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
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