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Pacific Rim National Park Reserve of Canada

The Species of the Rocky Shore

Lichen can be found on the rocks in the
This unique plant is half algae, half fungi!
©Parks Canada / G-4

What are all the gray, green, orange and black "paint" splotches on the rocks in the splash zone of the beach? They're various species of lichen! These unique plants-half-algae, half-fungi-slowly dissolve rock, creating soil that will allow more complex plants to grow in the area.

Some lichens are fragile and crumbly when dry, but are very slippery when wet; so for their safety and yours, avoid stepping on them if you can.

Sea Palm (Postelsia palmaeformis)
Sea palm anchored to the rocky shore
Sea palm survive in the "impact zone" by anchoring to rocks
©Parks Canada / M. Hobson, 1982 / I-4

Your eyes haven't tricked you if you see palm trees at the edge of the sea; but when you do see them, beware. This brown algae grows only on rocks where the surf action is violent; it's as resilient as rubber, bouncing back after each smashing wave.

Unfortunately humans aren't made of rubber and can't survive what the sea palm can survive. When tidepooling, always watch the waves, and stay well out of their reach. Surge channels, sea caves, and rocky headlands can be extremely dangerous areas.

Gooseneck Barnacles (Pollicipes polymerus)
: A cluster of Gooseneck barnacles clinging to rocks
Gooseneck barnacles can be found on surf-swept rock
©Parks Canada / M. Reid, 1991

Gooseneck barnacles cluster together on surf-swept rocks, spreading their feathery feet with each wave, attempting to capture plankton in the watery turmoil.

These barnacles, like sea palms, live in areas with strong surf. If you explore where these are growing, watch out! Pay close attention to the waves; they are unpredictable. Mixed in with moderate waves can be larger waves known as rogue waves. Rogue waves have swept people to their death from the rocks in Pacific Rim National Park Reserve of Canada.

California Mussel (Mytilus californiamus)
California Mussels cover the rocks in the mid tide zone
California mussels are anchored to rocks via "bysall threads"
©Parks Canada / B. Campbell, 1978 / E-17

Mussels dominate the mid-tide zone, covering the rocks. They grow on top of other species, and they grow on top of each other. Each mussel anchors to whatever is handy with cables of protein called byssal threads. After every storm they survive, they attach new cables, ensuring they won't be swept away by the next storm.

Look closely in a mussel bed; discover a community of worms, crabs, snails, acorn barnacles and more, all living between their shells and threads.

Mussels were a traditional food source for the coastal First Nations peoples, but naturally-occurring plankton containing toxins can make eating mussels deadly. Paralytic shellfish poisoning can occur in any bivalve or hinge-shelled animals. Only eat bivalves from areas approved by the Department of Fisheries and Oceans.

Ocher Starfish (Pisaster ochraceus)
Ocher starfish
Mussels are the favourite food of the voracious ocher star
©Parks Canada / J.Bennett, 1978 / E-28

Ocher starfish aren't fish at all, they're spiny-skinned creatures called echinoderms. They are the most abundant type of starfish in the intertidal zone and come in three colors: purple, brown and yellow.

These voracious predators prefer mussels above all other food. The hungry starfish will surround a mussel with all five of its arms, slowly pull open the mussel, and then... the starfish will extrude part of its own stomach through its mouth to digest the mussel within its own shell.

Acorn Barnacles (Balanus glandula)
Acorn barnacles exposed during a low tide
Acorn Barnacles close up and wait for the tides to rise
©Parks Canada

It's high tide and you're underwater. Picture yourself standing on your head fanning the water with 12 hairy legs. Using this technique, the wily barnacle captures plankton in the water. When the tide falls, the barnacle seals itself within its white shell fortress.

When exploring, listen carefully; can you hear them clicking their trap doors tighter to conserve body moisture?

Surfgrass (Phyllospadix sp.)
Surfgrass exposed at a low tide
Surfgrass is a flowering plant that is found in almost all open coast communities.
©Parks Canada / W. McIntyre, 1978 / K-3

Surfgrass is a flowering plant that is found in almost all open coast communities. Its numerous long strands provide excellent food and shelter for many other plants and animal species. Numerous creatures can be seen scurrying and swimming for shade and cover when strands of surfgrass are gently brushed aside.

Giant Green Anemone (Anthopleura xanthogrammica)
Giant green anemones anchored to the rocky shore
Giant green anemones are active predators in the tidepool
©Parks Canada / B. Campbell, 1979 / E-5

This isn't a green flower, it's an active predator. Attaching itself to the rock, when small creatures brush past its tentacles, microscopic barbs shoot out into the prey, paralyze it, then draw it back into the anemone's mouth. To gently exploring fingers, the barbs make the tentacles feel sticky.

