you're wearing the right clothes. Don't wait for a sunny day out on the west coast, sometimes you might wait a while ;)
Our trip starts in front of the Wickanninish Centre, then we'll head down the beach to the left, eventually up and over the rocks to a patch of cobblestones that are just beyond, and if you are feeling adventurous, a little further to the small island with a few trees. Because we will be climbing some rocks, you will need pretty sturdy footwear.
Beach / tidepool etiquette:
· So that you can return on your next visit and see the same creatures, please leave them where you find them. Please don't collect shells.
· If you turn over a stone, put it back in place when you are finished looking
· If you dig a hole, fill it back up
· Pick up any garbage you might find
THIS WILL HELP PRESERVE THE INTERTIDAL ZONE!
NOTHING HERE CAN HURT YOU, SO FEEL FREE TO TOUCH THINGS GENTLY
Salt vs fresh water:
The intertidal zone is as dependent on salt water as we are on fresh water.
· The ocean brings food, washing it in to shore and supporting creatures that are used for food for other creatures.
· The ocean brings moisture. Some of the creatures are almost completely made of water and need to be kept wet.
· The ocean brings oxygen to creatures that need it.
· The ocean brings protection from the sun as well.
Now what exactly is the intertidal zone, you might be wondering?
It's the area between the high tide and the low tide
What are tides?
The water comes up the beach twice every 24 hours and goes down the beach twice every 24 hours. Do you know what causes this?
The moon is out in orbit around the earth, and its gravity exerts a certain force on the earth. This gravity is not strong enough to pull the earth, because the earth is much bigger, but it is strong enough to pull the water in the ocean. More water moves toward the moon, and makes the water rise there, or get deeper there. That causes a high tide. As the moon goes around the earth, it pulls the tide along with it. So that causes one high tide every day, in all the oceans all over the world.
The other high tide is caused by something else that has to do with the moon. You learn in school that the moon orbits the earth, right? Well, actually it orbits a point inside the earth that is not exactly the center of the earth, so that the earth and moon are actually in orbit together around that one point. As they orbit one another, they create something called centrifugal force. Does anyone know what that is?
Have you ever been traveling in a car and gone around a corner just a little bit too fast? What happens to that pair of sunglasses you left sitting on the dashboard? They go flying to the side of the car that is on the outside of the turn, right? That is centrifugal force.
Now when the earth and moon orbit each other, something like that happens. The part of the earth that is on the outside of this spin experiences the same force as your sunglasses on the dashboard of your car. Because the earth also has gravity, the water is stopped from actually flying away from the earth, but the water in the ocean does move towards that area, which causes the water to rise on that side of the earth and cause a high tide.
So that is why we get two high tides every day. When the water is pulled to those two spots on the Earth, there is less water left elsewhere on the earth. So that is where there is a low tide.
What does all of this mean to you? When you are out on the beach, you probably want to know whether the tide is coming in or going out - so you don't get stuck on an island or something. Tide tables tell you when the high and low tides will be and how high they will get.
Let's say there is a 2 foot low tide today at 8AM, and a 9 foot high tide today at 2PM. If you walk to the edge of the beach at low tide, and put a stick in the ground, 6 hours later at high tide there will be about 7 vertical feet of water above your stick!
The best time to explore the beach and the intertidal zone is during the low tide, so you can see more.
The Sandy Beach:
Welcome to the sandy beach. OK now use your imagination! What are the qualities of this habitat? If you had to sit here for a few hours, how would you feel?
· Would you get a sunburn?
· Would you become hot?
· Would you have people stepping on you?
· Would you get cold, wet, hungry?
· How could you adapt and become more comfortable here?
Now if you stay here as the tide comes in, what will change?
· The water will come up the beach, probably over your head
· Some things will get covered
· Waves will come closer
· Sand will be moving with the waves
· Would you still be hot? Feel the water temperature!
Intertidal Life on the Sandy Beach:
What do you think might live in this kind of habitat where you are standing right now?
Clams - look for holes, under sand - how is it adapted to life here? Will this guy get sunburnt? Will the waves bother it when the tide comes in? How does it eat down there? Red tide, siphons, etc.
Blood worms - near surface during high tide, and deeper down during low tide - how is it adapted? What does it eat?(Part of the cleaning crew on the beach) Oxygen stored in hemoglobin.
Beach hoppers - turn over some kelp- see holes, how are these guys adapted?
Purple olive snail
Crabs -dead vs molted: the many intact crab shells you find on the beach are not there because the poor crab died! Actually, most of the crab shells are discarded because they are too small. As the crab grows, his soft body gets too big for his hard shell. Eventually, the crab will do what is call molting, and a slit will open up at the back edge of the shell. The crab will then pull its entire body out of the shell and walk away from it. A recently discarded shell will still have hairs and whiskers on it. What do you suppose happens to a crab that has no protective shell? How well would those pincers work if they were not hard and sharp? Immediately after molting the crab is at its most vulnerable and will find some crevice to hide in. After a few hours, the outside layer of the crab's soft body will harden into a new shell. The interesting part of this molting business is that crabs can only mate immediately following molting. When the male senses that the female is about to molt, he will grab onto her shell and follow her around until she molts, so that they may mate. He will stay with her afterwards in some species in order to protect her from predators.
