Intertidal

Intertidal Zone = area between high and low tide ©Deryk Tolman What is the intertidal zone? It is defined as the area of the shore between the lowest and highest tides. In the Gulf Islands the intertidal area is approximately 2.5 meters in elevation change between the mean low tide and the mean high tide. The width of the intertidal zone fluctuates widely depending on the slope (flat beach vs steep rocky shore).

Intertidal zone = between high tide and low tide

Challenges of living in the intertidal zone Waves ©Graham Cook Predators ©Dynamosquito Challenges of living in the intertidal zone Moisture ©Clara Chew Salt Temperature ©Keryn Gedan Waves: organisms can be dislodged or washed away if they are not properly adapted ( Moisture: organisms are completely submerged in water at some times and high and dry at other times Salinity: Salinity changes depending on the tide, and can be quite high sometimes due to evaporation. Organisms must adapt to a wide range of salinity levels Temperature: Organisms must be adapted to the temperature of the ocean, as well as the air temperature. Air temperature varies widely depending on the time of year, from freezing cold in the winter to baking hot in the summer. Predators: When organisms are out of the water, they are vulnerable to a range of predators.

Why Live Here? FOOD OXYGEN HIDING SPOTS Energy Rich (food) The intertidal zone is very productive. Meaning there is a lot of energy entering into the food web within and nearby to the intertidal zone. Nutrients flow from the land carried by rain, rivers, and streams. Kelps, algae, and eelgrass capture sunlight and convert it to carbohydrates. Wave energy brings organic material such as seaweeds and driftwood. Oxygen Wave energy and proximity to the air cause the intertidal zone to be rich in oxygen. Deeper places in the ocean can be difficult places to live because of a lack of oxygen. Hiding Spots There are lots of places to hide from predators. Burrowing in the sand, or hiding under rocks. These hiding places can also protect organisms from exposure to the elements (extreme fluctuations in temperature, sunlight). HIDING SPOTS

How do they… Stay attached? ©Jerry Kirkhart There are many adaptations that organisms use to stay attached. Limpets have a foot like a suction cup that they use to stick to rocks. Barnacles make a ‘cement’ that they use to attach themselves. Adaptations to help protect from predators include: spines (like urchins); hard shells (like oysters and mussels); hiding under rocks and seaweed (like crabs and fish) Adaptations to keep from drying out: Shelled organisms like oysters and mussels close tightly to keep moisture in, urchins carve holes in rock to create pockets of moisture, anemones fold tentacles in to trap in moisture.

How do they… Protect themselves? Urchins have sharp spines to discourage predators from eating them. Many organisms have hard shells to protect themselves.

How do they… Keep from drying out? ©Stonebird Keep from drying out? Oysters and other bivalves tightly seal their shells to trap in moisture at low tide. Other organism like snails have a mucous that keeps them moist.

©Isabel ©USFWS – Pacific Region Plant or Animal? ©Aurel ©Ingrid Taylar ©pfly Corals (top left) and sponges (top middle) are animals. Corals are colonial invertebrates and sponges are multicellular invertebrates with few tissues and no organs. Eelgrass (bottom right) is a plant, bull kelp (top right) is not! Bull kelp was once considered a plant, then was put into kingdom protista, and currently it is proposed that kelp and other species of algae should have their own kingdom. Sea anemones (bottom left) are animals, as are seastars (bottom middle).

©NOAA Photo Library ©Paul Kaiser Who lives in Eelgrass? ©Sylke Rohrlach Source: http://wanderinweeta.blogspot.ca/2013/02/tiny-discoveries-and-mysterious-bubble.html Many species call eelgrass meadows home, including Dungeness Crab, juvenile Salmon, and Pacific Herring. Top left photo is a coho smolt, top right is a kelp crab, bottom left is a nudibranch, bottom right is an amphipod. Eelgrass meadows can capture and store carbon at rates up to 90 times that of the equivalent area of forests! This helps to reduce ocean acidification and combat rising atmospheric CO2 levels. Eelgrass meadows produce oxygen. Eelgrass roots help to bind sediment, protecting beaches against wave erosion.

Have you seen… A Purple Star? ©bibliomaniac15 ©Liza The Purple Star (or Ochre Star) can be purple, orange, yellowish, reddish, or shades of brown. Has tube feet (see image on the left) that allow it to move. Like mini suction cups, the starfish can pump water in and out of the tube feet to either stick to a surface or release its grip. They feed on marine invertebrates like mussels, barnacles, snails, and limpets. They push their stomach out of their mouth to digest prey externally. They can regenerate lost arms. A Purple Star?

Have you seen… A Purple Shore Crab? ©Dan Hershman Usually purple, but can be olive green or reddish-brown. Small species, males up to 5.6 cm (shell width), females up to 3.4 cm. Feed on algae and single celled organisms like diatoms. A Purple Shore Crab?

Male or Female Crab? Male Female On their undersides male crabs have a shape that looks like a lighthouse, whereas female crabs have a shape that looks like a honeycomb. Female

How can we be good explorers? Ask students how they would behave in a friend’s house. Would they poke their friend’s parents? Take toys home with them? Explain that the intertidal is home to many creatures, and that they should be treated respectfully. Guidelines for Intertidal Exploration: Be careful Be respectful Wash your hands before handling anything Handle creatures gently, and only for a short time Don’t turn over rocks bigger than your head Always gently place organisms and rocks back where you found them Don’t take anything off of the beach

This education resource was produced by the Mayne Island Conservancy Society thanks to the financial support of: