The Intertidal Community Red Tide The intertidal zone is an environment in constant Red tide is a natural phenomenon that can occur off our Life at transition. Twice daily the tides move in and out. coast during the summer months. It stems from a popu- Plants and animals submerged one hour are lation explosion of single-celled algae (Alexandrium spp.), the Edge exposed the next. Severe changes in temperature, which usually lasts a few weeks. The water is coloured by pressure, light, salinity and oxygen content occur the algal bloom, hence the name red tide. with each tidal shift. It’s no wonder that life at the The algae produce toxic substances that concentrate edge seems strange to us, the surroundings are so in the bodies of shellfish, such as mussels, clams and different from our own. oysters, making them unfit for human consumption. A single rock can shelter crabs, fish and clams, Even after the red tide passes, shellfish can remain toxic and provide growing space for barnacles, sea for years. This toxic buildup can cause paralytic shellfish poisoning in humans. anemones and mussels. Each of these creatures is Heed all posted warnings of red tide. Paralytic both predator and prey in the intertidal ecosystem. shellfish poisoning cannot be detected simply by looking It is a community in balance, where all organisms at a clam. If in doubt, contact Fisheries and Oceans have a purpose. Canada. Your safety depends on it! Rules for Exploring the Beach M Watch where you step. Some intertidal creatures are hard to see. M If you move a rock, do so carefully. Return the rock to its original position before you leave. M Keep a safe distance from intertidal creatures. They live in a harsh environment, and may Over 600 kinds of algae have been identified along the protect themselves with claws, spines or sharp British Columbia coast, and fish, seabirds and other shells. marine creatures number close to 5000. Yet these species M Do not remove anything from the beach. are just a fraction of what exists in the world’s oceans People often collect kelp, driftwood, rocks, today. sand and gravel. All these materials provide essential habitat for beach dwellers. Driftwood and kelp also supply critical nutrients that work their way up the food chain to salmon and killer whales. For More Information Beaches are fascinating places, BC Parks especially when the tide goes out. Many creatures http://wlapwww.gov.bc.ca/bcparks favour this intertidal zone, or area between the high and low tides, because it offers food, shelter and safety. We hope that as you learn about the many fascinating plants and animals in the intertidal zone, you will appreciate the importance of conserving them and their unique habitats in protected areas. Ministry of Water, Land and Air Protection 03/2002 Intertidal Zones Sea Urchins The intertidal zone is the most accessible area of the ocean, Pointed spines cover the shell of the pincushion-like sea urchin. Look among the harmless spines for tube feet, which also makes it highly vulnerable. By understanding similar to those of the sea star. and respecting intertidal life, you can visit the Sea urchins are grazers that feed on seaweed and seashore without impacting its inhabitants. small animals. They, in turn, fall prey to sea stars, sea SPRAY ZONE otters and people. The Japanese and some First Nations groups consider raw sea urchin eggs, or roe, a delicacy. The green sea urchin is a common urchin of sheltered, rocky shores and tidepools. Its scientific HIGH TIDE ZONE name – Strongylocentrotus droebachiensis – may be the longest in the world. Immature urchins are often found clinging to the underside of large rocks. MIDDLE TIDE ZONE Sea Anemone Sea Stars LOW TIDE ZONE Sea stars are not fish, although they are sometimes called starfish. These animals have at least five arms, but can have as many as 24. If a sea star loses an arm to a hungry gull, it can grow a new one as easily as we grow a fingernail! SUBTIDAL Ochre Star ZONE Green Sea Urchin Invertebrates Sea Cucumbers ANIMALS WITHOUT BACK BONES An elongated caterpillar-like body identifies the sea cucumber. Warty bumps cover the animal’s smooth, Sea Anemones elastic skin. Specialized tube feet, resembling dust mops, At low tide, look for sea anemones grouped in tidal pools surround the mouth and filter plankton from the water. or nestled among rocks. If you spot a large cluster of If disturbed or stressed, sea cucumbers spew out pink-tipped anemones, they are probably aggregate their internal organs. A complete new set of organs anemones (Anthopleura elegantissima). grows back within a few weeks. Despite their flower-like appearance, anemones are Look for the slow moving, reddish-brown California animals. The anemone’s stalk-like base is usually attached Examine the sea star’s rough surface for a small sea cucumber (Parastichopus