1. Intertidal

2. 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).

3. Intertidal zone = between high tide and low tide

4. 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.

5. 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

6. Adaptations of Organisms
What adaptations have you seen that help organisms to:
©Jerry Kirkhart
Protect themselves from waves and currents?
Protect themselves from predators?
There are many adaptations that organisms use to protect themselves from waves and currents. Mussels, limpets, barnacles, and many other organisms attach themselves to rocks to keep from getting washed away. Some types of shrimp, clams, and worms will burrow in sandy/muddy bottoms.
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.
©Stonebird
Keep from drying out?

7. Adaptations of Organisms
Source:
How would a creature in a sandy environment protect itself from waves and predators?
©Roberto Verzo
A common strategy for animals living in sandy places is to bury themselves in the sand. This allows them to hide from predators and protects from fluctuations in temperature. Clams and polycheates (big worm-like organisms) are examples of this.
A common strategy for animals living in rocky places is to hold VERY tightly to a rock and shield themselves with a shell.
How would an organism in a rocky environment protect itself from waves and predators?

8. ©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 were 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).

9. Plants vs. Seaweeds (most) Plants: Photosynthesize Have roots
©Eric Heupel
(most) Plants:
Photosynthesize
Have roots
Absorb moisture and nutrients through roots
Have leaves
Have stems
Reproduce by seed
(most) Seaweeds:
Photosynthesize
Have holdfasts
Absorb moisture and nutrients along whole surface
Have blades
Have stipes
Reproduce by spores

10. Why is Eelgrass so important?
Provides food and habitat for many creatures, including Dungeness Crab, juvenile Salmon, Pacific Herring and many others
Produces oxygen
Absorbs CO₂
Prevents erosion
©NOAA Photo Library
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 roots help to bind sediment, protecting beaches against wave erosion.

11. Purple Star (Ochre 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.
Feed on marine invertebrates like mussels, barnacles, snails, and limpets.
Pushes its stomach out of its mouth to digest prey externally.
Can regenerate lost arms.

12. 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.

13. 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

14. 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
©Bureau of Land Management Oregon and Washington

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