INTERTIDALZONES

Illustrations by Amira Maddison

EXPLORINGSuggested age range: Grades K-5 Materials required: Scissors, glue ortape, pencil crayons or markers.Time required: 1 hour +

High and low tide are caused by the gravitational pull of the moon. The tidal force causes the earth and the water to bulge. These bulges of water happen during high tides. High tide occurs in two places at once: 1) on the side of the earth closest to the moon becauseit experiences the moon’s pull the strongest. 2) on the side of the earth facing away from themoon because of earth’s rotational pull is stronger than the moon’s gravitational pull. Everywhere else onthe earth the ocean recedes to form low tide. The cycle of two high tides and two low tides occurs

within a 24-hour span in most places on coasts around the world. DID Y

OU KNOW?

PACIFIC NORTHWEST COAST INTERTIDAL ZONES AND SPECIESThis activity will help you discover the variety of species that call the intertidal zones in B.C. home. To create your own intertidal poster, print this document single-sided. Read about the cool beings and colourthem in (use a book or internet search and try to colour accordingly). Glue or tape page 9 and 10 together toform the poster base. Then cut out the coloured pictures of the different species and glue them onto theposter, according to the intertidal zone in which they are found.

The intertidal zone is the place between high tide andlow tide. It is the place where living beings must beable to survive through both dry spells and big waves.Explore beings that live in the three intertidal levels(upper, mid, and low tidal) on the next pages!

What is the tide?

King tides (a non-scientificterm) are exceptionally hightides. They are predictable,typically occurring during afull or new moon (when themoon is closest to the earth).

How to:

What is the intertidal zone?

UPPER TIDAL The upper or high tidal zone is covered only by the highesttide. It is the part of the shore closest to the forest.Acorn barnacles Sea anenomes

Kelp crabPurple shore crab

Sea anemones have rings oftentacles surrounding theirmouths. The tentacleshave stinging cells on themthat will immobilize theirprey such as crabs,fish, sea stars and sea jellies.

Limpets

These are crustaceans thatcement themselves in place.There is a little arthropod(jointed-legged animal) livinginside that cone-shaped shell!Barnacles stand on theirheads and shovel food intotheir mouth with their legs!

Purple shore crabs havepurple spots on theirpincers. They vary in colourfrom purple, dark olive, redand brown. They are easilyfound on and underboulders, where they liketo group. They mostly feedon green algae.

These crabs are in a largegroup of crabs called

spider crabs. Youngercrabs may be olive-green

as well as red or brown,and adults are brown to

camouflage well with kelp.

Limpets are cone-shaped,one-shelled snails foundliving in eelgrass, kelp and onrocks. They scrape the algaeoff the rocks for food.

UPPER TIDALGooseneck barnacles

Isopod

Sea lettuce

Decorator crab

Periwinkle sea snail

Gooseneck barnacles arefilter feeding crustaceansthat have a long protrudingneck that looks like the neckof a goose! They liveattached to rocks. Somepeople consider them adelicacy.

Decorator crabs areopportunistic artists! Theyattach seaweed, rocks andcoral to their hookedbristles on the backs of theirshells to camouflage andprotect themselves frompredators.

Isopods are green crustaceanswith 7 pairs of legs. Theymostly eat algae.

Sea lettuce is found on therocks. It has light to mediumgrass-green blades and is only2 cells thick. It grows in bothhigh and low intertidal zones,attached to rocks, pebbles,shells, and bits of wood. Itmay detach and float around,often collecting in tide poolsand washing up on beaches.

This small mollusk movesaround on its muscular foot.It lives in sheltered waterson rocks amongst the algae.

Mussels can filter 2-3 litres ofwater an hour! They do this tofeed and breathe. Californiamussels are a marine bivalvemollusk that grows in verylarge groups. They can growto full size (up to 130 mm inlength) in 3 years. They aregreyish-black in colour. Somepredators such as the sea starfind it incredibly difficultto open-up their hard shells.

MID TIDAL The mid tidal zone is exposed at low tide. It isboth wet and dry throughout the tidal cycles.

Red rock crab

Rockweed

MusselsRed rock crabs have black-tipped pincers. Theirshells range in colour from light to dark red andthey look like big red rocks when hidden in thesand. Their shells reach a width of 15cm across.

Rockweed is a brown algaeand is a favorite food ofperiwinkle snails, so they arefrequently found together.

Dungeness crabThese crabs scavenge alongthe sea floor for organismsthat live partly or completelyburied in the sand. Their dietcan include bivalves, worms,shrimp, fish, and small crabs.

MID TIDAL Hermit crab

Sculpin

Abalone

Turkish Towel

Sculpins typically inhabit tide pool and intertidalhabitats. They are bottom-dwellers and some spendtheir whole lives in one tide pool! As the tide recedessome sculpins become stranded under rocks and logs.Fortunately for them, they have the ability to extractoxygen directly from the air and survive for severalhours if kept wet.

Abalone are known for theirmetallic colours of blues,greens, reds and purples.They only travel a fewhundred metres over theirlifespan of approximately 50years!

Not really used by Turkishpeople as a washcloth, thisspecies of red algae has asurface texture like such acloth. Turkish Towel is ared seaweed that is coarseto touch. They can be redto purple in colour andiridescent when wet.

Like all crabs, the hermit crab is a decapod — it has five pairs of legs, including a pair of claws. The hermit crab uses its claws for defence and food shredding as well as eating. Thesecond and third pairs of legs help the crab walk,and the last two pairs hold the hermit crab in itsshell. A hermit crab does not create its own shell. Itmoves into larger shells as it grows — fighting withother hermit crabs for the shells if necessary — but itdoesn’t harm healthy snails.

LOW TIDAL The low tidal zone is onlyexposed at the lowest tide. Nudibranchs

Black Katy chiton

Mossy chiton

Gumboot chiton

Tiger rockfish

Gumboot chitons are the largest chitons inthe world, growing up to 36cm! They canbe detected using a metal detector becausethey have two rows of sharp teeth coveredin magnetite, an iron ore. They use this toscrape algae off rocks.

Black Katy chitons are oval and are made up of8 white jointed plates. The underside of theirshells and foot are pinkish-red or orange-red.They cling to the rocks and hide in theshadows and beneath seaweed.

Nudibranchs are known as seaslugs or naked gills. They are reallygreat at camouflaging as theyretain the colour of the food theyeat. Some even keep the foul-tasting poisons of their prey andsecrete them as a defense againstpredators.

Tiger rockfish are striped like a tiger withpink or red stripes. They can grow up to60cm long. These fish are solitary andsometimes territorial! They prey on rockcrabs, amphipods and small fish.

Chitons have a broad flat foot which they useto move and to stick to their rocky homes.Mossy chitons are covered by small interlacingplates with stiff mossy dark brown hairs. Theinside of their shells are a turquoise colour.

Moon JellyMoon jellies look like bells. They aretranslucent grey to blue in colour. They useshort tentacles to sweep food toward themucous layer on the edge of the 'bell'.

LOW TIDAL

Plumose anenomes are also known as whiteplummed anenomes. They can be manyshades of white, cream, brown, orange ortan. They sweep the passing water with theirtentacles to collect food.

Ochre sea star

Plumose anenome

Purple sea urchin

Kelp

The ochre sea star is a keystone species in thePacific Northwest coastal waters, meaning thatmany species depend on it. It eats many mussels,freeing up space on rocks for other beings. It hasfive arms covered with tiny tube suction cups andcan regrow a lost arm within one year.

Purple sea urchins are covered in pincers,tube feet and deep purple spines. They usetheir spines for protection from predatorsand for getting food in the kelp forest. If foodlands on an urchin's back, all those tube feetpass the food down to the urchin's mouth likea bucket brigade! Sea urchins are a main foodsource for the sea otter.

Kelp provides great habitatand nutrients to a variety ofmarine species. Sea otterswrap themselves up in thekelp stems while sleepingto prevent themselves fromdrifting away.

Sunflower starThese beings are carnivorous. They eat seaurchins, clams, crabs, snails, sea cucumbers,sand dollars, chitons and dead fish.

UPPER TIDAL

FOREST

LOW TIDAL

MID TIDAL