californicus) cruising the to a rock. Waving tentacles circular spot called a madreporite. This organ acts as an tidepools. This giant can reach 40–45 centimetres in equipped with stinging cells intake valve for the sea star’s internal water pressure length, but will contract to 15 – 20 centimetres when encircle the animal’s system. This system activates the animal’s tube feet, aggravated. mouth. Anemones which look and act like miniature suction cups. The tube are carnivorous, feet are used for holding onto rocks, for moving, and for trapping small animals finding and attacking prey. in their paralyzing Look in crevices, under ledges and in tide pools for tentacles. the purple or ochre star (Pisaster ochraceus). Clusters Since anemones of mussels and barnacles – their favourite foods – may California occasionally hitchhike, be nearby. You might also discover a sunflower star Sea Cucumber you may see one cruise by on (Pycnopodia helianthoides), identified by its bright orange the back of a large crab! or purple colour and numerous arms. It is the largest sea Aggregate Anemone star in the world, measuring up to 80 centimetres across. Crabs Kelp Crabs Isopods Crabs are one of the better known beach residents. Their Watch out for a yellow to dark brown crab sporting Look for the rockweed isopod (Idotea wosnesenskii) skeletons are also a common sight, since they shed their extremely long legs. The northern kelp crab (Pugettia under seaweed or clinging to rocks. This isopod is shells as they grow. Crabs help keep the beach tidy by producta) can reach around with a long-limbed claw and related to the land-dwelling sow bug, or wood bug. dining on both dead and living organisms. give you a forceful pinch. The Oregon pill bug Dungeness Crabs The decorator crab (Gnorimosphaeroma (Oregonia gracillis) oregonensis) is another The large dungeness crab (Cancer magister) is a master glues bits of sponge, species of isopod that of camouflage. When completely buried in sand, only its debris and seaweed to rolls into a tight ball, eyestalks and mouthparts are visible. Watch where you its back for camouflage, like an armadillo, step when a low tide exposes eel grass beds. Eel grass is making it look like for protection. the dungeness crab’s favourite hiding spot. a walking garden. Many isopods are scavengers. The red rock crab (Cancer productus) is a smaller, Look for The gribble (Limnoria dark red crab found on rocky shores. This crab often these sharp- lignorum) is known as Isopod hides under seaweed and rocks at low tide. nosed crabs Kelp Crab the termite of the sea because under seaweed it damages floats, docks, pilings and ships; however, or clinging to kelp. gribbles also play an important ecological role by recycling woody debris. Barnacles Snails All we usually see or feel of barnacles are Ocean-going snails carry their homes their sharp-edged, immobile homes. on their backs, making them well equipped for travel. Herbivorous Dungeness Crab Inside live small animals related to crabs. At high tide, watch this secretive (plant-eating) snails act like lawn animal open its door to feed. Feathery mowers, scraping algae and detritus Hermit Crabs legs trap small organisms by sweeping from rocks. Carnivorous (meat- If you spot a snail shell that through the water like sieves. eating) snails attack other shellfish, such as clams, by drilling holes suddenly sprouts legs, you’ve The familiar acorn barnacle (Balanus Dog Whelk through their shells. discovered a hermit crab glandula) cements its white, volcano- Goose Neck Look for tiny, dark blue periwinkles (Littorina) (Pagurus). Watch the crab move Barnacle shaped shell to rocks or mobile sideways along the beach in structures, such as crabs, seaweeds under rocks and seaweeds. Their larger cousin the dog search of food or a new home. and boats. Goose barnacles whelk (Nucella lamellosa) inhabits tidepools and rock crevices Since their own soft shell offers Hermit Crab (Pollicypes polyumerus) attach in the intertidal zone. limited protection, hermit crabs borrow the empty themselves to surfaces by Many animals, shells of marine snails. Be sure to leave empty shells on long, fleshy stalks. including fish and birds, the beach for the hermit crabs and other beach dwellers. Barnacles are eat snails. among the favorite foods of snails, crabs and Shore Crabs Acorn sea stars. Barnacle Periwinkle Gently lift a large stone and watch the small crabs scatter for cover. Be sure to replace the stone before you leave. Chitons During high tide, small armies of shore crabs Amphipods The chiton (pronounced ki-tun) is often overlooked patrol the beach, because of its dark colour and unobtrusive shape. dining on leftovers Every beach has a cleanup crew and amphipods are an This soft-bodied animal is protected by eight tough, and picking algae essential part of the team.