These delicate creatures may be older than you. In captivity they have been known to live at least 30 years. When exploring, watch out for white giant green anemone. In caves, where little sunlight reaches the anemone, the microscopic green algae that normally inhabit their body and colour their tissue, are absent.

Aggregate anemone (Anthopleura elegantissima)
Aggregate Anemones can be found carpeting entire rocks!
Aggregate Anemones reproduce via cloning
©Parks Canada / E-5

Aggregating anemones most often reproduce by cloning. One anemone will separate itself into two "daughters"; in turn the "daughters" will repeat the process of splitting themselves, forming 4 individuals from one original. This repeats itself over and over again.. Doing this, a colony of aggregating anemones can form extensive colonies carpeting entire rocks.

Any anemone within the reach of the opposing colony will be stung by them. For this reason a space will develop between the two colonies, a no anemone battle zone.

Tidepool Sculpin (Oligocottus maculosus)
Tidepool sculpins are common residents
Tidepool sculpins have the ability to change colour to match their surroundings
©Parks Canada / D-9

A master of disguise, the tidepool sculpin changes colour to match its tidepool, or buries itself in sand with only its large eyes protruding. From wherever it is hiding, it will lunge out, using its large mouth and darting movements to snap up food.

Each sculpin picks a particular tidepool as home and if they are ever swept from it, they use their sense of smell to find their way back to their tidepool.

Coralline Algae (Lithothamnion & Corallline)
Coralline Algae branching out in the tidepool
Coralline Algae looks like a coral but is actually a plant
©Parks Canada / J. Bennett, 1978 / I-5
This algae can form either a pink "paint" layer or tiny branching structures in tidepools.

Although they resemble corals, which are animals, the presence of chlorophyll for food manufacture confirms that they are in fact plants.

Lined Chitons (Tonicella lineata)
Lined Chiton glued to the rocks
A Lined chiton is glued to the rocks while grazing on coralline algae
©Parks Canada / H. Holmes, 1989 / E-15

Chitons resemble half a tiny football glued to the rock. They have eight interlocking butterfly shaped shells to provide flexible protection. This particular species is named for the alternating light and dark zigzag lines on its shell.

Probably the most beautiful chiton in this area, its bright pink lines help it blend in with its favourite food source: pink coralline algae. The chiton scrapes away at the rock encrusting algae with a strap-like tongue bearing tiny teeth harder than some steel.

Black Oystercatcher (Haematopus bachmani)
A black oyster catcher in search of a meal
Its black body and long orange bill make the black oyster catcher easy to identify
©Parks Canada / H. Hobson, 1985/ B-10-a

This bird may look like a crow with a carrot for a beak, but that distinctive beak comes in very handy. Despite the strong protective shell of most mollusks, (e.g. oysters and mussels) the oystercatcher can:

  • shatter shells with repeated hammering;
  • dart in quickly to sever a bivalves's mussels before it has a chance to close its shell;
  • chisel chitons and limpets from rocks,
  • probe the sand and mud for worms and crabs.

These birds nest on the ground just above the high-tide line on treeless rocky islets but apparently only a few select sites provide all the right conditions for survival. They inhabit the same areas year after year, and will often re-use the same nest sites.

In an effort to ensure the long-term protection of oystercatchers in the Broken Group Islands, park staff monitor the number and location of active nest sites in Barkley Sound, as they have done since 1970.

Harlequin Duck (Histrionicus histrionicus)
A pair of male Harlequin ducks floating on the water
In summer Harlequin ducks can be found feeding in white water rivers!
©Parks Canada / A. Dorst

For most of the year, Pacific harlequin ducks inhabit exposed rocky sea coasts from Alaska to Oregon using their stubby bills to pry invertebrates such as snails, limpets, crabs, chitons, and mussels from the rocks.

In summer however, they migrate inland to nest along turbulent mountain streams. Some Pacific harlequins spend their winter in this national park and their summers in Jasper National Park of Canada.

Harlequin ducks occur in two separate populations: one on the Pacific Ocean, and one on the Atlantic Ocean. The Atlantic population is low enough to be considered of special concern. In British Columbia and Alberta, harlequin ducks are not endangered, but there is growing concern over declining populations and human impact.

Parks Canada is involved in banding harlequin ducks as part of an international program throughout western Canada and the United States. It's an effort to gain knowledge of the habits and habitats of these unique birds, with the goal of protecting them throughout their summer and winter ranges.