An area that looks as if nothing could survive actually has quite a bit of life Let's go and check out another part of the intertidal zone. Follow me.
The ocean is the major player here in the intertidal zone, that much is certain, but the climate here on the west coast of the island also has a great influence on the variety and quantity of life in the intertidal zone.
· We get 300cm of precipitation on average in one year.
· We don't get a huge amount of sunshine either, because it is either cloudy and raining or foggy. Of that 300 cm of precipitation, 50 cm is from fog. This helps the life here, because most of it is made up of large quantities of water. Evaporation and drying out is to be avoided when your body is made up of water! It helps creatures stay cool and safe.
· As well, it does not freeze solid here in the winter. When the temperature drops below freezing, and the tide is out, intertidal creatures get frozen If the ocean were to freeze up there would be large chunks of ice floating around and getting washed up on the rocks, which would scrape many animals and plants right off the rocks.
The Rocky Shore
From a distance:
What do you see? Bands of color indicate different life zones, different creatures live in each one. Why? As the tide rises and falls, each area you see receives different amounts of water and sunshine
Now, if you were standing on that rock, how would you feel right now?
· How would it be when the tide came in and almost covered that rock?
· Would you get wet?
· Would you be hot?
· Would you be able to stay on there with all of the waves crashing in on you? Or would you get washed away?
· How could you adapt to living on that rock? Cover up from the sun while the tide was down and hang on really well?
· What about food? If you couldn't leave that rock, what would you eat?
Imagine how creatures living there must be adapted... Let's get closer and check it out.
Up close and personal:
What do you hear? What do you smell? What do you see? Touch...what do you feel?
How are these plants and creatures adapted to life here?
Lower Intertidal Zone - eelgrass, surfgrass, anemone, sea star
Middle Intertidal Zone - sea sack, mussels, chitons, gooseneck barnacles, sea star, coralline algae, urchins
High Intertidal Zone - turban snail, rockweed, spindle shell
Spray Zone - barnacles, periwinkle, limpet, lichens
Did you know that one of these animals is hanging on by a thread? Bysis threads
How do these creatures reproduce? Most of them are hanging onto the rocks and can't move....
Creatures here are dependent on the ocean. They are mostly water and don't like being dried out. The climate here really helps them out - that is why we have the most diverse intertidal life here along the West Coast of Vancouver Island - We have a lot of rain, and a lot of fog here. It does not get very hot here, and it does not freeze very often in the winter. The ocean brings food, water, oxygen to the creatures.
When you take a look at a tidepool, settle in and get comfortable around it. Spend about 10 minutes and try to imagine the ways tidepool inhabitants might be specially adapted to living here. Think about what the qualities of this habitat are: (Water temperature, waves, light, sun, wind, salinity?) The tide pools are an easy way to see what lives in the lower intertidal zones, many of the creatures that live in lower zones also live in tide pools.
What did you find?
· Anemones (some take real risks in reproduction by sending their eggs off to sea to be fertilized, some multiply by division, literally pulling apart to form two distinct creatures that are genetically identical),
· Chitons (spend their days scraping the sides of tidepools),
· Sculpins (camouflage),
· Snails (trap door for protection from sun and drying out),
· Hermit crabs,(always on the lookout for a new home because he can't build his own. Borrows from other dead univalves like snails)
· Shore crabs,
· Mussels (a sea star's favorite food, hanging on for dear life by a thread, many bysis threads that are created by the mussel to hold it to the rock)
How are these creatures adapted to life in a tide pool? Where do they get their food? What do they do when the tide comes in, what do they do when it goes out, how to they reproduce?
Some creatures you find here are not permanent residents, but very frequent visitors, like the sea star.
There is one more part of the intertidal zone that we should look at today. Follow me...
What are the qualities of this habitat? How would you feel if you spent the day here? Water, waves, sun heat, food?
What lives here? Crabs, isopods, worms, snails, anemones...how are they adapted to life here among the rocks?
Seaweed, kelp used in dairy products, car polish, eaten by humans, snails, urchins, becomes shelter when it is washed up on the beach.
There is another type of habitat that you can go and see at Grice Bay at low tide, it is called the mud beach.
And, If you have time, go back out to the same place when the tide is high and see the difference it makes. If you have read all the way here, good for you! Thank you for joining me today on our virtual beach walk.
If you have any questions, e-mail the author at email@example.com
Whelks to Whales: Coastal Marine Life of the Pacific Northwest
Marine Invertebrates of the Pacific Northwest
Pacific Intertidal Life:A Guide to Organisms of Rocky Reefs & Tide Pools from Alaska to Baja California
British Columbia Seashore Life
Copyright © 2000 Greg Swallow (site design, scripting)
All Rights Reserved