1. The Intertidal Zone
Sources used in the creation of this PowerPoint include:
Fish 351 class website <
Online PowerPoint Presentation <daphne.palomar.edu/panderson/PowerPoint/Chapter15>
Google Images
Nybakken,J.W. (2001). Marine biology: an ecological approach: fifth edition. Benjamin Cummings, San Francisco.
Castro, P. & Huber, M. (2000). Marine biology: third edition. McGraw- Hill, Boston.
Sverdrup,K.A., Duxbury, A.C., & Duxbury, A.B. (2005). An introduction to the world’s oceans: eighth edition. McGraw-Hill, Boston.

2. What is the Intertidal Zone?
Area of the shore between high tide and low tide
Also known as the littoral zone

3. What is intertidal zonation?
Banding of organisms in the intertidal zone
Zones are not absolute
Sorted out by ability to cope with stresses
Also called vertical zonation
Image from google images

4. Pacific Northwest Rocky Intertidal Zones
Image from google images

5. Areas where tidal ranges are high, intertidal zones can reach depths of about 10 meters (33 feet)

6. A Dynamic Environment with challenges
Temperature fluctuations
Light
Moisture/Desiccation
Wave Shock/Energy
Dissolved Oxygen
Food Supply
Images from google images

7. Rocky shores Zonation of rocky shores:
Splash/ Spray zone (rarely covered by water)
Upper intertidal zone
Middle intertidal zone
Lower intertidal zone (rarely exposed)
Upper zones have mostly shelled organisms
Lower zones have many soft-bodied organisms and algae
Slide Modified from: daphne.palomar.edu/panderson/PowerPoint/Chapter15

8. Rocky shores: Intertidal zonation and organisms
Slide Source: daphne.palomar.edu/panderson/PowerPoint/Chapter15

9. Different Stresses for Different Zones
Upper Zones
Exposure (air & weather)
Heat
Predation by birds and land animals
Wave turbulence
Lower Zones
Competition (food & space)
Predation by aquatic animals
Images from google images and Brian Moore

10. General Rule of Thumb…
An organism’s upper limit is determined by physical factors (i.e.desiccation,
temperature).
The higher an organism lives, the more capable it must be of tolerating exposure to air and sun.
Its lower limit is determined by biological factors (i.e. predation, competition)
The lower an organism goes, the more capable it must be of withstanding competition pressures for space and resources and avoiding predation.

11. Splash Zone (or Supralittoral Zone)
Above high-tide level
Seldom submerged
High air exposure
The greatest challenges are drying out and thermal stress
Image from Rick Keil

12. Splash Zone Limpets (aquatic snail)
Periwinkles dominate (sea snails)
Limpets (aquatic snail)
Lichens (a symbiotic association between a fungus and an alga)
Encrusting algae
Shore crabs
Periwinkle photo by Terry Klinger - University of Washington; other photos from google images
Lichens soak up water like a sponge and store it to avoid desiccation.
Algae in these zones are resistant to drying out.
Periwinkles can breathe air, tolerate extreme temperature, and go months without water.
Limpets can trap moisture under their shells. Then can also raise their shells off of the rock for temperature regulation.
Shore crabs scavenge dead carcasses and scrape algae off rocks.

13. Pickleweed a.k.a Sea Asparagus
a.k.a. Salicornia - is a genus of succulent, halophyte flowering plants in the family Amaranthaceae that grow in salt marshes, on beaches, and among mangroves.

14. Upper Intertidal Zone Submerged regularly (once or twice a day)
Affected by desiccation (the state of extreme dryness), competition, & predation
Image from google images

15. Upper Intertidal Zone Barnacles dominate
The barnacle is a hardy animal that is found in or very closely to sea water. Although it is frequently confused for a mollusc because of its hard outer shell, it is actually a crustacean, closely related to crabs and lobsters.
Barnacles are most often seen as roughly circular sessile invertebrates (which means that they cannot move on their own), and are permanently attached to the substrate they live on. In their juvenile form they are free-floating, but eventually they attach themselves to any nearby rock, shell, or other object and stay there for the rest of their lives. Their shells are composed of calcite.
Gooseneck barnacles
-acorn barnacles are also abundant; often larger barnacles are closer to the water, smaller species are found higher up
*keys to success - larval settlement pattern (upper-small;lower-large), desiccation tolerance, competition, predation (whelks)
Photo Credit: Trina (Fish 351)

16. Middle Intertidal Zone
Lower limit of barnacles is set by competition with mussels in this zone
Mussels are more prone to drying out than barnacles
Lower limit of mussels is set by seastars
Image from Rick Keil

17. Middle Intertidal Zone
Mussels
Barnacles
Seaweeds
Image from Brian Moore

18. Keystone Species: Pisaster !
Pisaster ochraceus, generally known as the purple sea star, ochre sea star or ochre starfish, is a common starfish found among the waters of the Pacific Ocean.
Voracious predators
How do seastars ingest their prey? Sea stars use suction in the tube feet for movement and feeding. They wrap their bodies around quahogs and other bivalves, using the suction from their tube feet to pull shells apart. When the prey is opened, the sea star pushes its stomach out of its body and into the bivalve, secreting enzymes that digest the prey's soft body tissues. The liquefied bivalve is then absorbed into the stomach. Sea stars feed often, and their size depends on the amount of food they eat, not on their age.
Often found in middle/lower intertidal (prone to drying out)
Image from Brian Moore
Sea stars ingest prey by inserting their stomachs into their prey’s shell and digesting the prey inside it’s own shell.
Bob Payne - Pisaster removal experiment --> w/ no sea stars, mussels take over and diversity in the middle intertidal decreases to nonexistent

19. Lower Intertidal Zone Submerged most of the time
Good place for predators and seaweeds
Compete for light & space
Image from google images

20. Lower Intertidal Zone Seaweed Surfgrass Anemones Seastars
Images from Brian Moore and Rick Keil

21. Photic Zone Green Algae Brown Algae Red Algae
Absorb short & long wavelengths
Ex. Sea lettuce (Ulva spp.)
Brown Algae
Capable of absorbing shorter wavelengths
Ex. Rockweed (Fucus gardneri)
Red Algae
Absorb short blue-green light
Ex. Encrusting coralline algae (Lithothamnion spp.)

22. Lower Intertidal Zone
Algae dominates this zone. Marine algae, or seaweeds, can be found in patches among barnacles and mussels of the mid-intertidal zone and in some areas the brown algae can extend as far up as the black zone eliminating all other zones.
In general though, they begin to form a distinct band below the barnacles. Zonation patterns of algae are governed by exposure to the tide and wave impact, as well as by species interactions such as grazing by invertebrates, and competition for space and light.

23. Which zone? How can you tell?
Pictures by Brian Moore and Rick Keil
Upper left - upper intertidal - barnacles (acorn and gooseneck); Upper right:Splash Zone - periwinkles!; Bottom - lower intertidal - seaweeds

24. What determines the limits of these species’ intertidal ranges?
Images from google images and Rick Keil

25. What would happen if you removed the seastars from this tidepool?
Image from google images
Seastar removal - mussels extend lower into intertidal - take over and diversity decreases